Surprised this hasn't been deconstructed on here yet?

[206 jock]

Or maybe it has.

VIDEO: Rescue helicopter makes emergency landing after technical fault (From The Westmorland Gazette)

[Sir Niall Dementia]

Precautionary landing into a nice, big clear area. No bent metal, grieving widows or orphans. Nothing to deconstruct really.

SND

[TorqueOfTheDevil]

Never fear, the usual suspects are 'debating' it on the SAR (H) thread...

[[email protected]]

A sort of 'friendly debate'.

So a Super Puma has to come and rescue the rescue S92

[Gwyn_ap_Nudd]

Not the first time a SAR aircraft has had to be rescued by another helicopter ...

[Ainippe]

Aircraft go U/S - what is to deconstruct?

[gsa]

So a Super Puma has to come and rescue the rescue S92

I thought it must have had got lost when it flew up Wensleydale low the other day, It made a change from the normal green ones we usually get.

[Democritus]

Originally Posted by Gwyn_ap_Nudd

Not the first time a SAR aircraft has had to be rescued by another helicopter ...

.....and not the first time a SAR helicopter has had an emergency - even yellow ones sometimes had them......

[[email protected]]

Yes but if you are going to do it then do it properly

That was a freewheel failure in the MRGB I believe.

Anyway I thought new technology prevented that sort of thing - so much more reliable etc etc

[Oldsarbouy]

Quite correct Crab it was a tech failure. We all escaped virtually uninjured thanks to a robust airframe, let's hope the S92 and AW189 never have to prove that they are as crash worthy.

[Thomas coupling]

OldSARboy:

I would suggest S92's and 189's are head and shoulders above the safety integrity of the venerable SeaKing.

In fact when the SK was built, I believe they had little or no understanding of safety cages and G tolerant materiel. Carbon fibre wasn't even in the dictionary.

Bless 'em.

[[email protected]]

TC - you will also know that composite materials - especially carbon fibre - have extremely poor resistance to impact damage.

They might be stiff and light and resist flexing well but when you hit them they fall apart.

Titanium is similarly fragile I believe.

[212man]

TC - you will also know that composite materials - especially carbon fibre - have extremely poor resistance to impact damage.

They might be stiff and light and resist flexing well but when you hit them they fall apart

I suspect there are one or two Formula 1 drivers that would disagree....though, of course, you can't lump all composites into the same basket - they are designed for their role.

[TeeS]

Yep, I've never felt comfortable hanging under that fragile Bolkow rotor head ;-)

[[email protected]]

Yep, I've never felt comfortable hanging under that fragile Bolkow rotor head ;-)

As long as you don't hit it with a hammer then it will be fine

they are designed for their role.

yes, to be light and strong in compression and flexion but not to take surface impact loads.

[John Eacott]

Originally Posted by [email protected]

Originally Posted by TeeS

Yep, I've never felt comfortable hanging under that fragile Bolkow rotor head ;-)

As long as you don't hit it with a hammer then it will be fine

Back to metallurgy class for you, Crab!



The Bo105 head is the same as is used in the BK117, and exceptionally strong.

But as a rigid rotor it has quite defined limits for sloping ground ops, and a completely different technique than you would be used to in (for instance) a Sea King. You cannot feed the disk into a level attitude and then pull power to bring up the fuselage with a rigid rotor, nor feed the wheels/skids down on landing, without keeping a very close eye on the MMI. I have no idea of the S92 controls but if they follow some of the limitations of the BK/Bo then it could have been a contributory factor in the OP's link.

It is not as easy to follow through on the AI in a rigid rotor as with an articulated head.

[[email protected]]

It is not as easy to follow through on the AI in a rigid rotor as with an articulated head.

I managed it quite well for nearly 2000 hours on the Lynx and I think you mean semi-rigid rotor since the whole point is that the titanium flexes to allow flapping.

Titanium is very strong but also very susceptible to damage which is why scratches can quickly lead to cracks and structural failure and why the heads are inspected so rigorously.

[John Eacott]

Originally Posted by [email protected]

I managed it quite well for nearly 2000 hours on the Lynx and I think you mean semi-rigid rotor since the whole point is that the titanium flexes to allow flapping.

Titanium is very strong but also very susceptible to damage which is why scratches can quickly lead to cracks and structural failure and why the heads are inspected so rigorously.

No, I meant rigid rotor: the Lynx has a semi rigid rotor system but the BK117 and Bo105 have rigid rotors. The only semi-rigid rotor on the BK or the Bo is the tail rotor.

I'm sure that we're all terribly glad that you managed quite well for 2,000 hours, but we lesser mortals with only 3,000 hours on a rigid rotor system found that care was/is necessary when carrying out sloping ground landings in the BK117, and a different technique is called for when compared to fully articulated heads.

Also, the MBB titanium head seems far more robust than the Westland one, since I have no recollection of scratches leading to cracks and structural failure. Maybe the construction is different: I do recall that the Lynx head was machined from a solid billet of titanium?

[[email protected]]

The original Lynx head was one piece but it was difficult to manufacture so they made a two-piece head.

Clearly the rotor head of the 105 doesn't flex but the blade attachments to it do (otherwise where does the flapping occur) so there are composite hinges instead of mechanical ones which I believe makes it a semi-rigid system even if the rotor head itself is solid.

I still can't see why sloping ground is more difficult in a 'rigid' system - you just have a quicker control response to cyclic and more control power.

Yes, you can generate rolling moments more quickly and you need to be very aware of bending stresses on the rotor mast if you use too much in-slope cyclic but it still isn't rocket science.

Perhaps the 105 head wasn't so critical on scratches because it wasn't designed to flex - the Lynx definitely was.

[John Eacott]

Since we're pedantically discussing the rotor head of the 105/117, the only possible relative movement between the blades and the rotor head is during changes of pitch. Flap and lead-lag movement is accomplished by the elasticity of the blades. Technically you have a rigid titanium rotor head and a hingeless or semi-rigid rotor system.

One all?

Back to the issue at hand, slope landings with a rigid or semi rigid system. Again, I don't know anything about the S-92 but would be interested in any input from a current S92 driver; at least it would clear up the speculation