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A standard means of informing Air Traffic Control of an emergency situation is to enter the code 7700 into the radar transponder. However, in a situation where the radios are busy and the crew is fully engaged in dealing with the emergency, manually entering digits in a control head, (especially in turbulent conditions) seems fraught with the potential to make a mistake, or distract from other important tasks.

The aircraft I flew in the Navy had a rotary switch with an "EMER" position that would immediately broadcast a 7700 code when selected. Do large modern airliners or business jets have a similar feature for convenience?

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    $\begingroup$ I flew B757's and B737's in the 1990's and early 2000's and we did not have an "emergency" setting/position on our transponders. Perhaps newer generation Boeing or Airbus aircraft have transponders with an "emergency" position. $\endgroup$
    – 757toga
    Mar 31 at 21:41
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    $\begingroup$ @757toga, same years I flew the 1970s era Prowler... I guess the Navy is that much more advanced! ;) $\endgroup$
    – Michael Hall
    Mar 31 at 21:44
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    $\begingroup$ Or, the Navy had many more emergencies! $\endgroup$
    – 757toga
    Mar 31 at 21:47
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    $\begingroup$ We used to joke that squawking EMER was part of the Tomcat climb checklist. $\endgroup$
    – Michael Hall
    Mar 31 at 21:50
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    $\begingroup$ @AdityaGuhaRoy your answer is interesting. Do you have a reference that confirms the airplanes noted in your comment have a transponder switch position that when selected automatically broadcasts a 7700 code? $\endgroup$
    – 757toga
    Apr 2 at 14:45

2 Answers 2

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In the 737, it's just the 4 dials (well, 2 sets of concentric knobs). Since we're basically always talking to ATC, the need to squawk 7700 is quite rare; all the emergencies I've declared have been done over the radio. At that point, they tag your target as being an emergency, and you get all the special handling you need.

If you had a case where you couldn't reach somebody on the radio (or break in to a crowded frequency), then 7700 becomes more important, and of course it's pretty easy to dial in. But for as rarely as it would be used, I could see a push-button to immediately squawk emergency as creating more false alarms than times it's validly used. One difference between airline and GA avionics, our transponder is on the center console, roughly in a flat horizontal orientation, so a push-button can be inadvertently activated with a straight-down motion. In GA with panel avionics, the face of the transponder is vertical, so possibly fewer opportunities for an unintended press.

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    $\begingroup$ How many emergencies have you declared? $\endgroup$
    – Anonymous Physicist
    Apr 1 at 14:59
  • $\begingroup$ Yeah, I wouldn’t recommend a push button where it sits now. $\endgroup$
    – Michael Hall
    Apr 1 at 15:35
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    $\begingroup$ @AnonymousPhysicist In the 737, probably a dozen or more, mostly for a medical issue with a passenger. In prior (Air Force) days, probably about that many. I've been pretty fortunate, flying well-maintained airplanes that rarely have serious issues; I know some people get those sorts of numbers in a year or two. $\endgroup$
    – Ralph J ♦
    Apr 1 at 16:02
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It's been a few years, but in the 9 years or so I developed Comm/Nav/Surv equipment for the air transport market I never saw any quick select buttons. If you wanted a code, you had to dial it in.

I can't imagine that it has changed as Boeing, Airbus, and the airlines really hate to make any change that would require a flight manual update and create a training requirement.

For a short while after 9/11, there was an industry study going on about a secure method to send/lock in the hijack code (the hijackers had turned off the transponders). When it was all done, the answer was to secure the cockpit doors.

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