Do regulations permit an airliner be equipped with a radio transmitter which cannot be controlled by the crew? [duplicate]

Question

This question already has an answer here:

• Why do pilots have the ability to turn off the transponder in-flight? 3 answers

In response to the case of MH370, an idea which has been floated is that of a device to transmit an aircraft's GPS position. Not specified is whether such a device would be operable by the flight crew.

Among the scenarios suggested to account for the aircraft "going dark" and its apparent flight path is intentional action by someone aboard.

To provide aircraft position (or any other parameter) reporting free of any possible interference by anyone aboard the aircraft would require installation of equipment inoperable by and therefore in a location inaccessible to anyone (crew included) during flight. That means such equipment could never be powered down while the aircraft is in flight.

Have there been/are there currently any regulations which would prohibit the installation of such a device for any reason - e.g. fire safety, possible interference with other radio equipment essential to safe flight (navigation, communication)?

Answer 1

All equipment on board needs to be interruptable, either by direct control input (turning it off) or via circuit breaker. This especially holds true for equipment that is capable of broadcasting or emitting radio waves, such as radio telephony equipment or the transponder.

If the transponder for any reason became damaged and started to send incorrect replies to ground interrogation, it needs to be shut off in order to not confuse ATC systems or other aircraft's TCAS. Electronic or electric systems also need to be shut down in case of eletrical fires or other safety hazards to the aircraft.

Answer 2

To my knowledge, there hasn't been any regulations, but airlines are still using the manual transponder because of the current SOPs.

It is part of all airlines' SOP to toggle the transponder to STBY while at the gate and departing. One of the reasons is to reduce the amount of radio waves present. Other reasons include the display of departing aircrafts while at the gate. Usually, it would be switched to TA/RA during the Before Takeoff Checklist (Airline SOPs vary. I don't speak for all).

So to answer your question, there's no regulations that I know of, so it's more of the airlines' choice. When I had a conversation with a long haul pilot, he mentioned that a couple of times the transponder would be left on TA/RA while at the gate, which means yes, it's do-able, but will airlines adapt to it, probably not at the moment. In the future, perhaps.

Hope that answers your question, or at least helped a bit.