Please don’t misuse it…
When learning to fly I was taught a mnemonic (one of many learnt during training), which helps me to remember the three very important transponder squawks which are used in varying emergencies:
75 – taken alive, 76 – in a fix, 77 – going to heaven.
This is to describe the following squawks and their uses.
- 7500 – Unlawful Interference – Hijacking normally.
- 7600 – Communication Failure – Radio Inoperative.
- 7700 – Other Emergency – Normally a May Day, where an aircraft or person aboard is in grave or imminent danger.
The main thing they do is alert any radar operator to your peril – and they generally do this by highlighting the aircraft in a very prominent colour on the display of the radar operator. The operator can then use this information to assist the flight much better, and if you have a Mode S transponder they will also have other information about the flight as well.
Of course we all hope we never have to use any of the emergency squawks, but we all use routine codes every day and will often have to change between them in flight, as we are assigned new codes by new ATC units.
A post in this months GASIL reminds us that as pilots we have to be careful how we set these squawks… particularly near or around 7500. Older transponders (in much of the GA fleet) are set by rotating a series of dials, whereas newer transponders are set with buttons and the code typed in.
The danger is that when changing squawk on an old style transponder you may scroll the dials through one of the emergency combinations. 7600 and 7700 can be resolved quite quickly by confirming with Air Traffic Control that no emergency exists… however they are unlikely to believe that having squawked 7500 (even fleetingly) no hijack situation exists, no matter how much you plead.
Fighter Jet Anyone?
The point made in this months GASIL, which I am emphasising is that you must select standby when changing transponder codes on older style units.
Change the unit to standby, change the code, then put turn transponder back to On (Or Alt if available).
If you do not then in the current climate, and especially in 2012 with the Olympics in town, you can fully expect to be intercepted by an RAF Typhoon from the Quick Reaction Force. This may take some explaining away…
… but if you do get it wrong you can find the Interception Procedures here!