S97 Raider
Did the S-97 rotors mesh in the air as described in the NTSB report based on the analysis of the video? Or has Rotor & Wing misquoted the pilots description of events by writing that the rotors meshed as a result of the hard landing?
From Rotor &Wing Article:
A glitch in the code caused the flight control system to miscue during the transition from takeoff to forward flight, and the aircraft began to wobble as the computer lost control of the separation between the counter-spinning rotors. The aircraft responded to pilot inputs more powerfully than it should have, causing the aircraft to slam into the ground. The force of the impact flexed the rotors enough that they made contact and shattered, Fell (Sikorsky Senior Test Pilot Bill Fell) explained.
From NTSB Accident Report:
3.0 VIDEO SUMMARY. Video of the accident sequence of events was reviewed. The video was filmed from the right rear quadrant of the helicopter. It showed the helicopter slowly taxing forward with all 3 landing gear wheels in contact with the ground. As the helicopter approaches the edge of the runway, the tail wheel lifts off the ground followed by the main landing gear lifting off the taxiway simultaneously. As the helicopter gets airborne, the nose pitched upward slightly with a slight right roll. The helicopter then rolls to the left about 20° angle of bank and the left landing gear contacts the ground. A right roll followed that went slightly past horizontal. The roll reversed to the left, exceeding 30° angle of bank, then reversed to the right, and as the helicopter rolled through the vertical plane, the upper and lower rotors intermeshed about the 1 o’clock position (as viewed from the cockpit), creating a cloud of blade fragments and gray dust. The right roll continued, exceeding 60° angle of bank, then reversed to the left, and then landed hard as the helicopter passed through the vertical plane. The rotors continued to turn, decelerating until they come to a stop 43 seconds later.
From Rotor &Wing Article:
A glitch in the code caused the flight control system to miscue during the transition from takeoff to forward flight, and the aircraft began to wobble as the computer lost control of the separation between the counter-spinning rotors. The aircraft responded to pilot inputs more powerfully than it should have, causing the aircraft to slam into the ground. The force of the impact flexed the rotors enough that they made contact and shattered, Fell (Sikorsky Senior Test Pilot Bill Fell) explained.
From NTSB Accident Report:
3.0 VIDEO SUMMARY. Video of the accident sequence of events was reviewed. The video was filmed from the right rear quadrant of the helicopter. It showed the helicopter slowly taxing forward with all 3 landing gear wheels in contact with the ground. As the helicopter approaches the edge of the runway, the tail wheel lifts off the ground followed by the main landing gear lifting off the taxiway simultaneously. As the helicopter gets airborne, the nose pitched upward slightly with a slight right roll. The helicopter then rolls to the left about 20° angle of bank and the left landing gear contacts the ground. A right roll followed that went slightly past horizontal. The roll reversed to the left, exceeding 30° angle of bank, then reversed to the right, and as the helicopter rolled through the vertical plane, the upper and lower rotors intermeshed about the 1 o’clock position (as viewed from the cockpit), creating a cloud of blade fragments and gray dust. The right roll continued, exceeding 60° angle of bank, then reversed to the left, and then landed hard as the helicopter passed through the vertical plane. The rotors continued to turn, decelerating until they come to a stop 43 seconds later.
I am sure Sikorsky was ruing the day of the NTSB report release. In my previous post I had posited that based on the long-range helicopter news footage of the aftermath they could have been looking for possibly thrown components...little did I know they were searching for the outboard few feet of all the blades!
Did the S-97 rotors mesh in the air as described in the NTSB report based on the analysis of the video? Or has Rotor & Wing misquoted the pilots description of events by writing that the rotors meshed as a result of the hard landing?
From NTSB Accident Report:
3.0 VIDEO SUMMARY. Video of the accident sequence of events was reviewed. The video was filmed from the right rear quadrant of the helicopter. It showed the helicopter slowly taxing forward with all 3 landing gear wheels in contact with the ground. As the helicopter approaches the edge of the runway, the tail wheel lifts off the ground followed by the main landing gear lifting off the taxiway simultaneously. As the helicopter gets airborne, the nose pitched upward slightly with a slight right roll. The helicopter then rolls to the left about 20° angle of bank and the left landing gear contacts the ground. A right roll followed that went slightly past horizontal. The roll reversed to the left, exceeding 30° angle of bank, then reversed to the right, and as the helicopter rolled through the vertical plane, the upper and lower rotors intermeshed about the 1 o’clock position (as viewed from the cockpit), creating a cloud of blade fragments and gray dust. The right roll continued, exceeding 60° angle of bank, then reversed to the left, and then landed hard as the helicopter passed through the vertical plane. The rotors continued to turn, decelerating until they come to a stop 43 seconds later.
From NTSB Accident Report:
3.0 VIDEO SUMMARY. Video of the accident sequence of events was reviewed. The video was filmed from the right rear quadrant of the helicopter. It showed the helicopter slowly taxing forward with all 3 landing gear wheels in contact with the ground. As the helicopter approaches the edge of the runway, the tail wheel lifts off the ground followed by the main landing gear lifting off the taxiway simultaneously. As the helicopter gets airborne, the nose pitched upward slightly with a slight right roll. The helicopter then rolls to the left about 20° angle of bank and the left landing gear contacts the ground. A right roll followed that went slightly past horizontal. The roll reversed to the left, exceeding 30° angle of bank, then reversed to the right, and as the helicopter rolled through the vertical plane, the upper and lower rotors intermeshed about the 1 o’clock position (as viewed from the cockpit), creating a cloud of blade fragments and gray dust. The right roll continued, exceeding 60° angle of bank, then reversed to the left, and then landed hard as the helicopter passed through the vertical plane. The rotors continued to turn, decelerating until they come to a stop 43 seconds later.
Did the S-97 rotors mesh in the air as described in the NTSB report based on the analysis of the video? Or has Rotor & Wing misquoted the pilots description of events by writing that the rotors meshed as a result of the hard landing?
From Rotor &Wing Article:
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From NTSB Accident Report:
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From Rotor &Wing Article:
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From NTSB Accident Report:
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No he is not seriously questioning the NTSB. He is throwing shade on the effort of Sikorsky to cover up a serious design flaw in the S-97 and the similarly designed SB-1 which allows the rotors to collide in flight at moderate roll rates.
However based on even more experience I have little faith in the media accurately reporting what was stated in an interview.
Define moderate...
You slag SK off at every opportunity.
Why...?
I understand the roll rate peaked at 100 deg per second. This is moderate for an air vehicle billed as highly maneuverable. Sikorsky billed the ABC rotors as being so stiff you could narrow the gap between rotors with no chance of them colliding in the extreme maneuvers that the concept was promised to be able to do.
So Nige how would you classify an aircraft that can damage itself in flight when it was not suppose to be able to, exhibiting vibration levels so high that test pilots limit the level flight speeds even in the test environment, and has so much drag that it can not even come close to the originally advertised 250 knots?
So Nige how would you classify an aircraft that can damage itself in flight when it was not suppose to be able to, exhibiting vibration levels so high that test pilots limit the level flight speeds even in the test environment, and has so much drag that it can not even come close to the originally advertised 250 knots?
So Nige how would you classify an aircraft that can damage itself in flight when it was not suppose to be able to, exhibiting vibration levels so high that test pilots limit the level flight speeds even in the test environment, and has so much drag that it can not even come close to the originally advertised 250 knots?
I understand the roll rate peaked at 100 deg per second. This is moderate for an air vehicle billed as highly maneuverable. Sikorsky billed the ABC rotors as being so stiff you could narrow the gap between rotors with no chance of them colliding in the extreme maneuvers that the concept was promised to be able to do.
I would not immediately conclude from this mishap that the concept as such is flawed. What seems clear is that the control logic needs some tweaking.
That said the prospect of this happening in flight is not so nice. So Sikorsky needs to make sure that even clumsy control input doesn't lead to such dynamic reduction of rotor diameter in flight...
I understand the roll rate peaked at 100 deg per second. This is moderate for an air vehicle billed as highly maneuverable. Sikorsky billed the ABC rotors as being so stiff you could narrow the gap between rotors with no chance of them colliding in the extreme maneuvers that the concept was promised to be able to do.
So Nige how would you classify an aircraft that can damage itself in flight when it was not suppose to be able to, exhibiting vibration levels so high that test pilots limit the level flight speeds even in the test environment, and has so much drag that it can not even come close to the originally advertised 250 knots?
So Nige how would you classify an aircraft that can damage itself in flight when it was not suppose to be able to, exhibiting vibration levels so high that test pilots limit the level flight speeds even in the test environment, and has so much drag that it can not even come close to the originally advertised 250 knots?
The aircraft broke up in flight[14] while traveling about 229 mph at an altitude of about 2,000 feet.[15] In January 2018, the US National Transportation Safety Board released its findings, saying that the aircraft had suffered from severe inflight vibrations, which resulted in a loss of rotor RPM, subsequent rotor flapping and rotor impact with the tailboom, causing the inflight break-up.
I suppose these don't count...
Nigel, I agree with you that Sultan seems in his posts to have a never ending vendetta against Sikorsky. He seems to take pleasure from twisting the knife. But in your efforts to strike back by bringing up the AW609 accidents as a comparison, you distort key facts.
Both the AW609 and the 525 accidents occurred while exploring extreme corners of their flight envelopes. Vdive recovery and simulated loss of an engine at Vmax respectively. The S-97 accident occurred lifting to a hover.
Both AW and Bell kept quiet and made no comments to the media regarding the probable causes of the accidents. And when the reports were published made no attempts to offer “Alternate Truths”. Sikorsky management by their actions following the S-97 crash in my opinion have not respected the name of the company founder.
Note that unlike Sultan, I did not blame the Sikorsky Senior Test Pilot for the misinformation in the article. I have little doubt it was either journalist error or Sikorsky PR editing. Test Pilots deserve our respect.
Both the AW609 and the 525 accidents occurred while exploring extreme corners of their flight envelopes. Vdive recovery and simulated loss of an engine at Vmax respectively. The S-97 accident occurred lifting to a hover.
Both AW and Bell kept quiet and made no comments to the media regarding the probable causes of the accidents. And when the reports were published made no attempts to offer “Alternate Truths”. Sikorsky management by their actions following the S-97 crash in my opinion have not respected the name of the company founder.
Note that unlike Sultan, I did not blame the Sikorsky Senior Test Pilot for the misinformation in the article. I have little doubt it was either journalist error or Sikorsky PR editing. Test Pilots deserve our respect.
CTR: Never disrespected the pilots. Just stated the obvious that the test pilots in a monitored test environment are unwilling to push out to hit the planned test point. This points to serious loads or other safety issues not simply ride comfort.
Nige: The 525 accident occurred when the ship was well above Vne and the pilot failed to take action to correct rotor rpm droop within the planned response time after simulated engine loss. No traditional helicopter can survive flight above Vne with the rotor rpm decayed to 60% of normal operating rpm.
As to 609 the aircraft had been to the accident speeds and above without incident before they reduced the area of the tail. Also new flight control software to improve high speed stability with the smaller tail had been finalized, but not installed on the fatal flight.
Back to the 97 it was marketed to be physically impossible for the rotors to collide due to their stiffness. This was always thought to be a questionable claim especially when the size grew above the X-2. Collision of the rotors at flight rpm for any reason invalidates the concept. As stated in the NTSB report the control input rates were greater in the accident, not how the rotors were fundamentally controlled.
Nige: The 525 accident occurred when the ship was well above Vne and the pilot failed to take action to correct rotor rpm droop within the planned response time after simulated engine loss. No traditional helicopter can survive flight above Vne with the rotor rpm decayed to 60% of normal operating rpm.
As to 609 the aircraft had been to the accident speeds and above without incident before they reduced the area of the tail. Also new flight control software to improve high speed stability with the smaller tail had been finalized, but not installed on the fatal flight.
Back to the 97 it was marketed to be physically impossible for the rotors to collide due to their stiffness. This was always thought to be a questionable claim especially when the size grew above the X-2. Collision of the rotors at flight rpm for any reason invalidates the concept. As stated in the NTSB report the control input rates were greater in the accident, not how the rotors were fundamentally controlled.
You slag SK off at every opportunity.
Why...?
Why...?
The S-92? Just a refuselaged 60 with higher vibration an noisier rotor and a transmission that will fail in 12 minutes after loss of lube (when the requirement for cert is 30 minutes).
The Cyclone? 10+ years late, $200m per aircraft cost for another 60 derivative.
The CH-53K? Another 10 year late program, unit cost exceeding 3 times the original estimate of $35M, and near program ending unsolved problems (main and tail rotors, main transmission, engines, and the structure). IOC is now pushed out to 2023. Who thinks this is a winner?
Looks like you just crapped on two dead Bell pilots to me.
What I read in the NTSB report that came out regarding the dampening / vibe isolation (or lack there of) in the collective/power channel tells me that they were set up by the FBW system design.
Granted, those reports provide a particular view/perspective on such things, and are the limit of my understanding of that crash.
Is everyone else at Bell satisfied that the pilots screwed that one up or is that just you?
Regarding your disdain for Sikorsky: we get it. We got it last year too, and the year before.
What I read in the NTSB report that came out regarding the dampening / vibe isolation (or lack there of) in the collective/power channel tells me that they were set up by the FBW system design.
Granted, those reports provide a particular view/perspective on such things, and are the limit of my understanding of that crash.
Is everyone else at Bell satisfied that the pilots screwed that one up or is that just you?
Regarding your disdain for Sikorsky: we get it. We got it last year too, and the year before.
When not limiting the control throws and preventing opposite or differing blade excursions between both discs it can't really be physically impossible. Or the rotor blades would have to be so stiff that they would either break before touching or be so thick that the drag would be ridiculously high. Effectively every Helicopter can chop off his own tail if given enough cyclic authority. Control limits can possibly prevent this but that goes out off the window once control logic runs havoc which apparently was the case here.
Nige: The 525 accident occurred when the ship was well above Vne and the pilot failed to take action to correct rotor rpm droop within the planned response time after simulated engine loss. No traditional helicopter can survive flight above Vne with the rotor rpm decayed to 60% of normal operating rpm.
Rigid rotor for noise control? We know that people who build ultralight gyrocopters want flexible rotor blades for "ride comfort". If the blades are too stiff, these enthusiasts complain about the flight comfort. If the vibration issue is overcome, do rigid rotors work the air less, and thereby substantially reduce noise? Or not? We know Boeing is pursuing a single main rotor design as a replacement for the Apache, with a pusher propeller. Bell is pursuing a single main rotor design for FARA, which we do not know if it will have a pusher prop. Does the Raider for a special forces variant add a shroud around the pusher prop for further noise reduction? A single main rotor should be quieter than dual counter-rotating rotors.
https://www.ntsb.gov/_layouts/ntsb.a...06X42741&key=1
Rigid rotor for noise control? We know that people who build ultralight gyrocopters want flexible rotor blades for "ride comfort". If the blades are too stiff, these enthusiasts complain about the flight comfort. If the vibration issue is overcome, do rigid rotors work the air less, and thereby substantially reduce noise? Or not? We know Boeing is pursuing a single main rotor design as a replacement for the Apache, with a pusher propeller. Bell is pursuing a single main rotor design for FARA, which we do not know if it will have a pusher prop. Does the Raider for a special forces variant add a shroud around the pusher prop for further noise reduction? A single main rotor should be quieter than dual counter-rotating rotors.
Ultralight gyros? How is that relevant?
