Totally mechanical RB. As previously stated if pulled on flight there would be no significant drop in NR.

Well, it's been a disappointing day for those of us that hoped the interim report might provide some clarity, some of the posts this evening have been frankly ridiculous.

A couple of pages ago I asked if the 135 has 'crash handles', similar to other EC types. Could someone in the know please clarify for me?

Ta.

Sven Sixtoo
No it didn't, it said ...

"Initial assessment provided no evidence of major mechanical disruption of either engine and indicated that the main rotor gearbox was capable of providing drive from the No 2 engine power turbine to the main rotor and to the fenestron drive shaft."

... which suggests to me that there is the possibility that there may be something to find in the tail rotor drive shaft department.

No.:= ... It doesn't!

No, it doesn't. Or no, you're unable to clarify?

:p

From the attitude of the ac when the fuel drain was taking place.

The amount of fuel drained would be limited to the level of the drain point, (near to the pump). Much like those boxes of wine, when the level of the wine gets to below the tap you can't pour any more wine out unless you tip the box.

In the scenario of the fwd transfer pump failing above 80 kts, ( greater nose down attitude), the unusable fuel is 59 kgs. Therefore if the ac on the strops is at an angle equal to or greater than the 80 kt attitude, that fuel will not be able to be drained until the ac is level. The same drain point/fuel level explanation applies for the smaller amount not accessible in the supply tanks.

Mind you, the report said that "approximately 95 litres of fuel were drained from the fuel tank", which doesn't necessarily mean that they drained it until it was empty, perhaps that's as much as their container could hold.

Probably yes. I have difficulties conceiving many other ways to end up with a fully stalled rotor and thus close to 0 RRPM on impact

...in that case (fenestrone failure) pilot must put engines to IDLE and make an autorotation to the ground. Let´s say, with that height and (maybe) low speed, in night, over the congested area, you have very good chances to enter the last stage of autorotation low speed (which is unforgivable in 135), or to make a high flare (due to lack of suitable terrain), which will result with rapid loss of rotor RPM...

I saw earlier that the 'rotor brake' had been discounted in an earlier reply but can't find where that was mentioned in the thread. Is it as simple as the rotor brake being locked out in flight?

It also seems very close to the engine controls from the panel diagrams I saw and I wonder if trying to shut down an engine in an emergency situation could also have resulted in accidental application of the rotor brake. Removing power from a misbehaving engine and applying the rotor brake might explain everything observed from the ground.

We should stay on solid ground. Therefore I am going to steer clear of any (so far) mechanical faults as mentioned in the AAIB prelim from now on.

The usual caveat: can a current operator confirm the feasability of this please as it's been a while since I drove the old girl? However my current experience on heavies should transfer across hopefully.
The pilot is coming to the end of his task having spent some considerable time doing the same old, same old. I recall getting bored/tired towards the end of some monotonous sorties and my mind wandering.
At some challenging stage in his flight he experienced a potentially benign run down or torque fluctuation caused by one of the ECU's stalling/surging (as witnessed by outsiders). "Normally" one determines the duff engine by comparing Nr movement with the suspect engine Ng. The duff engine drives the Nr out of its governed range thus enabling the pilot to select the correct engine for shut down. Perhaps this time the wrong engine was shut down whilst tired/confused. This left the duff engine driving the Nr and if that engine was providing less than nominal output the Nr will droop or even worse. He may have instinctlively raised the collective to maintain his cruise height anyway (or tried to stop his increasing descent) and the Nr would continue to decay - ever closer towards its point of no return (what is it in the 135? 82%?). He sees this and tries in vain to salvage the decaying Nr by chopping the remaining engine and lowering the collective but too late, he sees the looming deck and pulls for all its worth to salvage some of the RoD. By then there is very little Nr left, but what is left is washed out by that final application of lever. RoD continues unchecked and the cab hits hard with no engines or little minimal Nr. :\

Where does this obsession with the rotor brake come from?
It is a rather flimsy device compared to the aerodynamic forces involved and is strictly manual.

Jetranger, there may not be evidence of the Fenestron failure, but here's one to think about - pilot reacts to a PERCEIVED TR malfunction, which may have actually been some strange disruption to TR efficiency (Fenestron Stall?) and carries out TR drive failure drill, secures both engines and makes a very good stab at an EOL, but difficulty in judging height at night causes him to flare early with subsequent long fall raising collective to the stops. Would the Nr decay all the way? Dunno, but this may have happened before.

Its been a while since I flew a helicopter, but I don't think this is a recommended course of action.

cenzo

That's a good theory, and should be apparent to the AAIB by the position of the engine controls.

I've done EOLs at night, to a lighted and clear grass strip, and can easily perceive massive height misjudgements over a built-up area.

To sum up, the AAIB have said that nothing departed the ac prior to impact and that there is no evidence of major mechanical disruption of either engine and indicated that the main rotor gearbox was capable of providing drive from the No 2 engine power turbine to the main rotor and to the fenestron drive shaft.

So, all is well up to the point at which the mrgb is connected to the trds. Anything beyond that point could still present the cause for the incident, such as the trds, bearings and the trgb itself.


I hope some people sleep well tonight believing the papers and their own consciences, I'll be dropping off going through tail rotor scenarios.

Glasgow pub tragedy prompts West Midlands helicopter checks « Express & Star

From the aerodynamic side this will not be an absolute number. It will depend on weight and RoD. Edit: and altitude but this wouldn't have played a role here.
Stall (drag) depends strictly on AoA.
So, while in horizontal flight, a momentary drop to 75% might be recoverable at a certain mass, the same at a higher mass may not. Same applies, once a descent has started. This will increase AoA and thus increase the likelyhood of a stall at an RPM which was still recoverable in horizontal flight.
In a stabilised descent with collective fully down, somewhere in the mid to high 70s, maybe 80 should be about it for most helicopters with relatively high power/disc loading and thus range of collective movement.

A very puzzling and perturbing scenario from the AAIB report. And no scenario that I can imagine that can be aligned in any way with the (at least two, I believe) reports from inside the pub of a brief period between some "minor" ceiling collapse and the main impact.

TCIf the Nr goes up, there's no engine switching off going on!

Any information gleaned by a Radio Amateur would only be divulged to the AAIB (or other appropriate authority) as the person would otherwise be in contravention of the terms of his or her licence. Also, the divulging of information overheard on Air and Police frequencies is illegal. 2E0WOM

Sure, why not, must have been a wild guess....previous posters have been trying to explain how tedious and thorough the people from AAIB are....and then you come up with this???