H21 Heli crash videos
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H21 hele crash video
h21 hele crashhas anyone else noticed the flashes from inside the fuselage at approx 10 & 24 seconds? reminds me of the train versus nuclear flask "test" some years back where flashes were seen along the underframe of the locomotive immediately before impact & the power unit making a rapid exit through the locomotive roof! Perhaps there is a logical explanation for these flashes in this video,maybe connected with the undercariage failure, or was it stage managed stage effects? I bow to your greater wisdom fellow ppruners!
"reminds me of the train versus nuclear flask "test" some years back where flashes were seen along the underframe of the locomotive immediately before impact "
Jesus, reminds me of that well known TV series "I'm a conspiracy theorist, get me out of here."
MG: I agree
TC: I think you're right (no pilots on board)!
Jesus, reminds me of that well known TV series "I'm a conspiracy theorist, get me out of here."
MG: I agree
TC: I think you're right (no pilots on board)!
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See the remote control wire from the tail?
The ground pilot probably underestimated the difficulty of flying a RC helo.
Loss of control in 10 seconds would be average, without a long training program.
The ground pilot probably underestimated the difficulty of flying a RC helo.
Loss of control in 10 seconds would be average, without a long training program.
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The flashes are automax lights, part of the test equipment, they mark the exact location of three fuselage points at impact, because they mark the film very specifically.
Or they are the alien pilots, smiling for the camera....
Those landings are done at about 15 feet per second, based on some back of the envelope calculations I just did. The design sink speed of the Black hawk is 42 feet per second (including gear collapse) and it can hit at 12 feet per second without any damage. Therefore, these landings would probably result in no damage if done in an H-60!
This illustrates the power of the modern design requirements - the H-64 and H-58D are similar, I believe as is the S-92 and AB-139.
Or they are the alien pilots, smiling for the camera....
Those landings are done at about 15 feet per second, based on some back of the envelope calculations I just did. The design sink speed of the Black hawk is 42 feet per second (including gear collapse) and it can hit at 12 feet per second without any damage. Therefore, these landings would probably result in no damage if done in an H-60!
This illustrates the power of the modern design requirements - the H-64 and H-58D are similar, I believe as is the S-92 and AB-139.
Last edited by NickLappos; 31st Mar 2007 at 15:52.
Gatvol
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Couple of locations come to mind. One would be NAS China Lake, just a few miles North of Edwards AFB, or NAS Fallon Nevada.
It obvious a tethered aircraft on a hard landing, second one looks like something went wrong with the controls or maybe a Fixed Wing type thought he could fly the box. Or he could have run out of tether, thus no control. Dont think that was part of the test.
It obvious a tethered aircraft on a hard landing, second one looks like something went wrong with the controls or maybe a Fixed Wing type thought he could fly the box. Or he could have run out of tether, thus no control. Dont think that was part of the test.
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"The design sink speed of the Black hawk is 42 feet per second (including gear collapse) and it can hit at 12 feet per second without any damage. Therefore, these landings would probably result in no damage if done in an H-60!"
I was about to say those videos look like Army H60 pilots doing a type transition.
I was about to say those videos look like Army H60 pilots doing a type transition.
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Just to gain perspective 42 feet/sec is about 28 mph, which is almost the speed a test car will be doing when it hits a solid crash barrier (deformable offset is 40mph). I'm guessing only part of the energy is absorbed by the gear strut pressurisation and collapse, so 20g peaks would be seen as the fuselage contacts the ground. Probably at least a foot or two of deformation between pilots seat and ground to keep crew safe. Some design!
Mart
Mart
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Hi
in the context.... Helicopter crash-landing test
maybe nick and others can give some "numbers" to this...
seems a 76 somewhere in the video...
in the context.... Helicopter crash-landing test
maybe nick and others can give some "numbers" to this...
seems a 76 somewhere in the video...
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CS,
Great movie. That is a Huey first, probably at about 8 to 12 fps, since that is the speed where the skids bend to let the belly touch. The next machine is the S76 ACAP (a totally composite fuselage that was built in about 1982 for the pre-Comanche research). It was designed for 42 FPS as well, and you can see the pilot's seat (CP only for some reason) stroke fully in the last sequence. The seat is designed to start moving at about 20 G's and hold that G or less for its full 10" stroke, allowing the fuselage to be sacrificed while protecting the crew. The fuselage is designed to hold all primary cabin dimensions within about 6", and must keep out the primary masses (transmission and engines) for the 20G impact. The baseline S76, H-60 family and the S92 were designed to these fuselage requirements (as were the H-64 and the AB-139).
Great movie. That is a Huey first, probably at about 8 to 12 fps, since that is the speed where the skids bend to let the belly touch. The next machine is the S76 ACAP (a totally composite fuselage that was built in about 1982 for the pre-Comanche research). It was designed for 42 FPS as well, and you can see the pilot's seat (CP only for some reason) stroke fully in the last sequence. The seat is designed to start moving at about 20 G's and hold that G or less for its full 10" stroke, allowing the fuselage to be sacrificed while protecting the crew. The fuselage is designed to hold all primary cabin dimensions within about 6", and must keep out the primary masses (transmission and engines) for the 20G impact. The baseline S76, H-60 family and the S92 were designed to these fuselage requirements (as were the H-64 and the AB-139).
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Amazing vid, CS-Hover. I spent a while as a crash engineer in the auto industry, before i decided engin's were my thing (heli powertrains even better!). The numbers are actually suprisingly simple to work out - in metric, sorry: 
Say machine is descending at 42 feet/sec or 12.8 m/sec, and limiting peak deceleration allowed is 20g. Using
Vel^2 = 2 x Accel x Dist (remember to convert accel to m/sec^2)
gives minimum crush distance of 0.42 m or 1.4 feet. This is the ideal case assuming everything neatly collapsed at exactly 20g - trust me it doesn't!
In practice, the landing gear is designed to collapse at 10g (thanks Nick), over a distance of ~0.6m. This means once fuselage contacts (denoted on film by automax flash) machine is still decending at speed worked out from
Vinit^2 - Vel^2 = 2 x Accel x Dist
which using example figures gives 6.8 m/sec. Same equation as above then means fuselage must crush 0.12 m or 0.39 feet. In practice frame crush will be a series of small collapses, each below 20g, so that 6" requirement will soon be used up.
If design is optimised machine does not bounce as all of the impact energy is absorbed in the collapse. In practice crew seating will also collapse to ensure any peaks stay below 20g. Crew gets out and walks away to post on PPRuNe about the advantages of flaring on EOL.
Mart
Say machine is descending at 42 feet/sec or 12.8 m/sec, and limiting peak deceleration allowed is 20g. Using
Vel^2 = 2 x Accel x Dist (remember to convert accel to m/sec^2)
gives minimum crush distance of 0.42 m or 1.4 feet. This is the ideal case assuming everything neatly collapsed at exactly 20g - trust me it doesn't!
In practice, the landing gear is designed to collapse at 10g (thanks Nick), over a distance of ~0.6m. This means once fuselage contacts (denoted on film by automax flash) machine is still decending at speed worked out from
Vinit^2 - Vel^2 = 2 x Accel x Dist
which using example figures gives 6.8 m/sec. Same equation as above then means fuselage must crush 0.12 m or 0.39 feet. In practice frame crush will be a series of small collapses, each below 20g, so that 6" requirement will soon be used up.
If design is optimised machine does not bounce as all of the impact energy is absorbed in the collapse. In practice crew seating will also collapse to ensure any peaks stay below 20g. Crew gets out and walks away to post on PPRuNe about the advantages of flaring on EOL.
Mart
Last edited by Graviman; 1st Apr 2007 at 11:12. Reason: Ammendment for Nick's design data - thanks!
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Grav,
The landing gear will take about 10 G's before they give way, and they stroke about 2 feet, using air-oil and then a frangible honeycomb tube. The S92 uses a telescoped aluminum tube with a tube-cutter.
Then belly crush is programmed to take up the rest.
CS, look in the last sequence, taken inside the cabin looking forward. Note that the CP left seat strokes downward as the crash continues, and when the aircraft is stopped, the head is so far down it is almost out of sight. The seats in the H-60 and S-92 have wells below them so the seat mechanism disappears into the hole as the seat strokes downward.
The landing gear will take about 10 G's before they give way, and they stroke about 2 feet, using air-oil and then a frangible honeycomb tube. The S92 uses a telescoped aluminum tube with a tube-cutter.
Then belly crush is programmed to take up the rest.
CS, look in the last sequence, taken inside the cabin looking forward. Note that the CP left seat strokes downward as the crash continues, and when the aircraft is stopped, the head is so far down it is almost out of sight. The seats in the H-60 and S-92 have wells below them so the seat mechanism disappears into the hole as the seat strokes downward.
To put it another way, 42'/sec is a ROD of 2520'/min. I haven't flown the Lynx for a while but you could probably do an EOL without bothering to pull collective at the bottom, and walk away. 
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Trouble is this loading is seen on the design board/workstation as a once in an aircraft life load case, MG. Even though there would be many components that might "appear" undamaged, they would have accumulated all of their fatigue damage in one hit. Using the analogy, you would have dropped Nick's bean jar 
(although that is more for tubine blade creep, but same principle).
Mart
(although that is more for tubine blade creep, but same principle).Mart
Avoid imitations
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Importantly, 12 feet/sec = 720 feet /min!
It always gave me a warm feeling that, at the bottom of a 3 degree glideslope in a Blackhawk (+/- 500 fpm), if I ever found myself in zero/zero conditions, if necessary all I had to do was level the aircraft and let the undercarriage do it's thing.
The pilots' seats we had (I think they are standard fit) had a system that used the controlled extrusion of metal rods through dies in the seat backs to cushion the impact.
It always gave me a warm feeling that, at the bottom of a 3 degree glideslope in a Blackhawk (+/- 500 fpm), if I ever found myself in zero/zero conditions, if necessary all I had to do was level the aircraft and let the undercarriage do it's thing.
The pilots' seats we had (I think they are standard fit) had a system that used the controlled extrusion of metal rods through dies in the seat backs to cushion the impact.
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Shy, the seats are standard, just be sure nobody stores stuff in the seat wells under them. If so, the stuff will stop the seat stroke, and limit the safety enhancement, since stroke distance equates to G's of protection.
The pax seats have similar protection, they use the support wires drawn through dies, to absorb the energy, up to about 12 g's.
These are the kinds of protection that the "new" standards for LUH left out:
from the LUH rRFP (note they are low, and not even requirements):
The Light Utility Helicopter, operating as a Federal Aviation Administration (FAA) certified rotorcraft, shall provide for occupant protection in a crash through designs that protect aircraft crew and passengers. The Army requests information on industry's ability to meet the design standards for crashworthiness and crew survivability as defined by the Federal Aviation Regulations (FAR) Part 27 or Part 29, Sections 561, 562, and 785 as of December 13, 1989.
The pax seats have similar protection, they use the support wires drawn through dies, to absorb the energy, up to about 12 g's.
These are the kinds of protection that the "new" standards for LUH left out:
from the LUH rRFP (note they are low, and not even requirements):
The Light Utility Helicopter, operating as a Federal Aviation Administration (FAA) certified rotorcraft, shall provide for occupant protection in a crash through designs that protect aircraft crew and passengers. The Army requests information on industry's ability to meet the design standards for crashworthiness and crew survivability as defined by the Federal Aviation Regulations (FAR) Part 27 or Part 29, Sections 561, 562, and 785 as of December 13, 1989.