350 B3 Compressor Problem?

[Heli-pilot]

Hi, was hoping for some input on a problem I had with a AS350-B3 2 days ago.

 

I was on a photo job, hovering OGE at around 3-400 ft. ISA day.

I gave gentle forward cyclic, and pulled some power when the machine suddenly made that typical "compressor stall" sound, right yaw and lots of vibrations..

 

At first i thought I had a TR-failure, entered auto but quickly realised the machine had both power and pedals. Landed in a field close by and inspeced. Found nothing wrong, and compressor is pretty new and was recently washed.

 

Has anyone experienced something similar? suggestions?

 

Thx.

[Rotorhead]

Hi, was hoping for some input on a problem I had with a AS350-B3 2 days ago.

 

I was on a photo job, hovering OGE at around 3-400 ft. ISA day.

I gave gentle forward cyclic, and pulled some power when the machine suddenly made that typical "compressor stall" sound, right yaw and lots of vibrations..

 

At first i thought I had a TR-failure, entered auto but quickly realised the machine had both power and pedals. Landed in a field close by and inspeced. Found nothing wrong, and compressor is pretty new and was recently washed.

 

Has anyone experienced something similar? suggestions?

 

Thx.

 

 

Aside from the "typical" compressor stall sound (do you get that frequently?) It sounds like a case of Vortex Ring state, the auto was a good recovery if that was the case. Right yaw in an Astar would be the opposite of what you would get with a t/r failure wouldn't it? Right yaw would suggest more pedal than the M/R torque requires.

 

It will be interesting to hear what caused it.

 

RH

[Heli-pilot]

Aside from the "typical" compressor stall sound (do you get that frequently?) It sounds like a case of Vortex Ring state, the auto was a good recovery if that was the case. Right yaw in an Astar would be the opposite of what you would get with a t/r failure wouldn't it? Right yaw would suggest more pedal than the M/R torque requires.

 

It will be interesting to hear what caused it.

 

RH

 

Well, I figured most people have heard a compressor stall in a bell or astar. I've only heard it once in a 350 before. ( sounds like a thin metal plate under tension, than it pops out)

1st time I have encountered this problem in a B3.

 

I was thinking TR failure in those 2 seconds when it happened. When I am flying and get a strong yaw with a loud sound + vibrations.. I thought of TR failure and not which way I was yawing.

 

I can't see how it could have been a case of vortex ring due to the fact that the helicopter was in a small climb with lots of power available. It was excactly when i gave the machine some forward cyclic and added some collective power.

 

Big bang, hard right yaw and lots of vibrations..

 

So far the engineers have checked the compressor which seems to be perfect. Now they are looking more into the bleed valve and FCU.

[skullcap]

We had a issue like that in 1B engine years ago but was bearing in compressor let go and allowed the compressor to "float" around. It had made contact with housing and there was some banging but pilot able to fly for few miles. Am sure your guys have checked that though.

 

Check for exceedances, if the bleed valve had failed and Ng topped out might have reason for stall. If Ng had gone high then check for T4 exceedance as well.

 

Good Luck

paul

[Heli-pilot]

We had a issue like that in 1B engine years ago but was bearing in compressor let go and allowed the compressor to "float" around. It had made contact with housing and there was some banging but pilot able to fly for few miles. Am sure your guys have checked that though.

 

Check for exceedances, if the bleed valve had failed and Ng topped out might have reason for stall. If Ng had gone high then check for T4 exceedance as well.

 

Good Luck

paul

 

Thx Paul.

 

I can't confirm it, but the guy next to me is pretty sure he heard the "gong" right after it happened.. No limits was stored as exceeded.

[sherpa]

I had similar issues in a B3, although the symptoms weren’t as violent as you experienced them. It ended up being a faulty bleed valve. There is a chart in the MM for proper bleed valve operation.

 

Interesting you mention compressor wash, maybe just coincident, but it happend right after a compressor wash.

[bushrat]

Check the BV threash-hold as per MM, also check the P3 Transmitter as this is the signal that the fadec uses to control acceleration of the engine......also check Bleed valve p3 filter as per MM.... compressor unlikely to cause stall/surge on arriel 2 engines as only the 2b has an acceleration bellows which is only used in manual mode and the 2b1 has no acceleration bellows .

[Heliian]

If there was any sort of wind, you may have got the tail into it and disrupted airflow into the engine or tailrotor. A lot of incidents occur when untrained flight crews are doing aerial survey/photography and get into LTE but you'd think the B3 would have enough power.