Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

what speed when both engines fail

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

what speed when both engines fail

Thread Tools
 
Search this Thread
 
Old 28th Feb 2012, 14:58
  #1 (permalink)  
Thread Starter
 
Join Date: Feb 2010
Location: minneapolis
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
what speed when both engines fail

What speed to use when both engines fail and you have to drift down in a B737
seifly is offline  
Old 28th Feb 2012, 15:05
  #2 (permalink)  
 
Join Date: Aug 2005
Location: fl
Posts: 2,525
Likes: 0
Received 0 Likes on 0 Posts
It must be cold up there in Minnesota to be pondering that. Maybe any speed above clean min naneuvering clean would work depending on where you decided to land. Ask Sully.
bubbers44 is offline  
Old 28th Feb 2012, 15:11
  #3 (permalink)  
 
Join Date: Dec 2006
Location: finally based at home!
Posts: 106
Likes: 0
Received 0 Likes on 0 Posts
from the classic QRH from my company;


At or above FL270, set airspeed to 275 knots.
Below FL270, set airspeed to 300 knots.

below fl100 i would start to reduce towards min clean.

hope this helps.

Last edited by skyhigher; 28th Feb 2012 at 18:41.
skyhigher is offline  
Old 28th Feb 2012, 15:12
  #4 (permalink)  
 
Join Date: Feb 2007
Location: Scandinavia
Age: 47
Posts: 149
Likes: 0
Received 0 Likes on 0 Posts
V clean above FL200 for stall margin, Vp clean below FL200 is used in my airplane for drift down on one engine. If both went silent, I would use V clean if clean, and Vp for whatever config I have.

/Rookie
MD80rookie is offline  
Old 28th Feb 2012, 16:13
  #5 (permalink)  
 
Join Date: Jan 2008
Location: On the lake
Age: 82
Posts: 670
Received 0 Likes on 0 Posts
I have always thought that the best L/D speed is achieved at approximately 1.6Vso, but I'm not sure I can document the reasoning.
twochai is online now  
Old 28th Feb 2012, 16:28
  #6 (permalink)  
 
Join Date: Feb 2007
Location: Scandinavia
Age: 47
Posts: 149
Likes: 0
Received 0 Likes on 0 Posts
I have always thought that the best L/D speed is achieved at approximately 1.6Vso, but I'm not sure I can document the reasoning.
That is equal to Vclean, which is 1.5 Vso!

Love the restart idea though...
MD80rookie is offline  
Old 28th Feb 2012, 16:38
  #7 (permalink)  
 
Join Date: Jun 2009
Location: FL410
Posts: 69
Likes: 0
Received 0 Likes on 0 Posts
To make numbers simple:

Above FL100 = 280kts
Below FL100 = Fup speed

Dont forget to be configured!!!

Regards

B737-800W
B737-800W is offline  
Old 28th Feb 2012, 16:44
  #8 (permalink)  
 
Join Date: Sep 1998
Location: wherever
Age: 55
Posts: 1,616
Likes: 0
Received 0 Likes on 0 Posts
OK465, I'm with you. Windmill relight until I've got some air then assist after that.
FE Hoppy is offline  
Old 28th Feb 2012, 16:52
  #9 (permalink)  
 
Join Date: Mar 2001
Location: I wouldn't know.
Posts: 4,499
Likes: 0
Received 0 Likes on 0 Posts
Why not just follow the loss of thrust on both engines checklist? Says in step 5 in mine for the 737NG:

At or above FL270 set airspeed 275knots. Below FL270, set airspeed to 300knots.

However, below FL100 i would start looking where to set it down and slow down to up speed.
Denti is offline  
Old 28th Feb 2012, 16:58
  #10 (permalink)  
 
Join Date: Jul 2010
Location: LHR
Posts: 187
Likes: 0
Received 0 Likes on 0 Posts
Depends what you want to achieve. Don't you have a QRH?
HPbleed is offline  
Old 28th Feb 2012, 17:06
  #11 (permalink)  
 
Join Date: Jun 2009
Location: FL410
Posts: 69
Likes: 0
Received 0 Likes on 0 Posts
Denti,

i agree 1000000%, follow the QRH.

The numbers that i said before are just some figures to have at the back of your mind.

The question by our friend was not, what is the best speed for a windmill start.
The question was about Gliding Speed!!!

Regards
B737-800W is offline  
Old 28th Feb 2012, 17:14
  #12 (permalink)  
 
Join Date: Mar 2001
Location: I wouldn't know.
Posts: 4,499
Likes: 0
Received 0 Likes on 0 Posts
Ah, righto. Best glide should be right at up speed from what i remember, well, probably slightly above.
Denti is offline  
Old 28th Feb 2012, 17:36
  #13 (permalink)  
 
Join Date: Jan 2010
Location: The moon
Posts: 132
Likes: 0
Received 0 Likes on 0 Posts
At or above FL270 set airspeed 275knots. Below FL270, set airspeed to 300knots.
I think those speeds are to help with engine restart and not to do with the best glide speed. At that stage of the checklist it is assumed that at least one engine will restart. Funny enough the last two options on the loss of thrust on both engines are either one or both engines restart. It mentions nothing about both engines failing to restart
Johnny Tightlips is offline  
Old 28th Feb 2012, 17:43
  #14 (permalink)  
 
Join Date: Jun 2001
Location: UK.
Posts: 4,390
Likes: 0
Received 1 Like on 1 Post
I'm retired and haven't flown a big jet for some years but 250kn and sort it out from there flashed up in my head
Basil is offline  
Old 28th Feb 2012, 18:13
  #15 (permalink)  
 
Join Date: Mar 2010
Location: in a dirty cockpit
Posts: 431
Likes: 0
Received 0 Likes on 0 Posts
Well, if run out of fuel or any abnormal/emergency situation that led to a double engine out without chances to restart, I'd set the Vclean and hope to have a strip within my gliding range (for the B737 Classic, a good rule of thumb is 2.5 x Height)

Check this out, really interesting:

Loss of Thrust on Both Engines

Ciao
Breakthesilence is offline  
Old 28th Feb 2012, 21:55
  #16 (permalink)  
 
Join Date: Mar 2002
Location: Seat 1A
Posts: 8,561
Received 76 Likes on 44 Posts
RTFQ.

Cost index 0. Best range speed.
Capn Bloggs is offline  
Old 28th Feb 2012, 23:54
  #17 (permalink)  
 
Join Date: Sep 1998
Location: wherever
Age: 55
Posts: 1,616
Likes: 0
Received 0 Likes on 0 Posts
RTFQ?

He says you have to drift down. Why is that a range question? It could just as easily be a terrain question or a don't kill the pax with hypoxia question or many others.
FE Hoppy is offline  
Old 29th Feb 2012, 00:00
  #18 (permalink)  
 
Join Date: Aug 2005
Location: fl
Posts: 2,525
Likes: 0
Received 0 Likes on 0 Posts
FE, I agree, if your airport is near where you lost both engines get down first then at low altitude use min clean speed until you need to configure for landing. Dead sticking an airliner isn't hard, you just can't get low.
bubbers44 is offline  
Old 29th Feb 2012, 09:28
  #19 (permalink)  
 
Join Date: Jan 2007
Location: uk
Age: 75
Posts: 588
Likes: 0
Received 0 Likes on 0 Posts
what speed when both engines fail

seifly, are you a permanent pessimist; surely If both engines fail is more appropriate?
hawker750 is offline  
Old 29th Feb 2012, 12:34
  #20 (permalink)  
 
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes on 0 Posts
And 275kts at FL370 would be interesting.
RAT 5 is offline  


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.