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

Question re. the Gimli Glider

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

Question re. the Gimli Glider

Old 3rd Mar 2009, 21:18
  #1 (permalink)  
Thread Starter
 
Join Date: Dec 2007
Location: Cornwall-on-Hudson, New York
Posts: 875
Likes: 0
Received 0 Likes on 0 Posts
Question re. the Gimli Glider

I'm a writer doing a brief piece on the infamous Gimli Glider--the Air Canada 767-200 that ran out of fuel due in part to a liters/gallons mixup. I'm a pilot, but my experience only stretches as far as a Cessna Citation type rating, so my experience with RATs is nonexistent.

Question: Several of the accounts I've read of the incident say that the controls became more and more difficult to use as the airplane slowed to best-glide speed because the ram-air turbine didn't produce as much "hydraulic pressure" at low speeds as it did when extended into higher-speed airflow.

Is this possible? I should think a RAT produced electricity that either ran the hydraulic pumps or didn't. (They didn't have to power a whole lot of other stuff, as it was daytime and good weather.)
stepwilk is offline  
Old 3rd Mar 2009, 21:31
  #2 (permalink)  
 
Join Date: Feb 2005
Location: California
Posts: 349
Received 1 Like on 1 Post
I don't know the specifics of the RAT on the 767, but sometimes RATs produce electrical AND hydraulic power.
I'm sure you could google it.
f
fleigle is offline  
Old 4th Mar 2009, 00:22
  #3 (permalink)  
 
Join Date: Jun 2006
Location: Canada
Posts: 94
Likes: 0
Received 0 Likes on 0 Posts
B767 Rat

I used to work on that aircraft. The RAT only supplied hydraulic power. At low airspeeds, the RAT output decreases due to the fact that the RAT prop is not being turned fast enough.
Jetdoc is offline  
Old 4th Mar 2009, 03:31
  #4 (permalink)  
 
Join Date: Aug 2002
Location: Under the sea
Posts: 493
Likes: 0
Received 0 Likes on 0 Posts
130 knots is minimum speed for the RAT to do it's job.
extreme P is offline  
Old 4th Mar 2009, 04:42
  #5 (permalink)  
 
Join Date: Jun 2005
Location: AEP
Age: 80
Posts: 1,420
Likes: 0
Received 0 Likes on 0 Posts
Gallons/Liters mixup

Canada went through the convertion to metric, sometimes in the 1980s...
Back then, I often landed in Gander for refueling. They asked "how many liters"...
My flight engineers had to suffer converting POUNDS to VOLUME.
Many were confused by the difference of IMPERIAL gallons to US gallons.
xxx
So after 27.5 minutes of advanced mathematics, we got a number.
My flight engineer said "we will take xxx Imperial Liters"...
I do not think our Canadian friends appreciated his American humor...
xxx

Happy contrails

P.S. -
Have you ever been stuck in YQX...? You would love it.
Town is crowded, some 100 people or barely more. They all know each other.
One or two motels. Bars...? - Molson or Labatt, nothing else...
Congenial ladies looking for husband to marry and take them OFF the island.
Worst was, their local time (Z minus 3.5) did not exist on my Seiko Worldtimer.
And if you dont like it, I invite you to Iqaluit (Frobisher, Baffin Island).
BelArgUSA is offline  
Old 4th Mar 2009, 07:21
  #6 (permalink)  
 
Join Date: Feb 2003
Location: Brighton
Posts: 967
Received 5 Likes on 5 Posts
The mix up was pounds/kilograms, not litres/gallons. The airline was changing its mass units, and fuel was calculated in kg but that number of pounds loaded. The problem was compounded by the flight being conducted (legally) with an inoperative Fuel Quantity Indicating System, and the drip-stick physical check of fuel tank levels was invalidated by the point at which the error in calculation was made.

Previous posts about the B767 RAT are correct; hyd output only, to a restricted part of only one hyd system (cannot remember which) and said by Boeing to be effective down to about 130 kt. With engines windmilling, there would have been some hyd output from the two Engine Driven Pumps on the L & R hyd systems. I have not seen any reports of the flight controls being heavy.
kenparry is offline  
Old 4th Mar 2009, 08:53
  #7 (permalink)  
 
Join Date: Jan 2004
Location: Germany
Posts: 128
Likes: 0
Received 0 Likes on 0 Posts
There may be different configurations here, but on the '67 I am familiar with the RAT will only power the main flight controls through the Center Hydraulic System. So things like flaps, landing gear, brakes and spoilers, although normally (partially) operated from the C Hyd Sys, will not be powered. The HMG, also sitting in the center, will not receive hydraulic pressure either so you are left with BAT power only if both engines spool down.
Ka8 Flyer is offline  
Old 4th Mar 2009, 09:03
  #8 (permalink)  
 
Join Date: Jan 2008
Location: Denmark
Age: 79
Posts: 158
Likes: 0
Received 0 Likes on 0 Posts
RAT..

I flew the 767-300-ER for many years - excellent airplane.

The RAT etc. worked exactly as Ka8 Flyer explains.

brgds
grebllaw123d is offline  
Old 4th Mar 2009, 13:31
  #9 (permalink)  
Thread Starter
 
Join Date: Dec 2007
Location: Cornwall-on-Hudson, New York
Posts: 875
Likes: 0
Received 0 Likes on 0 Posts
Thank you for all the helpful replies--just what I needed to know.

Yes, I do know that it was in fact a pounds/kilograms mixup specifically, but what I meant was that basically it ended up equivalent to a gallons/liters mixup.

And yes, been to YQX, done that, used to help ferry Beagle 206s from the UK to Miami.
stepwilk is offline  
Old 4th Mar 2009, 18:32
  #10 (permalink)  
 
Join Date: Dec 2006
Location: The No Transgression Zone
Posts: 2,483
Received 5 Likes on 3 Posts
The RAT 75/67 on that type MAY supply power to the Essential or EMER BUS via a power transfer unit [PTU] off of the Center system provided that it is interfaced with a hydraulic driven generator [HDG],...of course you would have had to order that option,..I think that that crew was on BAT for standby gyro power
Pugilistic Animus is offline  
Old 4th Mar 2009, 22:43
  #11 (permalink)  
 
Join Date: Jun 2006
Location: Canada
Posts: 94
Likes: 0
Received 0 Likes on 0 Posts
On that specific aircraft, 604, in 1983, there was no HMG. This was one of the first B767s in operation. The RAT only supplied hydraulic power to the primary flight controls and one channel of the stab trim.
Jetdoc is offline  
Old 5th Mar 2009, 12:25
  #12 (permalink)  
 
Join Date: Nov 2006
Location: SoCalif
Posts: 896
Likes: 0
Received 0 Likes on 0 Posts
As you must already know, there was at least one book written on the accident. The one I read may have been titled, "Gimli Glider", and it was written for the non-aviator, probably by a non-aviator.

GB
Graybeard is offline  

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


Thread Tools
Search this Thread

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.