Changing transponder code
Avoid imitations
Join Date: Nov 2000
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......but you'll never get it to change a transponder setting. 
Join Date: Sep 2006
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Can anyone explain what is wrong with selecting 6 (or something other than 7) on the first digit then the rest of the code followed by the correct first digit? Rather than all this mumbo jumbo SBY or not krap.
Edit: Anyway I don't have one at all so what do I care
Edit: Anyway I don't have one at all so what do I care
Join Date: May 2008
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Can anyone explain what is wrong with selecting 6 (or something other than 7) on the first digit then the rest of the code followed by the correct first digit? Rather than all this mumbo jumbo SBY or not krap.
Some people in earlier posts have made the case that you could go through a code which has already been issued to another aircraft, and cause issues in the radar system. This may be valid, but new radar displays are fed from several sources and geared up for mode S so this may eliminate the problem.
The other case is that very old transponders can do "unpredictable things" when you fiddle with the numbers while the unit is on transmit. No real example or evidence has been made for this, so I think it's one of those myths you hear around the flying club on a wet day.
I will continue to leave mine on ALT and teach students to do so, however of the 12 aircraft I fly, only 3 have the old clunky tranx, most have upgraded to the nice easy punch the number in ones where the code isn't changed until you put in all 4 digits.
On that note, it does make changing from 7000 to an emergency code a bit more of a handful if you had a genuine emergency going on, no longer just a quick twist of one knob.
Join Date: Feb 2003
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I did once select 7700 instead of 7000 during an IMCR renewal test. It produced a remarkably relaxed comment from ATC (Farnborough, I think, or possibly Lyneham) along the lines of 'G-XXXX, you appear to be squawking emergency...' Cue frantic apology from yours truly and laughter from the examiner (just as well he had a sense of humour as I'm sure he could have failed me for that!)
One of A and C's aircraft, with a rather basic transponder. The rather nicer one I usually fly has a single button marked 'VFR' which does the trick nicely.
Tim
One of A and C's aircraft, with a rather basic transponder. The rather nicer one I usually fly has a single button marked 'VFR' which does the trick nicely.
Tim
