Where do we download Betaflight Configurator and Blackbox Explorer? I have picked up an older quad to get some experience in FPV flying.  I'm not sure of the make or model of the quad - it doesn't seem to have a label.  It does come with some printed instructions for setup and use, but these seem to be out-of-date.

The instructions say that I need Betaflight Configurator and Blackbox Explorer and that these should be downloaded from the Chrome Web Store.  However, those apps don't appear to be available from the Chrome Web Store.

After a few Google searches, I found that they were removed following Google's announcement that they were going to be withdrawing support for all Chrome Apps. I also found an announcement that Betaflight would be developing standalone apps to replace the ones that were going to be removed from the Chrome Web Store.  Unfortunately, those announcements don't say where the new standalone apps will be available from.

Now, I have searched, and I've found several sites that offer apps called 'Betaflight Configurator' and 'Blackbox Explorer', however, none seem to be official download sites (and several of them trigger safety warnings when I click on the links).  Besides which, everyone knows that we shouldn't be downloading software these days unless it is from a trusted source.

So my question is simple.

Where is the official download site for 'Betaflight Configurator' and 'Blackbox Explorer'?

Betaflight software is available from the Betaflight GitHub pages. These give the option of downloading pre-compiled binaries or the source code if you prefer to compile yourself.

Betaflight Configurator
Blackbox log viewer


Why do 48KHz ESCs increase flight time? I was looking at ESC settings for whoops/toothpicks and have seen how the 48KHz JESC firmware can increase flight time. Why is this? Thanks!

To clarify, the 48kHz is NOT running on the gyroscope or the FC firmware.
What 48kHz is referring to is the PWM Frequency in the ESC, namely the frequency at which the power MOSFETs on the speed controller switch on and off in order to provide power to the brushless motors and therefore thrust to the craft.
The reason in whoops and small/light craft 3" and smaller will see a flight time improvement is that the RPm ranges these crafts fly at, the switching down-time at lower PWM frequencies means the motor/ESC is having very small active braking events in the switching cycle, then overcompensating by driving higher throttle values to compensate (both of which cost energy).

In some cases, 96kHz will also work very well, although this is often limited to smaller whoop class quads, and I would caution against it on specific instances where the ESC design has a higher dead time value because these tend to suffer failures more often at higher PWM frequency when pushed hard.


Does frequently changing the amount of power to a bldc motor wear it out? If you had a brushless dc motor and kept it running but changing the power input every few seconds/minutes would it wear it out?

I ask because for a drone like aircraft I'm designing, making turns requires change in rpm and input power. If it helps, the motors are large and 167kv bldc motor with 100cc.

No, changes in speed should have little effect. The only wearing part of a brushless motor is the bearings, which are generally rated for a certain number of rotations and a certain load (and are reasonably easy to replace).

With IC engines there are complex issues piston and bore temperature, expansion, lubrication and heat cycling - but electric motors are much simpler.


How do I pick my gear when getting started with FPV multirotors? There are a large number of beginner and starter kits out there for people looking to get into multirotor FPV flying, all touting their various advantages over the competition.

What should I look for (or avoid) in an FPV drone kit, as someone who hasn't flown FPV before?

There are quite a few aspects of FPV, so a I’ll give a summary here. I’ll try to be concise so if any extra info is required or wanted, please let me know.

The first thing to look at when you’re flying FPV is the kind of aircraft, all the way up from a small Tiny Whoop to an X class (please not for beginners though!). In general, the larger props tend to give more flight time up to a point - it’s generally agreed that 7 inch props should be used for long-range because of this.

Video Transmitters

Another important thing to look at on your aircraft (excluding the advantages of different flight controllers etc, which I would love to talk about but would end up writing a massive wall of text) is the video transmitter, or VTX.

When looking at these, the first important thing is to check your local laws about what frequencies and transmitter powers you can use. Once you know that, keep in mind that more power tends to equal more range in open spaces, but can lead to more interference in places like abandoned buildings.

Another important fact to remember about the VTX is that you should manually select the channel on your VTX AND goggles as auto-scan sometimes picks the wrong channel and will cut out after a few feet. Also, never turn on your VTX without an antenna installed, or you risk damaging it. It is perfectly normal for your VTX to get warm on the bench when there is no airflow.

Finally, you will see people talking about Smart Audio - this is just a way to control the settings on the VTX from your transmitter.

Other hardware

Motors are very important. If possible, get brushless motors as they last longer and are more powerful.

When getting your first FPV quad, check out how repairable it is. It’s almost certain that at some point you will need to repair or modify it, so it’s good to know that before getting the quad.

Check what voltage your quad is designed to run at. If you have too little voltage, your quad will be underpowered, but if you have too great a voltage your quad may burst into flames (possibly a slight exaggeration to get a point across).

The ESC or Electronic Speed Controller is what tells your motor what to do, and you need one for each motor. If possible, get BLHeli_32 ESCs as they are more modern and natively support bidirectional Dshot so you can enable something called ‘RPM filtering).

When looking at flight controllers, the higher the value of X is in the naming format FX, the better. At the time of writing, F4 is the most common and F7 is becoming more popular. As I said, I won’t go into too much detail, but the higher the number, the more processes the CPU can complete per second so the more filtering and other leaguers you can have.

Goggles

There are two main types of goggles - box goggles and slimline goggles.

In general, slimline goggles are more expensive, lighter, arguably more comfortable and tend to have a narrower field of view and better quality displays. Box goggles, on the other hand, have massive screens and tend to be cheaper, however they are larger and heavier so may be less comfortable.

If possible, get goggles with a diversity receiver (or if you get Fat Sharks of Orqas, get a diversity receiver module like Rapidfire). This has two receivers and can either merge the two signals into one (cleaner) signal, or just automatically pick whichever signal is the strongest.

RC Transmitters

The most commonly used protocol at the moment is FrSky's D16, with Crossfire becoming more and more popular not only for long-range, but just for general flying.

When picking your transmitter, look for Hall gimbals, which use the Hall Effect to measure movement instead of potentiometers, so last longer and (apparently- I haven t used them) feel nicer.

Much of your transmitter will be personal preference, about the ergonomics and whether you pinch, thumb or hybrid-pinch.

Batteries

For anything more than 1S, you need a balance charger to make sure all the cells have the same voltage. To find the nominal voltage of a battery, multiply the number of cells by 3.7, as the nominal voltage of a single cell is 3.7.

I will leave you with this - don’t leave charging batteries unattended - LiPos are very dangerous if mistreated and can burst into flames if damaged or overcharged.


What are the advantages or buying a small drone vs a larger drone? I have been wanting to get into drones a bit more than i am right now for a while. In the case of drones bigger seems to be more expensive but what advantages does it have over a smaller drone, what disadvantages? I can think of a few right away:

bigger would have a longer battery life
bigger would have more thrust

but

smaller would cost less
smaller might be more nimble

What spec/ability differences do smaller and larger drones have?

The first thing you should consider is what you have room for. A larger drone will normally need more space to fly and can cause more damage if crashed. I would recommend a small drone if you are just starting out or if you can only fly indoors, in which case you would want a tiny whoop.

The next thing I would think about is cost. A larger drone will be much more expensive for the drone itself, the propellers, the parts (frame, electronics, etc.), and especially batteries. While a larger drone may have slightly longer flight times, one battery for a large drone might cost 10 times as much as a battery for a small drone. So, with smaller drones, you can get more flight time per dollar of battery. (you can buy 4-6 small batteries for the price of one large battery and get a lot more flight time for the same amount of money). So, if you're on a budget, I definitely recommend a small drone. It's also worth mentioning that larger drones usually use batteries with more cells so they can be more dangerous if they catch on fire or puff up.

Next, there is flight performance. Generally, it is true that a smaller drone is more nimble than a large drone, although Larger drones are usually capable of much higher top-speeds. I must say though, after having lots of experience with different drones I much prefer the performance of a large, powerful drone to a small drone because small drones often suffer from lots of battery sag due to the lower battery voltages and so they cannot sustain high throttle as well. Also, a larger drone can carry a GoPro or other camera with ease.

So in the end:

Get a small drone if: you only have a small area, you only have a little bit of money, you are very worried about damaging something, you want a lot of flight time for less money, or if you just don't want a big drone.
Get a larger drone if: You have enough space and money, you want high performance/top speed, you want something that can lift a GoPro/camera/payload, or if you just want a larger drone.


Tuning sharp turn prop wash When I do a split-S or make a sharp turn around an object, my drone shakes due to the prop wash.  I have heard that this prop wash (from abrupt turns) is the hardest to remove via tuning.  I've tried messing with the PIDs, and the filters.  I'm running RPM filtering, so I started with filters in the middle (default) of the sliders, and gradually moved them all the way to the right (least filtering).  My motors do not get hot.  The prop wash is mostly gone, but I still feel it/see it through goggles, and hear it.  Am I wasting my time trying to remove this last bit of prop wash?

I think prop wash is not entirely eliminable by tuning. If you have really good gear and tune you may be able to reduce it even further, but it will be there.

When you are doing sharp turns, you are flying into your own turbulent air stream and the effectivity of your motors compared to each other changes unpredictably and rapidly. The flight controller tries to compensate, but neither the calculation nor the the motors' reaction is instantaneous, so most probably the compensation will come too late and will not achieve the required effect, which will trigger further and further micro adjustments until the quad reaches more predictable air.

So the easiest way to eliminate prop wash is to move out of your own turbulent air as quickly as possible. When doing split-S don't just descend vertically, but start moving forward before arresting your fall so your motors will be over clean air.


What impact does a shroud have on the torque produced by the prop(s) of a multirotor that incorporates a properly designed shouded propeller? Based on the research presented here: "Hover and wind-tunnel testing of shrouded rotors for improved micro air vehicle design" and other reading that translates similarly well-designed shroud and rotor combinations into more general layman's terms, I have found that some authors indicate that there is a performance increase of 40% to 60% in static thrust for such a configuration. One source has indicated a theoretical increase in static thrust as much as 80%.

If we focus our attention on a multirotor design that is intended as a craft whose principal purpose is for inspections of stationary objects such as buildings and stationary infrastructure, and it is not expected to fly fast nor fly far, then the primary benefit from the shrouded rotor is the improvement of static thrust. Flight in translation will be rare and incidental to maneuvering around the object being inspected.

And assuming that the shroud can be manufactured with a mass that is less that the incremental improvement in thrust, this design will serve its intended purpose with the significant benefit of having some built-in protection from horizontal impact with obstacles.

The need for maneuverability will be equal to most other multirotor applications intended for inspections and as such yaw will still need to be produced by controlling the speed of the propellers by the flight controller.

What impact will the shroud have on the production of yaw by the torque produced by the propellers (rotors)?

Ducts and shrouds reduce tip losses; the reason we don't see them more often is that a well designed propeller should not have large tip losses.

Tip losses are greatest when there's a large pressure differential between the upper and lower side of the blade. In other words, the blade is highly loaded.

This question explains why large, lightly loaded blades are more efficient than smaller, faster spinning blades:

Why are larger propellers generally more efficient than smaller ones?

Notice that none of the answers mention tip losses - they're not the reason the small, fast prop is inefficient, they're just an extra problem. Fixing that extra problem with a shroud still leave you with fundamentally inefficient system.

  assuming that the shroud can be manufactured with a mass that is less that the incremental improvement in thrust,

For a well designed prop, a shroud adds more weight that it saves - and it's usually better to use that weight to increase the diameter of the prop instead of adding a shroud.

  significant benefit of having some built-in protection from horizontal impact with obstacles.

To work well, a shroud needs to have very little clearance from the blades. That means that if you hit anything, the shroud will hit the blades. You might cause less damage to the thing you hit, but you're still going to crash.


What is RPM filtering in Betaflight? I've seen a lot of buzz lately about the supposed advantages of using the RPM filtering option introduced in Betaflight 4.1. What is it and how does it improve inflight smoothness?

Multirotors are inherently a very noisy environment for sensors like the gyroscope which try to measure the actual motion of the drone. Mechanical vibrations and oscillations are present all over, primarily generated by the motors but also by parts in the frame. These vibrations manifest themselves as fluctuations in the gyroscope values.

 (cit.)

Flight control firmware relies on a clean measure of how quickly the drone is moving in order to function properly, so they employ a number of techniques to "filter" the gyroscope signal and remove as much of the noise as possible. Unclean signals can result in more inflight oscillations and hot motors. Several different kinds of filters are used, often simultaneously, to accomplish this. (e.g. static & dynamic notch filters, low/high pass filters, Kalman filters) The below image depicting the suite of filters employed by Betaflight helps get across how serious an issue this is, although it isn't quite accurate today. (the image was accurate in some 3.x versions)

RPM filtering (new in Betaflight 4.1) seeks to remove motor noise, one of the most prolific sources of vibrations on a multirotor. The frequency of motor vibrations are directly correlated with their rotation rate, so the Betaflight RPM filter takes input from the ESCs about motor speeds (using bidirectional DSHOT) and uses it to target a series of dynamic notch filters which selectively remove noise from the gyroscope values occurring at a specific frequency. There's a whole page on the Betaflight wiki about this.

Articles like this from Oscar Liang and this on the Betaflight wiki
provide instructions for how to set up and configure the RPM filter, as well as this video from Joshua Bardwell on the topic.


Crossfire signal strength - comparing Immortal "L" vs "T" Is there any detrimental effect on signal reception when mounting crossfire antennas in the Immortal "L" orientation compared to the traditional "T"?

The short answer is, yes. According to testing done here there is an observed 3db loss when folding the bottom half of a dipole which would be the same effect as cutting your output power in half.

See this graph from the link above. At the bottom in red is the bend of the antenna and the blue line is the gain.

The 'T' antenna is called a dipole and it's a very common antenna design. Changing the shape of the antenna will almost always change the antenna's gain and radiation pattern. Unless you have tested very carefully or are following a known and tested antenna design, chances are you aren't improving its performance. This article describes what one person went through to test folding a dipole by 90 degrees. Other things to keep in mind, the L shape allows your antenna to be polarized in two directions, while it might have worse reception under certain circumstances it may be better in others. This could be especially useful on a quad in situations where the orientation of the antenna would not be straight up and down.


When to replace bearings in a brushless motors? When, if ever, should I replace the bearings in my drone's brushless motors? Are there signs that a motor needs new bearings?

Learning how to replace bearings is a skill worth having.

It doesn't take much slop in a bearing to add a lot of noise to the gyro signal, and that will be amplified by the PIDs, causing hot motors or reduced performance.

If the quad is a high-performance or cinematic machine, its best to replace bearings as soon as they sound rattly or get free play in the bearings.

For everyday park fliers, it matters a lot less.  The correct answer is that you change them according to your ability to do the job, and the need for it.


Restore over-discharged LiPo batteries ~2.0V/cell I have a LiPo battery which is ~2.0V/cell, how can I restore it safely? By "safely" I mean how can this be controlled as I know LiPo batteries can be dangerous.

Firstly, I'll add the usual statement that mistreated LiPos can be dangerous and you are almost always better getting new ones.

In some cases, a 'smart' battery charger will refuse to charge cells which have dropped between a certain (manufacturer-determined) voltage. In this case, you can connect the battery to a current limited voltage source and charge the batteries manually with a very low trickle current - 0.1 to 0.2C is more than enough. It will take a while, but speed is not the aim here. You might be able to do this with the charger, by telling it the battery is a different type, or by using a separate supply. In either case, you must ensure the max voltage is within the normal range for the LiPo (4.2V/cell.)

You should only attempt recovery of a suspect battery in a safe, supervised environment - charging is the most likely time for such a battery to fail, and particularly so if it has been over-discharged.


USB Webcam Parts for FPV? I have a camera taken out of an old usb webcam. It has four wires attached to and labeled on the board: 5V (red); DM (white); DP (green); and GND (black). I was thinking I could use it just like a 'normal' FPV camera and get a video transmitter for it. However, it has four wires rather than three like most. I read that DM and DP are both data lines, but as a high/low pair or something. What do I do with these? Is the camera usable with something like this video transmitter?

These four wires are most likely a USB connection, red and black are power, and the other two are USB data. That means you can't use it neither with today's analog gear, like the VTX that you linked to (as it requires an oldschool analog TV signal), nor any of the new and shiny digital FPV systems, like the DJI system (as they use their own proprietary protocols).

However, you can use it for flying if you really want or need it — you just need a computer on your drone that can process the video feed, such as a Raspberry Pi, and some kind of digital wireless connection, such as WiFi or even 4G to stream that feed to your phone or computer on the ground. That's how a lot of commercial drones work, and you can build something similar yourself.

Whether you really need or want it is another question. Using such a setup for the "sporty" kind of FPV flying, i.e. racing or freestyle, is probably a bad idea, as the latency will be very high, on the order of hundreds of milliseconds if not more. Such systems are more suited for long range and autonomous craft, which generally fly themselves (and sometimes even do some onboard analysis of the video feed), or just as a not necessarily practical but fun-to-make project to prove to yourself how cool of a hacker you are (or as part of such a project, like a facial-recognition patrol drone or whatever).


What is the most thrust dense copter configuration? I need to make a compact drone that does not need to be fast, nor very power efficient*. I wanted to know what is the most mass I can lift with the smallest footprint**.

To make this question more answerable: which is more compact for the same amount of payload (say 50g), a helicopter, a quadcopter, a quadcopter with duct-fans, or another strange configuration like: the dronut, the rollocopter or the ball drone?

Are there any resources out there that have made such comparisons?

* Not exactly true.

** Footprint - in case it was not completely obvious what I meant - is the transversal area of the drone. Or consider it a volume and assign it the volume of the smallest sphere that can contain the whole drone while flying.

Assuming you can only use up to four motors (because if you used six, eight, or even more you could just lift something with brute force) the most thrust dense configuration would probably be a ducted fan quadcopter.

The reason for that is ducted fans essentially stop a lot of air from being propelled sideways and more air goes down. Ducted fans can provide more lift and are more efficient than open-prop designs.

A helicopter would only have one motor and would need to be much larger to provide the same thrust as a quadcopter. Those other configurations mentioned would also not have nearly the thrust of a quadcopter of a similar size.

So, the best option would be a ducted-fan quadcopter (or hexacopter/octocopter if you can use lots of motors) with oversized motors. A good propeller would be a large prop as it gives more thrust at the expense of maneuverability and acceleration. Wider motors give you more torque but taller motors give you more RPMs so that depends on the prop. (A heavy aggressive prop should go with a wide motor and a lighter prop should be paired with a taller motor)

If you don't really care about longevity, get a powerful ESC, high cell-count battery (probably 6s), and get a motor that is higher than normal KV for maximum thrust and power at the expense of the motor's longevity. But be careful to not go too crazy with the high KV as it could potentially burn out an ESC or destroy the motor.

Also, as durability is not really that important for the purpose of this specific build, make it as light as physically possible (but still rigid, you don't want vibrations or flex) so that it can lift as much weight as possible.

Hopefully, this helps, as I'm not really sure what all of the requirements of this drone are.


What is the typical glide ratio of Kline-Fogleman airfoils? Kline-Fogleman (KFm) airfoils, despite their seeming contradiction with known principles of aerodynamics, seem to be very popular in RC modelling, and are known to have a peculiar stall behavior, with a gradual transition to high drag without loss of lift, unlike the sharp stall of traditional smooth airfoils.

There's little information I could find about how the stepped design affects the airfoil's aerodynamic efficiency, however. The design seems to be plenty good for powered fun-flyer planes; I've seen at least some KFm slope gliders, too, and a well-circulated picture (provided below) states that the KFm3 variant has "fantastic flight characteristics" and is good for sailplanes... But there are no hard numbers that I could find on just how good these airfoils are (or how good they can be) in terms of lift to drag (L/D) ratio.

Are there any known numbers for the typical and best case L/D values of aircraft with Kline-Fogleman (KFm) airfoils, and if so, what are they? How does this characteristic differ between variants of the airfoil design?

This paper (AE-74-1054-1) from the University of Tennessee has a graph on page 15 showing the best they managed was 1:17 with the step on top and 1:8 with the step on the bottom but these were at a very specific angle of attack, and about half that was more typical.

  The wind tunnel results show that for this new airfoil the lift/drag ratio is lower  than for the flat plate, and the pressure data show that the airfoil derives its lift the same way as the inclined flat plate. This airfoil offers no discernable advantages over the conventional airfoil.

Anecdotally, that matches my experience with KFm gliders. They work about as well as a flat plate. Ok for a light-wieght park-flier with loads of thrust but no good for a glider.


Is the Experimental Aircraft Association (EAA) an appropriate association for those interested in building RC aircraft? I am new to building RC aircraft. I am wondering which association I should join. I found the Experimental Aircraft Association (EAA). Is that association suitable for people who are interested in building RC aircraft, or should I look for another association instead?
(Please provide answers relevant to major cities in the United States and Canada. Thank you)

As for EAA - No. They seem to be politically on the good side of drone (anti-RID / Docket ID FAA-2019-1100). They do not mention any CBO (community based organization) direction searching the site.  They are Oshkosh based, a legacy aviation mecca for stunt flight.  Their agenda is legacy (general) aviation and like the AOPA they are likely looking for money in a time of decline and diminishing interest.
Regarding CBO and recreational flight in the USA (current), the AMA is the closest, but they are not a CBO (yet). The CBO regs and the recreational flight test are late (and required).  Per the way the regulations work, until this is settled all recreational RC flight is in a "non-legal" (and not not totally illegal) state. If you do not fly under a CBO you need to be commercial (generally speaking).
Simply put, in the USA the technical requirement for all non-commercial 250gram+ recreational flight is to be conducted in accordance with a CBO.  You need the CBO rules but not the membership.
Look at the details surrounding the repeal of 336 and the following pivot in regulation and pay attention to the NRPM for RID (docket from above). I posted an anti-RID comment creator that goes over a lot of the drama under the hood.
There is a Federal requirement for CBO ruleset for rec flight. A CBO has a number of complex and limiting criteria that makes these orgs rare.
As a reminder on our dire situation, the FAA has missed all of the critical timelines for this work. The way the legislation is written the FAA recognized identification areas (FRIAs) will spell the doom of all rec RC flight in the USA due to a technicality still not addressed (short version: FRIA applications have a fixed window for application, after that no more can apply, so when a field has to move it has to close).
Right now there is no organization I would recommend joining and this is why I became a commercial (107) pilot. I fly under aviation rules, I insure myself and I am only beholden to the FAA and am entitled considerably more rights and privileges.  Anyone serious about this hobby should consider a commercial license, join that organization.
As for Canada, their laws are similar but more strict and actually enforced (unlike the USA).  You need some special permitting to fly more then 250 grams.


Vertical Flight Paths I've been searching around for software to allow a vertical flight plan. For example I want to flight 50m across a building at 20m AGL. Then drop 1m and fly back 50m. So on and so forth. I've read a bit into DJI, DroneDeploy, and Pix4D, but haven't been able to find anything. I've read something about double grids, but I believe that is for 3D models? I am not trying to capture a 3D model. I know that in at least Drone Deploy you can create multiple flight paths, but you have to land and restart for each altitude drop. I am also not taking any pictures. Looking for just the flight path. This could be done manually, but I'd prefer it to be automated.
Does anyone have any suggestions?

There is a software called UgCS which I believe should fit your requirements. It allows you to create waypoints with precise location and altitude. There are options like terrain following which allows the UAV to maintain a relatively constant altitude above ground level, a Facade scan tool which allows you to plan a flight path along a vertical plane at a certain distance from a wall, or there is the option to easily create custom waypoints with specific altitudes as shown in this flight path:


What is the correct process for transferring to a new transmitter? I’m looking to upgrade from my QX7 to the new Radiomaster TX16S Hall when it comes out.

I have several models saved to my current radio, and I’d rather not go through the hassle of rebinding all of them.

I have seen the Oscar Liang tutorial about model transfers in OpenTX, however many people are reporting it doesn’t work.

My question is: what process can I use to transfer my models over to a new radio whilst also carrying over the receiver profiles so I don’t need to re-bind my models.

I’m not sure if it is possible so ‘you can’t’ would be a reasonable answer.

Transferring models shouldn't be a problem since both radios run OpenTX.

However,  you cannot transfer bindings unless you are also moving an external module to the new radio.  For example, if you move a crossfire module from the QX7 to the Radiomaster, all your models are still bound at the module level, no re-binding required.  But if you are going to be using the internal module of the new radio then re-binding is required.


Streaming FPV over WiFi? I met a guy some time ago running a first person view (FPV) stream over Wifi. He said that the setup didn't use a complete Operations System Interconnect (OSI) network stack and this allowed them to stream video faster then one might over User Datagram Protocol (UDP). I don't recall the details but at the time he said it was a common trick used by Drone flyers, perhaps this was just the group he knew. I was wondering if anyone had any further information on this. I believe he was streaming 4K and was quite surprised. At the time I was messing around with a an early Raspberry PI and trying to stream video myself but I could only achieve a speed/quality that where far inferior by comparison.

This is done by placing streaming video data (RTP) directly into the Wi-Fi frames. Checkout https://github.com/svpcom/wifibroadcast/ project for more details.


What factors affect the noise level of propellers? I've noticed that the noise level of different quadcopters can vary quite a bit, especially in the sub 3" range. For example, some of the Tinyhawk models are extremely quiet, while other similarly sized builds end up much louder while flying.

I'm currently working on a park flyer build; while I won't be next to anyone, I do expect there to be people within earshot so I don't want to be flying a weed whacker. Rather than just buying props and testing them, I'd like to at least have a working hypothesis on which ones will be loudest before purchasing them.

Since only you can be the judge of what you feel is too loud, and noise level from a drone is the result of many parts working together, this is a tough question to answer and I'm not sure you will succeed in finding "the" prop to suit your needs.  That said, if reduced noise is what you are looking for, and we remove the other parts of the drone from the equation, I'd suggest stiffer props from the manufacturer of your choice.  After flying for a while, if you feel that the noise level is getting worse, change props (all of them).

In my experience, as long as the props are balanced (most manufacturers have gotten better and producing consistently balanced props), on the stiffer side, clean, and free of any kinks or abrasions, they will be as quiet as they can be.  This is why drones sound quieter when they are first flown compared to after a few landings when they get grass and other debris sticking to them, along with abrasions and kinks on them - making them less efficient and more noisy as a result.

I use DALPROP T5045C and HQ R38 props.  Both are on the stiffer side and both are quieter than the thinner, more flexible props I had used a few years ago.

I hope this helps.  Good luck!


How do you use the PID controller to compensate for a higher weight? How should you adjust the PID values if you add weight to a quadcopter (For example a GoPro), so that the flight characteristics stay as close as possible to how they were before?

I assume that the Feed forward values has to be increased, probably more on the axis with the highest angular mass. But do you have to change for example the I gain as well if the added weight introduces more drifting?

I'm afraid there is no simple answer to this question. Adding weight to the quad will change the way it responds so in theory you would need to redo the tune from scratch.

That being said, there are a few assumptions you can make.
Since the weight goes up, the inertia goes up as well. So it will respond slower to stick movements and will have a bigger tendency to overshoot. To compensate for the slower reaction you can increase the P-gain and/or feedforward. To fight the overshoot (and the effect of the bigger P-gain) you will need to increase the D-gain as well.
I assume I-gain will not be impacted a lot.


How do I re-charge the batteries of my S49 drone faster when outside? I have a small S49 quadcopter. After around 10-15 minutes, it often runs out of charge and needs recharging. My charger requires it to be plugged into a portable USB charger or to the mains. I have tried charging using my power bank, but it takes like 30 minutes to charge compared to 10 minutes at home using the mains.

What other methods of charging could I use to charge it that will preferably charge it faster?

I couldn't find manual or just the specifications for this exact drone, but from what you wrote and what I see on the images it uses 1-Cell batteries charged with some USB adapter.
You didn't specify which USB power-bank you have or which power adapter you use to charge from the mains.
I assume it's some-kind of phone charger. These days phone chargers typically outputs current of 1.0-2.0A. So my guess is that your power-bank isn't capable of outputting these kinds of current.
Try looking for a power-bank with QuickCharge (QC). They are capable of giving out currents up to 4.5A


How does Amazon's new drone land itself into a station? I am fairly interested in drone building and thought about a drone which automatically recharges itself by flying in to his station, but thought it was close to impossible without using extremely sophisticated tech that extremely pricey (D-GPS).
How can this low cost drone reliabely land in its small station? Can anyone guess how?
(this is the drone im talking about https://www.youtube.com/watch?v=EIQTR4qCoHU)

Remember - it only takes 3 points to get a solid fix on location in 3 dimensional space. I have been thinking about this a lot, I will also have a unit on day 1 and possibly the unit disassembled day 2 and posted on line (maybe)
For the Amazon device there is most likely a sonar/echo or similar system that creates a feedback loop for position. I also suspect use of RFID or similar "near proximity tech" to get the last few inches.
There are a lot of systems available and affordable, LIDAR in particular is really cheap (https://www.getfpv.com/matek-optical-flow-lidar-sensor-3901-l0x.html)
The tech is pretty standard and accessible, Roomba has been doing this in 2D space for almost 20 years with self docking features for the floor cleaning system.
Once you have experience with auto-leveling and GPS technology the task becomes trivial. The hard part is universality and compliance - will it work anywhere and also be legal/interfering.
There are still a number of unanswered questions - but form what I know here a few of the approaches that come to mind:

Echo location indoors (bouncing signals to determine position, similar to how the blind or bats can "see" using echos and reflection of sound)
LIDAR with some GPU strength and the addition of hyper- or hypo-visible light can create an invisible beacon.
Various systems for mapping, used commonly in drones for recovery operations such as mineshaft exploration, possibly offset to cloud computation.
Wifi stereo has a lot of research in phasing and image control of sound worth considering.
RFID or Bluetooth beacon technology, possibly with other AWS devices in house?
Augmented indoor GPS (using what signal is available + other systems)
Final landing could be simple optics targeting a unique pattern, key for orientation (downward simple camera looking for landing beacon)
Sonar, like a bat, can help with direction, distance, and obstacle avoidance beyond aforementioned echolocation.
Additional off-device processing - such is the case for Alexa, Siri, and other services.

Also note how the female receptacle is wide and allows the unit to dock with +/- 1 inch accuracy.
Also important, the FAA claims to have NAS authority indoors, but they have never been able to asset any enforcement action.
This device is a HUGE blow to the FAA's weakening grasp on NAS policy. The laws that regulate this device are NOT settled and the legality is open for debate. Per the Congressional charter, the FAA controls all airspace "0inch and up" and there has never been any official clarification for indoor operation.  A lot of questions remain unanswered.
FWIW, if f you fly this unit out of the house it is $40k minimum fine for violation of key BVLoS rules such as remote operation w/out spotter and BVLoS operation without an exemption.  There are many other rules, each $20k each per violation should anyone take this out to the porch. See and avoid is not met by the device and that one is huge and is the massive thorn FPV faces for proper recognition.  I will be following this close.


Grinding sound on FPV motor but no apparent damage I have been testing a new brushless motor for an RC plane. It is a 2200KV motor controlled by a 30A BLDC ESC. I heard a grinding noise coming from my motor, as demonstrated in the following video: Video Here

I have not been able to find a video where someone's motor produced a similar sound. I feel like I have checked many of the usual troubleshooting issues.

This is a new product and has never been crashed. I checked for damage from manufacturing and there aren't any dents or deformations.
Magnets on rotor seem to be level and secure
Unsure about state of bearings. I thought one seemed to be spinning strangely (as if misaligned) but when I reevaluated it seemed fine.
Shaft is straight
A few coils are every so slightly loose... doesn't seem like it would be enough to cause problems
Screws for mounting clear both the stator and rotor. Seem to be magnetically attracted to rotor, but when I removed the screws then the same sound was produced.

I would like to believe it's just the cause of a bad bearing, but there were a couple times where the motor spun just fine after I had reassembled it, which leads me to believe something else is awry. I'm just a rookie at RC, so I'd like to get the opinion of some more experienced ears.

Is it possibly an issue with the ESC? I did solder the ends of the power wires. I was careful not to overheat, but possibly not careful enough?

It looks like a bad phase to me. Check the resistance of each phase, wire 1 to wire 2, wire 2 to wire 3, and wire 1 to wire 3. If one of those is much higher resistance or shows no continuity, then you've got a bad phase. I suspect this is the issue.

Also try swapping the motor to a different arm. This will eliminate the ESC as the issue. If the problem follows the motor to the new arm, then the the issue is the motor, if it stays put then it's the ESC. A bad FET or gate driver in one phase on the ESC can cause the same symptoms as a damaged phase in the motor.


My esc cuts the motor when I move control surfaces a lot I finally built my plane and started testing it on my workbench. If I moved the servos a lot (using my transmitter), the motor would cut out, the ESC would play a tone similar to when I first turn it on, and after 3-5 seconds the motor would restart. During the reset, the servos still responded. I flew the plane with issue as I knew the extreme control inputs I had given in testing wouldn't be needed in flight.
I think the problem is probably that my BEC is too small, but I'd just like your confirmation.
Details about my setup:

I am using a 3 cell battery
The ESC has a 1-amp BEC.
I am using a Spektrum AR410 receiver (although I don't think this is relevant)
I have 2x 6 gram servos on extensions.
Depending on which direction you rotate the control surfaces, they do need quite a bit of force.

I think it's a combination of the BEC and stiff controls.
1 amp BECs are often just linear regulators, effectively a transistor that acts like a variable resistor. It takes in battery voltage and turns some of the power into heat so that the remainder is 5v. If you were running a 2 cell battery, it would have to dissipate 7-5=2v but with a 3 cell battery it's 11-5=6v. That's three times as much, so it can only manage a third of the current.
2 servos are normally fine with that set up, but if the stiff control surfaces cause the servos to draw more power than normal they could cause the BEC output voltage to drop to the point where the receiver or ESC shuts down. Or maybe it overheats and there's a thermal cut off - I'm not really sure of the failure mode, but at least it didn't catch fire!
If you're curious, you could check to see how hot it gets, and measure the voltage at the receiver when the motor cuts. There are also servo power meters, or you could, HobbyKing seem to have discontinued theirs.
You may be able to solve the problem by freeing up the hinges and pushrods, but a better BEC is cheap and it's not a good idea to fly with a set up that you know could fail.
The better BECs are known as 'switching' because they switch the power on and off rapidly and then smooth the output, so there's much less power wasted as heat. Sometimes these are known as UBECs, because some early ones were sold under the name 'Ultimate-BEC'.


Analog Graupner MC-12 with R-700 receiver I have an old Graupner 35Mhz transmitter and receiver which I would like to get running again. Bought batteries and connected power and a servo to the receiver but nothing happens when I use the transmitter. Both have the same frequency quartz.

Do you have any tips on how to verify that both the transmitter and the receiver are functional or how to debug? I have a basic oscilloscope and a multimeter at hands. Both batteries are loaded and connected properly, I think. When I connect the servo to the receiver I sometimes get a tiny movement of the servo as I am plugging it in.

Any helpful input would be highly appreciated

AFAIK servos are usually driven by a PWM signal (which the Graupner RX seems to put out as well) with usually 50Hz. So you could basically check if the RX is putting out PWM signals on the 7 outputs. Just connect your scope to one ground pin as well as one data pin. Then you should see a square wave on the scope. If the square wave has a duty cycle of 1000µs, it means 0° (so the left most position of the servo). 2000µs means that the servo is supposed to rotate to the right most position, usually 180°.

There are some exceptions with some servos (continuously rotating servos - similar to stepper motors, or some servos have more than 180° of rotation), they probably don't affect you though.

If you are unsure about the waveforms or something else, I'm happy to help. I wouldn't say that the tiny movement of the servo you described means anything. It's probably just the servo "snapping" into it's position after getting power or something to help the servo to find out its current position.


Why can't quadcopters handle failure of one rotor? Ardupilot can detect (and it logs) motor output mismatch. I think detecting in flight motor failure is possible with modern firmware and flight controllers. Then if one rotor fails, why can't we have the quadcopter fly like a tricopter, since we now have ESCs that can change rotation directions?

I saw a TED talk from a guy who had written quadcopter software to handle losing one motor. Perhaps you can find it.
With nothing to counter the unbalanced torque, the quad spun in yaw quite rapidly. Most software would attempt to counter this by increasing power on the motor opposite the dead motor, and decreasing power to the other two. Instead they allowed the quad to yaw and concentrated on maintaining stability.
Although the unbalanced lift would tend to tip the quad over, it would tip the quad back a fraction of a second later when it had spun 180 degrees. I guess the software also had to take account of gyroscopic effects, and the time taken to spin a motor up or down.
The demonstration was indoors, so I couldn't tell if the quad was capable of 'forward' flight, but it hovered and descended under control.
You may well ask why this isn't part of common quadcopter firmware. I can only speculate that it's because:

It's rare to loose a motor in flight (failures are usually a result of crashes)
The algorithm for 3 motor flight isn't public domain (maybe the above team sold it to the military or something)
Landing while spinning rapidly does almost as much damage as crashing.
People who care about redundancy just add more motors.


How low can I safely discharge a LIPO battery during flight? What is the minimum voltage I can safely discharge a LIPO battery during a flight?

For example, if I have a 3S LIPO battery, should I be aiming to land my RC plane before the battery gets below a certain voltage?

Related to that, is it the voltage under load that matters, or the open/resting voltage once it is disconnected?

The short answer is that you don't want to run batteries below 3.0V ever, and ideally want to avoid large current draw below 3.5V. For a 3S battery, once you start seeing voltages in single digits (3.33V/cell is 10V, below that), it's time to land as a quick reference point - although you can set more precise values of around 10.6V as the warning point through telemetry at a transmitter and/or OSD on an FPV display.

The real issue you're trying to avoid here is that in the Lithium-CobaltOxide (LiPO battery chemistry), below 3.0 volts (can be 2.8V or so in Li-Ion batteries), the battery starts plating lithium permanently onto the anode reducing the capacity and discharge performance of the pack.  Doing this greatly harms the battery, so avoid that at all costs.

The reason I reference the 3.5V point is that typically you have another 10% of battery capacity left in order to affect a safe landing approach pattern without being under time pressure to land quickly, and make a good safe landing - also under load, the battery that is at 3.5V in flight will tend to recover to 3.7-3.85V depending on craft and setup, which is more appropriate for storing a battery as you travel back home to the bench charge the battery to its proper storage voltage (3.8V).


How to prevent an ESC from overheating? I have a 5-inch drone with individual ESCs on the arms of the frame. The ESCs tend to get very hot (somewhere around 70°C) and I'm not sure what is causing this and how to keep them cooler. Are there any ways to keep the ESCs cooler without adding too much weight to the quadcopter? Or is there anything I can do in the tuning to keep them cooler?

There is enough room to add things like heat sinks. (although I don't want to add too much weight)

Under normal conditions operating on the arms of a multirotor, ESC temperature should be well-controlled by the airflow passing over them from the propeller exhaust. It isn't a good sign that your ESCs are reaching dramatically higher temperatures like 70° C, given that you should be expecting to see ~30-40° C on a regular basis. One of three things is likely to be happening here:

The ESCs are undersized for the motors/propellers you have them driving
The ESCs are broken and showing signs of wear
The design of the ESCs is bad
Your PID/filter tuning settings are bad

Without knowing the exact details of your multirotor setup, it could be the first case due to the ease of accidentally picking too small an ESC to pair with power-thirsty motors and propellers. If this is true, then you should replace the ESCs with properly sized units, because there is a possibility that the overworked ESCs could catch fire or spontaneously die on you. (not to mention the fact that the efficency of the ESC will be decreased at higher temperatures)

However, the likely causes change because you're running a smaller multirotor, as @QuadMcFly said in his comment below: (emphasis mine)

  I would add for a 5" inch drone it is extremely unlikely that the issue is related to the ESC. I have run even tiny 20A ESCs on some ridiculously overpowered setups and they come down cool when tuned properly. In the vast majority of cases, hot ESCs come from bad tuning or bad hardware, either in the FC or the ESC. The first place I would look is at flight logs of the gyro and motor output data. That will tell you right away if it's a tuning issue.

Mitigation of ESC Related Thermal Issues

The heat you see generated by the ESCs is likely related to the power losses in the MOSFETs (metal–oxide–semiconductor field-effect transistors) used by most all ESCs to switch the power and off between the three phases of the BLDC motor. There are calculable power losses that occur while the MOSFET is conducting electricity and when it switches state between on and off, both of which contribute to heat generation.

The most direct solution to the issue is to add a decently-sized heatsink to the top surface of the MOSFET transistors and capacitors on the ESCs. You'd likely have to remove the plastic insulation for the best heat transfer between the MOSFET casings and heatsink.

Something like this, although with the insulation removed:

(cit.)

When you re-affix the ESC to the frame arm, it would be best if you also put down some kind of electrical insulation like electrical tape on the surface of the arm between it and the ESC so that there isn't a risk of the frame shorting out an ESC component.


Will connecting my Mavic Pro to a an iPad Litchi app try to update my Mavic Pro firmware? I have an iPad that I keep offline and use the DJI Go app with.  If I install Litchi, return the iPad to offline mode and connect it to my Mavic Pro will it try to update my Mavic Pro firmware?   Is the litchi app compatible with all versions of DJI firmware?

An updated or new Litchi installation will not work with outdated firmware.  The drone will not connect until there is internet communication.   Once connected it seems it will not request updates or nag.


Are real-time OSDs for HD FPV video systems available for drones? In the last several years, several high-definition FPV video systems have become available. These systems do not use the NTSC or PAL analog video historically used with FPV systems and they are not compatible with the OSD systems, including some that are extremely sophisticated, customizable, and open-source, and are meant for use with analog standard-def video.

Are sophisticated, customizable OSD systems able to receive data from off-the-shelf flight controllers and to overlay data and graphics such as artificial horizons, altimeters, compasses, home pointers, etc on an HD video feed commercially available for hobbyists (outside of pre-built drone systems)?

One of the most popular HD FPV systems out as of writing is from DJI. The DJI Air unit, which serves as the VTX on the multirotor, has integration with Betaflight over a UART port on the flight controller which it uses to implement the Betaflight OSD.

I don't have one, so I can't confirm, but I believe most of the OSD elements available for the analog OSD are also available in the DJI system. (cit. UAVFutures) Joshua Bardwell on YouTube has a video listing out which OSD elements the DJI OSD supports.

Angle: Pitch/Roll
Battery average cell voltage
Battery current draw
Battery current mAh drawn
Battery voltage
Disarmed
ESC temperature
Fly mode
GPS latitude/longitude
GPS stats
PID pitch/roll/yaw
Power
Profile: PID and rate
RSSI value
RTC date and time

More element support may have been added since Bardwell's video was released in December 2019. Configuration of the layout of elements on the screen is supported through the OSD tab in the Betaflight configurator.


Video breakup problems with high power using The Force VTX? I normally fly with my VTX on 200mw but sometimes I need it to be more powerful. Whenever I turn it to a higher power setting, though, the video becomes worse. When I set it to 600mw, the video seems to lose some color and turn black and white at times. Also, very faint lines (white lines, not black lines) appear in the video feed. Does anyone know what the problem could be?

This is happening on BNF 4s Nazgul5. The VTX is The Force VT5804 V2.

This can be caused by too much heat building up in the VTX causing the electronics to suffer. Try mounting the VTX to have more airflow around it or put a heat sink on it. Sometimes a VTX just can't handle its own output power.

Another issue might be that electronic noise from the VTX is getting fed back into the video signal at the camera or FC connection point. Adding capacitors to various voltage rails sometimes can help.

Still another issue could be that the VTX is drawing too much power from the regulator that is supplying it. Try connecting the VTX directly to Vbat if it can take the higher voltage.

In general, noise in the video signal is the bane of FPV video problems. It can be a bit of black magic to fix.


One motor on quadcopter broken I have a small quadcopter and I realised one of the motors does not turn electronically, meaning it can't fly properly. There is no visible sign of something stuck in the motor, like some string or something. What can I do to diagnose/fix the issue?

So this method will vary based on whether they are brushed or brushless motors.

For brushed:

Spin the propeller with your fingers - is anything actively resisting the motion?

If yes, remove the prop and check for something not immediately visible, like a hair or carpet fibres caught around the motor shaft.

Remove anything you find and try the prop again.

If nothing is resisting motion, check the connections between the FC and the motor.

If all else fails, swap the motor with the one diagonal from it. If the problem travels, the motor is at fault. If not, there is trouble with the board.

It is worth noting that brushed motors are a consumable - the brushes wear out, and most aren’t rated for more than a number of hours’ use - see the diagram below:

(Image Source)

If the motor is brushless, start by again turning the motor, and check no screws are touching the windings.

Check all motor connections and see if there are any breaks.

If there is not active resistance, swap over two of the motors. If the problem follows the motor, it is likely a problem with the motor. If not, there is a problem with one of the ESCs.

If you do encounter active resistance, look inside the bell and see if any of the magnets have slipped. If they have, use epoxy and tweezers (though a toothpick also works well) to glue the magnet back in place. I’d recommend also buying a new motor as it is now likely to be slightly unbalanced which may cause oscillations.

See diagram of brushless motor:

(Image Source)


Working on a Quadcopter. Unsure if this flight controller supports an FS-IA6 receiver I am really new to drone building and I have had some awful luck trying to figure out what is compatible with what. Here is the link to the AIO flight controller I chose to use for my build. It won't be a tiny build but I will still use this flight controller --> The Flight Controller
I am also using this Fly Sky Remote and Receiver --> The Remote and Receiver
My main concern is using the FS-IA6 receiver with the SPI RX setup on the flight controller. Does anyone have advice on such a configuration? Any advice is greatly appreciated.

So, I don't believe the components you have are entirely compatible with one another. The FS-iA6 RX only has PWM/PPM outputs, while the BetaFPV F4 AIO 1-2S FC requires some kind of serial RX. The "SPI RX" module mentioned in the spec sheet appears to just be a small FrSky RC module that BetaFPV sells and not something that would allow you to connect to your RX.
I think your cheapest mode of recovery is to get a <$15 USD FS-RX2A receiver, like this listing on Amazon. This model is featured on your FC's Amazon listing, including a wiring diagram:

It has a serial port output (Flysky iBus), which should be entirely compatible with the FC and Betaflight.


Holy Stone HS110D Drone PCB Wiring - What does the circled wire in the picture do? Total drone noob here so please bear with me. I bought my first cheap drone and I crashed it while flying indoor and one of the rotors stopped working so I took it apart to replace the rotor. But then I saw this black wire (please refer to the red circle in the attached picture) sticking out and one end of this wire not soldered to anything on the PCB.

So my conclusion was either one end of soldering came off while I was taking the PCB apart or it wasn't connected to anything to begin with! So I would like to know the purpose of this wire and which one of my conclusion is right?

And if it was soldered to something please guide me where to solder it back. Thanks for your time in advance. I would really appreciate the help!

That is almost certainly the antenna and one end is supposed to be free. This is increasingly likely as the square black chip next to it (labelled PAN159CY) is the wireless transciever (radio) - and I can't see another antenna candidate or connector.


Is it safe to fly LiPo batteries after they get "puffy"? Some of my LiPo batteries got "puffy" after a few months. Is it still safe to fly them, or should I safely dispose of them?

You should dispose of them.

A LiPo battery has three parts: the anode (negative plate), the cathode (positive plate), and electrolyte (sandwiched in between the two plates). Electricity is formed by electrons moving from the cathode to the anode through the electrolyte (which helps the electrons flow).

The electrolyte decomposes over time, which results in the formation of elemental lithium and oxygen. Some of it combines into lithium oxide and sticks to the anode and cathode, but some of the oxygen remains a gas. This gas is what causes the puffiness you see.

Oxygen likes to burn, so if you use a puffy battery, the likelihood that the moving electrons will ignite the oxygen is much higher, so once it becomes puffy, you should stop using it and dispose of it.


How do I set up LUA scripts on my OpenTX radio? I’m looking at how to use LUA scripts and was wondering how to configure them I am OpenTX radio.

Thanks.

More info: at present, I don’t want to write my own scripts, only run scripts that I can find online, such as VTX control.

Oscar Liang has a really good page for this specific use case https://oscarliang.com/vtx-control/

And Joshua Bardwell has some really good videos that you can follow along with
https://www.youtube.com/watch?v=zFb5IJpM1XU


Drones capable of smooth plane/bird-like flight Multirotors are small rotorcraft with flight dynamics which result in an unnatural "flight experience".
Are there multirotor autopilots which would be able to simulate a more "natural" flying experience? E.g. an experience of flying plane which has more weight and a gliding capability, or as a bird which alters wing beats with gliding phases? I.e. a multirotor capable of flying in smooth curves, moving in parabolic curves altitude-wise (and thus simulating smooth glides), as well as smooth left/right turns? This would probably require some more advanced logic simulating these smooth curves using "helicopter" movements. Are there such drones which are capable of this, using very simple controls for the user?

You might be able to write custom flight control software for a multi-copter that would simulate this. You might get close just by radically limiting the pitch and roll rates and being gentle on the throttle. In either case it wouldn't be intrinsic to the design.
If you want smooth, soaring flight, you'd be best to build a fixed wing model with a fairly large wing span and low weight, similar to a soaring bird. A basic electric motor-glider like a Bixler is quite a popular FPV platform because they fly fairly slowly and smoothly, and are easy to fly (which is important when you're trying to make sense of the view through goggles).


Drone wobble/bounce while flying I recently gave my newly built (with old equipment) its first flight. As you can see throughout the video there is a wobble as I fly.
https://youtu.be/foo7Tw1gYNY
I am running an SP Neo F3 FC with Cleanflight on a QAV-X Charpu frame.
Just wondering if any of you know what are some of the things I should look for that might cause this.
Edit: I re-calibrated the accelerometer which was a bit out, but still experienced the wobble.

Try lowering your $D$ coefficients by $10$ in each direction. If that doesn’t help, slowly try increasing your $I$ coefficients.
[Make sure you first implement (and TEST!) a kill switch any time you are modifying PID terms (particularly $I$ terms) as you can create an unrecoverable flyaway situation!]


How much air-intake space do I need in front of my DJI Spark's propellers? I've got a DJI Spark that I sometimes use for close-proximity flying such as inspecting the roof of a house.  The stock propeller guards protect against flying laterally into an obstacle, and the bottom proximity sensor and general vehicle geometry make it unlikely that I'll descend into something, but there's nothing protecting the top.

I'd like to build propeller guards to protect against ascending into tree branches or similar hazards.  How much air-intake area do I need to leave, and does the shape of the gap matter?  (For example, are mosquito netting on a frame and a rigid open grid equivalent if they've got the same cross-sectional area?)

Single-rotor model helicopters, flown indoors, will "suck" themselves onto the ceiling when the rotor is within about half a rotor diameter if you're not quick to reduce throttle.  The sucking won't happen until you're that close, though.

That gives you an upper bound for how far away an intake shield should be from a rotor without strongly affecting handling efficiency.  More generally, the farther the shield is from the rotor, the better.  Stiffer is also better because the shield is on the intake side and is thus being pulled toward the rotor.  A grid with thick beams is of course stiffer than a floppy fabric.  So if what you're guarding against is tree branches, not tiny debris, then use the most widely spaced mesh ("roll cage") that you can tolerate.

If you want to experiment with netting over such a grid, just feel how strongly it's being sucked against the grid.  The greater the sucking, the less efficient the rotors.  That may be the most practical way to convince yourself of a particular setup's performance.


How can I configure a servo in Betaflight? I’m looking to make a drone capable of deploying a parachute, so I need a servo release mechanism.

How can I configure a servo and map it to a switch in Betaflight?

Thanks.

There are multiple ways to enable servos in BetaFlight, but since you need only one servo it is recommended to use SERVO_TILT.

For servo to work you need a free pin on your board and this pin must have timer function.

Go to Configuration tab in Betaflight Configurator and enable SERVO_TILT and hit "Save and Reboot"

Then setup the switch you want to use on your transmitter and in Betaflight. Let's say it was AUX4. Make sure it shows in the Receiver tab and that the signal is received.
Then go to the CLI tab and type resource (resource list for older BF) and hit Enter.
What you're looking for is resources with MOTOR or PWM function. For example on my board there are 6 MOTOR outputs. I assume you fly 4-motors copter and you also have some spare MOTOR pads.
You need to remember the MCU pin and MOTOR number and of an output you want to use (C09 and MOTOR 5 for me).

Then you need to type:
resource MOTOR 5 NONE
resource SERVO 1 C09
save
Use your own MOTOR and MCU pin number instead of 5 and C09!
This will remap MOTOR5 pad to be able to work with PWM Servos.
Servos numbering in CLI starts from 1
After reboot you can go to the CLI tab and type resource again to make sure everything worked as expected.

Go to the Servos tab in Configurator and hit the checkbox with with your AUX channel on Servo 0 row (AUX4 for me).  If you can't see the servos tab check "Enable Expert Mode" on the top right.
Save.
Servo numbering on the Servos page starts from 0. So Servo 1 from CLI tab is Servo 0 here.

You can now power on transmitter and enable the live mode on the Servos tab.
Go to the Motors tab (remove props if you have LiPo connected!). There are servos output there.
If you switch the switch you set to AUX channel you should see Servo 1 output to change the value.

Now you've remapped MOTOR 5 pad to act as a servo output. You can connect your servo's signal wire to it and find any spare +5V and ground pads for it.
If the servo moves automatically as the quadcopter moves check that the CAMSTAB mode is disabled. The screenshot below shows it active, which you won't want if trying to manually control the servo.

If you don't have any spare MOTOR or PWM pad you can remap LED_STRIP 1 resource if you're not using it for LED.
Here's the guide how you can do this: https://youtu.be/jiD6aC0l1VQ

If you need more than 2 servos to control check Sources for how to use Channel Forwarding instead.

Sources:
1: https://github.com/betaflight/betaflight/wiki/Servos-&-SERVO_TILT-for-3.1
2: https://github.com/betaflight/betaflight/wiki/CHANNEL_FORWARDING-for-3.1
3: https://youtu.be/jiD6aC0l1VQ
4: https://youtu.be/cHi1fKP1LRI
5: https://oscarliang.com/betaflight-resource-remapping/


Why are micro pusher-prop quadcopters becoming more popular? Recently, I've seen a rise in popularity of small drones using pusher props. Some of these include the FullSpeed TinyPusher, BetaFPV Beta95X/Beta85X V2, Diatone Taycan and Tinawhoop, and originally the tinyhawk. Why are pusher prop designs for small BNF quads becoming more prominent? I haven't seen any 5-inch BNF quads with pusher props which leads me to wonder, are there advantages to having pusher props on a micro drone that wouldn't benefit larger drones as much?

I have a working theory for why this may be the case; some micro-quad designs support this theory more than others.
Due to Newton's third law, the thrust force created by the propellers also has the effect of trying to lift the propeller up off of the motor in traditional multirotor designs where the propeller is on top of the motor. Aside from ensuring that the propeller can't spin independently of the motor, this is the reason why drones have propeller nuts (or a similar mechanism) to securely hold the propeller to the motor.
Many micro-quad designs, including some of the ones you link to in the OP (e.g. the Diatone BNF TinaWhoop and the FullSpeed BNF Cinewhoop) instead feature the pusher-prop configuration you mention, with the propeller underneath the motor, and forego the inclusion of propeller nuts or bolts screwed through the propeller into the motor.

(FullSpeed BNF Cinewhoop cit.)
I don't have one of these quads to confirm my observations from looking at the images, but it appears like these designs have the propeller attached to the motor with a simpler mechanism that likely doesn't provide as much strength in the vertical direction. If my hypothesis is correct, this would mean that the propellers could theoretically fly off more easily if the motor wasn't in the way of the path the propeller wants to take during flight.


Help finding ESC for brushless motor I'm very very new to hobby electronics however I have studied a bit about basic electronics in school. I have four EMAX 0802 Brushless Motors and I want to drive them with an Arduino Nano. I know that I need an ESC, however the motors came with a specific connector. They are also very very tiny motors and I would like my ESCs to be fairly small too.
Here is a picture of the motor:
<img src="https://i.stack.imgur.com/DkiyE.jpg" alt="
" />
Does anyone have some advice on the best way to control this brushless motor? I assume that I am going to have to re-solder the connector since it is designed specifically for a prebuilt drone.

ESCs for these tiny motors are always built into a single board that also contains the flight controller (and often the receiver and video transmitter). I'm afraid you won't find them individually. The quadcopters that they're designed for just don't have room for separate components, and everything is so tiny that the plugs and wires would be a significant weight penalty.
That said, there's no reason that a larger ESC won't work. The smallest generally available is about 6amp, but you might find 10 or 12 amp units for the same price and size - small stuff is rare and doesn't get updated as often as the more common sizes.
FWIW, I think that's a 3 pin JST 1.25mm connector. Measure the pin spacing to check.


Flying a UAV with a banner? I want to attach a banner to a UAV like this:

I have two questions:

Firstly, is it even possible to fly a UAV like this with the banner visible?
What sort of design considerations would I have to take into account when attaching a banner to a UAV?

Briefly sketching forces that act on the banner, we can see that there needs to be two strings connecting to the aircraft at A.
There's also no force that directly counters the weight of the banner, but aircraft tend to solve this problem by simply increasing the length of the banner and having the power to overcome the added air resistance.

It should be possible so long as the aircraft has enough spare thrust and lift to counteract the drag and weight. Many model aircraft have good power-to-weight compared to their full size equivalent.

For the banner attachment, you need a secure point to attach it to the aircraft, well away from any propellers or control surfaces. Usually this is on the bottom rear of the fuselage.
It is a good idea to include a 'weak link', which will break if the banner snags; this leaves the banner behind, but saves the aircraft being pulled from the sky.
You will also need to weight the banner to hang in the correct orientation - making the vertical part of the banner support bottom heavy should suffice.

You can fly banners from both fixed-wing or rotary wing aircraft, in slightly different ways. Fixed wing banner extends behing the aircraft, whereas on a helicopter or multirotor the banner hangs below.

Image source


In drone racing with multirotors, how does one navigate the course? Whenever we watch drone racing, there is usually a course marked out in cones.

However, when there is an obstacle such as a Jacob’s Ladder, the racers know the order to go through each of the gaps. Similarly, we sometimes see racers fly through the same gate twice in a row.

How do they know to do this?

Is there a special way of marking out the course that is universal, is there a briefing prior to the race, or is there another method?

I've gone out and asked an actual racer about this one.

There are usually some visual cues. The course is laid out in cones, the flags are asymmetrical so you know on which side you should pass, the gates you must fly twice through usually have something (bright fabric, a flag, ...) next to them on the side that you fly around before going back into the gate, etc. and the cones themselves are not just a flat string but are laid out in certain patterns; for example, when the sequence of cones terminates in an arrow this usually indicates you should go upwards (or higher, i.e. in the case of two gates stacked on top of each other), while a perpendicular line marks the entry point of the cone string.

Sometimes the track elements are colored differently (and asymmetrically) to indicate the direction. Some elements just have canonical uses based on their shape: you should pass through gates, fly besides flags, dive the dive gates... The Jacob's ladder specifically is almost always passed top to bottom in sequence (while whether you should go right or left varies track to track).

That said, there is no universally accepted, set-in-stone standard for these cues. Which ones are used depends a lot on the materials available to the race organizers, how much time they have to set up the track, the track's layout, etc. For instance, flags can either be fabric on a springy pole (in which case you fly on the convex side), or they can be inflatable and curved to hang over the ground (in which case you fly under the overhang on the concave side).

Most drone racing leagues have their own standard of how different track elements and maneuvers should be marked on the racetrack and try to stick to it. Even then some smaller local or regional events of the league may be limited by the organizers not having all the required materials. Also, one cannot mark everything on the more complicated, technical tracks, or mark it in an unambiguous manner. Sometimes some parts of the track are formed by the terrain itself, i.e. an abandoned building or natural rock formation. In that case there's no standard and the track designers must get creative to even make it clear where the gates are!

So visual cues aren't everything. A lot of races rely on communicating to pilots how the track should be flown before the race. Sometimes it's a verbal briefing, sometimes a printed schematic. Sometimes the track is published well in advance so pilots could train on their home field or in a simulator. There could even be a video walkthrough or a DVR of a practice run. Additionally, many leagues actually perform a physical walk through of the track on or before race day (much like Formula 1 car racing), so that the marshals and pilots can discuss challenges, specific items and hazards, etc.

In the end, for serious racing, how the track itself is marked does not matter. During the actual race the speed at which everything is happening does not leave you any time to think or figure out what's coming next by parsing the track. The racer just knows in advance which gate or maneuver comes after the one he's flying through, and anticipates it, most likely along with the one after that as well. Knowing the track is a very important factor in winning a race, as in order to have the fastest (which usually means shortest) trajectory, the pilot must start the necessary maneuvers for passing the next gate while he has not yet passed the previous one.

Besides training beforehand and learning the track from the given materials, the racers are always allowed to fly some laps around the actual final track before the race in order to memorize its layout. This is critical as the actual racetrack will always slightly differ from whatever training track they might have constructed for themselves. During these training laps they also figure out the best way to tackle the elements of that particular track in the speediest way possible, and thus develop an optimal trajectory, or racing line, as it's usually called.

So, in the end, the on-track markings are there just to aid in the initial few laps as the track is being learned by the pilot, and after that, memory takes over.


How can I set up differential thrust for a model airplane? I have a Taranis Qx7 Radio and built an FT Mighty-Mini Scout which flew great, but now I want to put an extra motor and fly it using differential thrust. My understanding is that it needs to be set up on the Mixers Page on the radio, and also I'm not sure how to wire it up.

Some good info at Flite Test with video content as well. If you can create a "mix" in opentx (which takes some getting used to) you can apply the same methodology to setting this up.  There are lots of video tutorials etc.. for this.  Once you can do mixing on your Taranis, the content below may help.

In the example, they are using a Graupner radio (the same to dislike opentx??), but the idea should be the same.  What you are doing is attaching the thrust of the two motors to the rudder channel input so it will change each motor as you yank the rudder.

Flite Test demo of differential thrust


How to tell if you have a brushed or brushless motor? I understand there are 2 main types of motors: brushed and brushless motors. How can you tell visibly what type of motor you have without researching/reading the manual?

As a general rule-of-thumb, brushed motors usually have two wires, while brushless motors generally have three.

Image source


Betaflight with Mamba F405 MK2 stack 40A ESC's and XING-E 2207 motors problem I build a quad using Mamba F405 MK2 stack 40A ESC's and XING-E 2207 motors.
Here are some pictures of my configurations on Betaflight and BLHeli Configurator:
https://imgur.com/a/mFLDiVp
Also video of issue in Reddit:
https://www.reddit.com/r/Multicopter/comments/inphxg/why_is_this_happening_with_my_motors/
I used to have two issues:
I set Bidirection Dshot with 4khz PID loop freq and because using F4 FC I had to change to Dshot300. Then when trying to set little bit the Throttle after arming the quad the motors suddently spin super mega fast (very dangerous).
When I arm the quad the motors start spinning even that I have set not to spin when armed.
What I did for the first issue is to remove bidirectional dshot. Seems that because the ESC only support Dshot 600 when I set Dshot 300 it start behaving pretty bad.
Any clue if using F4 flight controller I can use Dshot600 with bidirectional dshot?
Also any clue on how to solve the start spinning motors thing?
Thanks

If you have airmode enabled as a feature then the motors will spin on arm no matter what other settings you have.
It sounds to me like you may have accidentally set your ESC's to bi-directional in BL-heli configurator which is NOT the same as bi-directional DSHOT protocol.  Check out this video for explanation on the difference : https://www.youtube.com/watch?v=DXfAnCLr3q0&t=65s


Betaflight - Angle mode - motors spins once I arm the quad I have my quad using Mamba F405 MK2. When I arm my quad the motors start spinning.

I also set the pid_at_min_throttle = OFF but same behavior. Don't really know why is having this behavior. Any clue?

Airmode is a great feature if you race or fly freestyle. As you found out it spins up the motors at 0% throttle. You usually want this to be enabled since lowering the throttle to 0% would stop the motors and this results in a fast death roll of the quad.
But Airmode also helps during fast rolls when certain motors cannot spin faster or slower to get more consistent behaviour independent of the throttle position.
The default setting has airmode always actived. But you can disable the permanent airmode and enable it with a switch in the modes tab. I usually do my setup this way: One AUX channel controlls both angle mode and airmode in a way that DOWN  enables angle mode and UP enables airmode.
I take off and land in angle mode without active airmode. That way the props can stop and do not spin after arming the quad. At the same time this setup ensures that airmode is always active in acro mode.


Can I mount my RX and VTX antennae next to one another? I've heard that it is bad practice to mount a 2.4 GHz RC receiver antenna next to a 5.8 GHz FPV VTX antenna because the transmitting antenna will negatively impact the receiving antenna's reception. For example, this is said to be true in this Rotor Riot video at 1:40.

Is this true? If so, how close is too close and how can I mount the two antennae to minimize the interference between the antennae?

The distance is dependent on the wavelength of the lowest frequency. You can calculate the wavelength $\lambda$ (m) from $\lambda = c \div f$, where $c$ is the speed of light in a vacuum (ms-1) and $f$ is the frequency (Hz.) Taking the centre frequencies of the ISM bands we get:
2.4 GHz: $$\frac{299 792 458 }{ 2 450 000 000 } ≈ 0.12 = 12 cm$$
5.8 GHz: $$\frac{299 792 458 }{ 5 800 000 000 } ≈ 0.05 = 5 cm$$
(Quick 'sanity check' tip: 5.8 GHz is about twice 2.4 GHz, so we expect the wavelength to be about half; looks good.)
The smallest separation is usually recommended as a quarter of the longest wavelength, which for 2.4 GHz is only 3cm - quite manageable. That said, greater separation helps so put them as far apart as your frame practically allows.


When flying FPV with a 5.8ghz video transmitter, is an Amateur Radio License (Ham license) required? What are the legal requirements I need to know when operating a 5.8ghz video transmitter like the ones often used for flying FPV?

Are the rules different around the world?  Is a technicians class amateur radio license sufficient?  What about the requirement to transmit your call sign every 10 minutes?  Is that necessary in this use case and if so, how do you comply?

No, you do not require an Amateur licence to use this equipment.

Most RC equipment that operates at 5.8GHz (or 2.4GHz) makes use of what is known as an ISM band, a series of frequencies made available for anyone to use (historically for Industrial, Scientific and Medical purposes) subject to certain restrictions - such as transmitter power.

These restrictions have been set so that everyone gets fair use (rather than becoming an RF shouting match) and to minimise the harm caused if misused.

So long as the equipment complies with your local regulations for ISM equipment you are able to use it. The difficulty can be verifying this compliance without test equipment; reputable products will usually be correctly tested and constructed, whereas some inexpensive/unbranded clones might have cut corners to save money which means they are no longer legal. It's generally safe to assume it complies if it is supposed to, but different countries may be more strict on enforcing this.

However, having an Amateur licence may allow you to do more. If your jurisdiction allows using Ham gear on drones then - so long as you comply with all requirements (usually things like regular ID, no secret encryption and not commercial use) - you would be free to use the power limits and frequencies granted in your licence.


What is the best drone for beginner fliers? My brothers would like to start drone flying, as they haven't ever flown my Syma before. I am looking for a small, inexpensive pocket or medium drone for beginners that will probably get thrown into our magnolia tree.

There's no single 'best' starter drone, as new ones are released every few months. However there are lots of good options under \$30, and some as cheap as $15.
What you're looking for is something small and light, so you can fly it indoors without breaking things. It should have rings around the props to protect them and anything it hits.
Syma, Eachine and Hubsan are popular brands but there are others.
Do get more than one battery. They typically only last about 5 minutes and take an hour to charge. A charger that can charge more than one battery at a time is a bonus too. That said, 10-20 minutes is enough for most people - at least after the first time.
'Headless mode' is quite a useful feature for beginners, it allows you to ignore yaw. Forwards is always 'away from you', whatever direction the drone is facing. It's not essential though, and can be confusing or lead to bad habits.
'Altitude hold' should be useful but I've found these drones always need an experienced pilot to trim them first. It's good for an experienced pilot to teaching kids under 10, but not for teaching yourself.
Many cheap quads have tiny 'jelly bean' transmitters, which can be difficult for those with big hands. If you think this might be a problem, you can spend a bit more for a proper sized controller. There are various hacks for extending the sticks too.
Don't buy one with a simple recording camera. Until you pay enough for one that can transmit the signal to you in real time, the footage will be rubbish because you can't point the camera and frame the shot. The first time you do it, it's cool to see a blurry, poorly coloured picture from the air but the novelty quickly wears off. View your first drone as a trainer and indoor toy that will take the knocks of learning while you save up for something better.
Don't bother buying loads of spares, these little things don't break very often, and it's as likely to be a motor burning out as a broken prop, and a pack of spare motors can cost more than the drone.
That said, they are very prone to picking up stray hairs and winding them around the props and motors. Try not to spend all your time bumping around on the floor, and check for hairs after each crash.
When you're learning, try to pop up into a hover a foot or so off the ground and concentrate on holding the right height. When it has drifted half-way to an obstruction, cut the power and land. Don't try to fight it because you'll just crash harder. Put it back in the middle of the room, review what you should have done and try again. When you can control the height, try correcting the drift but still land and review when it gets half-way to an obstruction. If you struggle, find a larger space to practice for a while.


Why are most multirotors built with an even number of rotors? The most common types of multirotor are quadcopters, hexacopters and octocopters (with four, six and eight rotors respectively).

Are there scientific reasons why most drones built with an even number of rotors?

Yaw authority and ease of mixing is generally the answer - since yaw response isn't necessarily the most linear, being able to have N number of motors contribute to yaw in one direction with the same number in reverse is the simplest motor output mixer configuration.
Tricopters do work and are relatively common among odd-numbered multicopters, but once you've exceeded four rotors, there aren't many meaningful performance improvements possible for the added complexity of requiring an odd number of motor outputs and doing a custom mix for that.
There are some slightly exceptional cases such as a forward puller motor mounted perpendicular to an otherwise conventional even-motor copter frame (see FliteTest MilleniumFalcon), but these aren't really a convention odd-numbered motor copter configuration.


Freshly built quadcopter/drone flips on takeoff I just finished building my first quadcopter/drone and it flips when I try to take off.

What could be wrong?

What troubleshooting steps should I take to fix it?

There are several things that can be causing this with different likelihoods.

The first thing to check is - are your propellers on correctly? It is an easy mistake to make and always worth a check.

The next thing to check is that all of your motors are working correctly. Start by spinning each of the motors by hand and see if anything fella obviously wrong, for example, a magnet out of place. If nothing feels wrong, remove the props and individually spin up the motors in Betaflight to test them.

The next port of call is your gyro. Plug your quad into Betaflight or whatever firmware you use and move it around - does the virtual representation of the quad match up with your movements in real life? If not, that is almost certainly the cause.

Now make sure the motors spin in the correct direction and the correct position to match the graphic on your configurator by using the motors tab with the propellers off

If all of these have failed, swap two of your motors and see if the quad flips in the same direction. If the problem follows the motor, you have a faulty motor. If the problem stays in the same place, you likely have a faulty ESC.

If your ESC is not faulty and your motors are also fine, it is also possible that your resource mapping is incorrect. In the Betaflight CLI, type ‘resource’ and ensure that the correct pin from the microcontroller is assigned to the correct motor.

You should also check that your motor direction is correct in Betaflight, and your motors are spinning in the expected directions in real life. If not, that can be fixed either in BLHeli or by swapping round any 2 wires from the motor to ESC.


Series or parallel connection for drone batteries? What is the difference between adding two drone batteries in series vs a parallel connection for flying the drone?

Batteries in series = add the voltages, ie two 3S 1300 30C packs becomes 6s 1300 30C.

Batteries in parallel = add the capacities, as above you get 3S 2600 60C.

There's no particular pros or cons for either, many larger commercial drones use combinations of packs in series and parallel to get the power source they need.

For smaller quads though the overhead you get in extra weight from the leads, connectors and wiring is greater so it's generally less practical.


Can a 45C 11.1V 4500mah battery damage a 30A esc if a motor draws less amps? I am really new to this, I am planning to build my own tricopter drone which can be controlled via raspberry pi using wifi and use Arduino as a flight controller to communicate via USB. I am hesitating on which battery to pick as I am planning to keep drone for longer time (more hours for recording) at least 4 hours. So I am thinking to use a 45C 11.1V 4500mAh battery with 30A esc and a C2204 1200kv motors which draws 11A, the battery will feed power for all 3x30A esc and 3xMotors question is will it damage the esc? if it will damage the esc which esc do I need? and will the battery power motors, raspberry pi and arduino all together?

A larger battery can supply more current, but will only supply as much as the motor and ESC pull from it. Once the battery is large enough to provide the power the motor needs, making it larger won't increase the power - much like increasing the size the fuel tank in a car won't change the engine power.
If your motors will only draw 11amps, you don't really need 30amp ESCs. 20amp ESCs would be fine, unless there's a chance that you might want to switch to 4s (14.8v) batteries and push the motors harder in the future.

will the battery power motors, raspberry pi and Arduino all together?

I think the pi and Arduino require 5v, and they would probably like to be isolated from the electrical noise of the motors and ESCs. The usual solution for this is a PDB (Power Distribution Board) with a 5v output. This is a simple circuit board that splits the battery power to multiple solder pads to simplify connecting up the motors. They often also contain filtered 5v and 12v outputs. They're only about $5 so most people use them.
The alternative is to use fixed-wing ESCs, which usually have a 5v supply built in. This is called a BEC (Battery Eliminator Circuit, from the days when people carried a separate 5v radio battery) and supplies 5v on the red wire of the receiver plug. I wouldn't recommend this though, as multicopter ESCs will generally have a faster and smoother response, and support a range of high-speed protocols such as DSHOT. Also it's generally considered a bad idea to connect more than one 5v supply, so you'd be paying for and carrying 2 unused BECs.
I should add that a 4500mAh battery is a lot for three 2204 motors to lift. Half that size would be considered a large battery. I would suggest starting with batteries that are half or even a third of that size. That way you can have a light machine for testing and then parallel two (or three) batteries together to see how it flies with the extra weight. Two smaller batteries will probably cost about the same as one larger battery.


Should VTX ever be lower freq./higher power than the control transmitter? I can find video transmitters from 5.8GHz down to 433MHz with the latter being ideal for longer range, but I don't see nearly as much diversity as far as control transmitters. Am i correct in saying that a lower frequency transmitter will almost always go much further than that of a higher frequency, with transmit power being secondary in affecting range? The extension of this would be that the control link would be lost far before the video if the video is TX'd on 433MHz and control on 2.4GHz. I assume that this would be dangerous since, for example, if video is gradually lost, you have a chance to return the craft to a location if better signal, but you don't have obvious warning signs for control being lost.
Edit - I know that there are 72MHz control transmitters, but i don't know of any way to use them on a quadcopter.

There's a few factors that you're missing. The first is that the RC world is dominated by traditional line-of-sight control, and 2.4GHz provides more than enough range to fly a model plane to the limits of vision. There aren't many long range system because few people need them. Even for FPV, long distance flying means a long walk or losing your model when you crash.
The other is that control is very low band-width compared to video. A typical 2.4GHz protocol includes error detection and can reject a lot of packets and you won't notice so long as one or two get through every second - maybe even less when you're at extreme range and not manoeuvring hard. A video signal needs most of the data to get through to be flyable. Analog video has no error handling or rejection, and while digital systems do, there isn't enough spare bandwidth to ignore any data. Even a corrupt picture is better than black screen!
Good RC systems these days do include RSSI (Received Signal Strength Indication) in their telemetry, so you know when you're reaching the limits of your range - and models with GPS can be set to return-to-home automatically if they loose the RC connection.
Finally, it's entirely possible to use 72MHz on a quad, with a FC that takes individual inputs for each channel - however the range is no greater than on 2.4GHz, and there was rarely any interference rejection on the old analog radios, we used to use the glitches as an indication that we were flying too far away!


How hot should an ESC get? What is the maximum safe temperature that a brushless drone ESC should get? What could happen if a brushless ESC were to go over its maximum temperature tolerance?

Like you said in your answer, it does depend on the ESC... so you definitely want to look into the specifications for your particular components.  However, to be safe, a good rule of thumb suggested on this forum is that you want to be able to put your finger on it without discomfort for five seconds.  If your reflex is to withdraw after only 2 seconds, chances are you're running a significant risk of overheating it.

As to what happens if you exceed the temperature... it's not pretty.  Insulation on electric components starts to melt, resulting in shorts...  Overheating will typically result in a pretty instantaneous failure.

It's always a good idea to keep your ESC exposed to a constant airflow.  If you put it inside a closed compartment, ensure that you have some way that airflow is being sent through that compartment.


In what direction should I orient the dipole antenna on my 2.4 GHz RC transmitter? My RC transmitter has a movable antenna that allows me to change its orientation, like this one:

In what direction should I point my 2.4 GHz RC transmitter antenna for best range and signal penetration?

The antenna should be aligned to match the orientation of the antenna on your aircraft; generally this will be vertical, but for more acrobatic aircraft a compromise of 45° might be appropriate for greater reliability but lower performance. For more detail see this question.

Some manufacturers of off-the-shelf equipment will recommend an orientation in their user manuals - in this case, follow the instructions they give.


What is a good 3'' BNF that can be used indoors and outdoors? I am looking to get a new quadcopter that will work in a variety of places. I want it to be a 3'' drone so that I can fly it both outside and inside. I would prefer if it had prop guards or ducts of some sort, but that's not necessary. I want a drone with decent performance and a good analogue FPV system. I already have a good transmitter (Jumper T16 Pro) and good FPV goggles (Skyzone Sky02X) so I am looking for a BNF. I'm looking for a drone that won't break the bank, but will be good quality and will last a long time.

Depending on your budget I would look at these two options:
Diatone Taycan: this is a cinewhoop style quad that is more than powerful enough to fly outside as well. It will not be as nimble as your typical freestyle quad but if that is not what you are looking for you can't go wrong with this one.
HGLRC Sector 132: This option will be cheaper as the Taycan but seems to offer good value for the money. By default there are prop guards that allow you to fly indoors (not ducts) and if you remove them, you can start freestyling outdoors.
Just based on the type of build, the Taycan should be more sturdy and last longer than the Sector 132. That being said, this is a hobby where you can destroy any type of quad if you start pushing your limits and try out more challenging moves.
Regardless of your choice, it is a good idea to implement throttle scaling when you fly indoors. This can be done on your remote and tied to a switch.