EMS AS350 Crash Tucson
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Initial radar data indicated that the helicopter was on a steady southeast course, at 131 knots ground speed, and 900 feet above ground level (agl). The last 8 seconds of radar data indicated that the helicopter descended 600 feet. The last radar return was at 1341:32, approximately 140 feet agl, and 0.25 miles from the accident site. The pilot did not transmit a radio distress call.
so 8 secs@ 131 kts is 584 yards? and 4500ftm = 200 yds or 1 in 3 down to the 140 feet agl. probably thought he had it there ( so no mayday) and slowing and then the bit in red is 1 yard down for every 10 forwards.
i have no idea of auto descent normal rate, but assume to acheive the 4500 he must have had the coll full down and the high 131 A/S, but the last 440 yds looks like a much reduced forward airspeed, on the average.
but the horrible picture seems to show a slower rate across ground, almost going into the dreaded J curve for the last sixty or seventy feet.
very sad.
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Difficult stuff - from the NTSB Preliminary...
Whump Whump sounds like rotor blade slap from maneuvering.
Rapid intermittent popping sounds seems like a series of compressor stalls.
The positive coning angle on the rotor in the picture seems to indicate the rotor was turning at that point.
Flight trajectory became increasingly vertical could be the final portion of descent after speed reduction, powered or not.
Impacted the ground in a level attitude appears to indicate the very final portion of the descent prior to impact had rotor control for a flare?
A 4500fpm rate of descent is not normal for autorotation in an A-Star (or any other helicopter I am familiar with) unless possibly the rotor is at an adverse value. After impact the main and tail rotor blades apparently have little torsional/twisting damage. Not sure what that indicates.
Decades ago I trained pilots in the AS-350D and had them pick it up and set it down hydraulics off, prior to doing a circuit with hydraulics failure on downwind so they would have an idea what they were dealing with when transitioning towards the hover. This actually shortened hydraulics off training, and increased pilot confidence if necessary to make a hydraulics off approach to a point at such other than an airstrip, etc. The B series hydraulic off flight I am not familiar with; I suspect it is more unpleasant than the D-model.
Condolences.
WIII
Rapid intermittent popping sounds seems like a series of compressor stalls.
The positive coning angle on the rotor in the picture seems to indicate the rotor was turning at that point.
Flight trajectory became increasingly vertical could be the final portion of descent after speed reduction, powered or not.
Impacted the ground in a level attitude appears to indicate the very final portion of the descent prior to impact had rotor control for a flare?
A 4500fpm rate of descent is not normal for autorotation in an A-Star (or any other helicopter I am familiar with) unless possibly the rotor is at an adverse value. After impact the main and tail rotor blades apparently have little torsional/twisting damage. Not sure what that indicates.
Decades ago I trained pilots in the AS-350D and had them pick it up and set it down hydraulics off, prior to doing a circuit with hydraulics failure on downwind so they would have an idea what they were dealing with when transitioning towards the hover. This actually shortened hydraulics off training, and increased pilot confidence if necessary to make a hydraulics off approach to a point at such other than an airstrip, etc. The B series hydraulic off flight I am not familiar with; I suspect it is more unpleasant than the D-model.
Condolences.
WIII
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From my memory of a test flight in an AS350D, the RoD reached nearly 3000 fpm at 90 kts. I don't know whether that extrapolates to 4500 fpm at 131 kts.
The RoD on a textbook auto at 70 kts should be a lot lower at 1500 to 2000 fpm. We also performed a zero speed auto and the RoD was about 3000 fpm. With lots of height to recover, of course.
The RoD on a textbook auto at 70 kts should be a lot lower at 1500 to 2000 fpm. We also performed a zero speed auto and the RoD was about 3000 fpm. With lots of height to recover, of course.
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Interesting
I don't remember values that high but good information.
It doesn't appear the helicopter fell from the sky as one witness indicated, due to the impact attitude being flat - implies some pilot awareness and controllability post the low pitch attitude picture.
I remember on engine failure the AS350 rotor decays rapidly, like other low inertia rotors; lot like the H300C.
I can imagine a pilot getting startled by the hugely loud low rotor horn (that's what I remember from the D-model), being delayed in collective reduction, and getting behind the recovery curve.
He may have just had too much ROD to effect a recovery at the bottom.
Very sad stuff.
WIII
It doesn't appear the helicopter fell from the sky as one witness indicated, due to the impact attitude being flat - implies some pilot awareness and controllability post the low pitch attitude picture.
I remember on engine failure the AS350 rotor decays rapidly, like other low inertia rotors; lot like the H300C.
I can imagine a pilot getting startled by the hugely loud low rotor horn (that's what I remember from the D-model), being delayed in collective reduction, and getting behind the recovery curve.
He may have just had too much ROD to effect a recovery at the bottom.
Very sad stuff.
WIII
What makes me doubt the low RRPM is that the blades in the picture appear absolutely straight, i.e. no tulip shape.
Normally the blades on the AS350 are not extremely rigid.
So I would expect a more curved shape of the blades if the RRPM was really very low. And to explain the attitude in the picture by LoC due to low RRPM would require VERY low RPM.
There might be some merit to the Hydraulics problem theory. Just speculating though, which I know I shouldn´t....
Normally the blades on the AS350 are not extremely rigid.
So I would expect a more curved shape of the blades if the RRPM was really very low. And to explain the attitude in the picture by LoC due to low RRPM would require VERY low RPM.
There might be some merit to the Hydraulics problem theory. Just speculating though, which I know I shouldn´t....
Have any of you had a bird strike in an AS350?
Working through the brief report, I'll assume for the moment that the pop pop sounds were the symptoms of a compressor stall. From that thought, hypothesis of a bird flying into an engine, compressor stall, and then ... and another bird, at about the same time, hit the aircraft as well.
At 131 knots, if a bird hits the wind screen of the AS350, is it likely to bounce off or penetrate or crack the windshield?
The few pictures I saw didn't suggest to me a broken windscreen on the left side, but I didn't see the right side where pilot sits.
If you had both a compressor stall and a pilot hit by a bird (Yes, I am guessing here), the pilot at the controls might be having difficulty dealing with the engine problem due to impact injury ... up to partial incapacitation. Partial suggested due to generally remaining in flat attitude (as reported) up to impact.
I realize I've pulled this out of my backside, but I recall a case over 25 years ago of a pilot temporarily dazed by a turkey buzzard smashing through his windscreen and being knocked groggy. He then came to and managed to fly his aircraft home, even though he had (IIRC) a broken collar bone. He was up a few thousand feet, however.
I also have no idea what typical bird activity is in Tuscon at this time of year, so this may be a very dumb bit of speculation.
Working through the brief report, I'll assume for the moment that the pop pop sounds were the symptoms of a compressor stall. From that thought, hypothesis of a bird flying into an engine, compressor stall, and then ... and another bird, at about the same time, hit the aircraft as well.
At 131 knots, if a bird hits the wind screen of the AS350, is it likely to bounce off or penetrate or crack the windshield?
The few pictures I saw didn't suggest to me a broken windscreen on the left side, but I didn't see the right side where pilot sits.
If you had both a compressor stall and a pilot hit by a bird (Yes, I am guessing here), the pilot at the controls might be having difficulty dealing with the engine problem due to impact injury ... up to partial incapacitation. Partial suggested due to generally remaining in flat attitude (as reported) up to impact.
I realize I've pulled this out of my backside, but I recall a case over 25 years ago of a pilot temporarily dazed by a turkey buzzard smashing through his windscreen and being knocked groggy. He then came to and managed to fly his aircraft home, even though he had (IIRC) a broken collar bone. He was up a few thousand feet, however.
I also have no idea what typical bird activity is in Tuscon at this time of year, so this may be a very dumb bit of speculation.
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Bird strike
Never thought of it. I know a BK117 that had both condition levers pushed to idle after a goose hit the upper middle windscreen. The pilot figured it out just prior to entering the trees and wound up saving the aircraft and possibly all on board. Stuff happens very fast and one has to get really determined to deal with it in a hurry or the outcome may not be good. The shock value must be very difficult to overcome.
I flew a AS350D for five years. Never had a strike but some years after it was sold the entire left front, including a portion of the Lexan windscreen, was broken and mangled by hitting a seagull. I'd say at 131 knots a large bird could get through to affect the pilot.
I flew a AS350D for five years. Never had a strike but some years after it was sold the entire left front, including a portion of the Lexan windscreen, was broken and mangled by hitting a seagull. I'd say at 131 knots a large bird could get through to affect the pilot.
Seems oddly reminiscent of this unsolved B3 accident:
DFW07GA119
“The pilot's encounter with a vortex ring state and his inability to maintain control of the helicopter.” I hope we don't get a similar wildly speculative explanation pulled from the hat here too.
DFW07GA119
“The pilot's encounter with a vortex ring state and his inability to maintain control of the helicopter.” I hope we don't get a similar wildly speculative explanation pulled from the hat here too.
Last edited by JimEli; 7th Aug 2010 at 14:14. Reason: corrected link
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A company pilot hit a duck in a AS350B2 couple of years back. He would have been in cruise about 1000agl. It smashed thru center of bubble and splattered all the occupants in blood, guts and feathers. They managed to land ok at the aerodrome nearby.
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Incapacitated pilot
In the case of an incapacitated pilot, I can see one of the medical crewmembers pulling back on the cyclic in a last ditch effort to pull out of the fatal dive at the last second. This may have been responsible for the flare or leveling off before impact. If the crash investigation evidence shows an unrestrained med crewmember at time of impact, this may be the reason. Usually in cruise they would be strapped in.
DUCK!
Here are some photos of the Baptist EMS A-Star encounter with a flock of birds.....the windscreen sure got quacked!
Baptist Med Flight - a set on Flickr
Baptist Med Flight - a set on Flickr
