Do laws on 'drones' in Australia apply to fixed wing model aircraft? I've been looking at the CASA RPA rules (specifically under 250g and under 2kg non-commercial) and there doesn't seem to be a section on fixed-wing aircraft. Do the rules for 'drones' (for instance these) apply to fixed-wing aircraft. I assume they do but I just want to be sure.
I'm trying to get into model aviation, so expect more of these small questions from me.

In case you would prefer an answer with citations (as different regulators have different views on this), at the following link is CASA web page regarding "Recreational unmanned aircraft (including models)". There is a link on this page to the  "... rules for flying model aircraft and drones." - this phrasing demonstrates CASA consider model aircraft and drones to be subject to the same regulations.
However, there are some differences in Australian regulation between commercial and personal/recreational use - follow the links above for the latest information.


When I power up my flight controller and ESC's, I hear a series of beeps. What do all of the beeps mean? How can you use the series of beeps you hear when powering up to diagnose issues with your equipment?  Should all of the beeps be synchronized or is it ok if they are slightly off?  Are there different patterns you might hear and if so, what do they all mean?

The normal blheli startup tones are similar to beep beep beep... boop. boop

The first 3 beeps are the ESC's powering on and initializing then there's a pause followed by two more beeps which means the throttle signal has been received.

https://youtu.be/_hkzm8ZXsxE?t=58


Free simulators to use when actual RC flying is not possible Due to the COVID-19 pandemic, I haven't been able to fly any RC aircraft for many weeks.

Given that the pandemic shows no signs of slowing down, I'm preparing for the continuation of this situation for quite some time.

To keep skills current, are there any good free RC simulators for airplanes, helicopters, or drones? I'm interested in web-apps, desktop software (for any OS), and even smartphone/tablet apps (for any OS too).

For quadrotors, there are simulators for racing drones, such as the DRL one Velocidrone.

For camera platform drones you have droneSimPro, Liftoff or DJI's own one. There are loads of them, and the physics engines are all improving in all. A fair few are free or very cheap or have a free version.

At the other end of the scale are programs like Phoenix R/C Pro - which has models for quads, helis and fixed-wing - and to be honest, if you plan to fly in any commercial aspect, at $200 it's worth paying the money for this one.


why do drone frames have spaces and holes This may sound like a very dumb question, but I am building my first quadcopter and I just realized that some frames have these perfectly symmetrical holes/spaces.
I used up all the screws on mine, so I don't think I have to actually use those spaces, but why are they there?
Is it to allow the user to make more modifications? Are some of the spaces/holes deliberately made to fit certain screws for modifications?
This is the drone frame that I am specifically referring to, but this applies to a lot of other frames (and even electronics in general) as well.

A major consideration is weight reduction; if material can be removed without significantly reducing the strength of the item, this will result in an increased payload or flight duration. This is particularly evident in the motor arms of the product you linked, as the triangular shapes are renowned for their relative strength.
Another advantage of this is that it allows additional equipment to be attached easily, with cable ties or similar; in some cases I expect the cut-outs will be designed with this in mind - for example; a selection of parallel cut-outs can allow for a wider range of battery sizes to be securely attached to a frame.


What does Feed Forward do and how does it work? PID tuning involves P, I and D gains to help the quad follow RC commands.

Whenever there is an error, P would "push" the quad to reduce the error. So how does Feed Forward come to play?

The way the PID controller works is whenever the actual rate of rotation of the quadcopter does not equal the setpoint, or desired rate of rotation (which you set by moving the sticks), it sends a signal to the motors to compensate and bring the rate closer to the setpoint.

This signal is a sum of four terms: The P, I, D and FF. Since it's a sum, you can think of them as each pushing the quad in a certain direction independently, some terms adding up and others counteracting each other.

The P term is the difference between the setpoint and actual rate, multiplied by the P gain. So the amount of force applied by the P term is directly proportional to that difference. You can think of it as a spring that tries to move the quad back whenever it's bumped out of position. The further it's moved (bigger difference between setpoint and actual rate) and the stiffer the spring (bigger P gain), the stronger it will pull.

The reason why the FF term is needed is because the signal that the PID controller outputs influences the acceleration, not the speed directly. This means that the quad will not get up to speed immediately, but take some time depending on how hard it pushes itself. So when you want to sharply begin a maneuver you want the quad to apply a lot of force in that direction to get going and then sustain the rotation with a smaller force.

The PID controller, however, is meant for stabilizing. It does not distinguish between you bumping the stick and the quad being bumped out of position by an obstacle or gust of wind. So when you move the stick it "stabilizes" itself at the new speed as if you didn't move the stick at all and it was bumped by something instead. You can think of moving the stick as moving the other end of the spring that the quad is attached to. The spring doesn't care which end was moved, just that its length changed.
This means that the PID controller won't apply as much force to start the rotation as it potentially could, which means it is somewhat slow to speed up when you move the stick, and, more importantly, slower to slow down when you move the stick back to center (and can even overshoot).

You can make the reaction faster by increasing the P gain, but to a point, as higher P gains lead to oscillations, when the quad's movements lead to big P terms which in turn cause bigger movements and so on.

So instead the FF term was added. The FF term does not consider the current rotation rate at all, so it does not contribute to the PID loop's stabilizing action and is thus unable to cause oscillations. The only thing that it looks at is the sticks. The force applied by the FF term is proportional to the rate at which you move your stick (multiplied by the FF gain).
So when you, for example, initiate a roll and bump the stick to the right, the FF term will detect the fast stick movement and give a burst of force to get the quad going. Then, when you finish the roll and return your stick back to center, the FF term will detect the opposite fast stick movement and apply a corresponding force, helping the PID controller stop the quad's rotation faster and avoid overshooting.


recommendations for a DIY/dev platform lifter drone I was mainly wondering if there was something in the drones world, similar to what the ender3 is to the 3d printing community -- that is, a cheap kit massively owned by makers and open source enthusiasts.
I'd like to get a list of components I can, afterwards, highly customize. I can make 3d prints.
For now, what I've found for the features I want, are :

a thingiverse post of the mavic air/pro cloned foldable frame.
However I don't know if it's as worth as the "open flat frames" used
in plenty of youtube videos for DIY racer drones... In the sense of
payload carrying ability and speed limits/agressive maneuvers.
pixhawk as the flight controller board and px4 firmware. I would need at least one extra pin (more is appreciated) for controlling a
servomotor for custom experiments. Is there any better solution?
found out that the more blades I get on a propeller the more silent it will be. However I didn't found any foldable propeller
with more than 2 blades... You guys did?
some sliding design for swapable battery, such as on the autel evo 2, that I can't afford because it costs 2k$ and I don't even
know if it's customizable... Any thingiverse post you guys saved**?**

But my BIGGEST wonderings are for the FPV feature :

All the tutorials I've found use some DJI digital "fpv unit" to cast what the drones sees into operator's goggles. But if I don't want to wear goggles, but instead, still cast onto the remote controller screen, is there any build logs/tutorial for that?
How to get the remote controller screen to be displayed on a smartphone? Is there such famous couple <RC remotes, android app> that not only work with DJI models or specific brands? Or some generic opensource project I could flash on micro controllers and buy appropriate antennas. For now I've found the 300\$ skydroid T12 or the 800$ herelink but they are too expensive for me on a budget.
I heard about betaflight for assigning maneuvers to keys of a custom controller (such as gamestation ones), but these devices aren't radio-enabled (long range + anonymous), nor able to redirect the videostream into a smartphone, isn't it ?
Is there android apps for fully controlling a drone through smartphone (virtual joysticks on screen) over wifi while getting its point-of-view livestream on the phone screen?

By thanking you

To answer your main question, I'm afraid there's nothing as widely used the Ender3.
It sounds like you want to build something with more lifting capacity and space than a race quad, with GPS.
There are two main styles of frame that might suit you.
One is based on the old 'DJI Flamewheel', which has plastic arms attached to hub of two flat plates. You can build these with as many arms as you want but the arms are only available in one size.
The other option is the many designs that use carbon fibre tubes. The tubes are very light and strong, and fairly cheap. Commercial designs use injection moulded or CNC aluminium fittings, but these would be perfect for 3d printing. Here's one I found but I'm sure there are others.
Unlike a 3d printer, the mechanical design of a drone really isn't all that important. You could use bits of broom handle and plywood, and it would still fly. That's lead to a wide range of designs and no clear market leader.
I'll have a go at the other questions:

sorry, I don't know much about the options here.

more blades is less efficient, which is probably why you can't find any multi-blade folding props. I'm not sure that more blades are quieter, unless you're comparing it to the same size 2-blade prop spinning faster.

most people use Velcro straps, which are lighter than sliding mechanisms, and work with a wide range of battery sizes. Batteries need replacing every few years, and you can't guarantee getting the same exact size.

the DJI video unit is the only real option for high quality digital video at the moment.

This is different to the video used in quads like the Mavic, that transmit via wifi to a phone.
Racers use much cheaper analogue gear based on old CCTV signals, but the picture quality is limited to old PAL/NTSC TV resolution. It's easy to send an analogue signal to a screen, and you can buy screens with built-in receivers. You can't always see screens in strong sunlight, which is why people use goggles.

Systems that transmit to a phone are generally proprietary and only available as part of a complete drone. They also have a noticeable lag, due to the video compression/decompression required, and other processing on the phone. That's why they're preferred for taking video, but not for high-speed flying. At the moment you can't have both (although the DJI air unit is close).

betaflight is the firmware run on race drones. It's not aimed at autonomous flight like the Pixhawk.

No, because there's no common wifi module for drones.


Finding the velocity and position for small distance from IMU sensors I am working on finding Velocity and Displacement from an IMU sensor (MPU9250). I have a Navio2 RPi4 setup, which gives me raw data (acceleration, Gyro, Magnetic).
As per my research this can be done in following method;

Finding the Attitude from the raw data. (Using quaternion method or Transformation Matrix)

Once the attitude data is available, calculate the gravity force acting on the acceleration data and eliminate the gravity from Acceleration to find the Linear Acceleration

Integrate the computed Linear Acceleration to find the velocity and Position.

Following the steps above I was able to compute the Attitude from the IMU sensor by following the  example provided by Navio2. The example uses Quaternion method (Mahony filter) to fuse the raw data and give the quaternions.
The output is verified and works perfectly. Now I have to move to step 2 i.e, finding the gravity acting on the acceleration.
Using quaternions to find the gravity :
gx = (2 * (q1 * q3 - q0 * q2));
gy = (2 * (q0 * q1 + q2 * q3));
gz = ((q0 * q0) - (q1 * q1) - (q2 * q2) + (q3 * q3));

This gravity values are subtracted from the acceleration data to find the linear acceleration. Once the linear acceleration is available, integrating it with the time gives the velocity and position. The implementation is experimented by moving the IMU sensor to 100cm. However the position output is not as expected. The units of the raw data have been taken care just to have a sanity check with the implementation.
I have moved to convert the quaternions back to rotation matrix and compute the velocity and position data.
My question is how to find the gravity acting on the acceleration using the Rotation Matrix converted from Quaternion.
I request the community to help me with their valuable inputs and references.
Thanks.

This is the best damned reference on rotations: Representing Attitude: Euler Angles, Unit Quaternions, and Rotation by James Diebel of Stanford University (dated  2006-10-20).
You didn't specify, but you're almost certainly using the Tait-Bryan convention-- which is first yaw, then pitch, then roll-- for rotation axes. You're also possibly using NED for translation axes, but that's less clear.
You can see all the mappings in Sec. 5.6.1 in the above link. You might check that you have correctly mapped your quaternions to the rotation matrix. It's very easy to mess up a sign value. Pay special attention to the fact that the inverse of a rotation matrix is its transpose, so it's very easy to have the right rotation matrix values but in the transposed order.
To get to your specific question, using eqn. 35, you can see how to map an inertial frame acceleration into the body frame, using the rotation matrix. It's a simple matrix multiplication, and in your case, and assuming NED, the vector z is [0;0;9.805].
Lastly, I would suggest getting this to work in simulation first, before trying empirical. Rotations are tricky because they're so pedantic, and it's easy to approach them backwards.


LiPo 4S battery's output voltage higher than 14.8v I have a LiPo 4S battery which the output should be 14.8v but it outputs, fully charged, 15.6v. The issue is that I have a voltage limit of 15v on a non-drone device that gathers data from sensors. So, my first thought would be to discharge it a bit until it drops below 15v. Does that make sense?
Also, I would like to know if that "over voltage" can be avoided?

As others pointed out, 16.8 volt is what that battery should be reading (unless there is a specific chemical composition that makes that different).
Discharging a battery to use with your application is an anti-pattern, please avoid.  Put a voltage regulator in there with the correct amp rating (draw) and you will be all set.
Pololu has some 1-2a 12v step-downs that cost $3-10. You can also go adjustable, here is a 9-30v 1 amp step up/down.
I know a few good ones on Amazon. Bottom line, this is a common part, easy to use, and I have had high reliability for nearly identical situations.


Can a lipo battery be charged with more than 0.5 amps? Using ISDT q8 to charge my 1205mAh 6S lipo battery. I'm wondering if I can change the default settings and charge with more amps?
Is this recommended or will it degrade the battery much quicker. Any information would be much appreciated.

You definitely can charge your 1205 mAh 6S LiPo at a current higher than 0.5A. For most of the LiPos we use on drones, the recommended charge rate is 1C, which for your battery, would be about 1.2Amps. (A 1C charge rate is 1 Amp for every 1000mAh)
A 1C charge rate is a good middle ground, but you can use a lower charge rate (~0.5C) for safer but slower charging, or a higher charge rate (~2C) for faster charging at the expense of the battery's longevity (and more risk of fire).
And as @ifconfig mentioned, this similar question should also help answer your question.


Quadcopter getting hot after a flight I have a small quadcopter and after around a 10 minute flight, I can feel it gets very hot. Is this normal?

"Hot quadcopter" is a bit broad of a term, a lot of things can be hot in there.

Maybe it's the VTX, then it's normal, they can get hot up to 80C. You might want to use a heatsink though, depends on your VTX.
It might be the Flight Controller's CPU itself. For example, F7 processors can get hot up to 70C
It also might be motors. If you can barely touch them then:

You might have a bad tuning on your quad:

High D gain
Not enough filtering

Conductivity problem, you might have too long motor screws and they are touching the windings.

Sources and additional info on hot motors:
https://oscarliang.com/check-motor-screws-touching-winding/
https://oscarliang.com/mini-quad-motors-overheat/
https://youtu.be/eo2sjTNS0pc


How to get a licence to fly a drone in the city of Prague for a week? I would like to take my drone and go fly in the city of Prague - it's super beautiful there during lockdown. (I'm close by anyway so don't worry, I'm staying safe) But -
According to Czech law it's illegal to fly a drone within city borders. You need to get an extra licence/allowance for that. My own shortcoming is, I cannot speak Czech.
Does anyone of you have any prior experience in getting this licence? I read that you can apply for such a licence, but I neither know where nor how. On the other side, I read that people already got into trouble, especially when flying in Prague (residency of the president, etc. etc.)
I do have a registration and the required European licence to fly a drone. I'm really looking for specific allowance for Prague.
(I already asked in travel and they were kind enough to forward me here)

(Caveat - I don't understand Czech either!)
There does indeed appear to be a restriction on flying around Prague - this is mentioned in English on the Czech CAA website.
There also appears to be a country wide airspace restriction/notice relating to Unmanned Aircraft - see this PDF Document for a 'working translation' in English. There are details on flying within a number of airspace types, but it looks like Section I.2(e) is relevant for the Prague restriction:

Prohibited  areas  (LKP),  restricted  areas  (LKR),  dangerous
areas  (LKD),  and temporary  segregated  areas  (TSA)  and  temporary
reserved  areas  (TRA)  activated  by another user
The  UA  operation
shall  not  be  conducted  in  LKP,  LKR,  LKD,  and  in  other  TSA
and  TRA activated  by  another  user,  or  in  restricted  areas
published  in  AIP  SUP  or  NOTAM,  except when it is permitted by an
appropriate operational authorization issued by the CAA.
The  UA operation  UA  in  the  LKR9  restricted  area  may  be  conducted
without  the  CAA approval, provided that conditions of operation in
CTR, in a congested area, or the conditions of other local areas are
observed. The UA operation in LKR9 restricted area is also possible
based on the operational authorization issued by the CAA.

Based on this (while accepting that the translation might not be finalised/accurate), you should just need an Operational Authorisation from the Czech CAA.
I believe this page contains documentation relating to Operational Authorisations - but is all in Czech!
It looks likely you will need some understanding of the language to be sure you are compliant. Your best chance for official guidance on this would be to contact one of the people listed at the bottom of the page from my first link; but again there is no guarantee you have a common language.


Does the sharpness of a propeller blade affect efficiency? Some of the propellers I have used on drones have sharp edges (sharp enough that they have cut me) and others have comparatively dull edges. Does the sharpness of the leading edge of a propeller impact the efficiency of a quadcopter at all? Would it be better to use propellers with sharp or dull leading edges for race drones?

Rounded leading edges are better for subsonic aerofoils.

Props and wings have to work at a range of angles of attack. The airflow has to split to pass either side of the aerofoil, and a rounded leading edge allows the separation point to move smoothly. Sharp leading edges cause a lot of drag at extreme angles of attack when air has to flow across the sharp edge.

That said, the sharp edge on some props is just mould flash and can be sanded off with fine sand paper.

Sharp trailing edges are OK aerodynamically but easily damaged, and dings in thin plastic can cause drag, so there's a practical limit to the sharpness of a trailing edge.


Betaflight attitude update rate only 100hz? In the tasks.c file, this line in particular
[TASK_ATTITUDE] = DEFINE_TASK("ATTITUDE", NULL, NULL, imuUpdateAttitude, TASK_PERIOD_HZ(100), TASK_PRIORITY_MEDIUM)

If I understood this correctly, attitude is updated at 100hz only by default. Why then do we need gyros which update at 8kHz rates?

I haven't quite dug into the source code to confirm my suspicions, but this file lends credence to the idea that this task facilitates accelerometer-based attitude calculations and not gyroscope-based calculations.
From line 274 to line 280 in the file you link to (tasks.c), the TASK_ATTITUDE task is said to be enabled if the accelerometer device is enabled (in the Betaflight Configurator):
#if defined(USE_ACC)
    if (sensors(SENSOR_ACC) && acc.sampleRateHz) {
        setTaskEnabled(TASK_ACCEL, true);
        rescheduleTask(TASK_ACCEL, TASK_PERIOD_HZ(acc.sampleRateHz));
        setTaskEnabled(TASK_ATTITUDE, true);
    }
#endif

Given that these are the only times that the TASK_ATTITUDE task is mentioned in this file, I doubt that this 100 Hz task is related to gyroscopic sampling.


what HD cameras should be used and for what purpose? I was looking for a camera the other day and I came across a few options. GoPro Session 5, Caddx Orca, Gopro Hero 8 Black, Insta360 One R, and the GoPro Hero 7 silver. I realize that these are all good cameras and I was wondering how to choose the right one. Are there certain ones better for certain scenarios? Should I choose based on durability? Should I choose the cheapest option? What are the best ways to choose an HD camera for a quadcopter?

I don't know about all the cameras, but here is my opinion.

If you want the best video quality you can get today and not be too heavy for a 5" FPV drone, then you want the GoPro Hero 8.  That will obviously change quickly if something better comes along.  The Hero 8 also has great stability with Hypersmooth or you can opt to use ReelSteady Go with it.  Downsides are the size, weight, form factor, and cost.

The benefit of the GoPro Hero 7 is that it is slightly lighter than the 8, has a removable lens, accepts ND filters better, and Hypersmooth is still quite good.  However, it does not work as well with ReelSteady Go.

The GoPro Session 5 was the go-to camera for FPV drones for years and lots of people still use it because of its size, weight, and form factor.  However, GoPro does not make them anymore so they are not as easy to get.

If you want stabilized HD footage for a drone that can't carry a GoPro, then consider using the Insta360 Go.  They are tiny, lightweight, and can thus be used on very small drones.

If you are not looking for the best quality, and the cost is more important, then consider some of the cheaper options like the Caddx camera.

I'd say the best way to choose a camera all depends on what your needs are, what you want out of it etc.  If you just want decent videos for Instagram, you will have a different answer than someone shooting cinematic footage for commercial use.

And one final bit, be sure to get some sort of protection plan on the camera because you will most likely kill it at some point.  If you can buy the camera from Best Buy, they offer a great Geek Squad protection plan.  Another option for the GoPro cameras is the GoPro plan.


Is it possible to control an RC plane using reaction wheels? I recently had an idea involving reaction wheels and a model airplane. Would it be possible to control an RC plane using reaction wheels rather that servos and control surfaces? Would a reaction wheel controlled plane be able to function similarly to a "normal" model airplane and would this be practical at all?

Yes, it would!

A YouTuber, Thomas Stanton, has actually built a helicopter controlled with reaction wheels in this video!

However, for a fixed wing aircraft, you would also have to consider the location of the reaction wheels relative to the centre of mass, and you would most likely want to house the reaction wheels internally to avoid adding extra drag.

You would also have to have a reaction wheel for each axis.

However, this should be relatively simple, so the answer to your question is yes, it is possible.

In answer to your other question of practicality, as far as I am aware there have not been enough studies in the RC sector to say for certain, but my personal opinion is no, it would not be practical due to the added mass and the problem of weight distribution, plus the limited space inside an RC aircraft and the advantageous torque traditional control surfaces give.


Is it better to have a bottom heavy quadcopter or a top heavy quadcopter when it comes to a quadcopter stability? Does it matter where the battery is mounted? Or is it best to have the centre of gravity aligned with the propeller plane where the thrust is generated?

It depends on what kind of stability you're after. Nicolas Petit wrote a paper on this several years ago, the graphics below are taken from Pages 4 and 5.

The summary is that a higher CG is better for x-y position stability, a lower CG is better for speed stability.

Background

Before we begin, let's assume we're only talking about a drone flying purely forward and so all dynamics are related to pitch.[*]

Second, let's define the CG, center of gravity, relative to the aerodynamic center (similarly to in https://aviation.stackexchange.com/questions/19388/what-is-the-difference-between-centre-of-pressure-aerodynamic-centre-and-neutra). The aerodynamic center is the idealized point where all the drag forces are acting around it evenly. In other words, it can be thought of as the spot where half the drag rotates the quadcopter into a pitch up orientation, and half rotates it into a pitch down orientation.

Here's the relevant image. It shows forward flight, and that's the same as position-holding flight with a backwards wind.[**] The red arrow is for when the CG is above the aerodynamic center, and the blue arrow is for when it's below the aerodynamic center.

Top-heavy CG: increases position stability, decreases velocity stability

When the CG is above the the aerodynamic center, the drone tends to tilt forward when there's a gust of wind. This ensures positional stability, because as the drone is pushed backwards it naturally leans forward which reduces the speed at which it accelerates backwards.

However, since the CG is above the aerodynamic center, when flying forward the drone wants to trip over its AC and pitch even more forward. This means that forward velocity is somewhat underdamped, results in a less positive-- or even negative-- feedback cycle.

Bottom-heavy CG: decreases position stability, increases velocity stability

In this case, the CG is below the aerodynamic center. When there's a sudden gust which destabilizes the drone, the drone tilts away from its holding position, which combined with the gust's force, accentuates the positional error.

But on the other when flying steadily forward the drone tends to want to pitch back toward the vertical, instead of tripping over its own feet. This means that forward velocity is well damped without a positive feedback cycle.

[*] Roll functions exactly the same way, but it's distracting to write "pitch/roll" each time we're talking about a rotation.
[**] This is a basic tenet of aerodynamics and fluid flow, which is that it's indistinguishable if the object is moving through the fluid or the fluid is moving around the object.


Can Reinforcement Learning be used for UAV waypoint control? I want to make a drone which can follow static and dynamic waypoints. I am a total beginner in the drone field so I can't figure out whether I should use Reinforcement Learning or other learning methods for the drone to make it follow both static and dynamic waypoints. If RL is the best choice for the task, then how would I go about training the model before uploading it to the flight controller. And if RL is not required, then what should I use in order to achieve this task?

Currently, I have no clue about which software to use for the task. I am very interested in this field and I would love to learn more. Please let me know how I should begin with this task.

Reinforcement Learning can be used for UAV control. This video details a method to use RL for quadcopters.

In summary, you program a model of your UAV that effectively simulates your drone.
You then create a policy and value neural network to control your drone and train it using your simulation.

I'm pretty sure similar methods are used in zipline's autonomous drone delivery network that manages 65% of the entire country of Rwanda's blood deliveries.


ESCs for inverted flight? What types of brushless drone ESCs are reversible and will work for flying inverted?

ESCs loaded with recent versions of BLHeli (BLHELI_S and BLHELI_32) will support reversible motor direction, either through Dshot commands (obviously only supported when using Dshot signaling) or with zero-throttle centered around the middle throttle position, 1500µs (supports Oneshot/Multishot in addition to Dshot).

These modes can be set up in the BLHELI Suite configurator.


Mamba F405 gps loiter mode I ordered a new mamba f405 a few months ago and I am  curious whether it is possible to have loiter mode on Mamba f405 flight controller like one in pixhawk ?

The Betaflight firmware has very few GPS assistance modes. AFAIK, the only one is GPS Rescue Mode which allows the quad to return to where it took off in an emergency.

For more GPS modes, I'd recommend looking into the iNav firmware, which has a lot more options for you and supports the Mamba F405 flight controller. The iNav GPS mode you'd be looking for is the NAV POSHOLD mode, which allows a multirotor to maintain a constant 3D location in space.


Is it common to break ESCs? I'm pretty certain my ESC is broken, so I went looking for some on amazon. I found a decent one for a good price, as well as a 4 pack that was a better cost per unit. I don't really want to have extra escs lying around because the space where I'm allowed to keep my electronic what-nots is rather small, although they would be helpful for quick repairs. Which leads me to my question,
Is it common to break ESCs, especially when starting out?
If I'm going to go through a couple ESCs, I'll by the 4 pack, but if I'm probably not going to break any more then I'll buy the singles whenever I need a replacement.

Aside from quality control issues with the product, the only real way to destroy an ESC faster than the effects or normal wear and tear (minimal) is to mistreat it:

Using it with a voltage higher than its rating
Using it with a motor that's dramatically too large
Drawing more current than its rating

Frequently stalling the motor against tree branches or alike

Not adequately cooling the MOSFET transistors when used in high-power applications

I will say, there's something to be said for having all of the ESCs on a model be the same make and model. This would minimize the risk of asymmetric behaviors between the ESCs in-flight.


Is Psychiatric History an Obstacle to Obtaining a Part 107 Certificate? Certain psychiatric conditions will prevent persons from obtaining a commercial pilot's license. Do the same restrictions apply to Part 107? If so, what means are there of obtaining clearance?
Background Reference: Guide for Aviation Medical Examiners: Item 47. Psychiatric Conditions

There are no specific medical restrictions placed on drone pilots in the US, however the pilot should not have reason to believe their state of health (physical and/or mental) will affect the flight:

§ 107.17 Medical condition.
No person may manipulate the flight controls of a small unmanned
aircraft system or act as a remote pilot in command, visual observer,
or direct participant in the operation of the small unmanned aircraft
if he or she knows or has reason to know that he or she has a physical
or mental condition that would interfere with the safe operation of
the small unmanned aircraft system.

Source: eCFR 14.I.F.107.B.17


How do you waterproof your electronics? I fly FPV drones a lot in the winter where it is wet and snowy.  What is the best way to protect your equipment from shorting out from water?

The first step I take to help protect my gear from shorting out from water is to apply silicone conformal coating to all the electronics I can.  I cover the ESC, flight controller, vtx, and any other exposed electronics.  I find that this also provides some protection from random solder drips or conductive grains of sand.

However you have to be very careful because conformal coating will block electrical signals that you want to work, like your USB port.  Also don't coat the barometer if you FC has one.

What other tips do people have for protecting their gear from bad weather?


How do DJI drones achieve such long flight times compared to traditional FPV drones? DJI is able to achieve ~30 minute flight times with their dones. Whereas, a typical FPV drone is only ~7 minutes
I see this as a huge achievement by DJI, I am interested to understand how they were able to achieve this advancement

The flight characteristics of these two crafts are quite different. A DJI drone is flown at much slower speeds than FPV drones So, if a FPV drone was flown slowly and cautiously, would the battery extend to be comparable with DJI's?

I have read elsewhere that the energy cost of FPV drones is due to the small blades, the motor needs to spin faster to compensate. This would imply that if you increased the blades (and the arm length) you would get longer flight times...?

Or has DJI really advanced that much in ESC performance, motor performance, battery chemistry to reduce energy losses?

There's no magic technology, it's just a difference in design goals. FPV drones are designed for speed, performance and robustness, DJI drones are designed for duration and carrying a gimbled camera.
Larger, slower turning rotors are more efficient at producing lift but have a lower top speed. That's why helicopters can hover and propeller planes with the same size engine can't - but the plane is faster. Photography drones (such as DJI) use large rotors and exploit that efficiency for duration. Race drones use smaller rotors because they want to go as fast as possible.
The other factor is that photography drones typically carry larger batteries for longer duration, while race drones want to keep their weight down for maximum agility and acceleration. A photography drone will fly so long as it can produce more thrust than its weight, typically they have less than a 2:1 thrust-to-weight ratio and can't maintain altitude when angled more than 45 degrees from horizontal. Race drones can have a 10:1 thrust to weight ratio, and commonly fly at pretty extreme angles.
So long as a race drone has enough duration to complete the race, any extra battery capacity is just dead weight, slowing it down. For their pilots, changing the battery every few minutes is a small price to pay for the performance.


What's the purpose of airmode and idle up? What are airmode and idle up and what do they do improve my freestyle flights?

Airmode and idle up both seek to increase a control authority and stability during ultra-low throttle moves.

In normal flight, when the pilot commands the multirotor to pitch or roll (cyclic), the flight controller responds by increasing thrust on one side of the craft and decreasing thrust on the other side by the same amount proportional to the cyclic rate commanded. This symmetrical change in thrust allows for quicker rotation than would otherwise be possible if the flight controller only increased power on one side.

The trouble comes when a pilot tries to change the attitude of the multirotor when the throttle commanded by the pilot is near zero (min_throttle). The flight controller obviously can't decrease the speed of a motor below zero (aka. idle speed), so it has to do something to ensure it can achieve the cyclic rate the pilot wants. Without anything to fix this behavior, the flight controller would only respond with as much as it could without making any motors increase thrust more than the others can decrease thrust. This results in massively decreased control authority at low throttle because the flight controller can only provide minuscule adjustments to motor thrust.

This is where idle up and airmode come into play, although they solve the problem a bit differently.

Idle Up

Idle up is setting configurable in the RC transmitter which changes the throttle curve at the low end so that it the bottom-most throttle position doesn't actually correlate to the transmitter sending zero throttle to the multirotor. Instead, it would send some low value that you configure, usually below 10%.

This would allow the flight controller to speed up and slow down motors by the amount you configure for the increased idle speed, which is a lot better than what it could otherwise accomplish at low throttle.

Airmode

Most modern flight controller firmwares support airmode, including Cleanflight and Betaflight.

When enabled on the flight controller and the pilot commands a large rotation while at low throttle, the flight controller temporarily pretends that the pilot's throttle command is high enough for it to slow down motors to zero throttle and still achieve the cyclic rotation rate the pilot wants. When the pilot commands less cyclic rotation rate, the flight controller stops pretending that the throttle command is higher than it actually is.

For a graphical explanation of this functionality using graph paper, I recommend taking a look at Joshua Bardwell's video about airmode.

To see what this looks like visually during low-throttle maneuvers, I recommend watching Le Drib's video about idle up vs. airmode. (link starts at relelvant section)


Do flexible propellers affect multirotor efficiency? There are a wide variety of materials and methods for making the propellers used on drones. This leads to certain propellers having different characteristics than others. Some propellers are more flexible than others and I am wondering how that would impact the efficiency of a drone?

It's really a challenging question to answer because flexible and stiff propellers both have their advantages and disadvantages in terms of efficiency.

Flexible propellers are typically lighter than stiff propellers, so they spin-up more efficiently than stiff propellers.  On the other hand, when a propeller is spinning at higher speed, a flexible propeller will have a tendency to flex upward and flatten out vs a stiff propeller that is designed to resist flexing (stiff propellers will still flex, but not as much as a flexible propeller).  With a flexible propeller, this could result in a scenario where you have more throttle to give, but the drone won't go any faster.  To some degree, you might also notice that the drone is less controllable - might not take a corner as well as a stiff propeller would.

If you have a lower powered motor, a flexible (lighter) propeller might be your best option because you may never reach the point where efficiency is an issue.  However, if you have powerful motors, and your desire is for speed, then a stiff propeller will probably be more efficient at higher speeds than a flexible one.


Learning to fly: One crash at a time Question
Is there a comparison of model types versus the milestones that reflects which plane is best for learning in ?
Background
I bought an EPP flying wing some time ago and have taught myself and a few friends and family members, as well as any stranger with some curiosity, to get up into the blue yonder. My experience has been that it takes around 200-300 flights before you can hold a figure 8 pattern. It seems that the initial flights are the largest learning block since the flights are quite short and the window for learning the smallest as the person gets longer flights in they tend to learn quicker. Roughly the learning curve goes as follows :

The first 50-100 flights, with flight times of 5-15 seconds, one gets the control down (Dive, climb, left and right).
The next 100-200 flights, with flight times of 15-30 seconds, one can start transitioning to powered flight.
The 200-300 thereafter, with flight times of 30 seconds to a few minutes, one gets comfortable with it flying back at you and across your view.

Basis
The general claim is that a slow flying, top wing is best for learning but I have had fair success with a flying wing. I intend to use a discuss launch glider next as you can give the person a longer flying time for the initial learning curve and I was wondering what others experiences/learning curves were with different model types.
Rationale
I'm curious about the folk who selected the "wrong" thing to learn on and how they got along none the less. Perhaps it turns out that one type of craft is better for learning on then some other; granted a top wing is the likely result.

The big problem with learning to fly is that some of characteristics you need for a good trainer are the opposite of other requirements.

Large models are less affected by wind, because their flying speed is proportionally higher relative to the wind speed. However small models are a lot more robust in a crash. and cheaper, so less discouraging when you crash.

Highly stable models return the model to straight and level flight but neutrally stable models (like a flying wing) are less affected by gusts.

Traditionally this leave you with the option of a small, stable model and waiting patiently for calm weather, or a faster, less stable model and an instructor (or lots of crashes and repairs!)
These days it's possible to use electronic stabilisation to tame a neutrally stable aircraft, and to reduce the effect of gusts on a small model (although it won't stop it disappearing down wind!)
IME it takes an hour or two (on a simulator, or accumulated flight time) before a beginner can keep a model under control and steer the right way when it's flying towards them. Most people can only concentrate for 5-10 minutes at a time, so that's 10-20 flights (on a reasonably stable trainer, suitable weather and an instructor avoiding crashes). It then takes few months to a year before progressing on to an aileron model that isn't stable in roll - maybe 10 hours of flight time, say 100 flights of 5-10 minutes each.
Obviously if you don't have an instructor and are just doing short glides, those first couple of hours will translate to a lot of flights. If you're starting with an aileron plane (like a flying wing) you'll need to reach that 10 hour mark before you're really flying.
Older people take longer to learn, and missing a few weeks due to bad weather or other commitments puts them back a few steps. It's common for people to struggle through weeks of poor conditions then suddenly 'get it' when we have a nice calm day because they're not fighting the gusts.
I've taught a couple of people who practiced extensively on a simulator and flew a trainer competently on their first flight and an aerobatic model 5 minutes later.


How to enter DFU mode on my flight controller? How can I enter DFU mode on flight controllers, in particular on my CL Racing F4S flight controller?

Ref.: https://cl-racing.myshopify.com/products/clracing-f4s

There are three ways you should know to enter DFU mode.

The first, as mentioned before, is to push down the bootloader button and power on your board.

The second method is to be used on boards that don’t have a bootloader button (which is increasingly rare). You will need to bridge two bootloader pads on your flight controller to enter DFU mode. Check the specific diagram for your flight controller to find out exactly what pads you need to bridge.

The last method is to enter the CLI and type either ‘DFU’ or ‘BL’, which will then put the FC into DFU mode. Obviously this method won’t work if you’re entering DFU mode because you ant connect to your computer.


Proper rotor fastening (Nyloc nut) I am trying to figure out how to properly fasten my rotors on my quadcopter. I am pretty sure the nuts are Nyloc, but here is a picture for reference:

I read online in many places that you should just tighten the nut until you can't anymore with your hands, and some people recommended using pliers or socket wrenches. My problem is, no matter what tool I use, the nut will not tighten past the point where its top is flush with the shaft (I don't know much about Nyloc but this seems by design). Here are the motors I am using (https://www.amazon.com/iFlight-2750KV-Brushless-Racing-Quadcopter/dp/B07Y9JK2MW). This first result is what I achieve almost every time after tightening as far as the nut will go:

But this causes issues because I can tip the rotor in different directions with my hand, and so it seems like it would wobble when turning, and the fit is definitely not secure. (I at first thought this was because the 5mm hole in the rotor was too large for the 4mm shaft, but I was told that the threading in the shaft was 5mm so it would be fine). This second result was achieved after inserting two washers between the nut and rotor, tightening down the nut, untightening and removing the washers, and the tightening the nut once more.

I removed the washers because while I had read that some people tighten their rotors with washers, the gap seemed too large for this to be the solution, so I assumed I was doing something incorrectly in the mounting. Where did I go wrong, and how should these rotors be mounted?

I've had the same thing happen when using these same motors and props (and others). The propeller seems to get stuck at a point where it is not flush with the motor. From my experience, the solution is as simple as tightening it further. I use a tool like this that allows me to apply more force than a typical prop-tightening tool.
It should look like this when fastened correctly, with the prop sitting flush with both the motor bell and the nut:


Why do a quadcopter's opposite rotors spin in the same direction? All the quadcopters I've seen have four motors, arranged in a square-like shape. Two of these rotors spin one way, and two of them spin the other way so that the main body of the quadcopter doesn't rapidly spin as it flies. (Conservation of angular momentum.)

I find it interesting that the two rotors that spin in the same direction are opposite, not adjacent. Why not put the two anticlockwise-spinning rotors on one side and the two clockwise-spinning rotors on the other side? That seems the natural way to do it.

So what makes the opposites-spin-the-same design better?

This design is to prevent unwanted yaw when moving, or vice-versa.

Consider the following two actions:

When a quadcopter yaws, it does so by creating a speed difference between the opposite-rotating rotors; creates a torque that rotates the quad.
When a quadcopter moves left/right, it does so by slowing all the motors on one side of the frame and/or speeding those on the other, imparting a slight roll - the thrust is now slightly sideways, so it moves. (This is the same for front/back.)

From this, you can infer that if the same-direction rotors were on the same side as each other, when creating a speed difference to yaw the aircraft you would also impart a roll. Similarly, when trying to roll the aircraft would yaw.

The image below shows visually how an opposite-corner rotation quadcopter moves:


Why do the motors on my drone keep spinning up and max out when I run up the throttle on my radio on the bench? When I test my drone for the first time and I run the throttle up form my remote with the props off the motors keep spinning even when I bring my throttle back down. Will my quad flip out if I put the props on and try to fly it? Why does this happen? It seems fine when I spin the motors up from the motors tab.

TL;DR;

This is a result of I term windup from the PID controller. It's completely expected and normal with props off, and will be fine when you put props on and go fly! Almost everyone new to RC multirotors asks this question on their first build, so don't feel bad!

Detailed Answer

The detailed answer to this question is related to how multirotors maintain stability in flight. Multirotors use a control system called a PID controller. This is a feedback loop control that takes information from the sensors onboard the flight controller and then executes change via the motors based on how the commanded input is different from what it is sensing. For more information check this white paper from the national instruments lab.

To understand this problem, the component of the PID controller we need to examine is the I constant, often referred to as Ki. Essentially this is based on the integral calculation between the sensed value and the setpoint or target value. What this means is that I get stronger the longer there is a difference between the sensed value and the target value. Hence change over time. What you're seeing as the motors slowly spin-up is the buildup of that Ki value getting stronger and stronger as flight controller is trying harder and harder to execute a change that it can sense, but can't impact. No props means no force to execute change, hence the windup.  This is often referred to as I term windup.

Here is an excellent video from Joshua Bardwell on the topic:


Does the LaForge V3 Fat Shark Receiver receive audio from VTX? I installed the Mach 3 VTX that has a built-in mic for audio that is transmitting to the LaForge v3 receiver in my fatshark dominator v3 goggles. Video works great and Smartaudio is also working. I hear nothing but static from my earbud.

I tested the earbud and it worked on my phone. I also made sure I am plugging the earbud into the headphone jack next to the HDMI port on the goggles. I'm pretty sure I have everything set up correctly but before I try ordering another VTX and swapping parts out I want to make sure that my setup is compatible with Audio.

The V4 has audio, but I can't find any information about whether or not the V3 has it. I did however see that a manual mentions a VTX audio option in the menu. But since it doesn't say which version, the easiest thing to do would be to see if you can find that option and make sure to turn it on.


How can I safely parallel charge my LiPo batteries? I have multiple LiPo batteries that I want to charge up so I can get out flying as fast as (safely) possible.

With my existing LiPo charger, how can I parallel charge multiple batteries at once?

Only parallel-charge batteries with the same number of cells.

Safe parallel charging requires that the voltages on individual cells be close to each other. A difference of 0.1V per cell is considered to be the maximum safe difference (I found it online, and have used ever since, although I have no scientific proof of that).

One way to compare the packs before parallel-charging is to compare their total voltages and make sure that the maximum difference between any pair of packs does not exceed 0.1V times the number of cells. However, this may be unsafe due to the fact that some packs may have more unbalanced cells than others, so it is better to compare each pair of cells that will be charged in parallel.

With many packs of uneven charge, it may be possible to divide them into groups whose cell voltages are close enough to be safe to parallel-charge and then charge each group separately.

A parallel-charging board with enough protection is recommended, with fuses limiting the total current of each pack being the minimum. Some boards also have fuses or current indicators for each cell of each pack for more safety.

Choose an appropriate charge current, which equals the sum of charge currents of all parallel-charged packs. Charging at 1C times the number of packs seems to be reasonable and safe if there are no large differences in capacities and cell degradation between packs.

Regular safety rules of charging single LiPo packs apply, for example never leaving the batteries unattended while charging, keeping away from flammable materials, etc.


When flying FPV in a group, what are the best video transmission channels/frequencies to use to avoid interference? When flying FPV drones in a group setting it is very important to choose appropriate video transmission frequencies so you don't interfere with others that are flying near you.  What are the best channels to use ( depending on where in the world you are ) for groups of 2-6 people?

To answer this question, there are two things you need to know.  First you need to be able to map the various channels and bands to their frequencies.  Second, you need to understand Intermodulation Distortion (IMD).  The quick explination of IMD is that two or more radio frequencies can combine to cause interference on a third frequency.

Using the above chart you can see how the different bands and channels overlap.  In general, when flying with just one other person, you are fine to choose any two channels that don't overlap frequencies.  However as you add more people to the mix, you have a higher chance of causing IMD.  To help with that issue, many races now operate using a group of channels called IMD5 or IMD6.

If you are in a group of 5 people, the recommendation is to use R1, R2, F2, F4, and E5.  If you are in a group of 6 people, use R1, R2, F2, F4, F8, and R8.


Why do higher voltage batteries need lower KV motors? I've noticed that higher voltage batteries need lower KV motors, why is this?

They don't necessarily, however a given amount of power will be required to rotate a motor at a certain RPM with a given propeller.

kV, the voltage constant of a motor, is the maximum RPM it can turn at per volt of power supplied. Example:

A 4S (15V to make math easy) battery will turn a 2000kV motor at 30,000RPM (with no load, inefficiencies, etc)
a 6S (20V) battery will need a 1500kV motor to achieve the same RPM

In theory, the result is the same amount of power (watts) required to achieve the same RPM/power output/etc. A 4S 2000kV motor will draw say 20 amps, or 300 watts. To get the same power output, a 6S 1500kV motor will draw 15 amps (still 300 watts), and spin at the same RPM. Higher voltage but lower current generally results in less heat, because of ohm's law. Current creates energy loss over resistances (ESC components have internal (small) resistance, which is why they heat up, which is why they have a current rating in the first place).

A lot of Bardwell's videos go into the details of 4S vs 6S, but they work out to be pretty much the same. The reason larger models go with higher voltages (and lower kV to achieve the desired RPM) is because they are much higher wattage, and achieving that higher wattage strictly with higher current is unrealistic (Large scale planes would be drawing 500-600 amps at 3-4S voltages, dangerous and expensive).

To reference an earlier comment, the voltage "rating" of the motor is just the suggested voltage. The actual rating of the enamel coated wires would be much higher, but you will destroy components from drawing too much power under load if you went up to those voltages.


How can I set up appropriate motor mixing for a frame of a custom layout? First, whilst this post is mainly about how to program in Betaflight, it also involves ESC layout so I feel it is appropriate for this Stack Exchange.

For example, I intend to create a frame that is in a dead cat format with the front two arms spread further apart, but in the form of a hexacopter. I assume this process will be the same for copters with other numbers of motors.

I also need to configure the six ESCs for the motors, however I am using an F7 flight controller (in this case an Omnibus F7 Pro) and as such only have 4 motor outputs.

I know that I need to map 2 motor outputs to timer-equipped pads, however once I have done that I need to add a custom motor mix for the frame I have designed, using the two motors I have remapped. How can this be done using Betaflight?

Once you've performed the necessary resource remapping commands to assign the extra motor functions (e.g. M5, and M6) to alternative pads on your flight controller, you can then set up custom mixer rules to tell Betaflight what to do with the additional motors.

However, if one of the predefined mixer types works for your build, you can just load it using the Betaflight Configurator or via the CLI by sending the command mmix load <name> where <name> is one of the mixer types from the link above.

Otherwise, you'll need to configure your own mixer rules. Following the instructions from the Betaflight Wiki, you'll need to use the CLI in the Betaflight Configurator to formulate and send mmix commands.

First, you'll need to send mixer custom to enable custom mixing.
Send the mmix reset command to remove any existing mixer rules.
For each of the motors you need (starting with M1 and ending with M6 for your hexacopter) send an mmix command with the following space-separated parameters:

Motor number for the rule (in the range 0-5, so subtract one from the M motor port number).
Number from 0.0 to 1.0 indicating how much throttle should be mixed into this motor. If this motor shouldn't be affected by the throttle, enter 0.0.
Number from -1.0 to 1.0 indicating how much roll should be mixed into this motor, where positive numbers mean that a roll command over 1500µs should increase the motor's power and vice versa. If this motor shouldn't be affected by the roll axis, enter 0.0.
Number from -1.0 to 1.0 indicating how much pitch should be mixed into this motor. This value obeys the same conventions as the roll axis parameter.
Number from -1.0 to 1.0 indicating how much yaw should be mixed into this motor. This value obeys the same conventions as the roll axis parameter.
An example mmix command is: mmix 0 1.0 0.0 -1.0 -1.0

Remember to send the save command to save your new mixer configuration.

This is all quite confusing, so here's an example from the same Betaflight Wiki page showing what the mixer commands would be like to use the M1, M2, M3, and M5 ports if te M4 port were broken on your flight controller.

mixer custom
mmix reset
mmix 0 1.0, -1.0, 1.0, -1.0
mmix 1 1.0, -1.0, -1.0,  1.0
mmix 2 1.0, 1.0, 1.0, 1.0
mmix 3 1.0, 0.0, 0.0, 0.0
mmix 4 1.0, 1.0, -1.0, -1.0
save


What size screws do I need for this motor I am using this gimbal motor.

I need to know what size screws do I need to use. I am developing egg and a frame that has 5 mm thick walls, and based on the chart I know I need to use 4m screws. I want to know how much longer do I need to make the screws to perfectly fit this motor. I need help with this because I do not want to buy the wrong size screws and then have to buy more because I don't want them to be so short with a camera or far off mid-flight or I don't want them too long to short them.
Here's a picture of the chart I'm referencing to may provide some further help.

4-M3 means that you need four screws (on each side), each with a metric M3 thread. M3 is 3mm diameter.
The length of the screw obviously depends on the thickness of the thing you're bolting the motor to, plus a little for the base of the motor.
The amount of bolt in the motor is important. Obviously you need at least a couple of mm so that it grips, and there's another couple of mm of clearance, but any more and it'll touch the coils. It won't stop you spinning the motor by hand but it'll break the insulation on the coils, short the coil to the case and the motor won't work.
So if you're bolting through a 5mm thick frame, order 8mm long M3 screws. They tend to only come in 2mm steps. The length quoted is the specification is the length of the thread, not counting the head.
If you don't fancy cutting and filing a slightly long screw, you can put extra washers under the head.
Also, when ordering screws, you want 'cap head' not 'dome head' or 'countersunk' in order to use the largest possible Allen key. The small ones tend to round off and slip.


What is the meaning of 'control of a building' in the UK Air Navigation Order on Unmanned Aircraft? The UK drone regulations include the requirement that camera drones are not flown "within 50 metres of any vessel, vehicle or structure which is not under the control of the SUA1 operator or the remote pilot of the aircraft" (source: CAP 393 Article 95(2)(c)) but don't go into detail about what 'control' means.

For the purposes of meeting this regulation, what criteria should be met for a vessel/vehicle/structure to be considered as being under the control of the remote pilot? For example, I would imagine your house would be considered under your control, but (inspired by this question) what would you need to do to consider a shared residence to be so?

[1] The CAP393 document defines SUA as "Small Unmanned Aircraft"; this is analogous to a drone or UAV.

I found what looks to be a reasonable answer in CAP 722 - the UK's drone rules guidance document.
In short, it appears a vessel, vehicle or structure can be under your control if you have the permission of the captain/driver/owner, and any people are under your control. For people to be under your control, they must be willing and able to follow guidance and safety instructions of the pilot.
The long version (correct April 2020):

Article 95(2)(c) makes reference vessels, vehicles and structures being under the control of a remote pilot or operator.  A vessel or vehicle could be said to be ‘under the control’ of a person if:

That vehicle or vessel is present for the purpose of participating in the flight operation; and
The operator of the vehicle or vessel (for example the driver of a car or captain of a ship) and any passengers are under the control of the remote pilot and can reasonably be expected to follow directions and safety precautions to avoid unplanned interactions with the small unmanned aircraft; and
The owner or other person with an interest in the vessel or vehicle (such as a lessee) has granted permission for a UAS to operate within 50 metres of that vehicle or vessel.

A structure could be said to be ‘under the control’ of a person if:

The owner or other person with an interest in the structure (such as a lessee) has granted permission for a UAS to operate within 50 metres of that structure; and
Any occupants of the structure are under the control of the remote pilot.

For completeness, as the document referes to control of people:

Persons under the control of the SUA operator or remote pilot can generally be defined as:

Persons solely present for the purpose of participating in the flight operation.
Persons under the control of the event or site manager who can reasonably be expected to follow directions and safety precautions to avoid unplanned interactions with the small unmanned aircraft. Such persons could include building-site or other industrial workers, film and TV production staff and any other pre-briefed, nominated individuals with an essential task to perform in relation to the event.

Spectators or other persons gathered for sports or other mass public events that have not been specifically established for the purpose of the flying operation are not regarded as being ‘under the control’ of the of the SUA operator or remote pilot.
In principle, persons under the control of the SUA operator or remote pilot at a mass public event must be able to:

elect to participate or not to participate with the small unmanned aircraft flight operations;
understand the risk posed to them inherent in the small unmanned aircraft flight operations;
have reasonable safeguards instituted for them by the site manager and SUA operator during the period of any flight operations;
not have restrictions placed on their engagement with the purpose of the event or activity for which they are present if they do not elect to participate with the small unmanned aircraft operation.

Note: As an example, it is not sufficient for persons at a public event to have been informed of the operations of the small unmanned aircraft via such means as public address systems, website publishing, e-mail, text and electronic or other means of ticketing, etc. without being also able to satisfy the points above. Permissions have, however, occasionally been granted for small unmanned aircraft flights at public events where these involved a segregated take-off site within the main event, with the aircraft operating only vertically within strict lateral limits that keep it directly overhead the take-off site. Such flights may also be limited by a height restriction and the tolerance of the aircraft to wind effects and battery endurance.


What is the purpose of adjusting the thrust angle for model aircraft? I have a few model aircraft and know that the motor is often slightly offset. I have heard conflicting reasons as to why this is done. Some people claim it is because of motor torque and other people say that it is done because of other things, and not really because of torque. What is the most significant reason that the thrust angle is usually adjusted on model aircraft?

Typically the motor will point down and to the right. There can be various reasons for this.

I've included a plans excerpt from https://aerofred.com/details.php?image_id=91062

Downward angle

Sometimes it's to align the motor with the true flight direction, because the wings need some AOA (Angle Of AttacK) greater than 0. In the excerpt above, you can see that there's a 3 degree downward tilt. If you look at the original plan, the wings are mounted flat to the fuselage. A 3 degree AOA is pretty normal for cruise flight, so this motor is mounted so that it's pointed in the direction of movement.

If it were not pointing downward, then when you changed thrust it would have a tendency to momentarily sink/climb.

Another advantage of pointing down is that it increases pitch down tendency (or decreases pitch up tendency) when power is applied. Pitching down is safer since it drives you away from stall, instead of toward it. This is especially valuable in the case of positive pitch stability craft where there is a natural tendency to pitch up as airspeed increases.

You'll find that full-scale aircraft have the motor aligned with the fuselage, but their wings mounted at a 2-3 degree incidence angle so that the fuselage is level while the plane is flying forward. It turns out that the squishy humans seated inside prefer not to be seated on a slope.

Pointing to the right

In some models, the motor can be turned to the right so that its thrust counteracts the p-factor, which tends to turn the plane to the left. This makes the plane easier to handle when under high power at slower speeds when the rudder is less effective.


Headless mode on a drone I have noticed my drone has headless mode listed as one of it's features.

This poses a few questions:

What does this mode do?
How is it different from normal mode?
How does it work?
How do I enable it?

What is headless mode?
Headless mode is a specialized flying mode that is common in store-bought drones. It eliminates the need for focusing on the drone’s orientation and enables a much easier Line of Sight flying experience. This can make drone flying easier especially for beginners still learning how to control the flight path of the drone.
Whilst it may be useful for beginners to learn flying using this mode, it wouldn’t be too recommended. You can then get used to this mode and then have trouble unlearning it and learning how to fly the drone properly.
The only thing is that when you launch the drone, the front of the drone must be facing away from you to launch properly.
How does it work and how is it different to normal mode?
When you take off with the drone pointing forward, algorithms within the drone’s microcontroller will ensure that any directional changes are compensated. The drone will take instructions based on your current orientation as opposed to normal mode where the drone moves in regards to the drone's orientation, no matter where you are regarding the drone.
For example, if you are in normal mode and the drone is facing toward you, and you press left, the drone will go right (as left in the way it’s facing means right in the way you are facing) whereas, if you are in headless mode, the drone will move left in the direction you are facing the drone.
This diagram illustrates how normal mode is different from headless mode:

(image source)
This is another diagram showing a more detailed visual of how the drone will move differently in normal mode compared to headless mode:

(image source)
How do I enable it?
This will vary from drone-to-drone so one specific answer cannot be given. If your drone has it built-in (which most do), there should be something in the instruction manual saying how to enable it. Most likely it’s a button that needs to be pressed on your controller.


At what voltage per cell should I store a LiPo? Some sources say you should store your batteries at 3.85V per cell, other says it should be 3.7V.

My charger (ISDT Q6 Lite) on the "Storage" mode has a thumbs-up mark at 3.7V, probably indicating that it's the best voltage, at the same time when I ordered some CNHL LiPos, they came charged to ≈3.85V per cell.

Are there any papers/experiments about storage voltage or maybe this difference is neglectable?

This question seems to be quite the debate in many places. However, the general consensus falls between 3.7 and 3.85v per cell. You can find a similar inquiry here: Storing at 3.7 or 3.85v and here: LiPo storage voltage

It seems that generally, the difference between storage charging to 3.7v, 3.8v, or 3.85v is negligible for most people. However, I would recommend 3.7-3.8v per cell. I store my LiPos at 3.8v per cell and all of my year-old LiPos perform almost like they are brand new.

The exact voltage you storage charge LiPos is important, but it is even more important that you just take good care of them and do storage charge them. It's better to storage charge LiPos to a close enough voltage than to not storage charge them at all.

Here is a pretty useful guide to LiPo batteries: Guide to understanding LiPo batteries


Diy drone Digital control/communication Is there a solution for digital drone communication through Wifi for diy fpv drones?
I'm searching for a way to build a drone that have multiple cameras and communicate with my computer through wifi, for control/autonomous drive/etc, i need something like the dji tello communications, but for a diy drone since i need the customization with diy drones (small form factor, long flight time, range, etc) which i need to control those parameters.
a diy solution is ok even preferred.

There isn't an easy solution, because this isn't a common thing to do.
The main issue is that real-time control for FPV requires very little lag. Wifi requires several layers of processing, on a computer where it has to compete with other processes for processor time. Your video needs to be encoded and compressed, and still work if some data is missing. Most digital video isn't real-time, and relies on a buffer to smooth out these delays - but you can't fly with images that are a few seconds old.
That said, it's pretty simple to stream video over wifi with a small computer like a Raspberry Pi, and there are lots of guides on how to do it. Similarly there are lots of ways to send other data over wifi - it's just networking, and there are lots of guides on how to use UDP or TCP/IP.
You probably can't use the same computer to actually fly the drone. Again it's a real-time system that needs to adjust the motors hundreds or thousands of times each second. I think you would be best to use a normal flight controller running iNav, and to send it control signals from the Pi, via S-Bus. Effectively the flight controller attempts to hover at a GPS position, and you send it a new position occasionally.
I've not actually done this myself, or even read about anyone doing it, but I suspect it has been done.


What are good specifications for a intermediate medium priced quadcopter? What are good specifications for an intermediate medium-priced quadcopter? I have flown a smaller quadcopter before and developed a bit of an understanding of how they work and how to control it.

I would almost certainly like a camera and the drone to be First Person View (FPV) but also some more advanced features. I would like the cost to be around $200.

Okay, as someone who has just recently passed through this stage, here's my take on it. Almost all of the considerations below stem from the maxim that the best drone for you is one that you will fly the most. Both progression and enjoyment in this hobby (and many other hobbies as well) are directly linked to how much time you spend doing it. Whenever you're unsure about a decision, besides other considerations ask yourself which option will keep you in the air more.

Now, to the list itself. Your "second" drone must be:

Indestructible. Durability is valuable for all quadcopters intended for acrobatic or racing flying, and you'll likely never stop bashing your drone into stuff no matter how high your skill, but unlike the pro pilots who probably break more drones a month than you will ever own, you don't have spares lying all over the place for when you do. For a long time, this is likely going to be the only "real" drone you'll own, so it better be durable. There are two main ways you can achieve that:

The "classic" approach is to have massive unbreakable arms, a titanium cage around the components, etc. That's pretty self-explanatory, though you'll have to pay for it in added weight (which is not that bad if you don't carry a gopro).
The other way is for the drone to be so light that it simply doesn't
have enough inertia to break anything, including itself or even its
own props. This is the idea behind the "toothpick" class of
quadcopters, which some consider an excellent choice for
beginner-intermediate pilots, in part for this reason.

Basic, but high-quality. What I mean by that is that you don't need the fanciest F-infinity processors, top-end performance motors, the lowest-latency camera, etc. What you do need, however, is for all the components to be high-quality and well-built by a reputable manufacturer. i.e. an F4 FC made by a well-regarded manufacturer is better than an F7 FC by a knockoff noname brand. Not only will this reduce your cost (by picking basic components) and add to reliability (by picking trusted brands), it will also make things simpler for you and less heartbreaking when you do break something.
Easy to maintain. However durable your drone, you will crash it, break something and need to fix or replace it eventually. And when it happens, you'll want your drone to be easy to disassemble and reassemble, have replaceable parts, etc. First, this rules out the non-DIY type of drones, but the DIY ones are also not created equal. Some frames make accessing the guts as easy as unscrewing three bolts, while others need more disassembly. A bigger drone is significantly easier to work on, with less tiny fiddly parts, while a small one (3" and smaller), while frustrating to work on at times, will likely break less. For larger (5 inch +) frames, replaceable arms are a very good feature to have, and a simple replace procedure (i.e. unscrewing one bolt versus disassembling the whole frame) is important as well. Toothpicks are an interesting class in that regard, in that they have a tiny whoop-like architecture, with only 4 parts: the frame, motors, camera, and an all-in-one FC+ESC+VTX board which the motors just plug into with pin connectors. This makes them way easier to maintain than other quads of this size, but also less upgradable, since three of the main components are on one board. Which brings us to...
Upgradable. This is closely related to the previous point, but slightly different. You want to be able to swap any of the major parts of the drone (FC, ESC, motors, camera, VTX, frame, etc.) for a different or better model without also having to swap the others or encountering any compatibility issues. This is mainly a jab at some prebuilt quads that have proprietary components in them which would not work well or at all with other off-the-shelf components.
Fit for your usual flying location. This is actually important for any quad, but as this one is likely to be the only one for some time, here it is especially important. The best quadcopter is one that you fly a lot, and so you want yours to be well-suited for the size, configuration, weather conditions and other considerations at the place where you fly the most, as this will maximize your flying time, frequency of flight sessions and enjoyment of the process, all very important contributing factors to how fast you learn and how much you enjoy the hobby. If you buy "the best-flying" copter but it won't fit in your flying field, you won't fly it much at all. The most important parameter here is likely the size class of your copter, which must fit the size of your location. Loosely, it's something like this:

if you mostly fly indoors, you need a tiny whoop (although it's likely you'll later want a separate outdoors quad anyway)
for a playground/backyard-sized outdoors location with lots of small obstacles (i.e. literally a children's playground) and gaps a larger (75-85) brushless whoop or ~2 inch quadcopter with detachable propguards will offer the most
enjoyment out of flying in such a tight space while still being able to rip in larger locations.
For something like an uncrowded street, large backyard or small park a toothpick-class 2.5 to 3 inch quad would be optimal;
for larger parks you can go either the toothpick or the 4-5 inch route, depending on how crowded the place is; the former is safer for everyone, less intimidating, and slightly slower, while 4-5 inch quads are noisy, heavy and can do some damage, but are still the undisputed leaders when it comes to flight performance.
finally, if you've got huge fields, shorelines or even mountains to fly over, you probably want a 5 or even 6 inch quadcopter that is able to cover the distance well. However don't fly too far without educating yourself on proper long-range operation first, there's a lot of stuff that you need to know (and buy :) in order to not lose your precious quad a couple km away in the first few flights.

Of the quadcopters that fit all the previous points, choose (or build) the one that you like the most subjectively. Maybe it looks cool, maybe you really like the manufacturer, maybe it's elegant. The factor of likability should not be underestimated. Whatever the reason for you to love the quad, the more you do, the more love, time and effort you'll put into it, making it a better quad and you a better pilot!

As a final word, I must reiterate. Whichever quad you pick, in the end the most important thing is that you fly a lot. Buy a good amount of batteries, a nice flight backpack, and make a habit out of going out and flying. You'll love every moment of it and of the rest of your life as well.


How to revive an over-discharged DJI Mavic battery? I left my drone on until the battery shutdown.  The Mavic battery bottom meter light flashes 16 times when checking charge.  When i place the battery on DJI chargers it will not charge and also flashes 16 times.  Keep in mind i did not store it this way and the battery depleted this low in the past 24 hours.  Is there a way to force the battery to charge up from a depleted shutdown state?

Short answer. Buy a new battery.
I heavily researched this and although there may be another solution I will share my experience.
The Mavic batteries have complex circuitry in them to maintain stability and longevity.  This is partly why the Mavic charger will not revive the battery.
Is there a way to manually charge it?  Well the answer is yes and no.   The cells inside the battery are probably okay if the battery did not deplete this far while in storage.  The problem is the circuitry will not allow a manual charge above failsafe levels restoring to a functioning DJI battery.   There are some videos and reports of people cracking open their batteries and doing various physical things to the circuitry to fix this issue.  I do not recommend this.  I found that opening the Mavic battery was not easy and left the battery case in disrepair due to it being glued or affixed with single use fasteners.  If there is a tool that can open the battery case gracefully i don’t believe it is something in a standard tool box.  On top of that the Mavic circuitry is precise to avoid radio interference and modding that could increase radio interference.
Once the battery was open, poorly, I was able to charge directly to the main leads.  The battery stack read about 10.5 to 10.6 volts on 3 cells.  Very low.  My hobby charger pulled it up to 11.1 volts static.  I was still unable to charge using the Mavic charger.  This led me to believe the circuitry remembers the charge state of the battery and will not continue if that battery has inconsistent untracked voltage changes.
I saw another video that shows desoldering the positive terminal while the balance lines are disconnected.   Then soldering it back.  I tried this and it did seem to refresh the charge level readout, but i still could not charge using the Mavic charger.  With my battery split open and looking like it would never be allowed in checked or carry on baggage i gave up and decommissioned the battery using a method that worked for me.  Once the battery became inert it could be disposed of properly.
I suggest contacting DJI before opening the case. Maybe they have a trade in policy or something when the Mavic depletes the battery too low?
Best bet is to get a new battery.


Which settings in Betaflight allows me to do flips and rolls? I see a lot of people flipping and rolling their quads, but on my last attempt, it fell out of the sky.

What are the settings in Betaflight that allow them to do this without stopping the motors?

It’s called Airmode.

It keeps the motors in a constant idle state, even at zero throttle. This gives you pitch, roll and yaw authority even when you are upside down.

You can enable it in the configuration tab in Betaflight.

You will notice that your props may try to spool up even when your quad is just sitting armed on the floor, but this is called I term ramp-up and is completely normal.

I tend to keep Airmode on all the time so have it set up in the configuration tab, but you can also map it to a switch in the modes tab so you only have it on when you want it.


Specs of the XT30 port on DJI M600 PRO I'm new here and so I would appreciate any answers,
I work in a research laboratory at Brazil and we have an M600 PRO.
I need to connect some components to the XT 30 port, so I need to know more information about this port. Power, maximum current supported, voltage, electrical diagram, compatibility, and all possible information about the capacity XT 30 port.
I'll use several components with maximum current estimated 7 A.
I had read several datasheets but the only information that I found is maximum current supported 10 A and 18 V. So, I would like to know more information about the XT30.
I would be so glad with your help.
Have a nice week.

Your question asks about the XT30 connector. I found this diagram which lists the specs of the XT30 connector:

However, this source suggests that the Matrice 600 pro has an XT60, not an XT30. It wouldn't make a difference in power though, as you are correct that the Matrice 600 can only supply 10 Amps and 18 Volts for a total of 180 Watts. This means that the only difference between using an XT30 and an XT60 would be the size of the connector. You can tell which connector it uses by looking at the side of the connector, in small letters it will say either XT30 or XT60.
The specs of the XT60 are as follows:

If your total power draw will be 7A at 18V, it should work fine. Just make sure that the total wattage you are trying to pull is under 180W.


What is the performance difference between a brushless motor with a wider vs taller stator? In the drone motor industry, there are a lot of variations in the stator sizes of brushless motors. There are several motors that have similar stator volume but one is wider and the other is taller. What are the inherent differences in performance between a drone motor that is wider stator vs one that has a taller stator with a similar stator volume? Would the stator shape influence which props it should use?

The simple answer is "more width equals more torque".

More torque let's you drive a higher pitch or larger diameter prop effectively. Given the same size prop, it will drive it with more effectiveness. Added torque allows the prop to spin up or slow down faster, which ultimate results in a better flying quad because it can more quickly and accurately respond to your stick inputs.

In the miniquad community, this is the reason a lot of freestyle pilots trend toward wider motors on a 5" prop compared to racers. It provides a higher level of smoothness because of how it reacts.

Another effect of more width is more efficiency especially with big crafts that are targeting flight time. You'll see lots of the big (15" or larger) propeller quadcopters with very wide motors. For instance a 5010 stator size. High performance isn't usually the goal here so a wider stator allows them to drive the big prop without lots of excess weight and power that they don't need.

Oscar Liang also has a good concise explanation of different motor stator sizes here

This is an endurance quad I built years ago with the 5010 motors I mentioned. Just to give you an idea of the scale and the uses of a very wide motor.


Is it a good practice to use a throttle limit of 90% for racing builds? I had read somewhere that it's a good idea to set a throttle limit of 90% for racing.  The reason given was that, in the last 10% of the throttle, the cost/benefit ratio for power to thrust would not be worth it.  Is there any truth to this?  If so, what is the recommended throttle limit for any build/all builds?

The reason why this is recommended for racers is likely due to the fact that during these high-throttle punches, the voltage of the battery sags from the load and so more current is pulled from the battery to increase the motor RPM.

Power is equal to VI when V is voltage and I is current, which can be rewritten (by substitution of Ohm's law V = IR in for V) as I^2 * R. This means that if more current is drawn to compensate for a voltage sag, the power consumed by the motors increases by a greater amount because the resistance of the circuit is constant. (for all intents and purposes) For example, in the hypothetical scenareo that twice the current is drawn, four times the power would be consumed. This results in quicker battery drain.

The 10% figure that you've heard isn't a hard line, but rather just a suggestion based on experience with miniquad hardware and its capabilities. This recommendation isn't just specific to racing; all quads would benefit from the efficency (energy extraction from the battery) boost from rarely using the top XX% of the throttle range. However, this is often more important in racing scenareos where it is often necessary to make the most of the energy in the battery pack you're using because you've selected the smallest and lightest one possible and need as much energy as you can get to complete the course in record time.


Stick commands does not register I'm trying to follow this playlist to set up a drone with iNav, but when it comes to calibrating the compass, the stick command doesn't seem to work (the status light on the FC doesn't flash rapidly as described in the video). When trying some other stick commands it doesn't seem to register either.

All the endpoint are set to min 1000 and max 2000. Min_check and max_check are 1100 and 1900 respectively.

The FC is a Matek f405 std, and the radio is a Taranis qx7s, in case that matters.

I figured this out rather quickly when I tried to arm the quad and it said that the throttle was not low. It turned out that throttle and pitch was switched in iNav....
So after changing that, everything worked...


Can you charge 1s and 2s batteries at the same time with the tinyhawk 2 included charger? I just got a Tinyhawk 2. It came with 2 batteries (2s and 1s) and a battery charger that you plug in to USB.
I know that you can't parallel charge batteries with different cell count, but it looks like there is separate logic for each port on this charger.
Does anyone know if it is possible to charge both batteries at the same time? I could try it myself, but I don't like burning batteries.

According to this source, yes you can charge both 1s and 2s batteries at the same time. This is because, like you mentioned, there are separate charge controllers. You can also choose whether you want them to charge to 4.2v or 4.35v per cell.


How to pick parts for a quadcopter flying on Mars? So let's say I wish to build a quad to fly a GoPro around in Mars. How should I go about planning the build (target AUW [all-up weight], motor to motor distance, propulsion & power system, etc.)? I'm especially interested in how the planning process would differ from what we do currently on Earth?

TL;DR:

You wouldn't want to be responsible for the design of such a project. :) Between the environmental constraints (atmospheric pressure, temperature, etc.) and physical requirements (extreme radiation tolerance, etc.), this would be an incredibly difficult thing to make.

Believe it or not, there is actual flight hardware being prepared to do something just like this on Mars in the near future as a part of the NASA Mars 2020/Perseverance mission. The Mars Helicopter Ingenuity is a fully-autonomous helicopter that is planned to be used for aerial reconnaissance and surveying of the Perseverance rover's path. It's a truly insane piece of engineering:

Some fun facts about the craft: (sourced from the Wikipedia articles linked to above and the YouTube video linked to below)

1.8 kg total mass, including 273 g of batteries
Set of two counterrotating 1.20 m diameter propellers

Maximums at ~2400 RPM and rotor tip speeds < 0.7 mach

Max power consumption of 350 W
Each full flight is expected to be < 90 sec, at a max altitude of 5 m above the martian surface
Total battery capacity between 35-40 Wh
Uses a blanket of CO2 gas around the avionics and batteries as an insulation layer

Operating conditions: (again sourced from the Wikipedia articles linked to above and the YouTube video linked to below)

Ambient atmospheric pressure ~0.01 atmospheres (one-hundredth of the atmospheric pressure at sea level on Earth)
Gravitational force 38% as strong as on Earth
Weak solar energy, resulting in the charging process requiring an entire Mars day
Night-time temperatures at about -80 to -100 °C, resulting in ~ 2/3 of the battery's energy stores being used to keep the electronics and actuators from freezing through
Dramatically higher ambient radiation levels due to Mars' lack of a magnetic field and ionosphere to deflect the solar wind and electromagnetic emissions

The YouTube channel Veritasium has an excellent video discussing this project and the development of the helicopter design with the CalTech/JPL engineers who built the thing, which I think is well worth watching.


How to create a motor startup tone with a BLHeli ESC? I am using a 32bit DShot1200 ESC, how can I make a custom startup sound for when the drone is powered on?

First, remove your props, plug your quad into the computer and plug in a battery.

You then need to go into BLHeli Suite 32 and read your ESC setup.

You will then have options to sync ESC music and you can upload your tones.

A more detailed guide with lots of detail for each step can be found here: https://oscarliang.com/blheli-32-custom-startup-tone-music/


Motor output limiting Can you configure your motor output limit on betaflight or DJI goggles?

I know you can do it through the fatshark goggles, but I do not have parts to build a drone, so I am asking before I get 2700 RPM/V Kv motors for a 5 inch.

Formula:

LIMIT = desired Kv / real Kv * 100%

Example of the formula being used:

LIMIT = 1800 RPM/V / 2700 RPM/V * 100% = 67%

I don't think that you can edit the throttle limit directly in the goggles, but you can change rateprofile in the betaflight OSD.

So what you can do is to set up a few different (up to six) rateprofiles in betaflight, and then change between those in the OSD. It won't be as granular as changing the limit directly, but it should be enough if you just want to change between a few different values.

To make it even faster to switch between the different limits, you can even assign a switch to do it.

Here is a guide on how it is done.


Modeling heat build-up in air-cooled outrunners I'm creating a thermal model for heat build-up in my outrunner motors. So far, I haven't found any online resources that discuss this. Here is the basic equations for forced convective transfer:

Q = h * A * delT, where Q is the heat transferred, A is the exposed area, delT is the temperature differential, and h is the heat transfer coefficient.

For forced air, h ranges from 1 to 1000, so it's easy to see why the devil is in this detail. A three-order of magnitude difference in cooling efficiency is huge, to put it mildly. Typical published values for forced convection are in the 10-100 range, but those seem ludicrously low for the amount of heat that a typical multirotor motor needs to shed.[*]

There are ways to calculate h from Reynolds and Prandtl relations, but without extensive modeling those are exceedingly hard to get in the turbulent flow regime around a spinning motor.

Although this particular application is a fixed-wing with a cowled motor, the basics still apply and only the airstream speed and volume changes.

Can anyone shed any insight?

[*] If you have a 100W motor that's 80% efficient, that's 20W of heat energy. To put things in perspective, it's like a 20W incandescent bulb, only much smaller. So if the heat weren't being dumped very quickly into the airstream, the motor would get excruciatingly hot. Ergo, we can conclude from all available evidence that the cooling coefficient is quite high.

My experience is that motor cooling does change enormously depending on how they are installed, but not three orders of magnitude.

My Funfighter motor initially got hot enough that a drop of water would sizzle off the outside, yet when flown without the cowl it could be merely warm at the end of a flight. Similarly I have a helicopter where the standard motor was too hot to touch at the end of a flight but a replacement with a built-in fan stayed cool. I've also noticed that you can put 100W through a 2204 sized motor on a pylon racer but not on a 3D model that prop-hangs a lot.

It's also worth considering that our flights are fairly short. Using a heat capacity of 0.4 J/g-C as an average of copper and iron, a 50g, 100W, 80% efficient motor would heat up 20*0.4/50 = 0.16 degrees C per second, or 10 degrees per minute. Even with no cooling, that would only raise the motor from cold to warm in a 3-4 minute flight. It's not "excruciatingly hot" because it has so much more mass than a light bulb and takes longer to heat up.

I guess this variability is bad news for anyone trying to estimate how much cooling their motor will experience, but it's good news for your average modeller who can just improve the airflow over an over-heating motor to fix the problem.

FWIW my rule of thumb for fixed wings is 50W for a 2204 motor, 100W for a 2208, 150 for a 2212 (based on the stator size, not HobbyKing's overall size numbers).

For quads, the peak power can be a lot higher because you only use it for short periods but the average power over the whole flight should be similar. 4s1500mAh battery over 5 minutes is 200W, or 50W per motor - just right for 2204 motors.


Help with finding a motor to rotate the plane of a propeller I don't really know if this is related to this community but it's for a drone so it's worth a shot.
I'm looking for some sort of motorized hinge or a motor that can move a propeller on the Y-Axis, a gif will be below on how it might move a propeller. (Pretend The Torus Is A Propeller)

I think what you are looking for is a servo. At least, that's what it's called in the hobby, officially it's a servomotor. Each unit consists of a motor, gears, a sensor to measure the position of the output shaft, and a comparator circuit. The electronics compares the requested angle to the actual angle, and drives the motor as required to minimise the difference.

They're commonly used to control the steering for RC cars and boats, or the control surfaces in RC planes. They are specified by their movement speed and torque. Better servos have ball bearings on output shaft, and you can get metal gears for tough applications.
You might want to look at the servos used for retractable landing gear on RC planes. These servos only have two positions, and are generally geared a bit lower for extra torque.
Servos generally run at 4-6v and are controlled by a pulse width modulated signal from an RC receiver. Alternately you can buy a 'servo tester' for about $5 to generate this signal, or it's easy to generate from an Arduino.