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Question re. the Gimli Glider

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Question re. the Gimli Glider

Old 3rd Mar 2009, 21:18
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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.)
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Old 3rd Mar 2009, 21:31
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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.
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Old 4th Mar 2009, 00:22
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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.
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Old 4th Mar 2009, 03:31
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130 knots is minimum speed for the RAT to do it's job.
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Old 4th Mar 2009, 04:42
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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.
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...

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).
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Old 4th Mar 2009, 07:21
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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.
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Old 4th Mar 2009, 08:53
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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.
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Old 4th Mar 2009, 09:03
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I flew the 767-300-ER for many years - excellent airplane.

The RAT etc. worked exactly as Ka8 Flyer explains.

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Old 4th Mar 2009, 13:31
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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.
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Old 4th Mar 2009, 18:32
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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
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Old 4th Mar 2009, 22:43
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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.
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Old 5th Mar 2009, 12:25
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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.

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