question: Why do planes require devices to be in "airplane mode" durring takeoff and landing?
comment: Straightforward: none. It's hard to imagine that every single passenger always puts their device into airplane mode. There's probably a ton of people who forget, don't care or are asleep. The myth is that these devices can cause the navigation systems or communications to malfunction. In reality none of that is hardly possible. The power output of mobile devices is way too weak to cause any disturbance, besides that the cabin of modern airplanes is very well shielded, and so are all of the systems on-board. The real reason behind putting your devices into airplane mode, or generally not being "allowed" to use them, is for security reasons. The airlines want you to pay attention to the safety instructions. And since take-off and landing is the phase in which most accidents happen, it's always good when the passengers aren't occupied holding their mobile devices in their hands. Either way, a phone that's not in airplane mode will for sure not cause an accident.
passages: BULLET::::- China: Prior to September 2017, all cell phones, even with Airplane mode, were never allowed to be used during the flight although other devices can be used while in cruising altitude. On September 18, 2017, the Civil Aviation Authority of China relaxed these rules and allowed all Chinese air carriers to allow the use of Portable Electronic Devices (PEDs) for the entire flight as long as they're in Aeroplane Mode.
   Section::::Possible future applications of concept.
  
  Section::::Possible future applications of concept.:Five-fold increase in airplane safety since 1980s, but flight systems sometimes switch to unexpected "modes" on their own.
   In a revised review in October 2013, the United States Federal Aviation Administration (FAA) made a recommendation on the use of electronic devices in "airplane mode"—cellular telephony is disabled, while Wi-Fi may be used if the carrier offers it. Short-range transmission such as Bluetooth is always permissible. The statement cites the common practice of aircraft operators whose aircraft can tolerate use of these personal electronic devices, but use may still be prohibited on some models of aircraft.
   When the "Aeroplane mode" is activated, it disables all voice, text, telephone, and other signal-transmitting technologies such as Wi-Fi and Bluetooth. Wi-Fi and Bluetooth can be enabled separately even while the device is in airplane mode; this is acceptable on some aircraft. Receiving radio-frequency signals, as by radio receivers and satellite navigation services, is not inhibited. However, even receiving telephone calls and messages without responding would require the phone to transmit.
   ALT2 mode is entered when 2 engines flame out (on dual engine aircraft), faults in two inertial or air-data references, with the autopilot being lost, except with an ADR disagreement. This mode may also be entered with an all spoilers fault, certain ailerons fault, or pedal transducers fault.
  
  Section::::Flight control laws (Airbus).:Direct law.
   The Federal Aviation Administration (FAA) of the United States has adopted the RTCA/DO-178C, titled "Software Considerations in Airborne Systems and Equipment Certification", as the certification standard for aviation software. Any safety-critical component in a digital fly-by-wire system including applications of the laws of aeronautics and computer operating systems will need to be certified to DO-178C Level A or B, depending on the class of aircraft, which is applicable for preventing potential catastrophic failures.
   Section::::Regulations on use.:United States of America.:Federal Communications Commission.
   Because of, among other things, electromagnetic waves emitted by this type of device, the use of any type of electronic device during the take-off and landing phases was totally prohibited on board commercial flights. On 13 November 2013, the European Aviation Safety Agency (EASA) announced that the use of mobile terminals could be authorized on the flights of European airlines during these phases from 2014 onwards, on the condition that the cellular functions are deactivated ("airplane" mode activated). EASA then formally confirmed this information on December 11, 2013. Tablets, e-readers, smartphones, MP3 players, and portable gaming consoles are affected by these announcements.
   Section::::Regulations on use.:United States of America.:Federal Aviation Administration.
   The flight mode of "normal law" provides five types of protection: pitch attitude, load factor limitations, high speed, high-AOA and bank angle. "Flight mode" is operational from take-off, until shortly before the aircraft lands, around 100 feet above ground level. It can be lost prematurely as a result of pilot commands or system failures. Loss of "normal law" as a result of a system failure results in "alternate law 1" or "2".
   Airplane mode
  
  Airplane mode, Aeroplane mode, Flight mode, Offline mode, or Standalone mode is a setting available on smartphones and other portable computers that, when activated, suspends radio-frequency signal transmission by the device, thereby disabling Bluetooth, telephony, and Wi-Fi. GPS may or may not be disabled, because it does not involve transmitting radio waves.
  
  The name comes from the prohibition by most of the airlines of using equipment transmitting radio-frequency signal while in flight; using airplane mode prevents devices from transmitting.
   BULLET::::- some airlines may require passengers to also turn off all devices during taxi, take-off, and landing (such as Kenya Airways and Malaysia Airlines) in addition to having these devices set to airplane mode
  
  BULLET::::- if present, most airlines may also require passengers to unplug these devices from charging ports during these times
  
  BULLET::::- some newer aircraft have separate “please turn off electronic devices” signs in place of the now unnecessary “no smoking” signs (as smoking is never allowed anyway) and that electronics should be completely shut off and put away when these signs are illuminated
   Until late 2013, use of an e-reader was not allowed on airplanes during takeoff and landing. In November 2013, the FAA allowed use of e-readers on airplanes at all times if it is set to be in Airplane Mode, which turns all radios off. European authorities employed this guidance the following month.
  
  Section::::E-reader applications.
   BULLET::::- The U.S. Federal Aviation Administration (FAA) announces that airline passengers will be allowed to use their personal electronic devices during all phases of flight, ending the years-long prohibition of their use during takeoff and landing, although a Federal Communications Commission ban on the use of cellphones to make calls or send texts or data in flight is to remain in force. The FAA states that pilots may still require personal electronic devices to be turned off under certain conditions, but that it expects airlines to implement new procedures to accommodate the gate-to-gate use of such devices by the end of 2013.
   Section::::Regulations on use.:United States of America.:State and Local Governments.
   During the transition from take-off to cruise there is a 5-second transition, from descent to flare there is a two-second transition, and from flare to ground there is another 2 second transition in "normal law".
  
  Section::::Flight control laws (Airbus).:Normal law.:Ground mode.
   The use of certain electronic equipment is partially or entirely prohibited as it might interfere with aircraft operation, such as causing compass deviations. Use of some types of personal electronic devices is prohibited when an aircraft is below , taking off, or landing. Use of a mobile phone is prohibited on most flights because in-flight usage creates problems with ground-based cells.
  
  Section::::Aviation safety hazards.:Ground damage.
   The FAA in 14 C.F.R § 91.21 prohibits the use of portable electronic devices, including mobile phones, for all commercial flights and for those private flights being made under instrument flight rules (IFR). It does allow that the airline (or, for privately operated aircraft, the pilot) can make an exception to this rule if the operator deems that device safe. This effectively gives the airline, or the private pilot, the final word as to what devices may safely be used aboard an aircraft as far as the FAA is concerned although the FCC restriction still applies.
   BULLET::::- ATC can be automatically informed about resolution advisories issued by TCAS only when the aircraft is within an area covered by a Mode S, or an ADS-B monitoring network. In other cases controllers may be unaware of TCAS-based resolution advisories or even issue conflicting instructions (unless ATC is explicitly informed by cockpit crew members about an issued RA during a high-workload situation), which may be a source of confusion for the affected crews while additionally also increasing pilot work load. In May 2009, Luxembourg, Hungary and the Czech Republic show downlinked RAs to controllers.
   BULLET::::- If MCAS is activated in non-normal conditions, it will only "provide one input for each elevated AOA event."
  
  BULLET::::- Flight crew pulling back on the column will be able to counteract MCAS.
  
  Boeing stated "...MAX production aircraft will have an activated and operable AOA Disagree alert and an optional angle of attack indicator. All customers with previously delivered MAX airplanes will have the ability to activate the AOA Disagree alert."
  
  Section::::Corrective work.:Autopilot disengagement.
   Section::::Approaches of free flight.:Ground.
  
  All of the data are sent to ATC and pilot requests a particular flight path. Communication will be from aircraft to ATC instead of aircraft to aircraft.
  
  In this approach the aircrew will not have the full situational awareness experience in the airborne approach. Aircrew will not be able to handle uncertainties or help out with the uncertainties in this approach. If one aircraft does not follow the directive ATC issues, the directive will have to be reissued and in turn increase the workload of ATM operators.
  
  Section::::Approaches of free flight.:Mixed focus.
   There are four reconfiguration modes for the Airbus fly-by-wire aircraft: "alternate law 1", "alternate law 2", "direct law" and "mechanical law". The ground mode and flare modes for "alternate law" are identical to those modes for "normal law".
  
  Alternate law 1 (ALT1) mode combines a "normal law" lateral mode with the load factor, bank angle protections retained. High angle of attack protection may be lost and low energy (level flight stall) protection is lost. High speed and high angle of attack protections enter alternative law mode.
   Flight control modes
  
  Aircraft with fly-by-wire flight controls usually have automatic flight control modes, in which flight control laws determine the functional transformation of input signals, read from sensors and other sources, to output signals, feeding actuators and other destinations; they are an application of modes in user interfaces. Their purpose is to modify the way in which human control inputs are translated to the flight control surfaces, and ultimately its path of movement, in a way appropriate to different situations or flight regimes.
   The aircraft behaves as in direct mode: the autotrim feature is turned off and there is a direct response of the elevators to the sidestick inputs. The horizontal stabilizer is set to 4° up but manual settings (e.g. for center of gravity) override this setting. After the wheels leave the ground, a 5-second transition occurs where "normal law – flight mode" takes over from "ground mode".
  
  Section::::Flight control laws (Airbus).:Normal law.:Flight mode.
   BULLET::::- Mode confusion was part of the events that led to the loss of Air France Flight 447 in 2009, and the loss of life of 228 people. The pilots reacted to a loss of altitude by pulling on the stick, which would have been an appropriate reaction with the autopilot fully enabled, which would then have put the aircraft in a climbing configuration. However, the airplane's systems had entered a mode of lesser automation ("direct law" in Airbus terms) due to a blocked airspeed sensor, allowing the pilots to put the plane in a nose-high stall configuration, from which they did not recover.
  