Can controller ask pilot change squawk to A7700?
 

Rencently I have experienced two scenario that pilots declared emergency due to short of fuel, one of pilots said he can not even fly to alternative airport because not enough fuel, and both of these two pilots did not change squawk to A7700, so my question is if pilot declared emergency, does controller have right to let pilot to change squawk to A7700?:confused:

Yes done it a few times! Saves co-ordination with other sectors during an emergency, every one gets there traffic out of your way!

Your question is already answered, but just in case you want to see it in action...4 mins 45 secs in this video.

Excellent, yet another illegal YouTube clip :ugh:

On a side note, when inside CAS in the UK it is advised to NOT change transponder code to A7700 unless directed by ATC. There are certain situations where this is not practical/possible hence the advisory not mandatory. It isn't much of a problem anymore as most radars retain the a/c ident as well as displaying the emergency code, however this wasn't always the case hence this advisory.

Excellent, yet another jobsworth on PPRuNe :ugh:

SloppyJoe
In similar vein yours is not really a useful contribution to the OP's question.
Happy New Year

P.S. Lighten up