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Falcon Runaway Trim

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Falcon Runaway Trim

Old 11th Mar 2016, 22:55
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Falcon Runaway Trim

I know this was a bizjet but I hope it isn't moved to the slower bizjet forum because it is applicable to most aircraft.

"BEA: Pilot's Skill Saved Falcon 7X with Runaway Trim

France's aviation accident investigation bureau BEA released its final report this week on the May 2011 pitch trim runaway incident involving a Falcon 7X in Malaysia, which caused Dassault to temporarily ground the 7X fleet. The report reveals how the crew recovered from an unusual and dangerous attitude.

The pilot flying used his military experience and applied a procedure he had learned for bombing. When the pitch angle increased rapidly, he rolled the aircraft sharply to the right, applying a 40- to 80-degree bank angle for about 20 seconds, according to the report. This decreased the pitch angle and stabilized the aircraft’s speed.

The failure lasted two minutes and 36 seconds, after which the temperature of an electric motor exceeded its limit, triggering a bypass of the primary trim control system in favor of another chain of control. During this period, the trijet climbed from 13,000 to 22,000 feet and its calibrated airspeed dropped from 300 to 125 knots. The maximum pitch angle recorded was 41 degrees and the highest load factor was 4.6g.

Although the manufacturer did provide details on the cause of the problem at the time, the BEA report highlights organizational issues at industry and authority levels."
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Old 12th Mar 2016, 07:36
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Having a tiny bit of insider knowledge on this, it's not a bad report, and while the FO's flying skills and familiarity with unusual attitudes certainly was a big asset, it's the crew performance under pressure that saved the day in my opinion.
During a violent pitch-up and temporary loss of control, the crew remained coordinated, PF and PM duties were clear and eventually swapped in a constructive manner, and communication remained open and level throughout.

Not a bad day's work
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Old 12th Mar 2016, 07:50
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A very good days work, I recon.
I note the BEA Rapport is in French. No surprises there, but I'd love to read it in the Queen's Australian.
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Old 12th Mar 2016, 08:46
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Some years prior to this a Beech 1900 in the US (can't recall where, or which operator) suffered a similar uncontrollable pitch up or trim runaway.

Following this we were taught in the sim the procedure of rolling in a lot of bank as first response remedy to counter the excessive pitch up. I recall spending about 15 mins going round in circles trying to figure out how to get the thing back on the ground!
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Old 12th Mar 2016, 17:47
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The failure lasted two minutes and 36 seconds, after which the temperature of an electric motor exceeded its limit, triggering a bypass of the primary trim control system in favor of another chain of control.
Probably a good thing it wasn't a nose down run away trim. You might have to roll a lot more than they did here to keep it under control.
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Old 12th Mar 2016, 18:17
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Although there is a lot less travel to the stabilizer towards nose down, the problem got tricky when we ran it in the sim: nose-down runaway without warning, autopilot engaged and fully configured at Vref +5, the problem only manifested when taking the a/p out at 500ft.... Unless you were right quick putting on full power and retracting some flaps, the adventure ended badly and short of the runway, which was a bit of an eye-opener...
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Old 12th Mar 2016, 23:54
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Probably a good thing it wasn't a nose down run away trim.
Happened to a Lockheed 18 Lodestar 50+ years ago. In this case it was an aftermarket electrical trim motor, and it ran away in the negative-G direction. An AD was soon issued to replace that motor with a less powerful one:

ASN Aircraft accident Lockheed 18-56-24 Lodestar N1000F Lake Milton, OH
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Old 13th Mar 2016, 13:55
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Similar close shave at Sydney Airport about 20 years ago (?) when Mystere 20 Falcon with two pilots flying to land Runway 16 in good weather. Co-pilot was PF when at 500 feet, the aircraft pitched up almost vertically. The captain took over and rolled the aircraft hard to get the nose to drop and thus increase speed. The aircraft dived and again pitched up almost vertically with both pilots on the controls. The aircraft waltzed around over the top of the airport alternatively diving and climbing steeply until the aircraft became controllable and a normal approach and landing took place.

The captain described the event on Pprune at the time but I recall his name as Mike but don't recall his user name. I was unable to locate anything in Pprune search function. He died about five years ago in France I believe.
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Old 13th Mar 2016, 19:08
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Just another reason to love those clunky 737 trim wheels.
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Old 14th Mar 2016, 00:00
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Just another reason to love those clunky 737 trim wheels.
There was a CB procedure for runway trim in one aeroplane I flew (not 737). I thought why don't we grab and hold the trim wheel 'til it's sorted out?
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Old 14th Mar 2016, 00:28
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This is it Centaurus.
VH-RRC, Sydney, 1987
https://www.atsb.gov.au/publications...aair198702851/
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Old 14th Mar 2016, 06:29
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Thanks for that report, Pithblot. I talked to the pilot some years later, and if my memory is correct I was quite certain he said that the aircraft did several climbs and dives before control was fully regained. The incident report gives the impression the climb and descent only happened once.

Either way, it was scary. The pilot also told me he learned from his flying instructor on Tiger Moths, to roll to the nearest horizon to get the nose down if caught in an extreme nose high attitude. He said it was that teaching that saved his life that day.

As a simulator instructor on the 737, I frequently meet airline pilots who have never heard of this recovery technique; despite it being published in the Boeing 737 FCTM. This suggests too much accent on button pushing in the simulator and not enough training on basic handling skills.
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Old 14th Mar 2016, 16:16
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There is an English language discussion of the technical aspects here: Falcon 7X LOC-I Due To Solder Defect - Aerossurance
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Old 14th Mar 2016, 19:13
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As a current simulator instructor on the 737, I frequently meet airline pilots who have never heard of this recovery technique despite it being published in the Boeing 737 FCTM.
I also consider that many 'new generation pilots' have forgotten there is a rudder, even when all engines are turning. Classic recovery years ago F70/100 'wing-icing on takeoff, a/c rolled, PF froze, PM stamped on rudder. They still live, I trust, to tell the tale. There is so much more to remember/learn after flight school than ticking boxes in the sim.
I, myself, still survive because my rudder did what my aileron did not on a single engine a/c.

Last edited by RAT 5; 14th Mar 2016 at 19:35.
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Old 15th Mar 2016, 01:01
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Never Fretter:
There is an English language discussion of the technical aspects here: Falcon 7X LOC-I Due To Solder Defect - Aerossurance
Do I recall a related solder joint failure on an A320? http://www.pprune.org/rumours-news/5...singapore.html
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Old 18th Mar 2016, 12:43
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Did the aerospace/avionics industry meanwhile convert to lead free solder?
Maybe there is more to change in the processes than just the material...
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Old 18th Mar 2016, 12:58
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Leadfree solder

I can foresee an interagency conflict - EPA vs. FAA (in the USA) - if it isn't already happening.
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Old 30th Mar 2016, 07:20
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Stab trim...

the 737-800 has stab trim cutout switches. Good thing in a case like this!
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Old 30th Mar 2016, 08:30
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I believe that was one of the fixes on the 7X as well after the fleet had been grounded.

CP
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Old 30th Mar 2016, 08:57
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You should watch the very good AA training videos posted in the Rostov thread. Very clear and well presented information on unusual attitude recovery.
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