Sir George,
By using the word "Instant" you are giving the air to ground part of the Airwave system more credit than it deserves.
The crew are not permitted to use their "personal" radios in flight.
The "Tactical" radio head is powered off the mission bus and gives access through a comms selector box to 4 channels at once out of a total of over 6400 available. Anything that is transmitted across the "In use" radio will have been recorded but it is very common for the observer to put his foot on the pressel and be greeted with the busy tone even when nobody else is on the net - frustrating enough when you are not busy but when things do get busy or in an emergency it's next to useless. Being on the mission bus, if one generator drops offline then the system is instantly off.

I've pretty much stayed out of this so far, due to little or no professional rotary experience. At this point I'll say this much.

Proper investigations of crashed aircraft take serious amounts of time, but the AAIB have made some preliminary findings public.

From what they have said, and equally significantly from what they haven't said or done… well it occurs to me that airframe investigations take serious time, but, bluntly, autopsies don't.

Perhaps there's some significance there. This is one of the more incomprehensible events I've encountered thus far.

No they have not!

No it's not, it is the way described in the emergency drills. It also allows the engines to be wound down and, if needed, closed down without taking your hand off the collective!

Which is why some of us have;

http://i52.photobucket.com/albums/g1...pse760e7d2.jpg

Fenestron trouble
 

Fortyodd2 - much as I thought. I saw the recovery on the news and the fenestron rotor looked pretty much trashed. I presume these things run in the 1000s of rpm. Could the loss of a blade lead to a complete destruction of the fenestron rotor?

I ask because the fantail on Cranbrook Windmill lost a blade a few years ago, which cause the whole remainder of the fantail to depart the mill and land on a car parked below. These things generally run in the tens of rpm, pushing 100 in severe winds. A fantail is a small windmill which turns the sails of the mill into the wind, it is generally located at the back of the cap of a windmill.

Question to those who operate an EC135 fitted with the fuel flow indication option:

I'm familiar with the time elapsing when shutting down using the EMER OFF SW. But I only have seen it on the ground with engines in ground idle....it takes a couple of seconds to actually shut down. What I would like to know: how long does it take to shut down when the engine is doing 100% N2 and, let's say, 60%Tq (and then pressing the EMER OFF SW)
I'm not suggesting it has anything to do with the topic......just my own curiosity to satisfy...

So basically: what is (appr) indicated FF in ground idle, and what is it when in 2x 60%Tq cruise?

Anyone?

Yellowbird,
I've also only done it on the ground whilst at idle - took about 3 seconds. The "usual" drill is that, on receipt of the fire warning, the first thing for the pilot to do is to establish safe single engine flight condition which would reduce the torque load to well below 2 x 60%. On the system closing the LP cock, then engine will only run until the fuel between the LP cock and the injectors is used up at which point the "flame" goes out.

Super VC10 - I think that AAIB were happy that all the bits were present. The damage to the fenesron was most likely caused when it impacted the roof having snapped off at the joint with the "Tube". I saw very little evidence of rotational damage.
The pilot would most certainly be aware "something" was amiss if a blade had departed.

Further to that, and I am no Helicopter expert, the AAIB said:The Helo experts above have said a loss of Tail Rotor (Fenestron) control and/or drive might lead to scenarios where closing the engines might be appropriate.

In Helicopter terminology, does the AAIB extract above just indicate the immediate gearbox output to the fenestron appeared intact? Or would it be understood that drive continuity was established all the way to the fenestron itself?

NoD

Thanks, I know all this...(as you know 2x 60%Tq results in 2'' OEI limit, which is considered a safe condition to establish a situation for yourself to manouvre yourself to a situation where it is safe to lower the collective to either OEI MCP, or, ofcourse, land safely

I just would like to know the FF figures for Ground idle (or Flight idle with ~12% tq) and Flight idle at 60%tq....I was hoping someone should be able to provide these figures.

In Flight ( without " idle " :E ) its around 90 - 95 kg/h:)

skadi

Might be of some use to someone ...
 

http://www.flightglobal.com/airspace...35-cutaway.jpg

Eurocopter EC135 Cutaway - Pictures & Photos on FlightGlobal Airspace

Shy, thank you, none of that is news, but your point on the pedals still having some effect is taken on board. The whole scenario is predicated on the startle effect, and surprise, in the force combinations changing in at the same time as something else is going wrong ... not a one thing goes wrong in level flight thing. Cheers, and appreciate your feedback. :ok:

Appreciate all feedback and the points on NR/EOL raised since my last musing.

Some of the theories being posted are somewhat far-fetched. From the evidence so far the most likey scenario, in my opinion, is that something
caused the aircraft to enter autorotation to an engines-off landing which was misjudged at the bottom end.

For anyone that hasnt attempted such a manouevre, either for real or in a simulator, it is somewhat challenging to say the least. Even when pre-planned to a well-lit open space it is one of the trickier exercises to complete in a helicopter and notoriously easy to mis-judge even when you've got everything going for you.

Having flown police operations for some considerable time in the past this thread has perflexed me. The interim report begins to indicate that fuel starvation may be worth a look. None of the EC135 operators have come out and said that he should have had sufficient fuel. So - if he had a double flameout, which I never considered when I was flying, there is the real possibility of rapid rotor stall. The recent follow up of a A350 accident in the USA( I know it is a single) indicated that even a rapid lowering of the lever might still cause the rotor RPM to droop to stall. Remember that the faster you are the more rapidly the nose will pitch down off loading the head. Their recommendation was that recurrent training should include aft cyclic simultaniously with lowering the lever to conserve RRPM - a major change in our basic training in slow speed helicopters. Some comments(Lonestar 50 #1129) seem to think you can recover. Guys there is no recovery when the blades STALL. There is no way to get the angle of attack below the critical angle and the drag increase is so large the the blades WILL surely stop. Remember that the tail rotor/fenestron is geared to main rotor - reduce M/R thrust 10%, tail rotor thrust reduces same or more. Likewise stall main rotor then tail rotor stalled. No main rotor thrust, no control, then gravity takes you where ever. Why no scream over the R/T I have no idea. Food for thought.

No it doesn't and yes we have!

The only thing it says about fuel is How do you get from there to Fuel Starvation as a probable cause?

DAPT, there are other aircraft at the Glasgow heliport and they haven't fallen out of the sky due to contam fuel.

The AAIB took over 3 weeks to publish their findings for G-WNSB (super puma), and that was with a surviving crew and an CVFDR to help them.

I don't think all of you are going to get the answers you want in a hurry.

@pofman
Ain't necessarily so (see henra's response to that musing), and even if it does eventually, not necessarily at the same time.
Note: I'd appreciate that if you'd comment on my post, you actually read it. Yes, it's a bit long, but I am thinking out loud. In case you missed the opening salvo, my point of departure was: witness reports of tumbling/rotating, and the idea that MRH had stalled at some point during this evnet. (initial point raised by henra).
That isn't what I said.

If you had followed the conversation, I followed up on henra's earlier point on there being a serious problem of trying to get out of stalled main rotor blades once they are stalled. (Aside: as with the VRS tests, in RW and more recently in the Osprey, has anyone (even way back when Igor was just getting S300 going) ever taken a helicopter up to altitude, deliberately reduced NR to where the blade stalls, and then restored NR, lift, control? Asking because I just don't know.)

From my vague memory of rotor blade aero class, I think the problem with restoring flying AoA and lift, etc, has to do with the airflow that gives you autorotation (from the bottom up through the rotor head) being disrupted and thus not working within the range designed for on most rotor blades ... beyond that, I'd need to ask the insights of any test pilots who've messed about in that range of rotor operations. Was never in my terms of reference. I have (since opening post) been advised that there are a few about who do something like that as part of their test and verification work. However, that is at the other range of operations, with max gross weight and max G loads taking the airfoil to its limits.

My other point would be that, whomever is flying the bird, if unaware that the MR blades are stalled, may still be operating under the assumption that, with the collective bottomed and helo descending, that the last bits of an auto are still in the offing. As noted before, and as you seem to agree, it isn't. That's a core point I was working out in re UPSET, UPSET Recognition, and UPSET training in the Rotary Wing Version.

In re the tail: if the Nr decays goes low enough to reach stall (we are NOT talking retreating blade stall due to high pitch/high speed here) then your TR/Finestron rpm will decrease porportionately (even if not stalled), and will provide reduced thrust/effectiveness until the airflow and AoA don't work anymore for it either.

It doesn't see the same airflow as the head.
(FWIW, it wouldn't surprise me to learn that most TR's would stall first, given what can happen at full RPM and unique cross wind conditions on some models, and loss of TR lift when the engines and the head are working ... )

Lonewolf.
Not only does the tail rotor not "see" the same airflow as the head, it doesnt have the same inertia as the head or the same thrust as the head (QED).
Believe me when I say that there is a dramatic and disproportionate decrease in tail rotor thrust when the main rotor thrust diminishes. I have the software from Westlands to prove it. A 5% reduction in main rotor thrust will cause about a 20% reduction in TR thrust.
The tail rotor needs every one of those 3984 revolutions to push out the bernoulli's:O Operating below this operational speed even by a small margin drasticallty reduces the TRE.
Interested to hear about the MR head stalled but pilot not knowing about it???
The only time it is stalled (other than intentionally) is in VRS. When else is it stalled without the pilot noticing until the bottom of an auto?