A question for the ATC people
 

Lets say an IFR aircraft is coming it to a controlled airport, (ADL,SYD etc) and at the point of selecting gear down, the transponder fails, (for whatever reason). Now would this be considered a minor problem, a major problem or no problem at all. Would this be viewed differently if it was a regular occurrence, just askin' :confused:

Gear down would be within ten miles so you are most likely on tower frequency. Not a real problem. The ADC may mention it or you may be advised after landing. Transponder failure is one of the reasons the capital city primary airports still have primary radar as a backup. At airports with the Advanced Surface Movement Guidance and Control System (A-SMGCS) installed, you will still be processes as a landing aircraft.

Arnold is the antenna being blocked by a gear door or gear leg ?

No, neither of the above, but I was just curious as to this being a problem disappearing from ssr in a control zone. Must admit I am somewhat surprised it would not be considered a problem, but there you go

It depends. Do you mean just in the CTR generally or an approach to land? Fuji answered the landing question. Same with airborne if it didn't come on we would ask you to recycle it.

In the CTR just doing airwork or something is more likely to be a problem, however primary will still see you.

Not sure that I agree with that, with parallel runways during PRM then you and the other aircraft one that parallel approach would be "broken out", during IVAs it could be a bit of a problem, especially if the system "coasted" (predicted) your track on the intercept to final (to continue across to or near the adjacent runway).

Don't overthink the question. As the OP stated the failure occurrs at gear extension so around five miles to run or closer for some light aircraft. In fact all acft approaching ML used to "drop out" when the acft entered the airport processing area which was there to reduce clutter although closer than gear extension. This changed with A-SMGCS.

Thanks SunnySA and Fujii. This post and a previous post on Airways names, with the accurate and reasoned responses to a sensible question, are why I believe PPRuNe is still a useful site.
On occasion I have had a self imposed boycott of the site because of the puerile behaviour of some.
Cheers,
Craven.