Clutha helicopter crash: "... all relevant risks have been identified..."

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Latest NPAS News

Thursday, 12th December, 2013

Chief Super "Safety is the number one priority for the National Police Air Service (NPAS). Our decision on whether or not to suspend operations or ground any NPAS aircraft is based on advice issued by the Civil Aviation Authority - the UK's aviation regulator and original equipment manufacturers. We remain, as ever, in constant communication with the CAA and other partners in the aviation industry. There is currently no notice in place from the CAA or the original equipment manufacturers to ground any aircraft and so we have not done so. If such a notice is put in place then we would immediately and carefully consider it.

?In light of the technical issue identified by Bond Air Services, as a precautionary measure, we are increasing fuel levels on all NPAS EC135 aircraft and increasing the minimum level of fuel which pilots are allowed to operate on.

?The investigation into the Glasgow incident remains ongoing and it would therefore be inappropriate to comment further on that incident or speculate on any connections.?

Mark Burns-Williamson, the Police and Crime Commissioner for West Yorkshire and the chair of the strategic board for the National Police Air Service, (NPAS), has just addressed the board this afternoon.

?We have had a report from the Chief Constable of West Yorkshire, Mark Gilmore, about the early information to come from the Glasgow incident at this meeting and I have reiterated that the safety, both of NPAS staff and members of our community is our paramount consideration,? he said.

?Both the Chief Constable and Chief Superintendent Ian Whitehouse, the accountable manager of NPAS, have assured the board that all relevant risks have been identified at this stage and all appropriate operational measures have been taken.?

Reply to
Terry Fields
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Terry Fields presented the following explanation :

Which seems to hint at there having been a fuel issue.

Reply to
Harry Bloomfield

R4's just said something about the Bond grounding being whilst they check out a fuel light issue, too, complete with Cranfield talking head. Apparently many of the Bond choppers are airborne again already, having been checked.

Reply to
Adrian

Apparently one helicopter of that model was found to have a faulty fuel gauge, reading low/empty when there was actually plenty of fuel on board. Difficult to see how this could cause the Glasgow crash though.

Reply to
Chris Hogg

In message , Chris Hogg writes

Unless I heard it wrongly, a low-fuel warning light came on, but the gauge read correctly (plenty of fuel). I guess the pilot may have seen the warning light, and decided to do a controlled emergency landing - but it went wrong. However, I'm sure we'll get the true story soon. I gather that the temporary stop on using that model of helicopter has been lifted.

Reply to
Ian Jackson

Even with the warning light on you still have several minutes flying time, how far were they from the heliport? Not very far...

A full supply tank will keep the associated engine running for 20 mins and each engine has it's own supply tank. I doubt that there is a single fuel guage/warning light, I'd expect three one for each supply tank and one for the main tank.

Soon may well be next year or later, with nothing obvious showing in engines (note plural) and gearbox it's going to take a lot of careful investigation to work out what went wrong. If they ever do.

Reply to
Dave Liquorice

Sounds reasonable to me. Lots of energy put into examining all aspects of that type of aircraft in great detail since the crash.

A potential problem is found - even if it's nothing remotely connected with that crash - and immediate action is taken to check the whole fleet.

Just because B happens after A, it doesn't mean that they are closely linked.

Reply to
Sam Plusnet

So, does this imply then, that the fuel gauge was in error and it ran out of fuel? Being quite low then I suppose this could account for it, but I still do not get the stationary rotors claim, as surely they could not stop so quickly without the inertia causing damage or as normally would be expected, auto rotation would kick in. Brian

Reply to
Brian Gaff

I was rather worried to note that these choppers do not have any sophisticated 'black box' in them, considering how much time they spend over built up areas at low altitudes. Do these machines have fly by wore for example? I just wondered if the software actually got zapped by something and went into landed mode spontaneously without any warning.

Was the site near any radio transmitters?

Brian

Reply to
Brian Gaff

See my message in the earlier thread.

When flying normally, the rotors rotate so as to provide down thrust i.e. downward air movement. In free fall with no power on the rotors, air movement relative to the rotor blades is upwards, i.e. the blades are driven in the opposite direction. In the process of going from powered flight to auto-rotation in free fall, the direction of rotation of the rotors must reverse, i.e. at some point they are stationary, if only momentarily. Perhaps it was at that point the helicopter hit the roof of the pub.

Reply to
Chris Hogg

No, the first report showed there was about ninety litres left in the tanks.

Reply to
Scott M

I THOUGHT auto-rotation consisted of lowering the collective to negative angles of incidence so the rotation continued in the SAME direction. Equivalent to pushing the stick forward in a normal plane to get from a level flight-engine on into a glide power off.

Of course to do that implies the collective hadn't stuck, due to a cracked hub or some such..

One scenario that makes sense to my (far too limited) understanding is that both engines flamed out, the popping and banging are attempts to restart, and the failure to auto-rotate was due to an entirely different issue and represented a failure to get the blades into the correct position TO auto rotate. Under those circumstances the blades would have eventually stopped and the phrase 'falling like a shot duck' would best describe what happened thereafter.

Again I am no chopper engineer, but how often is the ability to set the blades FOR auto-rotation checked? its not something you would normally do - set the blades to drop like a stone under power, or soften a crash not under power..

An dis there a common hydraulic system fr e.g. driving the collective and the fuel pumps?

The fact that the blades had stopped indicates loss of power AND inability to auto-rotate as well. And that, from an experienced pilot, in a sane mind and in possession of his senses, is an inconceivable choice to have made.

Reply to
The Natural Philosopher

You mean something like:

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Big broadcast transmitters do have air exclusion zones around them because of the field strengths. Not to mention hitting the mast or guy wires isn't very good either.

Reply to
Dave Liquorice

That is what I would expect as well but I'm not a pilot let alone an helicopter pilot.

From looking at the specs for the EC135 there is an awful lot of duplication of essential systems. It looks very much like if a single point of failure can be engineered out it has been.

But how long did the poor pilot have from sudden, unexpected, flame out on presumably *both* engines to realise what had happened and what was the appropiate action. Loss of *one* engine would surely mean throttle up on the remaining one and *increased* collective to get more lift. IANAHP.

Reply to
Dave Liquorice

Quite. The rotor blades certainly don't stop and go backwards! [Can you imagine what would happen??!!]

I've been trying to find a YouTube video of a helicopter doing a 'dead-stick' landing, but the only one I can immediately find is one of an autogyro doing one (but the principle's the same), and a model.

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[Unless you actually enjoy watching model helicopters flying, fast-forward to 5:40.]

Reply to
Ian Jackson

Complete and utter bollocks I'm afraid.

Tim

Reply to
Tim+

Oh well, it was only a thought. Seems it wouldn't happen in practice, from what others have said.

Reply to
Chris Hogg

The _pitch_ of the rotors reverses, not the direction!

Andy

Reply to
Vir Campestris

Apologies for the abruptness. I was on my phone earlier.

What you were forgetting is that helicopter rotor blades have adjustable pitch (controlled by the "collective" lever). Dropping the lever turns the angle of attack of the blade from nose up to nose down. This means that they can go from powered lift to unpowered "windmilling" without having to slow and change direction.

It's vitally important that rotor speed isn't lost during this transition and if the blade (when unpowered) starts to stall, the situation is on the verge of being unrecoverable. "Stalled blade"=falling out of he sky.

Tim

Reply to
Tim+

Brian, the blades of many modern helicopters are very lightweight and have little inertia. On the ground, with the collective (angle of attack) set low, I dare say that they may well whirl around for a while without power but in the air when providing lift (and a steeper angle of attack), without power, they will stop quickly unless the pilot takes very quick corrective action.

The likelihood is the helicopter suffered a failure of both engines (for reasons so far undetermined but possibly fuel starvation) and the pilot just didn't get the manoeuvre right. Once rotor RPM drops below a critical level, the situation is apparently unrecoverable.

Tim

"Brian Gaff" wrote:

Reply to
Tim+

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