US loses first Osprey
05-18-2015, 11:38 AM
#61
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Pretty amazing that there weren't more fatalities. Best for the crew and a speedy recovery. Not sure what altitudes are for HOGE / HIGE on an Osprey. Vortex ring state may have helped if they're coming straight down at that rate of descent.
05-18-2015, 12:09 PM
#62
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Oh, and nowadays the plane has a crew alerting system that warns of sink rate once you hit 800 fpm descent in a hover(which is well prior to the descent rates needed to actually get VRS on the Osprey). So I doubt the crew let a rate of descent develop to where VRS was the cause of this accident. Regardless of what caused the descent, I think the crew did a great job of keeping the plane level so the landing gear, airframe, and crash attenuating seats could be effective during the impact.
05-18-2015, 02:52 PM
#63
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Originally Posted by plift
Oh, and nowadays the plane has a crew alerting system that warns of sink rate once you hit 800 fpm descent in a hover(which is well prior to the descent rates needed to actually get VRS on the Osprey). So I doubt the crew let a rate of descent develop to where VRS was the cause of this accident. Regardless of what caused the descent, I think the crew did a great job of keeping the plane level so the landing gear, airframe, and crash attenuating seats could be effective during the impact.
05-18-2015, 03:37 PM
#65
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From a low hover you just add power and keep things level to absorb the impact. From a high hover the procedure does say it may be possible to regain airspeed and return to flight(the height necessary for this will of course depend on weight and ambient conditions). Once you get through translational lift you'd be fine on a single engine, about 30-40 knots. It normally doesn't take long to get through translational lift but being heavy will delay things. If it was an engine failure in this case, given the weight of all the Marines on board the crew may not have been able to perform the flyaway if they tried. Also I think they had trees in front of them obscured by the dust kicked up by the other two planes that already landed so attempting a flyaway would have been risky.
07-21-2015, 12:15 PM
#66
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Fatal Crash Prompts Marines To Change Osprey Flight Rules « Breaking Defense - Defense industry news, analysis and commentary
So a power loss/engine failure does appear to be the issue in the Hawaii crash. Interesting they said both engines suffered some sort of power loss before the left engine totally failed. The engine air partial separator system on it isn't the greatest and like the article mentions they've been testing an improved inlet to fix it. To get a rapid power loss though(basically over the course of a single flight operating in a dusty/sandy environment) that system would have to fail completely. The engines in normal service aren't replaced until they show a reduction in power down to 95% though. So its hard to say if they mean in this case the remaining operating engine experienced a power loss below that level or that it showed a power loss but was still within the acceptable range. Trivial to the end result though, even on a brand new engine making over 100% of its rated power they wouldn't have been able to hover in this case, to heavy.
Originally Posted by Breaking Defense
Investigators are still studying the training flight mishap in which an MV-22B Osprey‘s hard landing killed two Marines aboard. They have yet to officially declare the crash’s cause, but BD has learned that the plane suffered reduced power in both engines and a compressor stall that knocked the left one out entirely after spending an unusually long 45 seconds hovering over a dusty landing zone.
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