PPRuNe Forums

Go Back   PPRuNe Forums > Flight Deck Forums > Tech Log
Forgotten your Username/Password?


Tech Log The very best in practical technical discussion on the web


Reply
 
Thread Tools
Old 22nd Jun 2008, 16:09   #1 (permalink)
 
Join Date: Apr 2004
Location: UK
Posts: 305
Coffin Corner

How is the correct way to escape from Coffin corner. Is it by Descending to a "safer" altitude while carefully controlling airspeed ?
redout is offline   Reply
Old 22nd Jun 2008, 16:11   #2 (permalink)
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 17,058
Well, we don't recommend climbing.
BOAC is online now   Reply
Old 22nd Jun 2008, 16:36   #3 (permalink)
 
Join Date: May 2007
Location: UAE
Age: 48
Posts: 88
Just don't go there in the first place. Know your buffet margins. If you are foolish enough to end up in that predicament your solution would work.
Ayla is offline   Reply
Old 22nd Jun 2008, 16:47   #4 (permalink)
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 17,058
No it won't! The definition of CC is that ANY increase or decrease in speed will result in loss of control, so basically you are Gordon Ramsey'd as we say on UK TV.

Sentence 1 rules.

Last edited by BOAC; 22nd Jun 2008 at 17:06.
BOAC is online now   Reply
Old 22nd Jun 2008, 16:51   #5 (permalink)
 
Join Date: Jul 2000
Location: Thailand
Posts: 938
Surely you mean Gordon Ramsey'd. Jamie is just a cockney lad who uses slang, but he doesn't swear on TV!

Lots more power might help.
rubik101 is offline   Reply
Old 22nd Jun 2008, 17:04   #6 (permalink)
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 17,058
Whoops! Yes I do. Thanks. Edited. I actually watch neither, so please may I be excused?
BOAC is online now   Reply
Old 22nd Jun 2008, 17:26   #7 (permalink)
 
Join Date: Apr 2004
Location: UK
Posts: 305
BOAC what is the ans ? How does one escape without killing themselves.
redout is offline   Reply
Old 22nd Jun 2008, 18:56   #8 (permalink)
 
Join Date: Mar 2008
Location: USA
Age: 37
Posts: 71
Actually, the term "coffin corner" refers to a very small window between mach buffet and stall, not loss of control. And it is possible to maintain a given airspeed while descending, is it not? This is a very high altitude phenomenon, so you'd likely be at a pretty high power setting and all you have to do is reduce throttle. In fact not many aircraft have enough motor to get themselves into this situation to begin with.
gr8shandini is offline   Reply
Old 22nd Jun 2008, 19:06   #9 (permalink)
airfoilmod
Guest
 
Posts: n/a
Well

Reduce power and.... Stall. No increase left, at max altitude, can't climb, At Vne can't descend, you going to do uh What?? Including the word Coffin is not a mistake.
rubik: more power than wing has killed many an inattentive pilot.

Airfoil
  Reply
Old 22nd Jun 2008, 19:06   #10 (permalink)
 
Join Date: Jun 2001
Location: UK
Posts: 2,950
BOAC is, as ever, correct!

Why would you want to go there? You don't save fuel by climbing early above optimum.
fireflybob is offline   Reply
Old 22nd Jun 2008, 19:08   #11 (permalink)
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 17,058
I believe the actual 'coffin corner' was a one-way street, that real control loss was supposed to happen there with ANY change in Mach or IAS. It would require consumate skill to 'lower the nose' and fly out of it without increasing Mach no or reducing IAS. I suspect it was more a notional 'media' thing rather than a real one, but I'm sure someone will know better.

Ironically, for 'rubik', "Lots more power might help." - it was the converse. Too little power stopped people from getting up there as Lear pilots have discovered the hard way.
BOAC is online now   Reply
Old 22nd Jun 2008, 19:28   #12 (permalink)
 
Join Date: Jan 2008
Location: Room 757
Posts: 80
Sounds hard to reach such a critical Coffin Corner situation where ANY changes involve a Stall or Overspeed? Seems very hard to even approach this situation without stalling or overspeeding beforehand. You will always have some margin which is the way you would get out.

If you somehow get to such a critical situation I think anybody would rather have an overspeed in the recovery process than a shaker.


rcl
rcl7700 is offline   Reply
Old 22nd Jun 2008, 19:32   #13 (permalink)
airfoilmod
Guest
 
Posts: n/a
Coffin Corner "sounds hard to reach". Only if you can't imagine flying well past it. It isn't a destination, it's no man's land. It's real, have faith and believe.

Airfoil
  Reply
Old 22nd Jun 2008, 20:09   #14 (permalink)
 
Join Date: Sep 1998
Location: wherever
Age: 44
Posts: 1,143
In a modern Airliner you can't get near "coffin corner" without busting MMO so we should coin a new term for the limiting alt where MMO and AoA stall coincide.

Any suggestions?

How about Certifications Wall?
FE Hoppy is offline   Reply
Old 22nd Jun 2008, 20:36   #15 (permalink)
airfoilmod
Guest
 
Posts: n/a
What about

Hard "Hat"
  Reply
Old 22nd Jun 2008, 21:04   #16 (permalink)
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 17,058
redout - if you look at the bottom of the page you will see several threads about CC. Our friend John Farley posts (at #14) in one of them a good description of the situation.

Looks like your original question is best asked of a U2 pilot.
BOAC is online now   Reply
Old 23rd Jun 2008, 07:00   #17 (permalink)
Banned... Persona Non Grata
 
Join Date: Sep 2005
Location: NZWN New Zealand
Posts: 304
Quote:
Reduce power and.... Stall. No increase left, at max altitude, can't climb, At Vne can't descend, you going to do uh What?? Including the word Coffin is not a mistake. rubik: more power than wing has killed many an inattentive pilot.
Airfoil you can reduce power and use attitude to maintain airspeed. Airspeed is the critical factor.

Just don't apply for a job as a carrier pilot if you don't understand that sink can be controlled EITHER by attitude or power. You add new lustre to the term plain driver ... sorry I meant plane driver.
Kiwiguy is offline   Reply
Old 23rd Jun 2008, 08:22   #18 (permalink)
 
Join Date: Aug 2003
Location: Sale, Australia
Age: 69
Posts: 3,447
Believe the U2 had a spread of about 10 knots.
Brian Abraham is offline   Reply
Old 23rd Jun 2008, 08:53   #19 (permalink)
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 17,058
That's a big chunk of Mach, Brian - you sure? I assume that was at 'normal' operating altitude rather than any 'higher'?
BOAC is online now   Reply
Old 23rd Jun 2008, 09:06   #20 (permalink)
 
Join Date: Mar 2008
Location: Malvern, UK
Posts: 212
The Chuck Yeager Approach

To recover from CC.Tumble in an uncontrolled manner out of the sky until you hit thicker air. Ultimately you will recognise the uncontrolled state has now entered a recognisable aerobatic state (spin or inverted spin). Apply standard recovey technique. Simple.
Dont Hang Up is offline   Reply
 
 
This ad will disappear if you login
Reply
 


Thread Tools


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT. The time now is 07:02.


vBulletin® v3.8.7, Copyright ©2000-2013, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
© 1996-2012 The Professional Pilots Rumour Network

As these are anonymous forums the origins of the contributions may be opposite to what may be apparent. In fact the press may use it, or the unscrupulous, or sciolists*, to elicit certain reactions.

*"sciolist"... Noun, archaic. "a person who pretends to be knowledgeable and well informed".