Aircraft destroyed in Afghanistan (USAF E-11A (BACN))
That's my limited understanding anyhow. Not sure whether it applies in this case or not though.
PBA is pretty much correct - the initial Ice Crystals melt, cooling the surface temperature due to the phase change, additional IC hit the liquid water further cooling it (and the surface) until it gets cold enough that it freezes again. Eventually either there is an rpm change (accel) that initiates a shed, or the accumulation sheds on its own. The accel related sheds are the ones that tend to be a problem, since most of the accumulation will shed all at once. The CF6-80C2 main problem was this accel shed - ice would accumulate during an idle descent, then there would be a level off accel resulting in a shed that was enough to flameout the engine.
Obviously it takes a high concentration of IC before this becomes a problem - as I noted earlier often described as sounding like heavy rain on the flight deck. As VinRouge notes, ICI usually occurs over highly convective weather (e.g. thunderstorms) - the convection pushes moisture laden air to high altitudes, where it's so cold all that moisture turns into Ice Crystals.
Accident investigation concluded that the operating engine was incorrectly shut down after a catastrophic failure on the other engine. No restart of the undamaged engine was achieved.
https://theaviationist.com/2021/01/2...gine-shutdown/
https://theaviationist.com/2021/01/2...gine-shutdown/
Originally Posted by aviationist article linked above
However, the MC attempted to fly the MA back to KAF as evidenced by the following MC initiated radio call to Kabul Air Traffic Control (ATC) at 1254:55L: “…Mayday, Mayday, Mayday…it looks like we have an engine failure on both motors, we are proceeding direct to Kandahar at this time…”
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Reacting to a complete loss of thrust by attempting recovery to base at Kandahar, a couple of hundred miles away, when they were operating well inside gliding range of Kabul and Bagram suggests such a degree of unthinking panic by the crew that it’s easy to picture how the wrong engine got shut down.
Usual move-the-blame accident report from the USAF:
- Engine failure so violent that the CVR impact/crash logic is triggered.
- FADEC commands an immediate shutdown of the left engine, but does not announce this rather important fact on the Crew Alerting System (no L (Left) ENG SHUTDOWN message or L ENG FLAMOUT)
- In the seconds after FADEC shutdown the left engine the Left N1, ITT, N2 are all in the green, showing more power than the functioning right engine, still with positive fuel flow. Amber Left FADEC FAIL message displayed to crew whilst in truth the Left FADEC had commanded an engine shutdown.
- In the vibration and noise the crew shutdown the right engine, which is displaying lower thrust, N1, N2, ITT and FF.
- Crew Alerting System then reports R Eng Shudown, but still no caption for the left engine.
- Right engine shows zero fuel flow, rapidly decaying N1 and ITT but left engine still shows a positive fuel flow and a higher N1 & ITT.
- RAT leaps from its slumber and engages noise and vibration mode in the vicinity of the P2's right foot. This clearly supports...
... or maybe not.
Perhaps the mishap started with a catastrophic failure of the left engine?
Perhaps the crew were not aided by the FADEC commanding a shutdown without proper annunciation?
I find the repeated suggestions that the crew should have remained within parameters for a dead-stick landing a bit of a stretch. If the USAF really thinks that is a viable option on a big, swept-wing ETOPS jet then perhaps they should have such thoughts before an accident rather than expecting a crew to imagineer their way into one during the noise, vibration and confusing instrumentation of the mishap sequence.
- Engine failure so violent that the CVR impact/crash logic is triggered.
- FADEC commands an immediate shutdown of the left engine, but does not announce this rather important fact on the Crew Alerting System (no L (Left) ENG SHUTDOWN message or L ENG FLAMOUT)
- In the seconds after FADEC shutdown the left engine the Left N1, ITT, N2 are all in the green, showing more power than the functioning right engine, still with positive fuel flow. Amber Left FADEC FAIL message displayed to crew whilst in truth the Left FADEC had commanded an engine shutdown.
- In the vibration and noise the crew shutdown the right engine, which is displaying lower thrust, N1, N2, ITT and FF.
- Crew Alerting System then reports R Eng Shudown, but still no caption for the left engine.
- Right engine shows zero fuel flow, rapidly decaying N1 and ITT but left engine still shows a positive fuel flow and a higher N1 & ITT.
- RAT leaps from its slumber and engages noise and vibration mode in the vicinity of the P2's right foot. This clearly supports...
...the cause of the mishap was the MC’s error in analyzing which engine had catastrophically failed (left engine)
Perhaps the mishap started with a catastrophic failure of the left engine?
Perhaps the crew were not aided by the FADEC commanding a shutdown without proper annunciation?
I find the repeated suggestions that the crew should have remained within parameters for a dead-stick landing a bit of a stretch. If the USAF really thinks that is a viable option on a big, swept-wing ETOPS jet then perhaps they should have such thoughts before an accident rather than expecting a crew to imagineer their way into one during the noise, vibration and confusing instrumentation of the mishap sequence.
Another factor is that the BACN sortie profile is probably the most boring kind of flying possible and under-arousal is known to increase the risk of an inappropriate reaction to a sudden event. Mitigating this requires frequent rotation of crews in and out of theatre for simulator training and mentally rehearsing contingencies during sorties. Or, preferably to my mind, using drones.
Originally Posted by JTO
I find the repeated suggestions that the crew should have remained within parameters for a dead-stick landing a bit of a stretch. If the USAF really thinks that is a viable option on a big, swept-wing ETOPS jet then perhaps they should have such thoughts before an accident rather than expecting a crew to imagineer their way into one during the noise, vibration and confusing instrumentation of the mishap sequence.
In this case the aircraft was at FL400+, with heavy mission systems down the back, full of fuel and only230 miles away from main base. Yes, they could have stuck the aircraft on its ear for Bagram or Kabul (for what they expected to be a single-engine landing) but that would have left them doing a heavyweight recovery at a high-altitude airfield (particularly so at Bagram) with no thrust reverser available. [NB there is no fuel-dump system on the GEx as its performance category and ETOPS design does not require one - burning down to a desired landing weight is the only option.]
At the start of the mishap sequence a 30 minute cruise descent, for a single-engine recovery to the lower altitude of Kandahar, probably seemed sensible and when things went seriously wrong they did appear to change their plans. I would be tempted to give them the benefit of the doubt given the absence of CVR data.
Ecce Homo! Loquitur...
JTO,
All of which is premised on a single engine failure. But within a couple of minutes they knew they had lost both - and still decided to press beyond maximum glide range.
My question, with plenty of height and time and a serviceable engine - why didn’t they manage a relight? Or did they never realise their mistake and just continue to try and relight the failed engine all the way down?
Generally speaking though, in a modern ETOPS-capable twin an engine failure in the cruise does not necessitate an immediate diversion to the nearest suitable airfield.
Mayday, Mayday, Mayday…it looks like we have an engine failure on both motors, we are proceeding direct to Kandahar at this time…
Last edited by ORAC; 22nd Jan 2021 at 10:34.
The CVR quit at initial engine failure and the DFDR quit at 1251:29L with the aircraft at FL410. Everything the USAF board publishes in the report beyond that time is little more than guesswork. Having pointed a finger at the sub-optimal EICAS messages to the crew they then go on to display screenshots of the panel display beyond the DFDR-stop point. The screenshot of the EICAS at 1252L showing the Dual Engine Out message is a guess by the mishap board dressed-up to look like actual recorded DFDR data.
I really do have to question the use of 'simulated' data in this way as it is reliant on the system performing in a way that may not be true. The EICAS should have displayed the left engine being shutdown by the FADEC, but it didn't and they know that for a fact as the DFDR recorded it. Post the DFDR-failure the board opines that the EICAS messages and displays were back to being perfect again because they no longer have evidence to show that they were not. Same goes for the AC and DC power switch-over, RAT deployment and correct operation, APU light-up and correct operation, ECS, O2, engine relight attempts and methods et al. These are all presumed on the basis of the normal system logic, crew drills and in case of the RAT and APU, their door positions at final impact.
Below the Glidepath - not correcting
They ended up dual engine out because they shut down the wrong engine. That is indisputable. There isn't a single flight safety course that doesn't hammer home the "Kegworth" effect of startle reflex and response, the situation seems bad and disorienting, but if you act suddenly and reflexively, you may just make it as lot worse, as happened here. There have also been a multitude of accidents where EICAS messages are misleading or plain wrong following some major malfunction. There were other primary displays of engine condition, Engine Pressure Ratio (EPR) and Inter Turbine Temperature (ITT), and the digital readouts of Fuel Flow (FF), N2 (RPM core), and oil pressure to allow some element of cross checking to take place before touching any of the throttles. Not diverting into the nearest field with 40K of altitude is almost understandable, but not once it became a dual engine out situation.
It's not a blame game at this stage, it's all about understanding how you aren't going to make those same mistakes
I'm not sure we have a good grasp of what the crew were faced with. For example - the DFDR quits with the second engine, ok get that. Presumption that the APU starts ok (once at a suitable altitude) and provides AC power to the main systems again. Not a bad presumption but somewhat undermined by the DFDR not going online again. So just what systems and displays did the crew have available to them?
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Shouldn't have been. This was only 1:50 in the mission and the report says they were compliant with crew duty and rest period.
They ended up dual engine out because they shut down the wrong engine. That is indisputable. There isn't a single flight safety course that doesn't hammer home the "Kegworth" effect of startle reflex and response, the situation seems bad and disorienting, but if you act suddenly and reflexively, you may just make it as lot worse, as happened here. There have also been a multitude of accidents where EICAS messages are misleading or plain wrong following some major malfunction. There were other primary displays of engine condition, Engine Pressure Ratio (EPR) and Inter Turbine Temperature (ITT), and the digital readouts of Fuel Flow (FF), N2 (RPM core), and oil pressure to allow some element of cross checking to take place before touching any of the throttles. Not diverting into the nearest field with 40K of altitude is almost understandable, but not once it became a dual engine out situation.
It's not a blame game at this stage, it's all about understanding how you aren't going to make those same mistakes
They ended up dual engine out because they shut down the wrong engine. That is indisputable. There isn't a single flight safety course that doesn't hammer home the "Kegworth" effect of startle reflex and response, the situation seems bad and disorienting, but if you act suddenly and reflexively, you may just make it as lot worse, as happened here. There have also been a multitude of accidents where EICAS messages are misleading or plain wrong following some major malfunction. There were other primary displays of engine condition, Engine Pressure Ratio (EPR) and Inter Turbine Temperature (ITT), and the digital readouts of Fuel Flow (FF), N2 (RPM core), and oil pressure to allow some element of cross checking to take place before touching any of the throttles. Not diverting into the nearest field with 40K of altitude is almost understandable, but not once it became a dual engine out situation.
It's not a blame game at this stage, it's all about understanding how you aren't going to make those same mistakes
David
Shouldn't have been. This was only 1:50 in the mission and the report says they were compliant with crew duty and rest period.
They ended up dual engine out because they shut down the wrong engine. That is indisputable. There isn't a single flight safety course that doesn't hammer home the "Kegworth" effect of startle reflex and response, the situation seems bad and disorienting, but if you act suddenly and reflexively, you may just make it as lot worse, as happened here. There have also been a multitude of accidents where EICAS messages are misleading or plain wrong following some major malfunction. There were other primary displays of engine condition, Engine Pressure Ratio (EPR) and Inter Turbine Temperature (ITT), and the digital readouts of Fuel Flow (FF), N2 (RPM core), and oil pressure to allow some element of cross checking to take place before touching any of the throttles. Not diverting into the nearest field with 40K of altitude is almost understandable, but not once it became a dual engine out situation.
It's not a blame game at this stage, it's all about understanding how you aren't going to make those same mistakes
They ended up dual engine out because they shut down the wrong engine. That is indisputable. There isn't a single flight safety course that doesn't hammer home the "Kegworth" effect of startle reflex and response, the situation seems bad and disorienting, but if you act suddenly and reflexively, you may just make it as lot worse, as happened here. There have also been a multitude of accidents where EICAS messages are misleading or plain wrong following some major malfunction. There were other primary displays of engine condition, Engine Pressure Ratio (EPR) and Inter Turbine Temperature (ITT), and the digital readouts of Fuel Flow (FF), N2 (RPM core), and oil pressure to allow some element of cross checking to take place before touching any of the throttles. Not diverting into the nearest field with 40K of altitude is almost understandable, but not once it became a dual engine out situation.
It's not a blame game at this stage, it's all about understanding how you aren't going to make those same mistakes
I believe we’re all compelled to take way something that we can incorporate into our own operations. For me, above and beyond the drills of handling a failure, it’s that time is on your side with a failure when it occurs at mid/high altitudes. Commence the immediate action item/QRH, etc only when your ready and sure of what your facing.
I believe we’re all compelled to take way something that we can incorporate into our own operations. For me, above and beyond the drills of handling a failure, it’s that time is on your side with a failure when it occurs at mid/high altitudes. Commence the immediate action item/QRH, etc only when your ready and sure of what your facing.
Many good points are being made, but I would like to add / highlight the following;
1. The vibration was so severe the FDR & CVR thought there'd been an impact. That's pretty violent.
2. The crew were not trained for this event, nor had it ever been discussed. (This wasn't a simple :engine vibration" event).
3. Bombardier, to my knowledge have no QRH Procedure for Fan Blade Off.
4. By all accounts, these guys were competent and well trained, but perhaps felt they needed to bypass years of training to get the engine shutdown urgently or perhaps risk an airframe failure.
There has been an similar failure in a Gulfstream G650. Similar engines / airframe. The crew managed to contain the situation. Based on the FDR data, the manufacturer was able to come up with a procedure to manage the situation in future. That data has also created a sim profile and I can tell you its extremely violent and disorientating, and I was expecting it.
Rolls Royce are also aware of FBO (Fan Blade Off) events. Draw your own conclusions.
I can understand why the crew felt the need to shut it down pronto. The challenge is to be able to read the engine gauges when the aircraft is shaking so violently and convince yourself the aircraft will hold together while you figure it out.
Before you say something logical like "pull them both back to idle, advance 1 at a time", that apparently doesn't work conclusively. Counter intuitively, what works in the G650, is increasing airspeed to MMO / VMO at idle power and only slowing (without speedbrakes) once you get to 10.000'. Now, try figure that out when you've never seen the failure or trained for it and its happening. In a warzone.
RIP to two guys doing the best they could on a bad day.
1. The vibration was so severe the FDR & CVR thought there'd been an impact. That's pretty violent.
2. The crew were not trained for this event, nor had it ever been discussed. (This wasn't a simple :engine vibration" event).
3. Bombardier, to my knowledge have no QRH Procedure for Fan Blade Off.
4. By all accounts, these guys were competent and well trained, but perhaps felt they needed to bypass years of training to get the engine shutdown urgently or perhaps risk an airframe failure.
There has been an similar failure in a Gulfstream G650. Similar engines / airframe. The crew managed to contain the situation. Based on the FDR data, the manufacturer was able to come up with a procedure to manage the situation in future. That data has also created a sim profile and I can tell you its extremely violent and disorientating, and I was expecting it.
Rolls Royce are also aware of FBO (Fan Blade Off) events. Draw your own conclusions.
I can understand why the crew felt the need to shut it down pronto. The challenge is to be able to read the engine gauges when the aircraft is shaking so violently and convince yourself the aircraft will hold together while you figure it out.
Before you say something logical like "pull them both back to idle, advance 1 at a time", that apparently doesn't work conclusively. Counter intuitively, what works in the G650, is increasing airspeed to MMO / VMO at idle power and only slowing (without speedbrakes) once you get to 10.000'. Now, try figure that out when you've never seen the failure or trained for it and its happening. In a warzone.
RIP to two guys doing the best they could on a bad day.
Many good points are being made, but I would like to add / highlight the following;
1. The vibration was so severe the FDR & CVR thought there'd been an impact. That's pretty violent.
2. The crew were not trained for this event, nor had it ever been discussed. (This wasn't a simple :engine vibration" event).
3. Bombardier, to my knowledge have no QRH Procedure for Fan Blade Off.
4. By all accounts, these guys were competent and well trained, but perhaps felt they needed to bypass years of training to get the engine shutdown urgently or perhaps risk an airframe failure.
There has been an similar failure in a Gulfstream G650. Similar engines / airframe. The crew managed to contain the situation. Based on the FDR data, the manufacturer was able to come up with a procedure to manage the situation in future. That data has also created a sim profile and I can tell you its extremely violent and disorientating, and I was expecting it.
Rolls Royce are also aware of FBO (Fan Blade Off) events. Draw your own conclusions.
I can understand why the crew felt the need to shut it down pronto. The challenge is to be able to read the engine gauges when the aircraft is shaking so violently and convince yourself the aircraft will hold together while you figure it out.
Before you say something logical like "pull them both back to idle, advance 1 at a time", that apparently doesn't work conclusively. Counter intuitively, what works in the G650, is increasing airspeed to MMO / VMO at idle power and only slowing (without speedbrakes) once you get to 10.000'. Now, try figure that out when you've never seen the failure or trained for it and its happening. In a warzone.
RIP to two guys doing the best they could on a bad day.
1. The vibration was so severe the FDR & CVR thought there'd been an impact. That's pretty violent.
2. The crew were not trained for this event, nor had it ever been discussed. (This wasn't a simple :engine vibration" event).
3. Bombardier, to my knowledge have no QRH Procedure for Fan Blade Off.
4. By all accounts, these guys were competent and well trained, but perhaps felt they needed to bypass years of training to get the engine shutdown urgently or perhaps risk an airframe failure.
There has been an similar failure in a Gulfstream G650. Similar engines / airframe. The crew managed to contain the situation. Based on the FDR data, the manufacturer was able to come up with a procedure to manage the situation in future. That data has also created a sim profile and I can tell you its extremely violent and disorientating, and I was expecting it.
Rolls Royce are also aware of FBO (Fan Blade Off) events. Draw your own conclusions.
I can understand why the crew felt the need to shut it down pronto. The challenge is to be able to read the engine gauges when the aircraft is shaking so violently and convince yourself the aircraft will hold together while you figure it out.
Before you say something logical like "pull them both back to idle, advance 1 at a time", that apparently doesn't work conclusively. Counter intuitively, what works in the G650, is increasing airspeed to MMO / VMO at idle power and only slowing (without speedbrakes) once you get to 10.000'. Now, try figure that out when you've never seen the failure or trained for it and its happening. In a warzone.
RIP to two guys doing the best they could on a bad day.
In the race to place failing on the crew I do wonder what remaining value there is in a USAF mishap report. In examples such as this they make little or no effort to understand the failure, the dire situation faced by the crew or any curiosity as to why the aircraft systems were working against the crew. The input from Bombardier and RR seems minimal with no effort to resolve the apparent technical inconsistencies.
I met the crew of the Global that had the similar incident in 2006 whilst on recurrent. It was only a few weeks after it had happened.
They stressed that the vibration was so severe that they couldn’t read the instruments, and it continued all the way to touchdown once the engine was windmilling.
The crucial difference between the 2006 incident and this is the time taken to react. 24 seconds before the (wrong) engine was shut down in the case of the USAF crew. 1-2 minutes in the original event. The extra time to analyse the situation would have revealed the L engine indications decaying, even through the vibration. Perhaps if they had actioned the L FADEC FAIL procedure, they would have found it says ‘Monitor engine Instruments. NOTE EPR to N1 reversion may occur. RPM May reduce to idle setting. Engine may shut down’. This should have strongly indicated to them that the problem was the L engine.
In any emergency situations, military (RAF) training was always ‘Fly the aircraft’ as a priority. Yes we have huge vibrations, but we aren’t falling out of the sky so no need to rush into doing anything. An old bold QFI (who on reflection wasn’t that old) told me once that the Immediate action to anything in a multi engined aircraft should be to ‘wind the stop watch‘. If you aren’t about to hit the ground then take time to analyse.
It was a difficult situation for the crew, but one that they should have been capable of resolving. A less experienced crew faced with an identical (technical) situation had previously correctly diagnosed and dealt with this problem. So why didn’t this crew? What made them rush into shutting down the wrong engine?
For me, the startle effect clearly had a huge effect on the outcome of this tragic event.
As ever our thoughts are with the families and hope that the guys have found blue skies. But they should also be to re-examine the way that we ourselves respond to situations and strive not to fall victim to the startle effect if we are ever in a similar position.
They stressed that the vibration was so severe that they couldn’t read the instruments, and it continued all the way to touchdown once the engine was windmilling.
The crucial difference between the 2006 incident and this is the time taken to react. 24 seconds before the (wrong) engine was shut down in the case of the USAF crew. 1-2 minutes in the original event. The extra time to analyse the situation would have revealed the L engine indications decaying, even through the vibration. Perhaps if they had actioned the L FADEC FAIL procedure, they would have found it says ‘Monitor engine Instruments. NOTE EPR to N1 reversion may occur. RPM May reduce to idle setting. Engine may shut down’. This should have strongly indicated to them that the problem was the L engine.
In any emergency situations, military (RAF) training was always ‘Fly the aircraft’ as a priority. Yes we have huge vibrations, but we aren’t falling out of the sky so no need to rush into doing anything. An old bold QFI (who on reflection wasn’t that old) told me once that the Immediate action to anything in a multi engined aircraft should be to ‘wind the stop watch‘. If you aren’t about to hit the ground then take time to analyse.
It was a difficult situation for the crew, but one that they should have been capable of resolving. A less experienced crew faced with an identical (technical) situation had previously correctly diagnosed and dealt with this problem. So why didn’t this crew? What made them rush into shutting down the wrong engine?
For me, the startle effect clearly had a huge effect on the outcome of this tragic event.
As ever our thoughts are with the families and hope that the guys have found blue skies. But they should also be to re-examine the way that we ourselves respond to situations and strive not to fall victim to the startle effect if we are ever in a similar position.
01 at Dubai Air Show
Just reading the US Army maybe buying Sentinel R1 reminded me of this thread. I was reunited with seeing 01 at Dubai Air Dhow the other weekend three years after watching it fly into Mildenhall so here are my photos below.
