PENKO and a few others:
Far from me to dispute the fact that ATC is there for the pilots, not the other way around. I am a pilot too, and today I fly far more than I control ( I stopped handling an ATC mike 8 years ago ). And when I fly I want ATC to help me without arguing too.(they mostly do, no worries
)
Let's get away from Ego's for a second . and look at safety : back to the original thread.
Basics: If a pilot a has a serious problem that do need immediate attention and priority, emergency descend , whatever, : he should declare emergency and call Mayday , squawk 77, whatever and he will get the full support of everyone.
Pan-Pan will not get you anything basically.It just information that there is a problem on board nothing more.
And that was the original point here I beleive.
Telling the problem in long plain language will not help much neither. We need to use Mayday . and/or 7700 . period. Remember Avianca .
Some children of the magenta line ( but not only them I would dare to say reading some posts ) not born when Avianca crashed and not understanding this should perhaps refresh themselves by reading this excellent booklet last 2 pages :
http://www.skybrary.aero/bookshelf/books/115.pdf
As to descending straight ahead without telling anybody , or when it is over ( been there, got the T-shirt) while I can understand that as a pilot ( Aviate, navigate ,communicate, : yes comm is last, I know that ) I do not like it as a controller, because I am responsible to keep everyone clear of each other. But I know I have to live with that.
Doing an emergency descent staying straight on the airway axis ?
Use common sense and knowledge. turning 30 degrees will definitively help. ( (unless you are above FFM, SPI, DIK, SPR ,TRA, etc.. of course but you can't win all the time. Need a bit of luck too. But staight ahead under RNP5 /GNSS NAV ? No way for me.
Remember also TCAS is extremely bad or will even be inhibited with very high rates of descent.
Now some inside ATC info :
Modern ATC systems takes up to 10 seconds to display ALT and if it is from level flight to 4-5000 ft lower in one go, most systems ( mine did) will not display altitude asuming garbling .(at least for one update),
Then ATC might not notice , if you are cruising level flight not directly confilcting with anyone his attention/focus will definitively not be on you.
The airspace is such structured that the sectors ( read altitudes) below are not controlled from the same room or even the same country. Military will only clear the way below you if they see 7700 . They do not normally monitor civil a/c altitudes deviations.
So keep communicated until the end when doing an emergency descent ,and you're on your own relying on luck not to meet someone on your way down. Tell ATC a.s.a.p and you'll increase your chances someone will get them out of the way. Nothing more to it.