How NOT to moor up at the local pub

[MtB]

Absconding seems a possibility, given the circumstances of his arrest!

[mattlad]

The helicopter could have entered a condition known as "Vortex ring state" there is clear space on the one side but a building on the other which could have caused air to curl round and re-enter the rotor blades on that side causing a loss of lift on that side, hence the roll-over.

 

The other possibility is what used to be called "Fenestron Stall" (there is no such thing) now called Yaw Divergence, or in other words pilot error. The advice as I understand it is that it is preferable to turn against the main rotor torque than with it and with uneven air currents due to the building destabilizing the helicopter probably started a chain of events that caused it to crash. Really it was a manoeuvre that was never on, i.e. the pilot bit off more than he could chew!

 

I would like to point out that while I have some fixed wing flying experience on gliders and Cessna's I've only had one helicopter air experience flight (actually on a Jetranger!) so all I have said should be taken as speculation and NOT fact!

[Top cat]

The votex ring state is where a rotor craft gets into its own down wash and end up with a donut shaped airflow pattern through the rotor(s) with air passing though them in a downward direction. Once an aircraft gets into that state the only way to get out is a rapid horizontal translation ( normally sideways) to escape the vortex, you cant power your way out. Thats why you very rarely see a helicopter land vertically except for the last few feet. Heli pilots are trained to stay out of situations where a vortex ring could start.

 

I dont think the helicopter in question entered that state because it was too low for the votex ring to establish, the ground gets in the way. Its part of the ground effect.

IMHO the helicopter crashed because the pilot tried to land too close to the buildings, his rotor wash bounced off the buildings and he lost control. SAR pilots do that sort of thing and get away with it because they are very highly skilled and trained and their choppers have sophisticated gyros. BUT they only do it when they have a damn good reason, ie saving lives.

 

T C

[nicknorman]

Yes vortex ring occurs with zero airspeed and a rate of descent of more than 500'/minute or so. Mattlad is referring to recirculation which occurs when hovering in or next to buildings, although I suppose the aerodynamics are not that dissimilar.

 

Anyway the accident in question clearly shows mechanical failure of the anti-torque system whilst in the hover, most probably due to debris or an obstacle hitting the fenestron blades.

[pquinn]

I've had some mechanical failure of my anti-torque system,most probably due to pints of Guinness hitting my fenestron blades.

 

But it was usually on the way out of the pub. These clowns couldn't even put the correct order on the situation

[boathunter]

Yes vortex ring occurs with zero airspeed and a rate of descent of more than 500'/minute or so. Mattlad is referring to recirculation which occurs when hovering in or next to buildings, although I suppose the aerodynamics are not that dissimilar.

 

Anyway the accident in question clearly shows mechanical failure of the anti-torque system whilst in the hover, most probably due to debris or an obstacle hitting the fenestron blades.

Looks to me on the side on video that the main blades simply hit the building. You can see it happen and the damage to the building.

Edited July 21, 2015 by boathunter

[mattlad]

Mattlad is referring to recirculation which occurs when hovering in or next to buildings, although I suppose the aerodynamics are not that dissimilar.

 

Recirculation! That's the word I was trying to think of! I do apologise, I'd had a couple of beers.......

[MtB]

Recirculation! That's the word I was trying to think of! I do apologise, I'd had a couple of beers.......

 

Hmmm let's hope the beers don't 'recirculate'...

 

Edited July 21, 2015 by Mike the Boilerman

[nicknorman]

Looks to me on the side on video that the main blades simply hit the building. You can see it happen and the damage to the building.

It's a bit difficult to see precisely but it does seem as though something is ejected from/through the fenestron just before all hell breaks loose. The rotors go clockwise in this helicopter so the fuselage is trying to rotate anti-clockwise, and thus right pedal (pushing the tail left) is required to counteract the torque. To prevent tail rotor drift (in this case drifting left due to the push from the fenestron) one has to have the rotor disc tilted slightly to the right. But if the force from the fenestron is suddenly removed due to disintegration etc, the right -tilted rotor disc will cause the helicopter to drift right, in this case into the pub wall. Of course at the same time the fuselage will start rotating big time so the right drift is only fleeting, but perhaps enough to cause the contact with the wall.

[boathunter]

It's a bit difficult to see precisely but it does seem as though something is ejected from/through the fenestron just before all hell breaks loose. The rotors go clockwise in this helicopter so the fuselage is trying to rotate anti-clockwise, and thus right pedal (pushing the tail left) is required to counteract the torque. To prevent tail rotor drift (in this case drifting left due to the push from the fenestron) one has to have the rotor disc tilted slightly to the right. But if the force from the fenestron is suddenly removed due to disintegration etc, the right -tilted rotor disc will cause the helicopter to drift right, in this case into the pub wall. Of course at the same time the fuselage will start rotating big time so the right drift is only fleeting, but perhaps enough to cause the contact with the wall.

I was thinking something more simple - pilot cocked up and hit wall, the inertia was sufficient to rotate the tail anti-clockwise for a moment before bits of the blade broken on the wall hit it.

It puts that ridiculous James Bond film where he's being chased by a helicopter that's slashing it's way though buildings into perspective!

[pquinn]

Take a look at Abbeyshrule and tell me why this guy needed two attempts to land in the same place.The only reason I can see to land in that particular place was that there was a pub there.
https://www.google.i...46ced34c84d3d39

[brassedoff]

Removed by me......... dont want to come accross full of shit.

Edited July 22, 2015 by brassedoff

[Morat]

"Hold my beer and watch this"

[brassedoff]

Lol yer, get that man a drink