What are the advantages of squawking 7700?

  • I was reading this question about how do pilots send distress signals in emergency scenarios, and that got me thinking...

    In voretaq7's answer, he states that there are three ways to send distress signals, one of them is by the aircraft's transponder

    Three transponder codes are reserved for unusual/emergency situations:
    - 7700 for general emergencies.
    - 7600 for loss of communication (radio failure).
    - 7500 for hijacking or other unlawful interference.

    I can understand the reason to squawk both 7500 and 7600 in the appropriate situation, but I'm failing to understand why squawk 7700 in an emergency scenario.

    So that's what I'm thinking:

    • In case of a hijack, the ability to squawk 7500 to silent alert the ATC of the situation, without the hijacker knowing, is an advantage.

    • In case of a radio failure, where you can't alert the ATC over the radio, the ability to squawk 7600 and make them aware of your situation, is an advantage.

    • In case of emergency, where the pilots are trying to handle a lot of things (high workload scenario), to stop everything to configure the aircraft's transponder, when they are communicating with the ATC by radio, doesn't seem like a good thing to do.

    So, finally, here are my questions:

    • Is it common for pilots to squawk 7700 in emergency scenarios?
    • What are the advantages, for the pilots, to squawk 7700 in emergencies situations?

    changing to 7700 is probably just a single button press.

    There are a few examples in aviation where an aircraft has been in trouble, but due to language barriers has failed to correctly make the seriousness of this situation known to air traffic control. Look up Avianca Flight 52 as an example. They were low on fuel, and eventually crashed due to fuel starvation, with ATC not being aware how bad their situation was. Squawking 7700 would have saved lives in this case.

    Even if you are in communication with ATC and they request you to squawk 7700, which they most likely will, you fly the aircraft first. If I was really busy, I would probably just respond 'Standby'. If I was super busy and I am about to die if I don't get this right, I wouldn't even respond. Only when I have sorted myself out, will I then think about changing the squawk. To be frank, I wouldn't even bother replying back to ATC following the standby since they will know quicker than I can call them. Aviate, navigate, communicate. People have died because the pilot didn't do those things.

    Isn't it bad that everyone (including possible hijacker) knows squawking 7500 means a hijacker is on board? In this case the silent-signal isn't so silent.

    Very good answers, all. I am a Private Pilot and I agree with most of the answers here. If I have passengers on my flight, I tell the right-seater that in case of an emergency where I am incapacitated, he/she should input 7700 on the transponder and send out a distress call to a nearby ATC facility (which I also write down for them). The single engine planes I fly are very stable and if the pilot is incapacitated, a non-pilot can easily keep it flying until help "arrives" if necessary.

  • Simon

    Simon Correct answer

    5 years ago

    If you make a radio call, unless you are on 121.5 (or 243 military), then only the station you are talking to will initially know about the emergency. Initial calls should always be with the unit you are working with unless you are VFR.

    If you squawk 7700, then all stations in transponder range, including possible airborne stations such as AWACS and SAR will know right away that you are in trouble, with position, altitude and possibly aircraft type and flight number.

    If VFR, you might not be talking to anyone and may not have the frequencies of nearby units easily to hand.

    Squawking 7700 is definitely a good thing.

    You mentioned being busy. The mantra drilled into everyone is "aviate, navigate, communicate". In most circumstances, fly the plane, fly it where you want it to go, then tell someone about it. Squawking 7700 will be one of the last actions carried out.

    Nice informed answer. I think that is exactly what these transponders are designed to do; to provide that 'extra' link. A code, with no possibility of verbal garbling. A Wide Area distress, with no need to try to initiate comms, possibly in eighteen different languages to dozens of busy people, who mostly don't expect, and won't be able to quickly understand why you are calling them out of the blue, haha. No seriously.

    Thanks for your answer. If I squawk 7700, will it change how other nearby planes' instruments display me(radar, tcas, etc)?

    @GabrielBrito On "normal" aircraft, no. They have no equipment to interrogate other transponders apart from TCAS and AFAIK, regualr TCAS does not have any special symbology for displaying an aircraft squawking an urgency code. AWACS, SAR etc will but I don't know details.

    @Simon: What about ADS-B In/TIS–B displays? Unlike TCAS which is rigid and limited in its display, I am under the impression that there is basically no standardization of ADS-B/TIS-B displays. Therefore it is reasonably likely that some will choose to flag emergency aircraft to help VFR craft remain well clear. Sure, very few aircraft have them at the moment, but I suspect adoption will be reasonably rapid in glass cockpits since only a UAT or 1090ES transponder and a firmware upgrade are likely to be needed.

    Interconnection of ATC systems is making your first point moot; ATCs especially at larger airports can flag an aircraft as under an emergency, and every other screen within radar range would know in seconds.

    @Simon Are pilots expected to squawk 7700 when they are getting flight following or flying instrument under ATC control? I remember reading somewhere if you have an assigned squawk already, you're not expected to change it to 7700 unless specifically advised by ATC to do so

    @lemonincider Reasoning purely logically, not about regulations, that would require that ATC be made aware of your emergency, which may be difficult in some situations. Of course ATC can request that an aircraft squawk 7700, and normally you'd be expected to keep using your assigned code, but if using one of the urgency codes is called for then getting ATC approval seems like an unnecessary step. Just imagine if you needed ATC approval to squawk 7600! Consequently, it *makes sense* that squawking 7700 falls under pilot authority. Of course, expect an interview once safely on the ground.

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Content dated before 6/26/2020 9:53 AM