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Police helicopter crashes onto Glasgow pub

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Police helicopter crashes onto Glasgow pub

Old 2nd Dec 2013, 15:07
  #341 (permalink)  
 
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All Police aircraft are insured commercially, unlike the military.

Indeed. This will be covered under the operators Insurance i.e. Bond Helicopters, who wet lease it.
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Old 2nd Dec 2013, 15:16
  #342 (permalink)  
 
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jugofpropwash: Although fuel contam is a very very small possibility (why didnt it contaminate the engines much earlier just after receiving the dirty fuel?), once contam fuel gets thru the filters, be it one or two tanks, the time between both flaming out would be seconds...

EC135's dont worry about bird strike from an intake perspective. The engine intakes are well screened inside the Dog House surrounding the MGB frame. Of course bird strike can and does incapacitiate in other ways: through windscreens, into tail rotors etc.
JTobias: I though about pilot incapacity too...for a short while. Even if the pilot "lost control" of his ability to fly the a/c, the rotors would have continued at nominal Nr until impact and the rotors would have disintegrated. This appears not to be the case with these rotors.

Sven 62: When you flare at the bottom of your auto (even in this case) the Nr increases, not decreases. So assuming he misidentifies the landing surface and flares harder to "gain height", the Nr will rise. He may well then drop further before landing, but the rotors will still retain enough momentum to disintegrate on impact with the back of the cab/other objects.

Does any Mode S tracker device show the a/c's speed seconds before it dissappears off screen? I can't determine if he was in a hover or cruising when it all went wrong?

If I was in a hover and the wheel came off (MGB slowed) causing the Nr to decay, I would instinctively push hard fwd cyclic and at the same time dump the lever. IF...and a big big ..IF the Nr had then drooped below its mimimum recoverable, then my descent would speed up rapidly and as SASless insinuated earlier when the MRGB slows, it drags the FPT's down with it, this would cause the Compressors to stall causing misfires/banging etc as Nr drags Ng down. I would then be in a zero spd EOL situation and at the bottom, have little or no Nr to arrest the descent with lever..
The latest reports are suggesting the investigating team are not expecting to recover debris away from the crash scene. To me that means there was a catastrophic failure somewhere along the common drive train between and including engine(s) and MGB.
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Old 2nd Dec 2013, 15:21
  #343 (permalink)  
 
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Skadi - who made that statement?

It was DAVID MILLER, deputy chief inspector of the Air Accidents Investigation Branch, who gave his statement at 13.00 in a news conference.
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Old 2nd Dec 2013, 15:23
  #344 (permalink)  
 
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Robdean

The scenario I posted earlier posed the theory that the roof towards the front of the AC giving way and the craft sliding down into the hole using the fuselage as a 3 ton wedge (forward into the hole thus crushing the crew compartment which is not designed with a horizontal load of this magnatude in mind) this would account for the damage seen on the recovered cockpit.

Last edited by Technet101; 2nd Dec 2013 at 15:58.
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Old 2nd Dec 2013, 15:26
  #345 (permalink)  
 
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So much reading and, sadly, so much rubbish to filter
If you enter a practice autorotation, the blades rotate faster than the engines & the freewheels allow the engines to a "flight idle", ready to re-engage as soon as the rotor speed drops, due to collective input.
You are aware that a GTE's compressor will spin at around 35,000rpm, the free power turbine shaft will spin at around 20.000rpm and the main rotor NR will spin at around 250rpm yes

If the main rotor blades were to spin at 35,000rpm+ well, they'd end up in China, blade tip speed is obviously contolled due to mach restrictions

Surely you must have meant something else though?

Last edited by Mitchaa; 2nd Dec 2013 at 15:38.
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Old 2nd Dec 2013, 15:49
  #346 (permalink)  
 
Join Date: Aug 2013
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Data

A few things:

Helicopter returning to base at about 700-800 Feet, night time

Hi inertia Impact, no survivors

Low Main rotor Blade Damage

No distress Call

No post Crash Fire

No weather related


Initial findings by the AAIB have confirmed that the aircraft made a vertical descent onto the Clutha Vaults pub, and that no part of the aircraft detached in flight.

This type of helicopter was grounded for a time in 2012 because of safety concerns.

Eurocopter published an interim Safety Information Notice on the day following the accident, with no special measures recommended


Witness: there was no fireball and I did not hear an explosion. It fell like a stone. The engine seemed to be spluttering.
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Old 2nd Dec 2013, 15:52
  #347 (permalink)  
 
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Sven 62: When you flare at the bottom of your auto (even in this case) the Nr increases, not decreases. So assuming he misidentifies the landing surface and flares harder to "gain height", the Nr will rise. He may well then drop further before landing, but the rotors will still retain enough momentum to disintegrate on impact with the back of the cab/other objects.



I was postulating that, being out of options and already well into the touchdown flare, the lever was being raised rather fast to get over the obstruction, hence Nr drooping mightily despite the flare effect. It is speculative. Autos at night always scared me, even with NVG and an airfield underneath and all the time in the world to set it up for training. I take your point about residual rotation smashing the blades. SOMETHING reduced that to a negligible effect. If not the last vestiges of cushioning, then what?
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Old 2nd Dec 2013, 16:00
  #348 (permalink)  
 
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Interesting quote re the fuel load.
I flew the first ever Police T1's in Europe. They were fantastic ships with stacks of power and a fuel load of Maximum: 2.5hrs. I also flew the first semi glass panel "P1" Bond cab all those years ago and its fuel load was just around 2hrs. Today as the years have passed they have become fatter and heavier payloads and the lates P2++ I would suggest carries fuel for no longer than perhaps 1.5hrs (I stand to be corrected by any of the operators).
What version is the Strathclyde 135?

2hrs airborne before the crash, to me seems to bring it very very close to its minimum fuel?
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Old 2nd Dec 2013, 16:28
  #349 (permalink)  
 
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Has anyone speculated about vortex ring yet?
If he was hovering downwind at night, it could have occurred and that could explain the vertical dropping and the upright, 'relatively' soft landing. It happened to me one night over Belfast, but luckily I had enough height to get out of it. So sorry it had to happen in the first place though.
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Old 2nd Dec 2013, 16:29
  #350 (permalink)  
 
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correction

Quote:
Originally Posted by Thomas coupling
..... I would be keen to get a very close look at the combiner gearbox........
Agreed. I had a partial combining gearbox failure on another type. One engine then oversped when the shear shaft broke as designed and the engine automatically shut down at its overspeed limit. Fortunately my combining gearbox failure allowed the other engine to keep going. Maybe this crew were not so lucky and both engines shutdown as a result of a catastrophic combining gearbox failure. Not saying it was the case, just floating an idea.


FYI - There is no combining gearbox on the 135. Two driveshafts connect the engines to the freewheel units of the main transmission. They transfer the power of the engines to the main transmission.
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Old 2nd Dec 2013, 16:54
  #351 (permalink)  
 
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Just a thought....why land on the Roof Top behind the street lights...when the street and parking area were reasonably well lit?

Given a choice....of either landing on top of a building or taking the aircraft to the street (neither of which are first choices), I think the Street would be the choice most of us would have made.

I agree with the description showing some forward motion to the aircraft as evidenced by the marks on the roof top. Remembering the Main Rotor Blades rotate Clockwise...would that correlate with the damage to the one Air Con unit?

I find it interesting that the Light Standard on the right hand side of what might be the approach path of the aircraft was not damaged.

As the damage was far more extensive on one side than the other on the aircraft...was the aircraft leaning more towards that side?

Peering into the hole into which the aircraft wound up....does it appear the majority of the roofing timbers have been thrown towards one side of the hole....which would suggest the direction the aircraft was moving as it entered the Roof?

Viewing the photographs will reveal a lot of information.
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Old 2nd Dec 2013, 17:16
  #352 (permalink)  
 
Join Date: Dec 2013
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schematic EC135 MGB

Schematic for MGB - hope this helps people to visualise the mechanics as asked for previously.

(click thumbnail for bigger picture)



Source

http://www.eurocopterusa.com/images/...-Expo-2010.pdf
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Old 2nd Dec 2013, 17:17
  #353 (permalink)  
 
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SAS
Remembering the Main Rotor Blades rotate Clockwise
You sure about that?
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Old 2nd Dec 2013, 17:24
  #354 (permalink)  
 
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You are right.....it is German...not French.....counter-clockwise.
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Old 2nd Dec 2013, 17:25
  #355 (permalink)  
 
Join Date: Dec 2013
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PW206B Engine

Someone was asking about how the engines power the gear box.



Source - P&WC: PW206B2



Note the triangular flange that corresponds to the MGB input stage in previous post.

Source - Pratt & Whitney: Media Library - Pratt & Whitney Canada

There are other good images of the fenestron tail rotor here including TR gear box and control rod etc EC135

Edit: Turbomeca Arrius also power this aircraft.

Last edited by iranu; 2nd Dec 2013 at 18:16.
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Old 2nd Dec 2013, 17:28
  #356 (permalink)  
 
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Engines running

Good Point¡¡¡

Engines running post crash often produce post crash fires, this was a US EC135 crash in different scenario with engines running and post crash fire, NTSB determined that a kid on board the aircraft lowered colective and aircraft impacted ground.


Thomas J. Stewart, former Vashon resident, and 4 others killed in Arizona helicopter crash - Vashon-Maury Island Beachcomber


NTSB Says Five-Year-Old Girl Likely Contributed To 2010 Helicopter Accident | Aero-News Network
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Old 2nd Dec 2013, 17:32
  #357 (permalink)  

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(I know similar to this has been posted already, this is just my "two penneth" and the only thing I intend to add at this stage, pending the official AAIB verdict).

With regard to the lack of Nr. Most modern, light to medium twin engined helicopters have low inertia rotor systems. A low inertia rotor gives only one "stab" at fully cushioning the landing.

This was an urban area. It's quite possible, assuming that neither engine was available, that the original landing point (obviously chosen in a great hurry, probably instinctively) was found to be unsuitable in the last few seconds.

A second flare/cushion would not be so successful because of the lack of energy remaining in the rotor system and would be likely to result in an increased rate of descent and little or no Nr.
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Old 2nd Dec 2013, 17:46
  #358 (permalink)  

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Eh? Only if it was a practice!

Do the EC135 drills not include securing the engines?

Edit: A post above mine, to which this was a reply, has been removed, either by the OP or by a moderator.

Last edited by ShyTorque; 6th Dec 2013 at 21:28.
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Old 2nd Dec 2013, 17:48
  #359 (permalink)  
yme
 
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I think it shows both lack of respect and judgment, but hey fill your boots if you think you know the answers. Tell us all!
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Old 2nd Dec 2013, 18:24
  #360 (permalink)  

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Sid,

As you must know, I do not fly the EC135 and so have no reason to download the RFM. But every helicopter I have flown (and that's quite a few types, single and twins, including flying in the same police role), requires the engines to be secured in an emergency autorotative landing such as this appears to have been.

If the engines were running or not (I can only assume you mean that in this type they are selected to "Idle", rather than "Off" for an emergency autorotative landing), the Nr would still decay during the landing because they wouldn't respond to collective input, would they?

That was actually my point, not the detail of the cockpit switch selections and a possible explanation of how/why the aircraft appeared to be partly under control but then landed quite heavily, more than would have been expected.

If you wish you to take issue with my post, on this most serious of subjects, as one professional pilot to another, kindly point out my errors in a professional, rather than a belittling or sniping manner, if you can manage that. Especially as many unseen eyes watch this forum. Thankyou.
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