Greek Apache Helicopter crashes into sea.
Below the Glidepath - not correcting
The Exercise 42 (Wazzing and Zooming) run in was all the evidence needed to predict exactly how that was going to end up. They are not the first and sadly won't be the last.
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Oh well, if the pilot struggles to find work after, they should head South. I understand a vacancy or two may exist in Kenya flying the 139. The skill set appears fairly similar. 
Surely it was a dual engine failure caused by water ingestion!
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dTq
Interesting youtube is littered with these 'high speed stall' accidents
The point about coning angle is really interesting. There is effectively a conning angle at which a disk is in effect stalled, regardless of RRPM.
RRPM 'cancels out of the maths' when you look for stall.
Interesting youtube is littered with these 'high speed stall' accidents
The point about coning angle is really interesting. There is effectively a conning angle at which a disk is in effect stalled, regardless of RRPM.
RRPM 'cancels out of the maths' when you look for stall.
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megan
cone is proportional to the ratio of Lift (L) to Centripetal Force (Cf)
both L and Cf are proportional to RRPM^2
take a helicopter in the hover at low load and low RRPM (such that it is very close to stall AoA)
measure the cone
if load is increased the RRPM has to be increased to increase Lift
the AoA remains just short of stall and the coning angle is unchanged.
that coning angle is the coning angle just short of stall
(get well soon NL)
cone is proportional to the ratio of Lift (L) to Centripetal Force (Cf)
both L and Cf are proportional to RRPM^2
take a helicopter in the hover at low load and low RRPM (such that it is very close to stall AoA)
measure the cone
if load is increased the RRPM has to be increased to increase Lift
the AoA remains just short of stall and the coning angle is unchanged.
that coning angle is the coning angle just short of stall
(get well soon NL)
Last edited by AnFI; 25th Sep 2016 at 12:56. Reason: cleaner and politer
I should stick to your multi-engine rants and steer away from rotor dynamics!
I hate to inject technical questions into a thread here at Rotorheads but perhaps this is the time.
The Huey Cobra (for sure the Two Bladed Head models) had a tendency to do exactly what the Greek Apache did....smack the ground with the Collective Lever well up under the Pilot's Arm Pit while the Cyclic was nudging his Wedding Tackle.
You reckon the Apache Rotor system and flight control linkages might be susceptible to the same sort of thing?
Thinking "Pitch Cone Coupling" which is a section of the AH-1S Flight Manual contained at the Link below.
https://books.google.com/books?id=pX...upling&f=false
The Huey Cobra (for sure the Two Bladed Head models) had a tendency to do exactly what the Greek Apache did....smack the ground with the Collective Lever well up under the Pilot's Arm Pit while the Cyclic was nudging his Wedding Tackle.
You reckon the Apache Rotor system and flight control linkages might be susceptible to the same sort of thing?
Thinking "Pitch Cone Coupling" which is a section of the AH-1S Flight Manual contained at the Link below.
https://books.google.com/books?id=pX...upling&f=false
I hate to inject technical questions into a thread here at Rotorheads but perhaps this is the time.
The Huey Cobra (for sure the Two Bladed Head models) had a tendency to do exactly what the Greek Apache did....smack the ground with the Collective Lever well up under the Pilot's Arm Pit while the Cyclic was nudging his Wedding Tackle.
You reckon the Apache Rotor system and flight control linkages might be susceptible to the same sort of thing?
Thinking "Pitch Cone Coupling" which is a section of the AH-1S Flight Manual contained at the Link below.
https://books.google.com/books?id=pX...upling&f=false
The Huey Cobra (for sure the Two Bladed Head models) had a tendency to do exactly what the Greek Apache did....smack the ground with the Collective Lever well up under the Pilot's Arm Pit while the Cyclic was nudging his Wedding Tackle.
You reckon the Apache Rotor system and flight control linkages might be susceptible to the same sort of thing?
Thinking "Pitch Cone Coupling" which is a section of the AH-1S Flight Manual contained at the Link below.
https://books.google.com/books?id=pX...upling&f=false
SAS, I believe that LRP has the correct picture re the UH-1C and subsequent Bell rotors that incorporated pitch/cone coupling by design.
This particular AH-64 video reminds of several others:
1. BO-105 accident with Seifried Hoffman flying, in New Jersey, I believe.
2. Last year's NH-90 crash into a lake.
3. The S-67 accident practicing the demonstration routine at Farnborough 1974.
4. A similar UH-60 "incident" flown by a US Army crew and I can't remember the time, but it was filmed and SA got the blades back. An "almost " version of the first three. The aircraft is seen doing a vertical type manuever and the pullout is at first obscured from the camera by a tree line, and then, just when you'd expect to see the smoke, the ship reappears.
The issues in 3 and 4 were looked into in detail, and I'm suggesting that the first two are similar. It is altogether both possible, and easy, when throwing a helicopter around close to the ground, to put the machine into a position where the application of maximum power/collective and appropriate cyclic input is insufficient to sufficiently change the flight path of the machine given the altitude remaining. A related consideration is that there is sufficient collective range in most ( if not all ) machines at the speeds noted in these examples ( and the Apache accident as well ) such that application of full collective will demand more than the power available, resulting in rotor droop. With rotor lift being a function of the velocity squared, this can really aggravate an already bad situation.
In the case of the S-67, the video showed extremely high flapping/cloning prior to impact. In the case of the Army UH-60, each of the rotor blades had wrinkled trailing edges, the result of aft damper stop contact. Damper lag angle in an articulated head is a pretty much linear function with power: higher power=increased lag angle.
There may be other factors involved in this Apache accident, rendering the above thoughts irrelevant. Stuff happens: I recall the story of an accident that occurred with a UH-2 Kaman machine where a very high speed crash was finally attributed to one of the pilots heels getting sandwiched into the base of the cyclic.
This particular AH-64 video reminds of several others:
1. BO-105 accident with Seifried Hoffman flying, in New Jersey, I believe.
2. Last year's NH-90 crash into a lake.
3. The S-67 accident practicing the demonstration routine at Farnborough 1974.
4. A similar UH-60 "incident" flown by a US Army crew and I can't remember the time, but it was filmed and SA got the blades back. An "almost " version of the first three. The aircraft is seen doing a vertical type manuever and the pullout is at first obscured from the camera by a tree line, and then, just when you'd expect to see the smoke, the ship reappears.
The issues in 3 and 4 were looked into in detail, and I'm suggesting that the first two are similar. It is altogether both possible, and easy, when throwing a helicopter around close to the ground, to put the machine into a position where the application of maximum power/collective and appropriate cyclic input is insufficient to sufficiently change the flight path of the machine given the altitude remaining. A related consideration is that there is sufficient collective range in most ( if not all ) machines at the speeds noted in these examples ( and the Apache accident as well ) such that application of full collective will demand more than the power available, resulting in rotor droop. With rotor lift being a function of the velocity squared, this can really aggravate an already bad situation.
In the case of the S-67, the video showed extremely high flapping/cloning prior to impact. In the case of the Army UH-60, each of the rotor blades had wrinkled trailing edges, the result of aft damper stop contact. Damper lag angle in an articulated head is a pretty much linear function with power: higher power=increased lag angle.
There may be other factors involved in this Apache accident, rendering the above thoughts irrelevant. Stuff happens: I recall the story of an accident that occurred with a UH-2 Kaman machine where a very high speed crash was finally attributed to one of the pilots heels getting sandwiched into the base of the cyclic.
Last edited by JohnDixson; 26th Sep 2016 at 15:11. Reason: Additional thought.
I grasp what you have to say Brother Dixson....having done some investigative flying in a Hughes 500D one morning on Unga Island, Alaska.
What I discerned is how critical the last three feet of height above the surface of a saltwater inlet can be when performing such maneuvers. I you compound what you describe by adding in the G Loading that one can apply to the Rotors and Head before reaching a structural limit....which can be a consideration....it is easy to find oneself wishing there was more clear space beneath the landing gear.
As one discovers all those limits coming into place...it seems religious dedication as a philosophic convention can also permeate to one's cognitive thoughts as well.
I suppose I am not the only pilot ever heard to utter the words...."Thank You Jesus!" in similar circumstances after grasping the Earth was getting further away and all the component parts of the aircraft less a bit of seat cushion were still doing their job.
What I discerned is how critical the last three feet of height above the surface of a saltwater inlet can be when performing such maneuvers. I you compound what you describe by adding in the G Loading that one can apply to the Rotors and Head before reaching a structural limit....which can be a consideration....it is easy to find oneself wishing there was more clear space beneath the landing gear.
As one discovers all those limits coming into place...it seems religious dedication as a philosophic convention can also permeate to one's cognitive thoughts as well.
I suppose I am not the only pilot ever heard to utter the words...."Thank You Jesus!" in similar circumstances after grasping the Earth was getting further away and all the component parts of the aircraft less a bit of seat cushion were still doing their job.
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SASless re post 53
no
but it is alluded to in 8-36 in that manual example, refered to as mushing
its quite clear that folk dont understand what happens when you pull excess g
they seem to think it's about judging your trajectory to not hit the ground
whereas the disk making less total rotor thrust the more you (attempt to) pull (g) is not taught
megan
write your own paper
u can see the coning angle of the crashing apache is v high
the pilot pitch up, to pull more g, just reduces the TRT
this is a surprise to the pilot
pulling the lever up also has the opposite effect
he cannot alter his path at the rate he wants or is accustomed to being able to
there are many accidents from this phenomenon
mushing
pull more get less
it would be called high speed stall in an aeroplane and causes a similar large number of crashes
no
but it is alluded to in 8-36 in that manual example, refered to as mushing
its quite clear that folk dont understand what happens when you pull excess g
they seem to think it's about judging your trajectory to not hit the ground
whereas the disk making less total rotor thrust the more you (attempt to) pull (g) is not taught
megan
write your own paper
u can see the coning angle of the crashing apache is v high
the pilot pitch up, to pull more g, just reduces the TRT
this is a surprise to the pilot
pulling the lever up also has the opposite effect
he cannot alter his path at the rate he wants or is accustomed to being able to
there are many accidents from this phenomenon
mushing
pull more get less
it would be called high speed stall in an aeroplane and causes a similar large number of crashes
I understand that you have edited your post several times and the latest iteration is rather different from the first.
Oh yes, the accident reports are littered with them.....I think you mean 'accelerated stall' though.
Interesting to look down the original link and see some stills of a CH-47 also doing some kind of display - either it was an officially sanctioned event, or maybe a routine infarction now caught on camera?
it would be called high speed stall in an aeroplane and causes a similar large number of crashes
Interesting to look down the original link and see some stills of a CH-47 also doing some kind of display - either it was an officially sanctioned event, or maybe a routine infarction now caught on camera?
"Mushing" must be a single engine term.....although Dog Sledders have been known to use that to describe their mode of transportation.
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Well, the two major factors here are the excessive rate of descent, and the lack of altitude to recover. The natural tendency to apply aft cyclic only results in a pitch up attitude change, the panic induced collective increase results in a high coning angle, and less disc area to produce lift. Another 100 ft or so, and they might have gotten away with it.