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What do you think caused this Astar crash?


JCM5
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Inadvertent air-ground interface resulting in airframe de-optimization?

 

The T/R is turning and producing some anti-torque. It's possible that that control failed or jammed at a fixed position. I once had a student lock a leg straight and freeze...

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I don't have a lot of AStar time, but I don't think it would be so easy to take off with the hydraulics off without noticing. Unlike in some other helicopters, the spherical thrust bearings in the rotor head have a preset pitch to them, 60 kts, I think. So if the hydraulics were off on the ground, the collective would pop very noticeably. (I have less than 5 hours in AStars, so my facts could be way off on this.)

Edited by C of G
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I don't have a lot of AStar time, but I don't think it would be so easy to take off with the hydraulics off without noticing. Unlike in some other helicopters, the spherical thrust bearings in the rotor head have a preset pitch to them, 60 kts, I think. So if the hydraulics were off on the ground, the collective would pop very noticeably. (I have less than 5 hours in AStars, so my facts could be way off on this.)

 

Maybe….

 

The horn switch would need to be activated (on) for the horn to sound. If the pilot took off with the HYD switch off, then it wouldn’t be that far is a stretch to believe the horn switch is deactivated as well…. This is purely speculation. However, the manner of which the machine is being flown, it’s a hydraulic problem fosho, if not a full blown failure..... In fact, you can almost hear the thoughts of the pilot…. “crap, I got it……. Nope, crap……. I got it…….. Damit, nope…….. I got it…….. Nada…. Oh, geez…….”. It's good this was one they could walk away from....

 

Below 50 kts, pure strength, including leg strength, is required to fly the 350 with hydraulics off, -successfully……

Edited by Spike
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Yeah, I wasn't sure about the horn logic. I've only been through a full run up and system check once or twice and it's been a few years. I do seem to recall that in testing the system, it was important to ensure the collective lock is on prior to isolating the hydraulics so the collective didn't pop up. It's not like other helicopters that the collective would remain static without hydraulics. That's one reason why I think you couldn't really take off without knowing ahead of time that the system was off.

 

Peugeot horn aside. ;-)

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Although ISO feels stiff immediately and will pop you off the ground if you're not careful (locked), ACCU TEST you wouldn't notice mechanically until after the first few control movements use them up, but by then you might be off the ground. Oops.

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I would say there was a loss of HYD pressure. The reason for the loss, we will not know.

 

I have flown the AStar with out HYD both intentional (training) and also after a pump failed. It is probably one of the most dangerous maneuvers a pilot will have to do in the Astar. It is so easy to lose it like this guy. The amount of force on the pedal is incredible at low airspeed and hover. Hovering the Astar with no HYD takes a lot of strength, effort and practice.

 

If you lose pressure in forward flight, find a place to run it on, such as an airport. If it happens in a hover (IGE) then the accumulators should provide enough time to set it back down. If you take to long or move the controls to much and drain the accumulators then it will turn out much like in this video. In an OGE, use the accumulator pressure to gain airspeed and then find a place to run it on.

 

Like Spike said, there were several spots in the video where I thought the pilot was going to pull off getting it down. Then at the last second he lost it for good. Maybe even gave up trying a little or got tired and decided to just get it down.

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Likely another training accident and more than likely nothing wrong with the helicopter, it appears they may have just lost control.

 

They seem to be doing fine until time 6:39 in the video below. They appear to be practicing 360º pedal turns and landings.

 

In the beginning, they’re using the standard technique, for this type of rotor system, by starting the 360º pedal turn from into the wind and around with right pedal. They were working it around slow and controlling the yaw rate. They didn’t let the wind whip them around.

 

However, at time 6:39 in the video they make a left pedal turn and the trouble starts. As the tail turns downwind, the wind catches the left side of the tail and accelerates the left yaw in concert with the rotors torque reaction. This requires an immediate application of right pedal to counter the increasing yaw rate.

 

In this situation, if you’re late with the right pedal, and let the wind whip you around, with every successive rotation the wind catches the tail on its left side and accelerates the left yaw rate. You can see this in the video as the helicopter spins and the tail turns downwind and gets kicked by the wind, accelerating the left yaw.

 

Once the spin develops to this point they needed to apply full right pedal and forward cyclic to fly out (gain forward airspeed) in order to recover.

 

Some of the first reports noted possible tail rotor failure; however, it looks like a simple training accident, lost of control.

 

Preliminary Report

 

http://youtu.be/VYBp4t1uOmk

Edited by iChris
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From the beginning I thought it was a training accident gone bad - maybe a guy getting checked out in the Astar and the instructor inexplicably gave him a hydraulic failure in a hover or something. But after watching the video iChris posted, I still think it was a training accident.

 

Looks definitely like two separate people on the controls from time to time. You can tell when the instructor is doing the lift-offs, and you can absolutely tell when he takes over the controls, stabilizes the thing and brings it back down to earth. (But to be honest it doesn't look like the instructor is all that swift in the Astar either. His pickups and setdowns are rough - maybe hurried.)

 

At other times, you can tell when it's the new pilot on the controls. Whether this new pilot is just new to the Astar, or a guy who's not even rated yet is harder to tell. It could be either. What we can definitely tell is that he cannot fly. Every time he gets on the controls the Astar goes crazy.

 

Why the instructor was teaching pickups and setdowns is a puzzle. The student can't even hold a stable hover. Every time he gets on the controls he translates downwind uncontrollably and the instructor has to take over. The instructor must have been frustrated. The fun starts at 6:40. The instructor lifts the thing off and then it looks like he gave it to the guy in a hover. And awaaaaaaaaay we go! Looks like the instructor just let it go too far. Oopsie!

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At 6:41 you can see the machine “twitch” latterly and from there, things get fugly. The twitch may have been the HYD isolation switch being deactivated. Or, a demo-gone-wrong of how the HYD accumulators function. Either way, if the pilot pushed on the pedals and the machine didn’t respond, therefore, it must be a tail rotor failure, -right?

 

As already mentioned, just like the NYC ENG crash, the pilot reported he had a tail rotor failure which turned out to be an improper response to a hydraulic failure….

 

Again, purely speculation on my part…..

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