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AW139 incident - Houma

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AW139 incident - Houma

Old 24th Oct 2022, 14:01
  #141 (permalink)  
 
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The schematics raise questions for me.....the first being which Collective control rod is the one that was damaged and rendered useless by the arcing?

Were any Rod End bearings spot welded that would have caused the Collective Jamming?

Is there a Red Gate that must be "flipped" before the BAT Master Switch can be moved from ON to OFF? (The one visual seems to show there being one).

With the Main and Aux BAT Switches ON....and the BAT Master Switch Off....do the Essential buses have from the Batteries? Logic would say with the Master Switch Off there is no battery power applied to the DC system (assuming both GEN Switches have been moved to OFF.
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Old 24th Oct 2022, 15:32
  #142 (permalink)  
 
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Originally Posted by SASless
.the first being which Collective control rod is the one that was damaged and rendered useless by the arcing?
The lateral collective tube C3 which is overhead with inboard side connected to mixing unit and outboard side connected to the vertical C2 in L/H side shell.

Were any Rod End bearings spot welded that would have caused the Collective Jamming?
Per the report no. However, the tube failed longitudinally which allowed the tube to mechanically twist along that axis. So instead of the pilot pulling pitch and the C3 rotating as a complete tube, only the C2 side rotated and the mixing unit side did not rotate or was of limited rotation. While composites have great fatigue resistance, the more structural failure modes I see, the more I'd rather have a good ol'fashioned metal alloy part instead.

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Old 24th Oct 2022, 18:31
  #143 (permalink)  
 
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SASless - the red item is a gang bar, which allows you to switch off the batt master and 2 generators together in a one-er. Its not a gate. You are correct that the master switch needs to be on in order to connect the main or aux batteries.
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Old 24th Oct 2022, 18:36
  #144 (permalink)  
 
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Originally Posted by [email protected]
ECL power control cables

I can't find anything that suggests the ECLS can't control the FMM even in auto mode.
Note

Each engine trim beep switch controls the respective control lever from MIN to FLIGHT position when in AUTO mode, and from MIN to MAX position when in MANUAL mode
Not aware of the logic behind it.


Note

Both engines control levers should always be operated through the beep switches located on the collective control. They should be operated manually only in case of failure of the remote control (ECL FAIL caution message), or before starting, to position the lever to FLIGHT.
if electrical power is lost to the collective auto/manual switches, the solenoid should release and revert to manual mode.
ELECTRICAL BLACKOUT

Following a dual generator failure, if the batteries discharge completely (electrical blackout) the engines continue to run in AUTO mode: they are controlled by the EEC which is then electrically powered by the relevant Permanent Magnet Alternator (PMA).

Last edited by RVDT; 24th Oct 2022 at 19:33.
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Old 25th Oct 2022, 00:49
  #145 (permalink)  
 
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Itís been some time since Iíve flown the AW139 but Iím pretty sure that when the ECL is moved using the collective Beep Trim while the engine switch (also located on the collective) is in AUTO Mode, the engine will not respond. The ECL will cycle forward and aft but the engine remains controlled by the EEC. There was a maintenance procedure I conducted a couple of years back where by after performing a normal engine start, the ECL was beeped back to minimum. The engine was unaffected until the engine switch was switched from AUTO to MANUAL where it then decelerated to a specific value. We were checking that the engine did indeed decel to a specified value without flaming out. I believe it was a rigging check.
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Old 25th Oct 2022, 14:51
  #146 (permalink)  
 
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Reading the NTSB prelim and looking at the pictures, I have to say "Hat's off" to the crew. They successfully got on the ground after facing multiple unheard of failures. I'm sure going forward this accident will serve as great training discussion starter.
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Old 2nd Nov 2022, 01:44
  #147 (permalink)  
 
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Originally Posted by [email protected]

ECL power control cables

I can't find anything that suggests the ECLS can't control the FMM even in auto mode. if electrical power is lost to the collective auto/manual switches, the solenoid should release and revert to manual mode.

Within the FMM, as long as the engine is in AUTO GOV, the ECL rode end is not in contact with the metering valve control arm, but it's following it closely.
At the switch over to MANUAL GOV, either automatically (EEC failure) or selected by the pilot, the engine power setting does not change, but internally to the FMM the ECL rode end is now in contact with the teetering valve control arm. The pilots can then adjusted the ECL, and then the engine power, thanks to the engine beep switches as long as the Essential busses are powered, if no Essential busses, then the crew can physically move the ECL manually.
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Old 2nd Nov 2022, 01:51
  #148 (permalink)  
 
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Originally Posted by ghostfish1
Itís been some time since Iíve flown the AW139 but Iím pretty sure that when the ECL is moved using the collective Beep Trim while the engine switch (also located on the collective) is in AUTO Mode, the engine will not respond. The ECL will cycle forward and aft but the engine remains controlled by the EEC. There was a maintenance procedure I conducted a couple of years back where by after performing a normal engine start, the ECL was beeped back to minimum. The engine was unaffected until the engine switch was switched from AUTO to MANUAL where it then decelerated to a specific value. We were checking that the engine did indeed decel to a specified value without flaming out. I believe it was a rigging check.
You are correct, as long the engine is AUTO GOV you can move the ECL nothing happen on the engine power.
At reversion from AUTO to Manual, the power should not change more than 10% from its datum.
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Old 2nd Nov 2022, 08:30
  #149 (permalink)  
 
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Everyday is a school day - thanks JGtn
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Old 3rd Nov 2022, 20:13
  #150 (permalink)  
 
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Anybody hear anything from Leonardo on suggestions for QRH changes to ELECTRICAL FIRE/SMOKE?

My quick review of the crew's description from the NTSB preliminary report:
1. 7 minutes from landing they smelled plastic burning, no smoke, they turned the AC off.
2. A "few minutes later" they heard a "whoof" and the cabin filled with smoke, simultaneously low rpm warning and engine "overspeed" (overspeed N1, or just the PI to 145?), with collective lifting and cyclic displacing left.
3. Left seat pilot jettisons window to clear smoke, they try engine to idle but NR drops to the high 70's, they try diving but speed gets very high, so back to engine switch to idle/fly to get the RPM down.

Was hoping JGtn would tell us if the engines could have been switched to manual since at this point they are using the idle/fly switches to lower NR to descend, and it may have been smoother/easier manipulating both engines in manual and targeting a specific NR.

From the QRH: ELECTRICAL FIRE/SMOKE. If smoke or smell, try to identify cause and disconnect. If it cannot be identified then:
1. GEN 1, GEN 2 OFF
2. BATTERY MAIN OFF
3. OPEN WINDOWS TO VENTILATE COCKPIT
Note: AP2 and ATT will remain engaged but autopilot lights will be off.

Then it goes on.....

Not desk-flying the crew, they pulled a rabbit out of a hat, and I likely would be in a similar state of mind: VMC, 7 minutes out, smell plastic burning but no smoke, turn the AC off and let the greenies look at it on the ground. But from an OEM QRH perspective if on smelling plastic burning they had done step 1 wouldn't the #1 GEN have gone offline and stopped the 300amp current flow that was frying the collective tube? No "whoof" no need to jettison a window, no compromised integrity of the collective tube?
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Old 10th Nov 2022, 00:37
  #151 (permalink)  
 
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Originally Posted by malabo
Anybody hear anything from Leonardo on suggestions for QRH changes to ELECTRICAL FIRE/SMOKE?

My quick review of the crew's description from the NTSB preliminary report:
1. 7 minutes from landing they smelled plastic burning, no smoke, they turned the AC off.
2. A "few minutes later" they heard a "whoof" and the cabin filled with smoke, simultaneously low rpm warning and engine "overspeed" (overspeed N1, or just the PI to 145?), with collective lifting and cyclic displacing left.
3. Left seat pilot jettisons window to clear smoke, they try engine to idle but NR drops to the high 70's, they try diving but speed gets very high, so back to engine switch to idle/fly to get the RPM down.

Was hoping JGtn would tell us if the engines could have been switched to manual since at this point they are using the idle/fly switches to lower NR to descend, and it may have been smoother/easier manipulating both engines in manual and targeting a specific NR.

From the QRH: ELECTRICAL FIRE/SMOKE. If smoke or smell, try to identify cause and disconnect. If it cannot be identified then:
1. GEN 1, GEN 2 OFF
2. BATTERY MAIN OFF
3. OPEN WINDOWS TO VENTILATE COCKPIT
Note: AP2 and ATT will remain engaged but autopilot lights will be off.

Then it goes on.....

Not desk-flying the crew, they pulled a rabbit out of a hat, and I likely would be in a similar state of mind: VMC, 7 minutes out, smell plastic burning but no smoke, turn the AC off and let the greenies look at it on the ground. But from an OEM QRH perspective if on smelling plastic burning they had done step 1 wouldn't the #1 GEN have gone offline and stopped the 300amp current flow that was frying the collective tube? No "whoof" no need to jettison a window, no compromised integrity of the collective tube?

The engine systems are powered thanks to their own PMA (Permanent Magnetic Alternator) therefore remain in AUTO mode.
The engine mode switch FLIGHT or IDLE position being monitored by the EEC you can still control those two known status.
The GOVERNING modes either AUTO or MANUAL, selectable thanks to the GOV switches on the pilot collective should be operative, so they could revert to manual, but:
The ECL beep-trim, instead, need electrical power from the aircraft to operate the ECL, with the power OFF they are inoperative (the crew has reported it inoperative), it is then probably easier to control the engine power at two known power setting, rather than going all the way up to the overhead panel and try to adjust the power with no indication available.
Again that is an assumption.

Having said that, few indications lead us to believe than they effectively have lost the Essential busses such as the landing gear not being locked down, the engine beep trims inoperative, the engine not shutting down after having select the OFF mode on the engine mode switches ...

Not being a pilot myself, I can only say VERY GOOD JOB for having brought back the machine on the ground with no, or really little, personnel injuries!
Attached Files
File Type: pdf
Electrical Fire - Smoke.pdf (92.3 KB, 10 views)
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