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AW139 incident - Houma

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AW139 incident - Houma

Old 3rd Oct 2022, 02:37
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Megan, I was thinking that if the history recorders were similar to GE;s, collective position, along with a number of other useful parameters would be there. Of course if there were usable FDR and CVR data the FADEC data wouldn’t be needed. But the FADECs have their own dedicated power source ( for one-they typically have ship power as well. ), so if the ships power did in fact completely fail, the FADEC data will still be there.
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Old 3rd Oct 2022, 05:26
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Originally Posted by SASless View Post
As recently as November 21, 2021 the FAA issued an AD re chafing of wire bundles in the overhead panel of certain AW-139's that required detailed inspections and related corrective actions to include replacing certain Circuit Breakers.

I found the Congressional Record entry that displayed the FAA's AD.

Phrases like "could cause the loss of control of the aircraft" was part of the verbiage.


https://flightaware.com/live/flight/...0220924/2224ZZ
I guess the followings are what you're talking about.




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Old 3rd Oct 2022, 05:31
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and FYI regarding emergency egress windows.

Exterior markings




Interior markings





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Old 3rd Oct 2022, 19:13
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Originally Posted by JohnDixson View Post
Megan, I was thinking that if the history recorders were similar to GE;s, collective position, along with a number of other useful parameters would be there. Of course if there were usable FDR and CVR data the FADEC data wouldn’t be needed. But the FADECs have their own dedicated power source ( for one-they typically have ship power as well. ), so if the ships power did in fact completely fail, the FADEC data will still be there.
Remember the 139 is not FADEC.

Digital control yes. But not FADEC. It has manual mechanical backup.

CVFDR has it's own dedicated power supply.
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Old 3rd Oct 2022, 19:49
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Nobody....if the engine controls have a mechanical backup system....which I assume would mean it has Engine Control Levers (ECL's") which the Crew could use to deal with the Overspeed(s) under "normal" emergency mode(s).

If they lost the Screens that display engine information....what back up system is available to them for that information?


Or would they be reduced to using their ears to assess the Nr and engine speeds?
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Old 3rd Oct 2022, 19:58
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I’m confused. If you go to the Leonardo site and look in their 139 brochures, they cite the PT6C-67C engine with FADEC, whereas if one goes to the P&W Canada site and check the same engine, P&W says an EEC ( not a dual EEC ) which sort of implies some sort of emergency backup. There were no specifics re the EEC. Anyway, the existence of collective position data obtained from the engine control system electronics ( assuming all on board systems were down ) is iffy.

Last edited by JohnDixson; 3rd Oct 2022 at 20:00. Reason: Wording
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Old 4th Oct 2022, 07:43
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John, only knowledge of the aircraft is a copy of the flight manual, an example emergency page which may give an insight.


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Old 4th Oct 2022, 15:13
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Beep switches on the collective control the ECLs normally when you select manual on an engine - the ECLs can be moved by hand if the beeping doesn't work.
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Old 4th Oct 2022, 21:10
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Originally Posted by SASless View Post
Nobody....if the engine controls have a mechanical backup system....which I assume would mean it has Engine Control Levers (ECL's") which the Crew could use to deal with the Overspeed(s) under "normal" emergency mode(s).

If they lost the Screens that display engine information....what back up system is available to them for that information?


Or would they be reduced to using their ears to assess the Nr and engine speeds?
SOS.... The engine controls do have a mechanical backup system. ECL's through a cable to the FMM. ECL's can be beeped or (very carefully!) moved by hand. ECL's should be exercised daily by maintenance to prevent binding. If the cable binds a shear pin breaks and you lose backup.

You would need to lose all four screens to not have any engine info. Power supply for the screens is separated.

Leo sales brochure is misleading. Engine is NOT FADEC. It is single channel DEC with cable operated backup. But nobody knows what DEC is, so they just call it FADEC.
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Old 5th Oct 2022, 10:44
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Hi all,

FYI, a crack on the pitch control lever upper section (lever broken in two parts) close to the MR damper bolt have been recently reported on a Brazilian AW139 during a post-flight check, preliminary investigations are in progress.

Strange coincidence!
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Old 5th Oct 2022, 13:36
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What is the probability of something like that happening AND a very serious electrical fire occurring at the same time so that a Crew could lose Collective Control and encounter loss of normal and planned emergency control of the engines?

That is what is puzzling about the ERA incident.
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Old 5th Oct 2022, 14:38
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Thanks, Megan that info is an EEC not a FADEC, and backed up by other posts as well.
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Old 5th Oct 2022, 14:45
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Originally Posted by JohnDixson View Post
Thanks, Megan that info is an EEC not a FADEC, and backed up by other posts as well.
Yup, single channel digital engine control with a manual mechanical backup.
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Old 5th Oct 2022, 23:06
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There is no reason for the EEC reverting to manual when you loose the Essential buses. They are powered thanks to an engine driven alternator, the so called PMA (Permanent Magnetic Alternator)

The engine high site, has been probably induced by the collective control issue, as some reports mention the pilot trying to control it with no result moving the collective from min to max with no reaction.
As he still had the full cyclic control, the failure were on the linkages between the collective grip and the mixing unit (torque tubes, push pull rod or bellcranks?)
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Old 5th Oct 2022, 23:26
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The PT6 engine installed on the AW139 is EEC controlled.
Computer control in normal operation AUTO GOVerning mode
Manual control, thanks to an ECL (Engine Control Lever), in back-up operation MANUAL GOVerning mode.

To MEGAN and noooby, the EEC has its own hard drive called DCU (Data Collection Unit) attached to the engine.
It records all the engines cycles, fault events and exceedances.
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Old 6th Oct 2022, 03:02
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Originally Posted by noooby View Post
You would need to lose all four screens to not have any engine info. Power supply for the screens is separated.

The electrical fire/smoke checklist calls for switching GEN1 and GEN2 off and then BATTERY MAIN off. If you mistakenly switch off BATTERY MASTER instead of BATTERY MAIN at this point (and they are right next to each other) you will lose all electrical power and instruments. The engines will keep running fine, as they produce their own electrical power to do so.

Making this mistake in instrument conditions will result in loss of control and almost certainly game over. In my view quite a serious ergonomic design flaw of the 139, having those switches located together and named/labelled similarly.

Last edited by the coyote; 6th Oct 2022 at 21:43. Reason: spelling
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Old 6th Oct 2022, 10:28
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So which came. first....the Chicken or the Egg?

The Crew reported a very serious electrical fire AND a loss of Collective Control AND Dual High Side failures which did not respond to the ECL's and had to be controlled by switching back and forth between Flight and Idle....... am I understanding that is what they reported correctly?

For Coyote,,,,,had they confused the BAT MAIN and BAT MASTER switches.....what would be the result if they somehow switched BAT MASTER to OFF rather than BAT MAIN OFF?

Likewise....what if they had gotten it right and did as the procedure calls for....and turned BAT MAIN to OFF....what would have happened (re instrumentation and controls?

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Old 7th Oct 2022, 10:58
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[Hi
in the electrical fire procedure if you mix up with switches, you can easily end up with no more electrical power on board, which means no more indication, even the electronic stand-by indicator is gone, no more AFCS (AP goes off, so no more SAS).
In their case it looks like than in conjunction with the fire they had a collective control issue, they moving the collective with no answer from the main rotor, that explains the engine trying to compensate the collective movement going up adding fuel, but has the rotor is not increasing the collective torque NF therefore NR goes high.
with no indication available, the best way to reduce the engine power is then to select IDLE keeping them in AUTO GOV. Very good relation from the crew, then they have managed the descent circling down up to kill the engines just before to land. Unfortunately the gear were not locked down, as you need electrical power to control it in normal or emergency, it was nore up nore down, it then collapse up at touch down.


QUOTE=SASless;11308959]So which came. first....the Chicken or the Egg?

The Crew reported a very serious electrical fire AND a loss of Collective Control AND Dual High Side failures which did not respond to the ECL's and had to be controlled by switching back and forth between Flight and Idle....... am I understanding that is what they reported correctly?

For Coyote,,,,,had they confused the BAT MAIN and BAT MASTER switches.....what would be the result if they somehow switched BAT MASTER to OFF rather than BAT MAIN OFF?

Likewise....what if they had gotten it right and did as the procedure calls for....and turned BAT MAIN to OFF....what would have happened (re instrumentation and controls?[/QUOTE]
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Old 7th Oct 2022, 21:15
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We usedto have helicopters that you either didn`t have any AFCS/SAS,Steam instruments/hold your hand out of the windows,and fly around,quite successfully;now it appears ,even controls are affected by an electrical problem..Really,engineers really have screwed it up......(unless,of course there was a mechanical failure in the mechanical lever system)
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Old 7th Oct 2022, 21:52
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The AW139 did not become unflyable with no electrical on board, it will be unstable but.
It appears they had mechanical issue between the collective grip and the mixing unit,
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