S97 Raider
Originally Posted by The Sultan
History repeating itself?
The first S-69 built (73-21941) first flew on July 26, 1973. However, it was badly damaged in a low-speed crash on August 24, 1973 due to unexpected rotor forces and insufficient control systems.[2] The airframe was then converted into a wind tunnel testbed
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These shapes are highly reminiscent of the 'hopeless diamond' shape that eventually resulted in the F-117, albeit more evolved. Radar cross section test dummies for some high speed vehicle perhaps?
The Sultan, not sure how much you have ever flown. I suffered an engine roll back in a single engine turboprop trainer. I have had an engine roll back (reduce RPM from flight RPM) in both an SH-2F and an SH-60B in flight. In each case use of the various emergency throttle/lock out procedures restored enough power to fly home without securing the engine. (The SH-60B NATOPS called a "a partial power loss" ... but it's the same thing).
While I've had engines fluctuate while in a hover, I've never lost one (though we certainly trained for that malfunction a lot in the sim ... )
While I've had engines fluctuate while in a hover, I've never lost one (though we certainly trained for that malfunction a lot in the sim ... )
@212man Based on the water filled ditch/canal in the background of the photo of the S-97 and the fire truck, and the overhead you presented, it looks like the road at the far right of the overhead you posted. Taxiways in that picture are marked very clearly, while the one in the photo with the fire truck has no markings.
Lone,
Point is the 97 is single engine so "an" engine (implies more than one) rolling back is not applicable. Very possible it puked the engine. Question remains with exception of a PR flight why was the gear up (as "confirmed" by articles) when hovering/low speed over a hard surface? They obviously were not doing HV/auto testing. I guess it is always possible they landed after forgetting to lower the gear, but not likely. On the 609 we had a special rig we could land on should the gear fail to extend, do not see similar here.
Point is the 97 is single engine so "an" engine (implies more than one) rolling back is not applicable. Very possible it puked the engine. Question remains with exception of a PR flight why was the gear up (as "confirmed" by articles) when hovering/low speed over a hard surface? They obviously were not doing HV/auto testing. I guess it is always possible they landed after forgetting to lower the gear, but not likely. On the 609 we had a special rig we could land on should the gear fail to extend, do not see similar here.
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The Sultan;9850996]It would be the engine.
It's possible that English isn't your native tongue, or simply that you have never mastered it?
Just for you.
https://en.oxforddictionaries.com/definition/an
It is "AN" engine failure. It is also "AN" engine roll back.
Pants
Common definition of "the": used with a singular noun to indicate that it represents a whole species or class.
Since their was only one completed S-97 with only one engine "the" is the proper determiner.
Common definition of "the": used with a singular noun to indicate that it represents a whole species or class.
Since their was only one completed S-97 with only one engine "the" is the proper determiner.
Grammar aside, one has to ask what the real issue is here.
The S-97 Raider has experienced a minor mishap after years of development with a very limited flight envelope. The lack of flight envelope expansion is the issue not this mishap.
Anyone hear any news about possible causes in the last couple of weeks? Component failure, computer/software issues, etc?
Perhaps it threw a pusher prop blade like the iron bird did a while back? Noticed in the videos some personnel far off to the 9 o'clock in the grass possibly looking for something
Perhaps it threw a pusher prop blade like the iron bird did a while back? Noticed in the videos some personnel far off to the 9 o'clock in the grass possibly looking for something
Sans,
I have no idea, but am interested also. Tell us about this iron bird prop incident - did I miss the story somewhere? Did they have a dedicated iron bird?
I have no idea, but am interested also. Tell us about this iron bird prop incident - did I miss the story somewhere? Did they have a dedicated iron bird?
While shaking the proverbial trees among my industry peers for info on the Raider incident, I was told in passing about the tail rotor prop chucking a blade in the test pit on an iron bird rig a while ago.
Supposedly this was caused by some miscommunication regarding design loads with a supplier, and subsequently slowed progress as all changes were much more thoroughly scrutinized.
Same sources also relayed something that a lot of people have been suspecting - that the vibration is a large issue and the pilots were having difficulty reading displays in flight. Sounds like there is an internal belief that the fuselage may not be stiff enough.
Supposedly this was caused by some miscommunication regarding design loads with a supplier, and subsequently slowed progress as all changes were much more thoroughly scrutinized.
Same sources also relayed something that a lot of people have been suspecting - that the vibration is a large issue and the pilots were having difficulty reading displays in flight. Sounds like there is an internal belief that the fuselage may not be stiff enough.
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Sans-
In this video of a tie-down run of the S-97 you can see how the pusher prop drive is de-clutched as the main rotors come up to speed. If my understanding is correct, doesn't the S-97 de-clutch the prop drive during hover? If so, I can see potential unanticipated vibration and dynamic torsional load issues in the prop drivetrain from friction clutch chatter while accelerating the prop up to speed from a stop. The dynamic torsional effects produced by friction clutch slip/chatter during engagement are very hard to accurately predict. Seems possible that the prop system failed due to operating loads higher than anticipated.
https://youtu.be/VBJZhPbMHlU
In this video of a tie-down run of the S-97 you can see how the pusher prop drive is de-clutched as the main rotors come up to speed. If my understanding is correct, doesn't the S-97 de-clutch the prop drive during hover? If so, I can see potential unanticipated vibration and dynamic torsional load issues in the prop drivetrain from friction clutch chatter while accelerating the prop up to speed from a stop. The dynamic torsional effects produced by friction clutch slip/chatter during engagement are very hard to accurately predict. Seems possible that the prop system failed due to operating loads higher than anticipated.
https://youtu.be/VBJZhPbMHlU
S-97 Raider sustained ?substantial damage' in crash, but program moves forward
Most interesting takeaway is 20 flight hours in approx 2.5 years. Also explains where that 2nd prototype airframe has been.
Most interesting takeaway is 20 flight hours in approx 2.5 years. Also explains where that 2nd prototype airframe has been.
From the above referenced:
So pretty close to what caused them to crash the first XH-59A. It appears #1 is basically finished also like the 59A. You would think Sikorsky would have focused on near ground handling as a lesson learned from the previous program.
Does not bode well for this concept if you can not safely lift to a hover.
“The neighborhood of the root cause is the complex interaction between the ground, the landing gear, the flight control system and the associated pilot interactions,” he told a few reporters in a phone interview. “If you are familiar with the rotorcraft industry, this is a well-documented complex set of interaction as airplanes transition from operations on the ground to operations in flight.”
Does not bode well for this concept if you can not safely lift to a hover.
complex interaction between the ground, the landing gear, the flight control system and the associated pilot interactions
