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AW139 incident - Houma

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AW139 incident - Houma

Old 27th Sep 2022, 18:50
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For sure, you can move the ECLs manually - they have a mechanical link. I am having trouble understanding the "couldnt stop it with full down collective" description. Surely, if the collective is full down, there is more or less zero pitch - how can the helicopter not descend in this condition?? It kind of sounds like the crew were reducing engine power by cycling the mode switches instead of by retarding the ECLs....
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Old 27th Sep 2022, 19:39
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Originally Posted by Non-PC Plod View Post
For sure, you can move the ECLs manually - they have a mechanical link. I am having trouble understanding the "couldnt stop it with full down collective" description. Surely, if the collective is full down, there is more or less zero pitch - how can the helicopter not descend in this condition?? It kind of sounds like the crew were reducing engine power by cycling the mode switches instead of by retarding the ECLs....
I couldn’t reconcile the lowering of collective with the high side failure, either. I suspect there is a lot more to emerge.
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Old 27th Sep 2022, 20:50
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One of the media reports said the Pilots could move the Collective Lever in full range of motion....from down stop to top stop...without any reaction from the Rotor System.

If that is true....then there must have been something that happened to sever the mechanical linkage for the Collective.....arcing from a chafed wired bundle.....fire?

If you lose collective control....two ways of changing the amount of lift being produced.....speed or Nr.....or perhaps as in this incident....speed and Nr.

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Old 27th Sep 2022, 21:26
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They would have been able to use the ECL's to control RRPM. No ICS would have made communication between the crew difficult. I couldn't see in the video but would they have been able to lower the gear? Interesting to see what the primary cause of the electrical fire was. Yes, a lot more to emerge .
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Old 27th Sep 2022, 22:46
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I have never flown an AW 139 but worked alongside a few.
Reported by a pax that the left hand pilot’s window was jettisoned shortly after the problems started.
Photo on the ground after landing.
If the off/idle/fly switches were working that is interesting. But trying to control power and RPM by switching between idle and fly would be very problematic indeed.
Why would the manual throttles not work? When all aircraft power was lost the engines should have “Frozen” at the last selected power. I say SHOULD Have.
CVR/FDR will be interesting if they did have power to record events.
This is a very strange event.
Very glad all are OK.
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Old 27th Sep 2022, 22:50
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Originally Posted by 92Driver View Post
I couldn't see in the video but would they have been able to lower the gear?
Gear was down. Main gear collapsed on touchdown, nosegear not.

skadi
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Old 27th Sep 2022, 22:51
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But trying to control power and RPM by switching between idle and fly would be very problematic indeed.
Actually like flying a Sopwith Camel!
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Old 27th Sep 2022, 23:36
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Originally Posted by 212man View Post
Actually like flying a Sopwith Camel!
True but RPM overspeed was not a rotary engine problem.
The effect of inhaling castor oil on the crew’s digestive system in this scenario also may be a factor to take into account.
Very funny comment 212man.
I am reminded of the first time experiencing the dreaded drive shaft failure mode on the 92 off, relight, on ……repeat while imitating a bucking bronco and frantically trying to identify the engine. ( usually on a dark and stormy night at rotation from the rig. Kinda focuses your attention. “Immediate actions?”…..“A);Submit resignation, shut the sim down, B) Head for the bar!”……Sadistic, giggling, sim instructor: “Good Plan, Well done, Exercise Complete!”
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Old 28th Sep 2022, 00:33
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The one pilot's window was jettisoned to evacuate the cockpit of smoke and fumes most likely.

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Old 28th Sep 2022, 07:28
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The one pilot's window was jettisoned to evacuate the cockpit of smoke and fumes most likely.
yes, the pathetic little ventilation flap in the window itself is all but useless
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Old 28th Sep 2022, 08:40
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Originally Posted by [email protected] View Post
yes, the pathetic little ventilation flap in the window itself is all but useless
It’s fit for purpose, if it’s purpose is giving and receiving a manifest.
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Old 28th Sep 2022, 08:40
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Originally Posted by SASless View Post
One of the media reports said the Pilots could move the Collective Lever in full range of motion....from down stop to top stop...without any reaction from the Rotor System.

If that is true....then there must have been something that happened to sever the mechanical linkage for the Collective.....arcing from a chafed wired bundle.....fire?

If you lose collective control....two ways of changing the amount of lift being produced.....speed or Nr.....or perhaps as in this incident....speed and Nr.
Well, if they were dealing with a fixed collective pitch setting: Respect!
An interesting exercise in the FFS- not something you want to try in a real machine!!
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Old 28th Sep 2022, 09:51
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It'd be interesting to see if in all the kerfuffle with smoke etc, the Master was inadvertently turned off instead Main Batt. The engines/EEC would be getting power from their own PMA (alternator) and would have been controlled by the ECL's.
Yes the gear could have been down but maybe just 'drooping' position, not locked down.
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Old 28th Sep 2022, 17:30
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This incident does make one wonder how a Fly By Wire (FBW) flight control system would have fared with such an occurrence.

Knowing nothing of FBW (at least not enough to matter) perhaps those better informed might offer some insight.

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Old 28th Sep 2022, 20:26
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Originally Posted by SASless View Post
One of the media reports said the Pilots could move the Collective Lever in full range of motion....from down stop to top stop...without any reaction from the Rotor System.

If that is true....then there must have been something that happened to sever the mechanical linkage for the Collective.....arcing from a chafed wired bundle.....fire?

If you lose collective control....two ways of changing the amount of lift being produced.....speed or Nr.....or perhaps as in this incident....speed and Nr.
That would be some fire to burn through a 4 inch carbon torque tube behind the pilots seats, and in the ceiling. The other control linkages are in the left hand wall behind the LH pilot door. No real wiring in there at all.

When they say "reaction from the rotor system", I'm wondering if they mean RPM control rather than directional control. Otherwise how did they auto it as they did in the video?

Speaking of the video, I don't know if there is a clearer copy somewhere but the maingear doesn't look to be fully extended.PR ram looks like it hasn't worked. But it is VERY hard to tell from the grainy video.
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Old 29th Sep 2022, 05:20
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That a very good comment, in dead.
The Electrical fire/smoke procedure ask you to segregate the power source to the Essentials in order to determine which source is feeding the Ess buses, powering it alternatively from the Batteries or the Generators. You have to switch OFF both BATTERY MAIN and MASTER successively in conjunction with the GEN 1-2, if mixed up, not only you loose the ESS but the complete cockpit!
That might explain the AFCS issues, as it will be then inoperative.
The landing Gear needs the Essentials to be controlled, ESS1 normal operation, ESS2 emergency operation, if the electrical power is lost before the control, it free falls without locking itself down, may be the nose wheel thanks to the airflow, but certainly not the main ones.
The EEC are permanently electrically self-sustain by their own PMAs from 40% NR no need of the essential. If the IDLE and FLT mode were operating the EEC were perfectly alive.
May be because of a collective control torque tubes and rode issue/rupture to the mixing unit, explaining the impossibility to control the main rotor speed from the cockpit has lead the crew to play with the FLT/IDLE mode to control the engine power and then modulate between Power ON / Power Off.
It will have been difficult to do so with the ECL in manual and no indications in the cockpit. At least in AUTO GOV the engine power can controlled between two know power, IDLE and 100(102)% NR.

In any case, good job having landed this aircraft without human injuries.
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Old 29th Sep 2022, 21:32
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Originally Posted by SASless View Post
The one pilot's window was jettisoned to evacuate the cockpit of smoke and fumes most likely.
Not a good idea IMO.
I well remember an accident where the co-pilot, in anticipation of ditching, jettisoned his 212 pilot’s door which struck the MR and was then thrown into the tail-rotor. It became a non-survivable event.
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Old 29th Sep 2022, 21:49
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ISTR the 139 windows have to be pulled in not pushed out but my memory maybe playing tricks.
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Old 29th Sep 2022, 22:24
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Originally Posted by [email protected] View Post
ISTR the 139 windows have to be pulled in not pushed out but my memory maybe playing tricks.
That is the case for the cockpit windows, the cabin windows are pushed out.

Originally Posted by albatross View Post
Not a good idea IMO.
I well remember an accident where the co-pilot, in anticipation of ditching, jettisoned his 212 pilot’s door which struck the MR and was then thrown into the tail-rotor. It became a non-survivable event.
​​​​​​
If my cockpit was full of smoke, I’d be doing what I could to clear it. The window may have been kept in the cockpit rather than jettisoned, but if not, the tail rotor is on the right side, so there’d be less chance of contact.

This certainly looks like an “all bets off” event.
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Old 29th Sep 2022, 23:25
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The window was pulled inwards....not jettisoned to the outside according to some reports I. have seen.

What I took from the wording is there might have been a bit of rough treatment of said window in the process of getting some beneficial use of the opening in clearing out the smoke and fumes.

Which....seems very reasonable and understandable if the window was extremely small and wanted enlarging.




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