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Leaving transponders on ALT while on the ground

The FAA has just issued thislocal copy – presumably because they are having increasing problems with transponders off, or ON but not reporting altitude.

I wonder how many people turn off their transponder, or have it going automatically to GND mode? Mine switches to GND mode automatically, but I think it still reports the Mode C altitude then.

Administrator
Shoreham EGKA, United Kingdom

When I did my CPL/IR 2 years ago we were taught to switch to “alt” before entering the active rwy and to check that “gnd” is active when vacating the rwy.

LOAN Wiener Neustadt Ost, Austria

I think it depends on the type of transponder. A mode S transponder will squitter the “I am in the neighborhood” and will respond to inquiries specifically addressed to the unit for both location and altitude. The mode A/C transponders need to be in ALT mode. In the US, transponders are now requested to be kept on for ground operations, particularly at the major airports with ADSE-X systems that use multilateration so you can be located while in the movement area and on the runways.

KUZA, United States

Helpful info for me – thanks. I’ll start switching on Mode C at the hangar.

Up until now, like everybody else I’ve switched to Mode C before entering the runway, i.e. ‘Lights, Camera, Action’

In the #2 plane I’ll still use my ‘waivered negative transponder’ mantra after accepting TO clearance in the runup area. That works fine too when applicable.

Last Edited by Silvaire at 12 Jun 17:01

I never switch my transponder off other than by using the battery master. Haven’t done so for the last 20 or 30 years.

KUZA, United States

That, ‘local copy’ would suggest that it is all a buggers muddle. Now, interestingly, the manual that was made for my aircraft by the last owner, states, check transponder in grd mode, and on runways switch to alt.

I have always stuck it into ALT, pre taxi. And on receipt of a squack. On landing, I taxi without touching it, set to 7000 as a check item on shut down, then switch it off.

No one has ever complained…

Fly safe. I want this thing to land l...
EGPF Glasgow

I think at big places they want it on from push back to on stand for the surface movement radar feeds, however TCAS should only go (to TA/RA) on for line up and then off on taxi back in otherwise it can cause problems I understand.

Now retired from forums best wishes

I think at big places they want it on from push back to on stand for the surface movement radar feeds, however TCAS should only go (to TA/RA) on for line up and then off on taxi back in otherwise it can cause problems I understand.

Yes, but TCAS is still the keyword. If all keep their transponders on on the ground, everybody with TCAS wil get weird alarms on short final and also just after liftoff. No?

Mainz (EDFZ) & Egelsbach (EDFE), Germany

No?

No. TCAS is smart enough not to issue warnings about aircraft on the ground.

We leave our transponders on all the time. Not in ground or standby or even ALT mode, but TA/RA (which is ALT + TCAS). If some airport doesn’t like that, they will say “Callsign 421, Stop squawking”. That has happened to me once in the last seven years…

EDDS - Stuttgart

Most G1000 transponder implementations have an automatic ground switch. Then what?

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