A320/A321 Transponders
 

A quick question for you Airbus drivers.
On the night of RVSM I asked the 2 British Midland mail flights in/out of EGPH to squak mode A only to check some radar processing facilities, and neither seemed to be able to do so, saying that the transponder is either "off" "standby" or "on" with no apparent facility to supress the mode C.
So what happens if your mode C is corrupt and ATC ask you to switch it off, some frantic pulling of circuit breakers or a simple case of " c'est la vie " ?

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FATCO

Looking in FCOM 1, it says there are 2 different types of transponder fit for the 320/321. Both have a facility to switch off mode C, whether you have the twiddly-knob one, or the more hi-tech button pressing version!! So there is a way of doing it - and no disrespect to the chaps/chapesses involved - they must have been unable to see it.
Having said that - from what I remember from flying school, I think all Mode C capable transponders have to have an "Alt Reporting Off" switch - just in case the Mode C is reading incorrectly, to avoid confusing the controllers as you say.

Cheers!! :)

[This message has been edited by SLT (edited 26 April 2001).]

The bmi aircraft are fitted with transponders that have no facility for isolating the mode C.

FCOM 1.34.50 P1 refers.

Certainly on the ones I fly there are 3 switches on the LH side of the box and the bottom one is ALT on/off.
It does look a LITTLE like it could be the unit on/off switch, so maybe there is some confusion comming in there ( or maybe it is just a totally diferent unit without an on/off facility - but I would be surprised if that is the case.)

Like all aircraft I have ever flown there is a way of transmitting in Mode A only on 320 series aircraft

Most of the 320's I fly have a seperate Alt Rptg on/off toggle switch on the right hand side of the box.(dialled numbers box).

The 321's and some 320's have a rotary switch that includes an Alt Rptg off setting. (numeric keypad box).

Affrim, Alt Rptg on/off switch bottom left on mine...

Thanks for all the info - especially Capt Chambo who seems to have the definitive answer for the BMI fleet.
As a lapsed PPL myself, all the transponders I have used certainly had the ability to select mode C on or off, but most had mode A only........but that's another story.
Regards,

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FATCO

The Fat Controller

It may well depend on which TCAS BMI have fitted to the bus.
If the Alt reporting is suspect they could switch to the other transponder as it should
have a separate Alt info.