Of interest to BK117-C2 operators
Thread Starter
Of interest to BK117-C2 operators
Exactly.
Interesting reading, this report, the original accident report and the referenced 130-page report from engine OEM Safran. Twin-engine >500 ft AGL, blue skies, day-time. Bearing in engine # 2 seizes.
In theory, the twin should have guaranteed a safe outcome. While in the given situation not being able to hover on the remaining engine, the mishap pilot (4500 HRS TTRW, > 1000 HRS on type) would have been able to maintain straight and level 50 KTS forward flight, and then done a controlled auto, or run-on landing to a smooth and level surface.
In reality, exactly the fact that it was a twin resulted in a the worst possible outcome (all 4 pax fatally injured).
For starters, the chances of a bearing seizing in a single would be 50% of the same in a twin. If, say, a bearing goes every 10,000 hours, when you have 2 engines you'll see this happen in average every 5,000 hours. That's the flop side of redundancy. But that's just the beginning.
In a single, the pilot, on first indication of engine going, would enter autorotation. Probably the engine - at lower power settings - would stay on, and add at least some assistance for the touch-down at the end of the autorotation.
Here however, with two engines, we managed to slow down, almost to a hover, while figuring out what the Christmas tree of warnings, and a misleading First Limit Indicator (which indeed works very well in a single, even in a twin while both engines are running, but didn't work at all well in this OEI situation) could mean.
Then as said, mislead by the FLI (and not at all prepared for this scenario neither mentally nor by virtue of training) the mishap pilot shut down the wrong, the OK engine # 1. By which time not only both engines, but also the sole rotor had stopped spinning.
Interesting reading, this report, the original accident report and the referenced 130-page report from engine OEM Safran. Twin-engine >500 ft AGL, blue skies, day-time. Bearing in engine # 2 seizes.
In theory, the twin should have guaranteed a safe outcome. While in the given situation not being able to hover on the remaining engine, the mishap pilot (4500 HRS TTRW, > 1000 HRS on type) would have been able to maintain straight and level 50 KTS forward flight, and then done a controlled auto, or run-on landing to a smooth and level surface.
In reality, exactly the fact that it was a twin resulted in a the worst possible outcome (all 4 pax fatally injured).
For starters, the chances of a bearing seizing in a single would be 50% of the same in a twin. If, say, a bearing goes every 10,000 hours, when you have 2 engines you'll see this happen in average every 5,000 hours. That's the flop side of redundancy. But that's just the beginning.
In a single, the pilot, on first indication of engine going, would enter autorotation. Probably the engine - at lower power settings - would stay on, and add at least some assistance for the touch-down at the end of the autorotation.
Here however, with two engines, we managed to slow down, almost to a hover, while figuring out what the Christmas tree of warnings, and a misleading First Limit Indicator (which indeed works very well in a single, even in a twin while both engines are running, but didn't work at all well in this OEI situation) could mean.
Then as said, mislead by the FLI (and not at all prepared for this scenario neither mentally nor by virtue of training) the mishap pilot shut down the wrong, the OK engine # 1. By which time not only both engines, but also the sole rotor had stopped spinning.
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Be careful how you interpret the VEMD when reaching for the "OFF" switch.
Maybe even this part of the accident genesis is not only of interest to H145/EC145/BK-117 operators?
Well, as a pilot you should know your machine.
Reducing the speed below Vy to identify a problem is never a good idea.
The Checklist states: reduce to safe OEI speed - and in a C2 normally an autopilot could assist a single pilot, keeping speed and altitude.
Cause you're normally not dropping out of the sky in a twin with one engine misbehaving you should take the time to identify the faulty engine.
But even in a twin - looking for an area where you can autorotate into isn't a bad idea either, cause one engine disintegrating can take out the other one as well.
Due to the fire some valuable Information is missing - but reading the report I assume that the pilot, even with his flying hours, stopped flying and started trouble shooting - which ended fatal :-(
It helps to spend some time in a simulator and play through the different failure modes. It improves your coolness, when it happens in real, cause you have dealt with the same problems before....
Reducing the speed below Vy to identify a problem is never a good idea.
The Checklist states: reduce to safe OEI speed - and in a C2 normally an autopilot could assist a single pilot, keeping speed and altitude.
Cause you're normally not dropping out of the sky in a twin with one engine misbehaving you should take the time to identify the faulty engine.
But even in a twin - looking for an area where you can autorotate into isn't a bad idea either, cause one engine disintegrating can take out the other one as well.
Due to the fire some valuable Information is missing - but reading the report I assume that the pilot, even with his flying hours, stopped flying and started trouble shooting - which ended fatal :-(
It helps to spend some time in a simulator and play through the different failure modes. It improves your coolness, when it happens in real, cause you have dealt with the same problems before....
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Very good contribution, Flying Bull!
I totally agree. EngCHIP ist not something which requires immediate action. That's why it's a caution and not a warning message. And there might even be a Chip Burner (if I recall correctly it's optional in the C2). Meaning you start with "NR-PPAA. Check Rotorspeed, Set Power, Check resulting performance. If everything is adjusted according to situation, then Analyze the problem (Checklist) and put together your plan.
What happened exactly and why sadly the pilot could not live up to this essential systematics for twin-helicopters we don't know.
Time spent in a simulator to drill and repeat those "abnormal"-systematics is well spent...
I totally agree. EngCHIP ist not something which requires immediate action. That's why it's a caution and not a warning message. And there might even be a Chip Burner (if I recall correctly it's optional in the C2). Meaning you start with "NR-PPAA. Check Rotorspeed, Set Power, Check resulting performance. If everything is adjusted according to situation, then Analyze the problem (Checklist) and put together your plan.
What happened exactly and why sadly the pilot could not live up to this essential systematics for twin-helicopters we don't know.
Time spent in a simulator to drill and repeat those "abnormal"-systematics is well spent...
Good advice. Sim training is the way to go but not available to all. Flying single-pilot it is even more important to take things slowly and apply the usual Aviate, Navigate, Communicate. Non-failure engine problems can be confusing and the FLI needle can add to that. As an instructor I often witnessed pilots continuing to fly manually when diagnosing malfunctions even though the auto-pilot was available. Also if VMC with a good landing area available there is always the option to land and sort it out. If it means that you cannot take off again then so be it.
I find it interesting that the FLI shows a needle for both engines, whereas the EC155 only has a single pointer and you look at the digital readings to see which engine is limiting and what parameter - values are underscored. At lower levels they are both torque limited, so both torque values will be underscored, but as you climb you transition to N1 limiting and you can find (typically) one engine's Tq value underscored and the other's N1 value underscored, until a bit higher when up both N1s will be limiting. In this example, a similar system may have helped as the pilot would have been confronted with a single FLI pointer (which would have been No 2 TOT limited) and he could then have looked at the individual engine parameters and seen matching Tq and N1 (or very close) and wildly differing TOT - 770 C vs 890 C. Possibly this would have led to an easier diagnosis of the engine with the fault
