Mayday Calls
 

Hello all you RT knowledgable chappies!

Quick question.
In an emergency situation, I know the procedure is to call 121.5 for D&D assistance, but what if you're already working a frequency. Should you immediately switch to 121.5 and disregard the previous freq, or should you just stick with the ATSU you've got seeing as you're already in contact with them?

Cheers

ETC

I would say stick with the ATSU you are in contact with, if you switch frequency without telling them and then they can't raise you or you act eratically then they will try and trace you - requiring lots of phone calls - and maybe vector aircraft away from you. Increasing the workload. Also the controller you are talking to might be better suited to help than D&D. After all D&D are only located in the centres and approach controllers will have (possibly) a greater local knowledge

In Controlled airspace stick with the allocated frequency.If you change the squawk to A7700 you will have the undivided attention of every controller for miles around

Declaring emergencies
 

Declare the emergency on the frequency you are already on whether inside or outside controlled airspace. The controller should then pass your details to D+D and seek assistance from them as appropriate - this may mean you are then transferred to 121.5 or, as in most cases, "operational control" of the emergency will be granted to the agency you are working, although D+D will still have "executive control" of the emergency. If for some reason you can't get a word in on the frequency you're working, chop to 121.5 and declare the emergency on that but remember to tell D+D who you were working prior to the call and that agency doesn't know you've left their frequency. The point above about the emergency SSR is very relevant because, as soon as it's on, D+D will be chasing down who is/was working the aircraft wh.

Mayday Calls
 

Hate to sound a book worm type but the new CAP 413 edition on the web is your best reference for this. Latest Edition just out 1st May 2006
Chapter 8 should give you all the details.Available on CAA Website.

1.4.3 If a pilot is already in communication with a civil or military ATSU, before the emergency arises, assistance should be requested from the controller on the frequency in use. In this case, any SSR code setting previously assigned by ATC (other than the Conspicuity Code 7000) should be retained until instructions are received to change the code setting.
Hope this helps.:)

thank you people, that clears things up admirably.

ETC