7700
Joined: Dec 2001
Posts: 413
Likes: 0
From: down-route
Changing your transponder code to 7700 in an Emergency Descent is all very well, but the priority with a transponder is to turn it to TRAFFIC ADVISORY(TA) ONLY .
Imagine the excitement generated by descending to FL100 (or the MSA) in IMC with a TCAS "climb,climb"! Do you stop your descent or do you ignore the TCAS? What will the other recipients of the RA do? If you're in a busy environment how many a/c will then be carrying out TCAS manoeuvers? Then at sometime (when you can get a word in!) you declare a MAYDAY to go along with 7700!! If you manage to survive then it's the controler who dies from a heart attack!
As a pilot, if you have the presence of mind to think about the transponder during an Emergency Descent then the priority must be to select TA ONLY. You can then discuss your actions in denser air!!
Imagine the excitement generated by descending to FL100 (or the MSA) in IMC with a TCAS "climb,climb"! Do you stop your descent or do you ignore the TCAS? What will the other recipients of the RA do? If you're in a busy environment how many a/c will then be carrying out TCAS manoeuvers? Then at sometime (when you can get a word in!) you declare a MAYDAY to go along with 7700!! If you manage to survive then it's the controler who dies from a heart attack!
As a pilot, if you have the presence of mind to think about the transponder during an Emergency Descent then the priority must be to select TA ONLY. You can then discuss your actions in denser air!!
Joined: Apr 2001
Posts: 182
Likes: 0
From: a fence in the sun
There's some good stuff here, but we've not mentioned one vital factor, especially with regard to emergency descents.
Most busy radar controllers work with appropriate height filters on their displays. These prevent certain traffic being displayed on the radar. Filtering can be by code or code block, or by Mode C. For example, someone working airspace from FL200 to 300 may filter out all traffic below FL160, and all above 340, say (this is a generalisation, and the specific airspace will determine the filters used).
So, you're at FL400 above said guy's airspace, and you start an emergency descent. Everything will get very busy, both in the flight deck and in the centre - where the controller you are talking to (whose airspace stops at FL300 in this example) will be co-ordinating your descent with his colleagues.
IMHO, you should squawk 7700, because this will ensure your aircraft's position/data block/whatever is 'forced through' on all centre displays in your area. Then you won't come as such a nasty and sudden surprise when you plummet through said controller's airspace, only becoming visible on his display when you have forty seconds or so to his highest level.
If you don't squawk 7700, don't be surprised if ATC instruct you to do so - it'll be with this purpose in mind.
My final 'tip' for emergency descents is to make the initial call along the lines of:
'Pan pan pan, London Control, Birdseed 123, emergency descent, emergency descent, descending NOW FL100 we are able to fly headings'.
This could be an enormous help to the controllers involved.
A final thought - and credit to the BA pilot who I heard do this - if you need to descend but not declare an emergency, then I thought the following phraseology was near-perfect:
'London, Birdseed 123, we have a technical problem, we must have descent to FL100 now'.
[ 26 February 2002: Message edited by: NorthernSky ]</p>
Most busy radar controllers work with appropriate height filters on their displays. These prevent certain traffic being displayed on the radar. Filtering can be by code or code block, or by Mode C. For example, someone working airspace from FL200 to 300 may filter out all traffic below FL160, and all above 340, say (this is a generalisation, and the specific airspace will determine the filters used).
So, you're at FL400 above said guy's airspace, and you start an emergency descent. Everything will get very busy, both in the flight deck and in the centre - where the controller you are talking to (whose airspace stops at FL300 in this example) will be co-ordinating your descent with his colleagues.
IMHO, you should squawk 7700, because this will ensure your aircraft's position/data block/whatever is 'forced through' on all centre displays in your area. Then you won't come as such a nasty and sudden surprise when you plummet through said controller's airspace, only becoming visible on his display when you have forty seconds or so to his highest level.
If you don't squawk 7700, don't be surprised if ATC instruct you to do so - it'll be with this purpose in mind.
My final 'tip' for emergency descents is to make the initial call along the lines of:
'Pan pan pan, London Control, Birdseed 123, emergency descent, emergency descent, descending NOW FL100 we are able to fly headings'.
This could be an enormous help to the controllers involved.
A final thought - and credit to the BA pilot who I heard do this - if you need to descend but not declare an emergency, then I thought the following phraseology was near-perfect:
'London, Birdseed 123, we have a technical problem, we must have descent to FL100 now'.
[ 26 February 2002: Message edited by: NorthernSky ]</p>
