4
$\begingroup$

Following high-profile cases of disappearances such as MH370, as well as the lower-profile but no doubt common radar infringement and level / airspace busts that we don’t hear about often, is there a reason that commercial aircraft do not have a dead man’s switch?

Although I have no personal experience in aviation, this would have seemed a very simple way to answer the question of “was it pilot incapacitation?” Either it was, in which case the dead man’s switch triggers some sort of alert to ATC / on the FDR, or it was a case of outside interference in which case either they a) fake incapacitation by triggering a dead-man’s alert, which the scrambling of jets would soon disprove or b) they don’t trigger a dead-man’s, and so at least pilot incapacitation is ruled out in the subsequent investigation.

Of course there is the question of how a dead man’s switch could be implemented, however given the number of SOPs already taught, this hardly seems a limiting factor.

$\endgroup$
12
  • 7
    $\begingroup$ On a train, a released dead-man switch brings the train to a stop, since that's presumably safer than letting it run out-of-control at high speed. What sort of safer alternative do you think exists for a flying aircraft? "Just stop here, where-ever we are" clearly isn't it! $\endgroup$
    – Ralph J
    Sep 22, 2020 at 22:47
  • $\begingroup$ Welcome to aviation.SE! Any system would have to be more reliable, flexible and cost-effective than the second pilot, who's already sitting there. If an incident incapacitates both pilots simultaneously then it's probably something catastrophic (or deliberate) and an automated system might not help. For single-pilot aircraft Garmin has a system that monitors the pilot and can initiate an autoland but it's expensive and requires an autothrottle, which many smaller aircraft don't have. $\endgroup$
    – Pondlife
    Sep 22, 2020 at 23:01
  • 1
    $\begingroup$ The OP is proposing a dead-man's switch that sends a radio or satellite message, not one that autolands the plane. $\endgroup$
    – rclocher3
    Sep 23, 2020 at 0:59
  • 1
    $\begingroup$ @Harvey - Plus, the radioed position report provides confirmation that the pilot is alert, responsive, and functional. A simple push of a button would only confirm that the pilot is alive. Even if it were a specific code the pilot must enter. YouTube videos of ATC communications with pilots suffering from hypoxia. A pilot might be able to operate an autopilot or a coded deadman’s switch through rote or muscle memory while not being usefully conscious. $\endgroup$
    – Dean F.
    Sep 24, 2020 at 19:05
  • 1
    $\begingroup$ @Harvey I’ve ridden in a modern train cab; the alerter only goes off after X seconds with no control inputs, and if they still don’t do something (like press the reset button) within another X seconds, it dumps the brakes. This system was developed after a few crashes where it was discovered drivers were just putting a brick on the older spring style deadman switches to prevent false positives. $\endgroup$
    – StephenS
    Sep 25, 2020 at 21:31

1 Answer 1

7
$\begingroup$

Very intriguing question. I do wonder what it actually solves, though. Does it only solve the mystery of whether the very rare instance of incapacitation of the flight crew occurred? The Cockpit Voice Recorder does that if it is recovered. In the rare event that the CVR is unrecoverable, the dead man’s switch would only answer if pilot input occurred prior to a crash. How would it save lives? The pilot should already be in periodic verbal communication with Air Traffic Control.

On the other hand, a global monitoring system of the aircraft would make more sense. Each commercial aircraft already has transponders. In the US, each aircraft has ADS-b. This gives a nearly real-time position of each aircraft that can be tracked and archived. This would give searchers a better idea of where to search for survivors. Incorporating a 406 MHz PLB-style beacon into the Flight Data Recorder and the CVR would be even more advantageous in solving the mystery of what happened. Even an automated system that alerts ATC of when contact is lost with the transponder or ADS-b, or when the CVR or FDR 406 beacons were activated, or when the aircraft deviated too far off its filed flight plan, would be better than a dead man’s switch.

After all, in today’s era of modern telemetry and aviation security, would scrambling fighters be of any benefit to the passengers and crew on board while the aircraft is in flight? They would have no way of intervening to prevent a crash.

It’s only benefit would be to alert ATC of a terrorist highjacking in the event that the target were close to the airport. And, the overtaking of the cockpit happened in the last phases of flight. Now, the security of modern cockpits and heightened alertness makes the notification of ATC of a more likely.

$\endgroup$
4
  • $\begingroup$ Great answer, and I couldn't agree more that tracking of the FDR and CVR would be the best solution. I wasn't aware of all these other measures that could be / are already in place to keep tabs on aircraft. Still, for a sector so fond of redundancy, and of leaving nothing to chance, it does still shock me that a more robust solution other than "contact ATC, and if you don't you're probably dead anyway" does not yet exist. $\endgroup$
    – Harvey
    Sep 23, 2020 at 8:02
  • 2
    $\begingroup$ @Harvey - That brings us back to my original question. What would this solve? How does a deadman’s switch make aviation safer? If it does not make things safer, it is not a redundancy measure. A Cockpit Video Recorder would be a redundant system to the FDR & CVR. A deadman’s switch would only make sense if remote control of the plane were implemented as well. Also, aircraft flying IFR have mandatory reporting points and procedures. Especially in areas where radar coverage is sparse. Contact with ATC should be fairly regular and constant. $\endgroup$
    – Dean F.
    Sep 23, 2020 at 12:19
  • 1
    $\begingroup$ @Harvey - The system to which the mandatory reporting points is redundant is the fact that it is a requirement of all aircraft flying IFR in all airspace (this includes all commercial airliners flown by scheduled carriers), all aircraft flying VFR in 4 of the 6 types of airspaces, and all aircraft flying within 4 miles of an airfield with operating ATC at or below 2500 feet AGL to establish and maintain two-way communication with ATC. If 2-way communication can not be established and maintained, specific Lost-Comms procedures must be followed. $\endgroup$
    – Dean F.
    Sep 23, 2020 at 13:49
  • $\begingroup$ Seems that a tear-away floating PLB for water 'landings' would be a better plan. If a general vicinity is signaled, the chance of finding the FDR and CVR before they stop pinging become much greater. Non-water 'landings' are easier to find. $\endgroup$
    – Jon Custer
    Sep 24, 2020 at 16:36

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .