Helicopter down outside Leicester City Football Club
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Software cannot overcome the laws of physics but it can
Did you hear about the self recovery button on the cyclic of the H160 I think this a sign of things to come
- diagnose the problem in millisecond,
- analyze 100s of possibilities in a few millisecond more,
- apply the scenario that would maximize the chance of survival.
Did you hear about the self recovery button on the cyclic of the H160 I think this a sign of things to come
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Software cannot overcome the laws of physics but it can
- diagnose the problem in millisecond,
- analyze 100s of possibilities in a few millisecond more,
- apply the scenario that would maximize the chance of survival.
There is surely a case for more intelligent and intuitive safety systems, but this accident seems to have arisen from an unforeseen failure mode leading to a malfunction which in all likelihood was simply not recoverable. You can’t automate 'thinking of what you haven’t thought of' nor program a computer to fix in real time any catastrophe which sets the laws of physics in fundamental opposition to accident survivability.
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Not going to argue much around this but there are no laws of physics preventing tailles rotor flight . You have to equalise the rotor drag with drag from the body of the aircraft . If this requires 130 rpm , 130 rpm will be necessary ,if that's not humanly pilotable does not mean some autostab will find it impossible too .Most problems will be around oscilations and vibrations in the rotor disk but for an emergency descent it should work
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Well, EASA EAD 2018-0250-E back on 19 November required inspection of the duplex bearing on both 169s and 189s before they flew again. So hopefully there are no duff duplex bearings in service anymore.
I’d dearly like to know what the inspection was specifically looking for, as that would shed light on why the bearing failed. Knowing that would probably require access to Leonardo AMPs. Anyone know?
I’d dearly like to know what the inspection was specifically looking for, as that would shed light on why the bearing failed. Knowing that would probably require access to Leonardo AMPs. Anyone know?
Avoid imitations
Looking at the photo evidence in post#983 above, a thought that crossed my mind - would a simple left handed thread on the shaft have prevented this tragedy?
Having recently changed a rear wheel bearing, even my old car has a left handed thread on the left hand side stub axle, to prevent the hub nut coming loose in service.
Having recently changed a rear wheel bearing, even my old car has a left handed thread on the left hand side stub axle, to prevent the hub nut coming loose in service.
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For those with a good engineering understanding of this failure, would the tail rotor have been harder to turn by hand than normal, pre-flight, given the breakdown of this bearing? Obviously not easy to reach on a 169, but is on most smaller types.
Avoid imitations
Not going to argue much around this but there are no laws of physics preventing tailles rotor flight . You have to equalise the rotor drag with drag from the body of the aircraft . If this requires 130 rpm , 130 rpm will be necessary ,if that's not humanly pilotable does not mean some autostab will find it impossible too .Most problems will be around oscilations and vibrations in the rotor disk but for an emergency descent it should work
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With the length of the blade and the weight of the rotor, I think it would be very difficult to detect any tightness or "grittiness".
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Looking at the photo evidence in post#983 above, a thought that crossed my mind - would a simple left handed thread on the shaft have prevented this tragedy?
Having recently changed a rear wheel bearing, even my old car has a left handed thread on the left hand side stub axle, to prevent the hub nut coming loose in service.
Having recently changed a rear wheel bearing, even my old car has a left handed thread on the left hand side stub axle, to prevent the hub nut coming loose in service.
I don't know which way this tail rotor turns relative to the control shaft, but with similar threads the nut at one end would tend to loosen and the other would tighten. One LH and one RH would both try to tighten, or loosen - depending on the rotation.
# I will let you work out the rest for what happens if the bearing fails and what could possibly happen to the nut.
I am surprised that the attachment of the lever mechanism to the control shaft relies purely on clamp up with the nut. No key or index?
Maybe there should be a weak point in the shaft so that the integrity of the feedback is maintained so the servo does not go to full travel?
I am amazed that things like this can still develop in this day and age. Somehow folk have lost sight of the details.
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Looking at the photo evidence in post#983 above, a thought that crossed my mind - would a simple left handed thread on the shaft have prevented this tragedy?
Having recently changed a rear wheel bearing, even my old car has a left handed thread on the left hand side stub axle, to prevent the hub nut coming loose in service.
Having recently changed a rear wheel bearing, even my old car has a left handed thread on the left hand side stub axle, to prevent the hub nut coming loose in service.
Or, the tightening of both nuts on each end may increase the clamping effect on the rod and stop it from spinning, despite the failed bearing. Difficult to say really, and one for the design engineers.
Uplinker,
In your video....that was a Sikorsky S-58T that had the tail rotor drive failure.
The Pilot controlled the aircraft and was maneuvering towards a safe landing area.
He maintained power until he thought he could make an authoritative landing and cut the throttles to Flight Idle.
After the accident I had the opportunity to talk with him about the crash....and he was very bothered that he was unable to land the aircraft safely.
He did his best....but the odds were against him...but he flew the machine all the way to the ground and did not give up trying to land it.
The failure we see in the 169 under discussion was a very different kind and far more critical than that shown in your video.
It was a loss of thrust in the video and just the opposite (apparently) in the 169 crash.
The 58T was a drive shaft failure.....where the 169 was far more complicated a failure.
In your video....that was a Sikorsky S-58T that had the tail rotor drive failure.
The Pilot controlled the aircraft and was maneuvering towards a safe landing area.
He maintained power until he thought he could make an authoritative landing and cut the throttles to Flight Idle.
After the accident I had the opportunity to talk with him about the crash....and he was very bothered that he was unable to land the aircraft safely.
He did his best....but the odds were against him...but he flew the machine all the way to the ground and did not give up trying to land it.
The failure we see in the 169 under discussion was a very different kind and far more critical than that shown in your video.
It was a loss of thrust in the video and just the opposite (apparently) in the 169 crash.
The 58T was a drive shaft failure.....where the 169 was far more complicated a failure.
Put another way, comparing the two accidents the way you are trying to is a category error.
The failure we see in the 169 under discussion was a very different kind and far more critical than that shown in your video.
It was a loss of thrust in the video and just the opposite (apparently) in the 169 crash.
The 58T was a drive shaft failure.....where the 169 was far more complicated a failure.
It was a loss of thrust in the video and just the opposite (apparently) in the 169 crash.
The 58T was a drive shaft failure.....where the 169 was far more complicated a failure.
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130 rpm (Nr) is well below the normal operating range of modern helicopters. Most run around 275 - 350 or even higher for smaller machines, with a minimum in flight of 90% of that figure for aerodynamic reasons. Going lower would cause the blades to stall and loss of control of the rotor disc.
@ Uplinker
You lose TR , you spin faster and faster until at certain rpm the drag from the spinning body of the heli counterracts the rotor drag . Unfortunately no human can control a helicopter spinning like that , but a computer surely can ,go watch that rocket gently land after spinning from several km height . I'm not expecting the control system to be able to keep it right afterward it lands so the machine will be lost but the landing would be gentle and very survivable ( except some bad cases of fire / bad terrain ) .
Ahernar - I think you place too much faith in computers - an autopilot in a helicopter only has the same controls as the pilot to control its attitude. Yes it works faster and constantly but the sensors required to make them work have limits too.
And btw the rocket in your video didn't land, it crashed.
And btw the rocket in your video didn't land, it crashed.
@Ahernar How do you think humans deal with a 130 RPM fuselage? I think you might as well crash to the ground...
Since there is a lot of speculation about all kind of (unrealistic or irrelevant) ways to counter this, I'm surprised that emergency tail rotor recovery systems hasn't come up. From what I understand the idea here is to have some alternative way to create anti-torque trust at least for a limited time to allow landing. There's a patent from 2005 here for example, and I'm sure there are other potential solutions. Whether such a system would be able to overcome the trust from the TR going above "full" pitch is a question of course.
I'm more interested in finding the cause of the failure than to speculate about possible solutions without fully understanding the problem, but since it seems to be a returning topic it might be a better starting point than making automated systems for killing people while still in the air.
Since there is a lot of speculation about all kind of (unrealistic or irrelevant) ways to counter this, I'm surprised that emergency tail rotor recovery systems hasn't come up. From what I understand the idea here is to have some alternative way to create anti-torque trust at least for a limited time to allow landing. There's a patent from 2005 here for example, and I'm sure there are other potential solutions. Whether such a system would be able to overcome the trust from the TR going above "full" pitch is a question of course.
I'm more interested in finding the cause of the failure than to speculate about possible solutions without fully understanding the problem, but since it seems to be a returning topic it might be a better starting point than making automated systems for killing people while still in the air.
Originally Posted by [email protected]
And btw the rocket in your video didn't land, it crashed.
The high CG and the low lift of the landing legs prevented it from staying upright.
skadi
