Police helicopter crashes onto Glasgow pub

[RotaryWingB2]

Fuel quantiy probes are capacitive.

Low fuel sensor is a temperature operated switch. I.e. It gets hot when there's no fuel on it and brings on a caption. Separate circuits.

Supply tanks are different capacities, meaning #2 would flame out 90 to 180 seconds before #1.

[jimjim1]

It took a while but I finally found a reference to such a device.

Specialty Level Switches (http://www.omega.com/literature/transactions/volume4/t9904-15-spec.html)

Thermal level switches sense ... the increase in thermal conductivity as a probe becomes submerged in the process liquid.

[Fortyodd2]

To those unhappy with the AAIB progress to date, this from Rev 2 of the Eurocopter SIN:

"Please find the following information update:
• AAIB deputy chief inspector David Miller said in an interview “I can confirm that nothing detached from the helicopter in flight before the accident”.
• The wreckage has been transported to the headquarters of the Air Accident Investigation Branch (AAIB) in Farnborough.
• The complete investigation team led by the AAIB and including EC experts plans to start with the in depth examination of the wreckage on Monday, December 9th".

[SilsoeSid]

Not sure of the setup at the Scottish Air Ops, but who do they speak to apart from Police, Prestwick or Scot Info? Is the office manned when the ac is out? Who would/could they make a distress call to?

Anyway, thinking on a new one, TRGB CHIP ...

[cyclic]

Try "talking to Glasgow", the international airport just down the river.

[SilsoeSid]

Thanks cyclic, do you know if there is then a requirement for the pilot to call 'approaching the base'?

[cyclic]

Haven't worked there for a good few years but we used to call them landing and departing.

[chopjock]

TC
So he tries to identify the source but the noise(s) and (slight) drop in Nr troubles him to the extent that his best course of action is to remove the stalling engines. So he sets himself up for an auto and chops the throttles (all of this has taken seconds to decide and all the time the engines are popping and surging). He chops the throttles

If the NR was decaying for what ever reason, why would any one want to reduce the throttles?

Surely if you decide to auto rotate (and you still have tail rotor) you would want to have engines assisting? even if they were stalled, they would most likely recover whilst descending?

[SilsoeSid]

Thanks again cyclic, appreciate there's a call to Glasgow informing of the rtb, but is there then a call or 'blind call' to the base?

[airpolice]

Sid, there would be nobody at the base to hear it.

[NR DROOP]

:hmm:Helimed 5 might :hmm:

[SilsoeSid]

Thanks airpolice, just thinking that a base call might be the practise once Glasgow has been informed of an rtb, in order to inform the air ambo or any other ac at the base location of incoming traffic. Likewise a lifting/departure call.

[MightyGem]

Helimed 5 might
Probably not a night though, unless the Scottish Helimed work nights.

[NR DROOP]

Trust me they do.

[jayteeto]

Dave, they do inter hospital transfers. Not charity funded, they do an excellent job saving hours and hours of paramedic transit time

[SilsoeSid]

How about,

Call to Glasgow rtb
Change frequency
TRGB CHIP

... Some of you will know where I'm going with this one.

[Thomas coupling]

C'mon then Silsoe, I'll bite - why a TRGB chip and how does this conclude with no engines/no transmissions and no Nr?? Oh - and a vertical indentation mark in the roof with no fwd trajectory?:confused:

[SilsoeSid]

TC,
70 kts might ring some bells.

[DOUBLE BOGEY]

Silsoesid. If you know something, spit the f***er out and stop beating about the bush

[SilsoeSid]

I don't know anything, just putting another possible sequence of events on here.

[mickjoebill]

Supply tanks are different capacities, meaning #2 would flame out 90 to 180 seconds before #1.
Thinking through this unlikely scenario..
If one engine flamed out due to starvation, without warning, I presume it could stay airborn on a single engine?
If crew did not realise that the cause of the loss of power was a fuel indication issue (that would effect both engines) would they have tried to returned to base on the good engine?

Fuel exhaustion to one side, is there any common point where failure would stop fuel delivery in both engines, not necessarily simultaneously? I guess mechanically the systems are self contained for each engine, but can a Fadec fault or RF interference shut down both engines?
Rumours of Fadec failure occurring at Greek Olympics as a helicopter lifted from a very RF hostile area.



Mickjoebill

[Munnyspinner]

If the reported sortie times are correct and assuming it was tasked at if around 20:20? Then by 22:30 they would still have a margin over IFR reserve. If fuel had been an issue then surely they would have stopped at EGPH before routing via south of Glasgow and back to base.

[SilsoeSid]

Happy with that thanks W06, I was thinking more of the pilot's radio calls.

[SASless]

The Maryland State Police had a similar incident with a Bell 206 which crashed shortly after Take Off and wasn't missed for quite some time.

Is there any doubt there were numerous contacts between the Aircraft and the Police Command Post during this flight? The Command Post has a lot of information that would be of interest to the investigators.

[toptobottom]

SilsoeSid I don't know anything

:hmm:

[cattletruck]

Judging from the general direction the machine came to rest, there is a good possibilty the pilot was heading for a landing on the street. Perhaps at the last few seconds he noticed people standing there and had no choice but to change direction/speed and pull the remaining inertia out of the main rotors taking a self sacrificing chance in the heat of the moment to save those standing in his preferred landing spot.

[Adroight]

Of course. Obvious.

[Munnyspinner]

If TRGB chip, could this also suggest a more catastrophic failure on route to land as soon as practical? I have never understood why the emergency procedure isn't to proceed with immediate landing? However, this is consistent with reduced airspeed shallow initial descent then a sudden and uncontrollable descent if the TRGB did go.

[SilsoeSid]

toptobottom
SilsoeSid
I don't know anything
:hmm:

If you know of a different situation other than a tail rotor problem where you close down both engines in flight, I'd like to know! I'm not of the opinion that they had no fuel left or that it was contaminated, they are just so highly improbable to me, as is both engines failing at the same time for some engine malfunction. Even a double FADEC failure wouldn't necessarily cause things to happen as they did.

I'm just thinking of what might have happened for it to have ended up as it did, considering the ac was (or should have been) in forward flight when the first thing in the sequence of events occurred.

[Winch-control]

To me it is clear, there are but 2 choices.

Number 1. There was a failing on the part of the pilot.
Number 2. There was a failing with the a/c.

Given the failings of the AAIB, it will be a long time before Number 2. is proven.

[Cows getting bigger]

WC, there is a third option which is basically your number 2 followed by number 1.

[Ornis]

@Winch-control. In NZ it's sometimes years before the TAIC or CAA release a final report. If you were a pilot or knew anything you'd know that.

I don't think your stating the obvious is helping very much.

[SilsoeSid]

Problem is, some of us have in front of us the cards, the books and at times the aircraft, trying to work out what might have happened, for our own peace of mind. After all, it is us that know the finer details of operating the aircraft.

If we then throw an idea out there, however cryptic, we are leapt upon by those that either don't fly, don't fly rotary, don't fly at at night, don't fly twins, don't fly turbines, don't fly in controlled airspace, don't fly the 135, don't fly in the role, don't complete challenge/response pre to/landing checks etc etc.

While I'm painting I think these things over, while the coat dries I can look things up. When I'm forced to sit in front of jungle or dance programs, the same applies, it's as simple as that.

At the beginning of this thread I suggested that people needed to download things, ie the 135 flight manual.
When I highlighted that when the twist grips are wound off, the N2 stabilises at 60%; As the Nr decays, on reaching 60% the gearbox will once again then be driven by the engines, yet the replies went;

"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?"

As a consequence, I deleted my what I thought of as informative posts in a huff (2 Dec 10:04) in a case of 'what's the point' because the missile, shooting, laser, church etc theories were accepted as possibilities, as for using the utilisation of the nitesun or skyshout, nice thought with good intent, however..!


Am I losing it?
Well I guess if you were to see me sat in the seat with books on my lap going through various possibilities, twisting throttles, touch drilling and walking around our aircraft asking the airframe what could have happened, well maybe I am.

[rotorspeed]

Winch-control

You seem to have a personal agenda against the AAIB, given, as far as I'm concerned, your unfair and probably ignorant criticism of them in both your post 746 and above. I'm sure like any other organisation there is room for improvement, but I for one feel they do an excellent job with very thorough reports.

My own view is that if there had been any obvious mechanical problem, eg a failed TRGB, it would have been found within 2 or 3 days and information of some sort provided to the 135 fleet operators already. If the AAIB has not found obvious mechanical failing then they will feel less pressure to rush to conclusions and will methodically go through what is likely to be a very complex investigation, possibly with sensitive human factors involved.

The AAIB clearly have a huge responsibility to get their report right as it is likely to have ramifications for those with some responsibility - and don't forget that in the same way that we pilots don't want to fail and be criticised nor does anyone else, be it aircraft manufacturer, operator, ATC or anyone else involved. These reports have huge significance so we must be patient.

[DOUBLE BOGEY]

Sid. I understand how you are feeling. It's close to home for you. I have spent a fair amount of time on shift at the ASU and it can get claustrophobic when there is only one pilot. On the NS there are lots of us to water down the intensity of situations and it is easier to get on with it.

I think it is clear we will not really know what happened until the first report is released. No one seems to really know anything.

In the meantime it's best we just concentrate on our own jobs in hand. Be a little more diligent, and rest assured that what has happened is not the first time, and sadly it will not be the last...no matter how hard we all try.

Take some time out Sid and stay safe!!

Best Regards DB

[SilsoeSid]

Oh, and can we get away from the 'lack of distress call' red herring (imho), as I think in the very short period of time available, I'd rather be 'Warning crew and passengers', flying the aircraft and trying to work out what's happened ... than be talking on the radio.

Just my thoughts.

[mustpost]

A quick question for someone here who will know - was it usual for this sortie to go as far east as Dalkeith? I have lived in Central Scotland all my life and was not aware the the (Strathclyde Police Force) aircraft operated beyond the (old) boundaries. The force has recently been amalgamated into 'Police Scotland'.
http://upload.wikimedia.org/wikipedia/commons/4/48/ScotlandPoliceStrathclyde.png

[Jet Ranger]

If you know of a different situation other than a tail rotor problem where you close down both engines in flight, I'd like to know!

@SS
Yes, I agree with you...when you train autorotations on EC135 in Eurocopter factory, they tell you that you do that for, more or less, only one case - fenestron failure! In that case, you must put both eng to IDLE, and finish the flight with auto. If you enter last 100 ft with less than 60 KIAS, more or less, you will crash!

JR

[Ornis]

@SilsoeSid. While the answer might be simple -- even obvious -- when you know what it is the fact is you almost certainly don't have all the bits of the jigsaw to put together. Since the police are still appealing for witnesses who saw the helicopter maybe nobody does.

I can see you view solving this as a challenge but there are possibly aspects of this accident you will never know about.

deleted: SP

As you already know, often several things go wrong at once. Best wishes and take care.

[Munnyspinner]

Must post.
Strathclyde police vanished when all the Scottish forces were amalgamated into Police Scotland. So yes, quite common for the HU to cover a very wide area.

[mustpost]

quite common for the HU to cover a very wide area.
Indeed, so from 1st April 2013 there must have been quite an increase in workload for the PIC and crew...

[Mechta]

Whitehead06
We still have no definative answer to the question as to cause of this accident, so should not speculate.

Errr, it may have escaped your notice, but you're on Pprune...

[TorqueOfTheDevil]

Given the failings of the AAIB, it will be a long time before Number 2. is proven


Winch Control,

May I politely request that you stop slagging off the AAIB, for two reasons:

1. You are not contributing anything useful to this thread (admittedly you're not alone in this).
2. Unless you can prove that the AAIB have actually failed in their duty, your vitriol against them is completely unjustified as well as unpleasant. Can you provide facts showing the time limit for the AAIB to release a conclusive report into a crash? Because if not, they haven't failed - they simply haven't met your own personal, subjective, unrealistic expectations.

We all (including the AAIB) want to know what happened in this and every accident, but this tragic event isn't a simple one to figure out and at least the AAIB are maintaining a dignified silence while they pore over the available evidence. You are not poring over anything (apart from your own reflection perhaps) and you are not maintaining a dignified silence. Perhaps you could learn from them. The ball's in your court.

TOTD

[Burnie5204]

Whitehead06 - From the perspective of the guys on the ground. Absolutely Yes!

When they were drawing up and selecting NPAS base locations they decided through consultation with Police forces that the helicopters should be no more than a 20 minute response time away from any area in their primary deployment zone in order to both get the resource to scene within and appropriate time frame and provide sufficient 'on task' time.

From the Police perspective the 20 minute response time starts from the moment that the officer on the ground says "we need air support please!"

However NPAS said "whats the top speed of the helicopter?"
"So how far can it cover at top speed in 20 minutes?"

Then drew a big circle with that distance as its radius around the potential bases to determine where to place the helicopters.

However, their method assumed that the helicopter was already hovering over the base and able to accerate to top speed instantly and also go in a straight line without slowing down or diverting course for anything (like Class A airspace for exampe). They were forgetting, of course, the time for the message to get to the crew, the crew to work out location/routing to the task, head out to the heli, startup, run checklists, hovertaxi as required, lift and transition into forwards flight and accelerate to maximum permissible speed for that routing.

Thus the areas of responsibility are stupidly big in some cases.

Thankfully for my force the basing calculations worked out that we kept our helicopter at the same site and our neighbouring force kept theirs at the same location too because of the call volumes that each handle (ours was already providing air support for 3 forces and the other fr 2 forces) so our primary and backup air support is still coming from the same locations but many others (particularly in more remote areas) are suffering from lack of air support due to the distancea that each now has to cover.

[mbriscoe]

Sadly but nowadays not the only investigation that has to take place.

Glasgow helicopter crash: Clutha hate comments investigated by police (http://www.bbc.co.uk/news/uk-scotland-glasgow-west-25290793)

[SilsoeSid]

DAPT
What does SOP call for?

Please allow me to throw that one 'back at ya'!.
What does the 'S' in SOP stand for?

[falcon900]

Can anyone explain to me why fuel contamination cant be an issue here? There appears to be agreement that after a sortie of this length, the aircraft would be operating from the lower reaches of the tanks. If there was sufficient liquid in the tanks, there would be normal readings and no warnings activated. If the liquid wasnt fuel.....
With the onset of contaminated fuel being ingested, would the pilot not be quite confused by the symptoms (no criticism implied) and from what has been written, have about a minute before the other engine was similarly afflicted?
Could explain the popping etc sounds reported by witnesses, the stopped engines at impact, and the lack of fire. Could it not also have contributed to a loss of height before the decision to auto rotate was taken? Given that height for a successful autorotation was likely at a premium even in the cruise.....
The blades may have been turning very slowly at impact as a result of a desperate attempt to arrest the rate of descent, realising a successful landing was not possible. The final irony being that the pub roof by virtue of its unusual construction provided a degree of cushioning of the impact, but sadly not enough

[nomorehelosforme]

With all professional outfits these days surely they have strict controls/procedures to avoid any form of fuel contamination? Maybe a fuel supplier might like to make comment?

[Fortyodd2]

DAPT,
Standard Operating Procedures are for "Standard" situations.

Aviate, Navigate, Communicate - in that order.

Falcon900, I'm not aware that any suggestion has been made that fuel contamination is not a possibility. However, it is a requirement that both the aircraft and bowser/fuel Installation daily samples are retained so the AAIB will have something to work from. You may have noticed that when the aircraft was lifted from the building, one of the first things done before it went on the lorry was a fuel sample.

[SilsoeSid]

For starters, the check A involves fuel checks from 4 drains. 2 from the main tank and one each for the supply tanks. Also throw in the daily fuel checks at the bowser installation, the checks on the delivery vehicle etc etc. Throw in a few filters along the way and imho it's highly unlikely. Put it this way, it's not the same as a 45 gallon drum and a zenith pump operation.

Popping sounds; flame out with auto relight, are you thinking along those lines?

Thomson 757 Bird Strike - YouTube (http://youtu.be/cO5yEsRu6fM)

One point this Thomson incident brings out about radio calls, it is 11 seconds from the first flame that pops out of the engine to when the Mayday was broadcast. 'Nuff said

As for the lack of fire, again, watch the Auckland incident.

[falcon900]

Yes, but what about a contaminant that floats on top of the fuel? Harmless till the tank runs low enough for it to be ingested, and drain checks would never show it.

[Eric T Cartman]

Perhaps obvious - maybe it's even suggested to some u/t pilots theses days - but a thought re communicating a problem.....
I worked as an ATCO offshore from 1980 to 1982. The calm was shattered one morning when an inbound (Puma or S61) suddenly broadcast a Mayday, the callsign &, to me, what sounded like a check list & lots of numbers.
All tx/rx was, of course recorded by ATC.
He landed ok on his nearby destination platform & later called me to say he'd had a warning light(s) & was broadcasting some parameters that investigators would like if it had gone wrong & they'd ended up swimming. Smart thinking in a dodgy situation before cvr's .... :D

[cyclic]

@DAPT and how many real emergencies have you been involved in when a Mayday was required? I'm talking life threatening emergencies. It is always a little different when you are sitting at the controls of a properly out of control helicopter that seconds before was behaving normally. Go figure as they say.

[Non-PC Plod]

DAPT

The Mayday call is well ingrained as part of a drill when we recognize what has happened and we are executing the actions that we know intimately. If you have a really unusual situation, and you are concentrating on working out what you are going to do whilst the ground rushes up at you, I rather think it is going to slip down the priority list.

[SilsoeSid]

DAPT;
Standard operating procedure in an emergency as I have been trained military and civil is to broadcast Mayday call while while executing emergency procedure.
Failure to do so in training would result in repeating exercise correctly. It is pretty well ingrained as a result.

If that's the way you think you'll be able to do it fair enough DAPT, however it is well known that we can't concentrate on 2 things at the same time, we can multitask, but not concentrate on more than one thing at a time. Throw in an unexpected or multiple emergency and I'll bet that call gets shoved to the back of the list. My training involved putting out a call, if there was time, once the situation allowed.

Eric, nice post. Flying around our local city the other night, I was under no illusion that if I managed to get a call out, the first thing after the Mayday & c/s would be the problem/symptoms. Not SOP I know!

[SilsoeSid]

Cabby, Turbomeca or P&W ?

Proceed to take off and a very loud bang occurs while transiting into forward flight and a/c shakes and twitches.
ATC told a/c returning to stand and a further very loud bang and shudder occurred which made all concerned expect a failure.
I must ask, before or after TDP? I know neither of the engines failed as such, but to stop the take off (rejected before TDP?) and return to stand!
I know I wasn't there, etc etc, but I think I'd rather leave it in situ, than continue flight.

[WASALOADIE]

DAPT

The pilot in this case was previously military.

Mil Rotary use the WADFIR principle for dealing with emergencies.

Warn the crew
Achieve Safe Flight or Land
Diagnosis
FRC Actions
Intentions
Radio Call

However the principle can be tailored to suit the nature of the emergency. Note that Radio Call comes last and is done if possible and time permits.

I think that in this case, the pilot had enough to contend with in trying to achieve the second item in the best way possible at night, in an area with very few options.

I've seen some struggle to achieve all of this in training with the luxury of advanced notice and height and be able to achieve a full flare recovery, in daylight.

For all the armchair experts out there who are having a go at the AIB for not getting a preliminary cause out yet, give them a break! They must carry out the investigation thoroughly and and without jumping to conclusions. They have to determine what damage was caused prior to and after the crash. They have a mountain of evidence to sift through and must ensure they don't overlook any detail. I'm sure when they have the facts that they will report their findings.

Finally, I'd like to say, there is a lot of B0110x on this thread and some have you have demonstrated why you are not employed by the AIB or maybe you shouldn't even be employed within the aviation industry!

[jayteeto]

In the simulator with catastrophic type failures, I have observed decent pilots put out a perfect May day call then crash the aircraft. Others have not used radio and landed the aircraft. My brief is to make a call if it doesn't put the aircraft at risk. Stating you have 'failed' SOPs is quite frankly a load of bollocks

[pilotmike]

@Cabby:A different Macs engineer turns up and goes straight into the inspection ports on the donkeys with a horoscope.
If only all of life's problems could be solved so easily with a little astrology...;)

[Ornis]

The clue is in the meaning of the word "Mayday": "venez m'aider"; "come to help me".

I suspect the public think a helicopter is safer than an aeroplane because "it can land anywhere" but an aeroplane glides naturally, and thus there is normally more time available.

When learning and practising there has to be some framework and guidelines but always it's "first fly the aircraft". If you're going to crash a call just helps other find you.

On that theme, fitting data recorders won't make a flight any safer.

Finally, I don't know the statistics but it's uncommon for people on the ground to be hit when a small aircraft comes down, even in a city.

[Tandemrotor]

May I ask, what would a Mayday call have achieved here?

[RVDT]

Wikipedia - Mayday (http://en.wikipedia.org/wiki/Mayday)

Quel dommage! Dommage votre français n'est pas un peu mieux. Mais ce n'est à prévoir si vous vous asseyez en Nouvelle-Zélande!

F&*k Google - just ask me - a well known print on T-Shirts in Asia!

Autorotation - is as close to "natural" that any helicopter can achieve.

[m.Berger]

Aviate, navigate, communicate and in the event of risk to life,
the captain is in charge, not the rule book. The AAIB is not a rumour network and will carry out its work with its usual thoroughness. Although it is reported that four out of five accidents are due to pilot error, it looks to me as though this was not one of them.

[chopjock]

May I ask, what would a Mayday call have achieved here?

"Mayday Mayday tail rotor failure going down, 3 POB "

or

"Mayday Mayday engine failure going down..."

some useful information can be sent over the rt

[ShyTorque]

Stating you have 'failed' SOPs is quite frankly a load of bollocks

I completely agree. For all we know, the pilot may have had only single figure seconds to react to the entire incident before the aircraft hit the surface.

Before implying criticism of the pilot's actions, firstly none of us was there in the cockpit.

The obvious question is: What difference would a Mayday call have made to the outcome?

An ATC response would have resulted in a questions and answer exchange and the ATCO most probably could have done nothing of use, except for beginning to locate the aircraft and to determine the nature of the problem. By the very nature of this accident, i.e. over a populated area, folks on the ground were immediately aware of it - the very prompt reaction of the emergency services to the accident scene was reported.

Whatever happened appears to have been very sudden and I'm certain the pilot prioritised as well as he could in what was obviously a most dire situation. Sometimes things don't happen as a "text book" problem, such as they are practised in a simulator (or MS Flight Sim...) or talked about in the classroom. Some of the most worrying emergencies I've had to deal with in the air don't appear in the RFM. I've also had error messages come up that even the engineers didn't know about and that the aircraft manufacturer (initially) said did not exist.

In any emergency situation, the first priority has to be fly the aircraft and speaking to ATC is possibly quite a long way down the priority list, at least until under some sort of control because it detracts from the safety of the aircraft. It appears that poor Davey Traill never reached a state of affairs where a distress call got to the top of the hit list.

[RVDT]

Mayday call-

Obviously your call sign - preferably 3 times if time permits.

N
I
P

Nature - Whats up

Intentions - What you are going to do

Position - Where you are (obviously)

Globally Universal format (hopefully)

Who hears it and to what extent is with luck.

[Cows getting bigger]

Silo, re you post 722 (http://www.pprune.org/rotorheads/528850-police-helicopter-crashes-onto-glasgow-pub-37.html#post8192348), it has of course happened, albeit different scenario and on the P1.


http://dms.ntsb.gov/aviation/AccidentReports/kjc0nb55xiit4y55ucpgrkrs1/Y12082013120000.pdf

[SASless]

Perhaps putting it into the Pub was the Mayday call as it surely got the message out didn't it?:ugh:

Come on folks....it's Sunday and the Pub is open....there's a better place to have this argument isn't it?

[RVDT]

In the 135, an engine problem is indicated by multiple captions on one side or other of the CAD screen, clearly indicating which engine has the problem, as does the VEMD and T's&P's screen. The FLI needles have I & II on them to identify a good or bad engine and the VEMD screen will show low N1,Tq & TOT values on the left (#1) or right (#2) side of the screen.

There is a scenario that might actually be the complete opposite to which you interpret as "good versus bad".

The assumption is that pilots actually know how these things work.

Unfortunately history has shown the opposite in some cases.

[SilsoeSid]

Cows getting bigger

Silo, re you post 722, it has of course happened, albeit different scenario and on the P1.
http://dms.ntsb.gov/aviation/Acciden...2013120000.pdf


Mmm, I thought my post 722 was about the unlikelihood of inadvertently shutting down the wrong engine after an engine problem. The example you give is an inadvertent movement if the#1 twist grip out if it's detent and while manually controlling that engine, inadvertently moving #2 out of its detent. Did you read & understand your own link?

Of course on the T1 we know that the twist grips are smaller and we also know that on the T2, not only are the twist grips larger and have different textures, if the twist grip was to have been inadvertently moved out if it's detent (as in your linked incident), the CAD would display, 'TWIST GRIP' on the respective side thereby indicating to the pilot the problem, which is easily resolved by putting the twist grip back into its detent.

I think that all you have done here Cgb, is trawled the internet for a 135 incident where someone did something unexpected and somehow linked it to something unrelated. I guess this shows that knowing the 135 helps a bit in threads such as this.

[RVDT]

Sid,

WARNING - 100% conjecture.

Oops - my bad - normal here!

Engine Overspeed AEO at or about equivalent 30 sec power OEI. ~ .78 - 82 FLI depending………..

Needle split - not quite enough power to cause N2/Nr to go into overspeed function- N2 is what triggers Overspeed protection.

Looking at instrumentation - which one is really the duffer?

[HeliComparator]

SS just on the point of tail rotor failure drill, if you shut the engines down completely, as the airspeed reduces at the end of the manoeuvre, the drag from the transmission gears, oil pumps, hydraulic pumps and alternators (depending on type) will cause the fuselage to rotate once weather cocking effect is lost, resulting in a probable rollover.

Therefore it is advantageous to have a very small amount of torque on, to counteract these draggy losses. Depending on type, it might be that leaving one or both engines at idle provides this torque.

In the case of the 135 with which I am unfamiliar, but going on your comment about N2 at 60%, surely the heli should be on the ground by the time 60% Nr is achieved during an "engines idling" landing, thus any yaw will be minimal as a result of the ground contact, and anyway perhaps welcomed to counteract the drag yaw. The engines would remain at idle and so the max torque produced would be "not a lot".

Therefore I suggest that the RFM procedure would be fine in practice (not that I am volunteering to test it!).

[SilsoeSid]

RVDT, which N2 needle has taken the Nr up with it?

[F4TCT]

in the likes of a murder investigation say, the police can hold the body aslong as they deem there is no further evidence to collect...

Does the AAIB have this power also? given that the first funeral was infact that of the pilot..... It doesn't rule out that it was or wasn't incapacitation of course, however suggests there's been an opinion gained by the AAIB in this respect?

Dan

[topendtorque]

dead right Jetranger.

Been there done that, heard that, numerous times, always with just a few seconds to get the message out because it was always just above the trees from whence it happened. Like- "going down",,, new radio girl, 'wa's that?' me "goin down f*8yer", a quick 'oh' was all I heard before the HF aerial broke.

Another day me and the the chief pilot on a double - he has a free-wheel failure just above the tress. Him, "goin down", I'm already turning toward him and as I respond 'aawwright', I see him just disappearing below the trees a couple of hundred meters away.
Him - he hasn't understood my response, not surprising the way we talk at times, "goin down F*** yer". Me, 'alright - already on the way.' As I streak over at full throttle right over on my side to get a clear view from thirty feet above. I see an impression that will stay me forever. His yellow helmet centre frame in the '47J bubble, hands locked on the controls, his steel grey eyes track me from left to right, his panatella is broken - one end still in his mouth the other swinging, shwick - shwick - shwick, back and forth with the aircraft rocking violently as the blades just then collect the tail boom. Me, 'you Ok?', Him with a less urgent and laconic reply says, "yeah but the helicopter ain't."

I continue working as it as mayhem just then.

It would be hard to assume that a gentleman of this persons previous low level experience would not get some sort of squawk out, but it is very possible. The radio freq he has selected, doesn't have a responder in attendance say, or it is being used by other traffic and he is not heard above it. However it is not a factor that will break the bank of China, but it may have helped as a timeline indicator had one been heard.

The deliberate tone of my post is to help lighten up, as Sasless says, take a break, have a beer, wait for the preliminary, which should only take thirty days or so.

cheers tet

[SilsoeSid]

HeliC, totally agree.
Perhaps it all just happened to line up just at the last minute.

My point about the 60% was to highlight (imho) that the engines must have been switched off completely, otherwise the blades/head would have been mangled. In addition, if that action hadn't have been carried out by the pilot (imho), we would have probably seen many more casualties.

[topradio]

Like most here, I have been mulling this over and over. I have read most of this thread and don't think I have seen this exact scenario suggested.




1.The a/c returning to base suffered an incident that required an emergency landing in auto - just what we have yet to learn.
2. Pilot gets the a/c into auto and identifies what he thinks is an open space.
3. When the a/c gets to a few feet above the roof the pilot realises that it is a building and pulls hard to cushion the impact
4. The a/c lands very hard but not fatally (witness reports of initial crash) and the pilot shuts down the rotors and orders evacuation.
5. Just as the crew unbuckles and perhaps even start to get out, the roof finally gives way with the result we know about.


I would love to know the reported time between the initial crash and the roof coming in - it must be in the order of a least 5 to 10 seconds for the band to stop playing and comment on "bringing the house down" and then restart playing.
Just my 2p worth

[SilsoeSid]

Like most here, I have been mulling this over and over. I have read most of this thread and don't think I have seen this exact scenario suggested.
Page 15
Post 293 (http://www.pprune.org/8183503-post293.html)
2 Dec 05:55

[topradio]

Sid, thanks I stand corrected!

[Tandemrotor]

So on the basis of the current replies, it would seem a Mayday call would have achieved precisely........ Nothing.

One might reasonably postulate that is exactly what the pilot may have thought too??

[Arkroyal]

If the aircraft had been landed and shut down it would not have exhibited the degree of destruction evident from the wreckage.

It crashed vertically on to and through the roof with little or no NR, leaving an EC135 shaped hole with no evidence of forward speed. Why? None of us knows. The AAIB will hopefully work it out!

Edit: Agree Tandem. A May day would achieve nothing but distraction at a very busy time.

[jayteeto]

1990s, jayteeto plus puma and two colleagues plunging into jungle in Belize. Crewman shouts "MAY DAY MAY DAY MAY DAY VIPER 2 GOING IN!". Army signaller writes it all down as is his brief. After some head scratching, he can't figure it and asks his corporal what a mayday is?
Lesson learned, if a police control room is providing flightwatch, make sure they know the jargon. Did the cops get a call out? For future ops, it might be worth briefing the crew in advance to make a call if you are busy fighting the aircraft????
For the record, the emergency was caused by the tail rotor driveshaft and I was WAY too busy to think about the xxx radio........

[xlsky]

over and over: watch the destruction of the roof PLUS the destruction of the airframe. add it up. result: too many g's

some thoughts about distress calls. Thomson 757 was taking off on a busy airport, an early call to ask for priority and keep other traffic on hold and away from the scenario and following procedures seems sensible. Also, 2 qualified pilots on board to share workload, one can concentrate just to fly the a/c. Completely different situation with the airspace 500ft abv Glasgow City Center. Some other thoughts. I think there are some concerning aspects that the police is asking for more witness statements, inclusive possible private video footage, regarding the whereabouts of their helicopter before it crashed. Perhaps they already know a little bit more. They will tell when it's time to tell.

[Agaricus bisporus]

It crashed vertically on to and through the roof with little or no NR

Well, we'll see. RPM low maybe but I think the "vertical" bit will be proved otherwise. Probably more like an equal forward and vertical speed - both considerable - and both arrested almost instantly. But vertically? I doubt it very much.

[Fission]

I put a chopper into the ocean earlier this year and didn't get a call out - too busy flying and briefing the pax. Fortunately we all got wet and got out :) (Yay for HUET)

I've done some vertical autorotations (during flight checks only) that demand a massive pitch down attitude to get the speed back before flaring. Great for confined spaces, but not something I'd be keen to do at night in anger - especially if there was an unlit building in the way.

Fizzy

[Arkroyal]

Ag.

Just about the only fact so far released by the AAIB is that the aircraft descended vertically.

As for NR, the evidence is there in the photographs of the main ant tail rotor damage.

[Ornis]

The funeral has been held so the question of pilot incapacitation has likely been answered.

[xlsky]

Probably more like an equal forward and vertical speedin that case the heli must have been above the Clyde, to the South? Apparently he was last seen just North of the river and crash site, above the city; look in what direction the fuselage is facing. seems like loss of control to some serious degree, and clearly vertical descent, the roof looks die-cut. No shifted battens or crumbled sheets.

[SilsoeSid]

There are no plans to ground the West Midlands’ police helicopter in the wake of the horror crash in Glasgow at the weekend.

Nine people were killed when a police chopper smashed through the roof of the Clutha bar on Friday night, including two police officers and a civilian pilot in the helicopter.

West Midlands Police use the same model of helicopter, a Eurocopter 135, but the National Police Air Service (NPAS) has revealed they will continue to fly as usual – for now.

NPAS is led by West Yorkshire Police and a statement from the force’s crime commissioner Mark Burns-Williamson and Mark Gilmore, Chief Constable of West Yorkshire Police, said: “NPAS has been following the tragic events in Glasgow and our thoughts and condolences are with those colleagues and members of the public who may have been killed or injured in this accident, as well as with their friends and families.

“NPAS does not operate police helicopters in Scotland but does operate some 14 similar Eurocopter 135s across our fleet.

“We have been in communication with Police Scotland and our suppliers within the aviation industry including the Civil Aviation Authority, and are continuing to operate our service as normal.

“Safety remains the key priority for us in continuing to fly police mission.”
Coventry Telegraph (http://www.coventrytelegraph.net/news/coventry-news/no-plans-ground-west-midlands-6370203)


No reporting that any safety checks have been carried out, as suggested by the earlier Express and Star report.

"Police and ambulance helicopters in the West Midlands have been checked over by safety experts following the Glasgow tragedy that claimed nine lives.
Fleets have undergone rigorous safety checks, with the force’s Chief Constable Chris Sims saying: “Given we operate helicopters of a very similar design and style, there were concerted efforts from the National Police Air Service to check safety."

Express and Star (http://www.expressandstar.com/news/2013/12/04/glasgow-pub-tragedy-prompts-west-midlands-helicopter-checks/)

[zorab64]

The constant questioning of whether the Police (front or back seat) managed to get out a distress call needs some clarification.
I'd suggest that the seriousness of the situation is appreciated by the pilot ONLY, who will likely exclaim "sh!t" at most, while he tries to control the aircraft. Depending on what's happening, and certainly if he's had the time to chop engines, and how (switches or throttles), the remaining seconds are unlikely to be enough for the Police to think about, let alone do anything of use.

Most will keep quiet, in order to let their one possible saviour (Pilot) resolve the problem, whilst being ready to help where they can/when asked. If this event was as desperate as it would seem to have been, there appears to have been less than a minute from start to finish - with little time for it to fully register on all occupants.

If the engines had been shut down, Police radios will be unpowered anyway, with the possible exception of a hand-held radio, if fitted, in the cradle - although unlikely in the confusion that either Police occupant will have time, or presence of mind, to change the rotary selector (from where it's likely to have been for normal Ops) to be able to transmit.

None of this is implying that the Police are not capable, just that however many times emergencies are discussed & practiced in theory, when the chips are down, it's likely an emergency call is the last thing on anyone's mind, and certainly not in an event like this.

P.S. Just like to add my support for rotorspeed #809, torque-devil #819 & others re inappropriate comments towards AAIB. There are unlikely to be many organisations worldwide as respected for the thoroughness of their investigations as they are, however long it takes.

[rotorspeed]

DAPT

And I guess you think the pilot here should have squawed 7700 too, do you? Hmm, brace yourself for replies! Just what sort of rotary flying experience do you actually have?

[FrustratedFormerFlie]

Aviate,
Navigate,
Communicate

At that height, at night, in that location and with (one surmises) the aircraft going tecghnical in a big way, there'll be little time for (1), limited options for (2) and no bandwidth at all for (3).

[500e]

Zorab
"If the engines had been shut down, Police radios will be un-powered anyway, with the possible exception of a hand-held radio, if fitted, in the cradle - although unlikely in the confusion that either Police occupant will have time, or presence of mind, to change the rotary selector (from where it's likely to have been for normal Ops) to be able to transmit."
This was a discussion point on ground vehicles (before mobile phones) with emergency services, do you loose comms, or wire radios before isolators, some county's did others didn't.
Would tend to agree with FFF not enough bandwith

[Fun Police]

i tend to agree with the mayday being superfluous in this instance. given where the accident took place, there would be thousands of "mayday's" called almost instantly. it is a built up area...
let's let the matter be, the crew had enough on their plate with likely very little time to deal with the situation.

[Tandemrotor]

DAPT

It might assist your argument if you were to tell us WHY a 'Mayday' call was important in this situation?

Otherwise forgive us for thinking it would have been a complete and utter waste of effort/capacity.

[chopjock]

Tand
It might assist your argument if you were to tell us WHY a 'Mayday' call was important in this situation?

I can add to this, A mayday call, if time allows (in this and other situations) can give useful information for the crash investigators.
eg. "fire on board", "tail rotor failure", "engine failure", "run out of fuel", "jammed controls" etc…

Particularly if the aircraft is subsequently destroyed in the crash.

[Tandemrotor]

chopjock

That is absolutely, and categorically NOT the purpose of a 'Mayday' call. Nor would I expect the AAIB to formulate ANY opinions whatsoever on cause due to the content of such a transmission!

Professional pilots appreciate that.

To suggest otherwise is 'a little' naive?

[SilsoeSid]

DAPT I am surprised at the professional pilots that do not believe a Mayday call is important. It is the responsibility of the pilot flying. You might rethink your ability to respond to immediate action steps while transmitting a radio call.
http://www.v2helicopters.com.au/wp-c...D-LANDINGS.pdf

I am surprised at the other pilots here that do not believe that flying the aircraft is more important than a radio call.

Thanks for the link, it seems to back up what the professional pilots, as you put them, are saying;

THE FORCED LANDING:

ENTRY:
1. Lower collective.
2. Right Pedal.
3. Aft cyclic.

DESCENT:
1. Check:
- Rotor RPM
- Airspeed
- Balance
2. Select a suitable landing area considering the wind.
3. Set up type of auto to make landing area.
4. Mayday call.
5. Transponder 7700.
6. Passenger brief.
7. If time permits -consider the possibility of restart
-if restart not possible turn off : Fuel Cock
Master switch
Alternator.

Well blow my old sea boots, there it is that pesky Mayday call, right at the bottom ... below all that flying malarky.

Please explain why on Earth the Mayday Call and Transponder selection are a higher priority than 'Passenger brief'?

[SASless]

NOE....radio call? :rolleyes:

Yeah Right!:ugh:

It is so high on the priority list....this call telling Persons Unknown what is wrong with the aircraft.....and we must not ignore those Priorities.

I would stick to Priority number 1 through 10.....Fly the Aircraft!

[AtomKraft]

DAPT

In the movies you mean?

[chopjock]

I don't think anyone is suggesting get a Mayday call out at the expense of failing to aviate. However if time permits, then some information can be useful…. and the sooner the better means the message is more likely to be heard. I would certainly do it before briefing the pax.

[SilsoeSid]

DAPTIf you were the last aircraft in NOE flight the others would not even know you went down without a Mayday call.

Mmm, judging by that statement, you haven't done much tactical formation flying have you?

[zorab64]

500e - to clarify further to others who've already posted with technical details - the main TETRA head which controls all the Police radios is lost when both Gens go offline, in fact, thinking about it now, since TAC 4 also goes through the same head, I'm pretty sure it would also become unusable, even though the actual radio would still be powered by its own battery.

In addition, if the Pilot happens to be using ATC1 in a twin Garmin 430 fit, typical of UK Police-fit aircraft, that will also drop offline when both Gens are lost (as would happen when engines are chopped). In a fraught situation, he's unlikely to be able to do anything other than press the button & transmit - transmission goes out, or not, through whichever radio was last selected. With a double engine failure, it may or may not be ATC2.

Transponder - forget about it, fingers don't even go anywhere near them in day to day work, as it lives with the same code 24/7.

[Lemain]

Leaving aside whether a Distress call would have helped or should be prioritised higher or lower, if one pilot cannot manage the workload then, when carrying passengers or over urban areas at low level, there should be a minimum of two pilots. Yes, that would affect the entire costing and operability of much helicopter usage - the effect would be massive in some market sectors or even make helicopters non-viable, but safety of passengers and those on the ground should come first.

There are other benefits aside from sharing workload; two pilots working in the loop act as a restraint against over-confident, slipshod, or incompetent behaviour.

Please note, I'm not suggesting that any of that was a factor in this accident - we don't know yet - but it has been in others.

[Lonewolf_50]

Lonewolf, The discussion is EC135, am I right in thinking that as you refer to engine levers, your example isn't based on an EC135?
Yessir. The point being raised that I responded to is an issue common to twin engined helicopters, and some things that can go wrong with single engine failure as one tries to resolve it. You are correct that my point was not related to an EC-135 mishap. (It was also over 20 years ago)

[madflyer26]

DAPT,

Is it not fairly clear to you that this pilot and crew most likely had no spare capacity to get a distress call out? Unlike the very safe and controlled environment of a training flight, this event even to a highly experienced commander as Dave Traill would have been terrifying and his utmost thoughts and capacity would've been the saving of his aircraft and crew. The fact the Mayday was omitted really portrays a situation far beyond comprehension. The crew of the Super Puma that shucked its head in the North Sea managed "Mayday oh fxxk" very apt for that situation!!

MF26

[Thomas coupling]

Fortyodd says:
TC,
ATC 2 is direct off the battery so would be available. ATC 1 requires avionics on and either the shed bus switch or a generator online.
Airwave head is same as ATC 1.

I always thought a mayday was to tell someone you needed assistance and was a last resort to leave a record of where you went down to speed up any assistance needed. All this "leaving clues with ATC" is rather quite quaint, methinks :D. I would assume that David (a) had his hands full and (b) knew that ATC knew where he was. We still don't know if Stratchclyde Police Ops room received a message from the TFO's. Any radio hams out there - listening in?

Lemain: If we followed that advice then (a) there would be 10 dead now. Why not have two train drivers, two coach drivers?
Remember everything we do in life is all about risk.
Definition of risk: Frequency x Outcome. How often have police helo's flown over city centres x how often have they fallen out of the sky?
Now is most certainly not the time to make decisions like that.......and thankfully they won't.;)

[SASless]

Zorab,

If one retards the Throttles to "Idle"....do the Generators drop off line and thus cause a loss of the Mission Equipment?

Likewise...does the Garmin 430 require both Generators to operate or can a single Generator power that without any switch moving by the Pilot?

[Tandemrotor]

DAPT
A call stating TR failure,Engine out, Controls locked would provide a little more information as to the cause.
chopjock
I don't think anyone is suggesting get a Mayday call out at the expense of failing to aviate. However if time permits, then some information can be useful
Information? Useful?

Useful to whom? The Pprune pontificators perhaps.

If you are seriously suggesting the instantaneous assessment of the pilot (who may quite possibly not even KNOW why he is going down!) would be used as a 'guide' by the AAIB, I'm afraid you need to acqaint yourself with their work a little more.

In this particular case a 'Mayday' call by the pilot, even with a guess as to a possible cause, would probably have been worse than useless.

[Tandemrotor]

Lemain makes an excellent point. I asked this on 3 Dec:
Is it time Police flying became a twin pilot operation?????

As a result of this accident, and previous incidents, I will not be at all surprised if the continuation of police flying over urban areas now becomes the subject of a two pilot requirement.

For safety's sake, why wouldn't it?

Lack of payload/increased cost are no longer sufficient excuses.

I strongly believe it to be the way ahead, for many of the same reasons as Lemain.

[FrustratedFormerFlie]

Could indeed be the way forward. Specifcally as in Scotland with force merger, crews can anticipate greatly increased operating ranges. Indeed this flight, I hear, spent part of its duration on a job in the old Lothian and Borders police patch, which it would not previously have been expected to do. Was this planned on the ground? Or a requirement added during the flight?

Is the expectation, in the new 'Police Scotland' era, of airborne asset ability to respond to no-notice in flight re-tasking to low level, night, urban, single pilot ops over unfamiliar territory enough to prompt a rethink?

No doubt some will say such an appeal would be a thinly veiled 'more jobs for more pilots' campaign. I'm not so sure.

This investigation may, or may not, feed into the debate.....

[AnFI]

Is there a suggestion above that one would retard throttles if a TR failure were to occur under these circumstances?

[dazdaz1]

BBC Radio5..... No evidence of engine/gear failure, AAIB

[Onceapilot]

Is this type susceptible to intake icing?

OAP

[Sven Sixtoo]

Clutha helicopter crash: No mechanical fault found

Investigators have found no evidence of engine or gearbox failure in the police helicopter which crashed into a busy pub in Glasgow killing nine people.

Preliminary findings from the Air Accidents Investigation Branch (AAIB) found the main and tail rotors were not rotating at the time of impact.

The report also stated the Police Scotland helicopter had about 95 litres of fuel when it crashed on The Clutha.

The three crew and six people in the bar died in the crash on 29 November.

The report said that the helicopter took off at 20:45 with 400kg of fuel on board.

It stayed over an area of Glasgow's south side for about 30 minutes before making a short 10 minute foray over Dalkeith in Midlothian, some 38 nautical miles away.

The helicopter was granted permission to re-enter Glasgow air space at 22:18.

The report said: "No further radio transmissions from the pilot were received. Radar contact with the helicopter was lost at 22:22.

"Around this time the helicopter was seen and heard by a witness who described hearing a noise like a loud "misfiring car".

The report continued: "He then saw the helicopter descend rapidly. It crashed through the roof of The Clutha Bar, a single storey building on Stockwell Street in central Glasgow."

[skadi]

Very mysterious...
What then could cause the rotors to stop in such a short time???

skadi

[Conor.P.M]

Not a pilot so I'm curious, given the aircraft and conditions, what sort of flight time would 95 litres of fuel permit.

[staplefordheli]

The BBC quote has missed the most important detail in the AAIB report


The drive train was complete to the Fenestron through the MGB and no evidence of major disruption to either engine


in my mind that leaves very few possibilities with 90kg of fuel still on board
and two shut down engines and a very experienced pilot


Something was found very shortly after initial investigations started either off or on scene to give the AAIB a fairly big clue where this is going

[CJ Romeo]

It wasn't that sort of night, report even says so, 5 degrees and 2 degree dew point, I was in the area, it was very mild, if he came from the East Coast, its likely to have been even warmer.

[Sky Sports]

I've drawn a conclusion as to what stops both engines and slows a rotor very quickly, and given this report, it's still on the cards. But, I so so hope I am wrong!

[Arkroyal]

I would take issue with the AV8 report.

The fact that there was 95 kg of fuel in the tank does not preclude fuel starvation.

It's a long way from tank to engine!

I am not in any way suggesting this as a cause.

[LOZZ]

Air Accidents Investigation: S9/2013 - Eurocopter EC135 T2+, G-SPAO (http://www.aaib.gov.uk/publications/special_bulletins/s9_2013___eurocopter_ec135_t2___g_spao.cfm)

[rmcfarlane]

The fact that there was 95 kg of fuel in the tank does not preclude fuel starvation.

True, reworded. Thanks for pointing it out.

[Tandemrotor]

Point of Order:

The AAIB report states approximately 95 LITRES of fuel.

That's about 75 Kgs.

[helimutt]

BBC site is stating 95 litres NOT 95kg. So a slightly different amount.

[NorthSouth]

The report says 95 litres of fuel found, not 95kg. That's about 76kg - about 13% of full capacity. But I understand the fuel system is designed to prevent both engines being starved of fuel at the same time.

[jayteeto]

Approx 25 minutes to dry tanks with that fuel. What they do not say is which of the 3 tanks held the fuel, that is important.....

[Arkroyal]

Thanks

Expecting fuel to be in Kg, and somehow read it as such. Would such a fuel state cause any limitations to manoeuvring?

I note that apart from a reference to the 'silence' refered to by the eyewitness, nowhere does the report state that the engines were stopped.

[Non-PC Plod]

TC

Re your post #545 "1 x other" is starting to look like the only explanation which adds up.

[SkyCamMK]

Is wake turbulence ruled out yet or was it not a possibility from what is known/surmised? Sorry if it appears a silly question but as a recently retired fixed wing FI it is something that I might want to be considered if no obvious cause was given/found.

[nodrama]

Nor does it say if any fuel was lost as a result of the (very heavy) impact and if there was damage to the tanks due to such....so any fuel related hypothesis is pure speculation.

[blackdog7]

S/N 250 and up should have 49kg in the LH Supply Tank and 44.5kg in the RH Supply Tank - the Main tank transfer pumps will keep that amount in the supply tanks until it is empty.

This would indicate that the main tank was empty and the supply tanks were being depleted to keep the engines running.

Prolonged hovering can also result in up to 71kg unusable fuel in the main tank. The quantity of unusable fuel can be reduced to 7.5 kg when flying with 80 KIAS or more.

[yakker]

The report suggests the flight was started with 400kgs of fuel. The AAIB drained 74kgs, so 326 kgs used in a little over 1.5 hours? I'm no helicopter expert but this seems excessive.

[nodrama]

The engines are self-feeding by engine driven pump that 'sucks' from the supply tanks once the engine is self-sustaining

[nodrama]

Yakker, you're right, you are not. Police helicopters hover a lot. That uses lots of fuel.

[SilsoeSid]

staplefordheli

The BBC quote has missed the most important detail in the AAIB report

The drive train was complete to the Fenestron through the MGB and no evidence of major disruption to either engine

Sorry stapes, I cant see that anywhere.
Have you based your statement on the wording;

"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."


In reference to the fuel load;
"Once removed from the building, approximately 95 litres of fuel were drained from the fuel tank system.
Plenty to have made it back, however the total quantity at the time is till not clear. If you think about the angle of the ac when the fuel was taken, I would suggest that if they were using the forward main tank drain hole, there could be up to 59kg still in the main tank and a few more in each of the supply tanks. They may have been low on fuel, but possibly not below minimums.

[Feathers McGraw]

[edit] Missed the fact that the post #83 I was referring to is in an old thread from 2004. Ooops!

Looking at that post #83 here http://www.pprune.org/rotorheads/189945-ec135-5.html again, the comment in there about 71kg unusable fuel reducing to 7.5kg above 80kts caught my eye. Does that mean that in decelerating below 80kts that any such fuel becomes unusable again?

Also, post #83 says "When operating at different speeds with low fuel quantity between hover and cruise the FUEL PUMP lights will come on and off which is normal and also depends on the location of the C of G." So, with fuel quantity captions illuminating and going out as part of expected behaviour does that mean that a pilot could be tricked into thinking that any warnings are transient when in fact they are alerting him to a fuel state that requires more careful management?

[skyrangerpro]

av consumption is circa 200kg/h

[Arkroyal]

Sid

Not sure what you mean by the angle of the aircraft when fuel was taken.

It was taken after the helo was removed from the building, so probably substantially level.

How far was there to go to the helipad, and at what distance would one expects t to commence a speed reducing flare?

Edit to correct this infernal kindle spell corrector

[piesupper]

How far was there to go to the helipad, ?

About a mile and a half due west along the river.

[MightyGem]

Does that mean that in decelerating below 80kts that any such fuel becomes unusable again?
If the rear Fuel Transfer Pump has failed, yes.

[klingonbc]

Ref earlier Post from RVDT
Never worked with Dave T but met him thro training role, delightful chap, RIP and condolences to all affected.
Never heard of NIP as an acronym in the rotary world. In my experience real emergencies rarely follow the POH/FRC/Checks etc, and Aviate, Navigate, Communicate is always the mindset I was taught and now teach.
Chinook HC1 in late 80s, flying simple transit with first tourist co-pilot also called Dave who was handling pilot (HP) at time. Gen 1 caption illuminates, " Captain to Crew Gen 1 caption" "Dave you fly I'll get the cards out" FRCs just opening to the correct page when "we have a Hyd 1 caption as well" "now an AFCS 1 caption" "okay some nasty **** is about to happen - I have control - let's put this sucker on the deck now" To my delight Dave starts a Mayday Call unprompted. He surprises me, as at the time I thought a Pan Call would have been appropriate but hey let him handle the radio while I fly it the last few hundred feet into the flare and landing. As we flare the crewman shouts that he has Hydraulic Vapour spreading throughout rear of the aircraft and he is moving the few passengers we have on-board forward to avoid the danger. Successful landing in cropped field and rapid shutdown without starting the APU and everyone clambers out. Not sure of the timeframe but less than 90 secs perhaps. Point is: we didn't know what was going on with multiple indications but we flew the aircraft first and when Dave had nothing else he could contribute he put out a call. The problem turned out to be a Generator cable chaffing a Hydraulic pipe then "bang" the cable earthed and blew a hole in the hyd pipe. No fire down the back but I believe there was a similar incident after I left the squadron where a flash fire did occur. The mayday call by the way roused a Royal Flight Wessex to our aid as the first response - never did find out if there was a principle passenger on-board - but thanks Ma'am or Sir, we appreciated the response.
Things happen very quickly in some cases and flying the aircraft always comes first.
Klingonbc
(Added after below: "Kintyred - good to hear from you")

[kintyred]

Happy Days klingonbc.....I was that co- pilot!

[jayteeto]

That fuel burn is not excessive, it sounds about spot on. Allow approx 200 kg/hr, a bit for start/take off, waiting for cops to come out and it was 1:37 airborne.

[Feathers McGraw]

Does that mean that in decelerating below 80kts that any such fuel becomes unusable again? If the rear Fuel Transfer Pump has failed, yesThanks for that, I thought it might. I note that the AAIB stated that the 95 litres drained was from the "fuel system".

[RVDT]

In addition, if the Pilot happens to be using ATC1 in a twin Garmin 430 fit, typical of UK Police-fit aircraft,
that will also drop offline when both Gens are lost (as would happen when engines are chopped).
In a fraught situation, he's unlikely to be able to do anything other than press the button & transmit - transmission goes out, or not, through whichever radio was last selected. With a double engine failure, it may or may not be ATC2.

Confused by the reference to ATC1 and ATC2? Transponder? Which is what these CB's are on a 135. Most only have ATC2 with one transponder.

IF you lose SHED BUS and subsequently Avionics Shed you will NOT lose either of your Garmins or your Transponder for that matter (ATC2).

These are on the AVIONICS ESSENTIAL BUS.

Avionic Shed Bus 1 & 2 will have the likes of ANR, TAC, GSM, RAD ALT, MKR, DME etc etc.

Simple Test - walk out to your EC135 - BAT ON - Avionic Master 1 & 2 ON.

Tell us what you see because that is what you will get. :ugh:

[Grenville Fortescue]

I note that apart from a reference to the 'silence' refered to by the eyewitness, nowhere does the report state that the engines were stopped.

No, but it does say:

Preliminary examination showed that all main rotor blades were attached at the time of the impact but that neither the main rotor nor the fenestron tail rotor were rotating.

And which is certainly food for thought.

[the_flying_cop]

On the police setup, the comms head has a wheel from which you can select atc1, atc2 or any of the police radios (tac1-9) for transmitting. The two front heads can transmit on atc1 or atc2 (air traffic comms),
Whereas the rear observer station can only transmit on tac (police) channels. They can however monitor air traffic in the back.

This prevents observers from accidentally transmitting to atc from the rear. I believe atc1 and 2 are actually 1 radio behind the dash. I'm not a pilot so I could be wrong about the hardware setup, nor can I assist re the transponder

[Torque Tonight]

Fuel starvation or another cause of double engine failure does not explain zero rotation of the rotor system. Even if the aircraft was so deep in the avoid curve that an autoration could not be successful, I would still expect to see rotation.

[shortfinals]

The surreal bit is the rotors not turning.

The reportedly undamaged engines stop, the gearbox is fine, and the rotors stop.

It looks as if the helicopter came down almost vertically with the fuselage more or less pitch-neutral.

Where was the collective during the descent? And why?

[Pub User]

shortfinals & Torque Tonight

My thoughts entirely. At the sort of heights police helis operate at, I wouldn't have thought it possible to stop rotation before hitting the ground, even if you were trying to do it.

Maybe someone with EC135 experience could comment on the disc loading and rate of slowdown if drive is curtailed, for whatever reason.

[Grenville Fortescue]

AAIB Observations:

1. The helicopter struck the flat roof of the single story building with a high rate of descent and low/negligible forward speed.

2. At the time of the impact [..] neither the main rotor nor the fenestron tail rotor were rotating.

3. Initial assessment [..] indicated that the main rotor gearbox was capable of providing drive [..] to the main rotor and to the fenestron drive shaft.

The bulletin also states that the no.2 engine was capable of delivering power and that this may have been the case for the no.1 engine but that this has not yet been verified due to impact damage.

So, if the main gearbox and engine or engines were capable of functioning, just what could cause such a rapid depletion of main rotor rpm? :confused:

[Torque Tonight]

Pub User, Shortfinals, indeed, and I would expect any pilot, and this one in particular, to have the lever on the floor until rotor RPM was restored. Even a fully stalled rotor should still have some rotation as long as the lever was down. Surely this points towards a major mechanical failure of the transmission. Very odd.

[shortfinals]

If power delivery stopped and then the collective was pulled fully up that would slow the rotor rapidly. But why would power delivery have stopped, and why would the collective be high?

[rotorspeed]

Can't say I'm too surprised by this AAIB interim report. And I don't think TC will be either. Be interesting to know where the rotor brake lever position was.

[jayteeto]

I might have talked bull last post, you only lose the shedding bus on double eng fail, sorry to confuse!

[SASless]

We are getting down to a Fuel Problem of some kind.

If the MGB was capable of rotation by hand turning the engine drive shaft....it isn't a MGB failure which would be the most common cause of Non-Turning Rotor Blades.

The only question that needs answering now is why the Blades stopped turning....everything else is secondary.

Who has the numbers....Total Fuel Capacity (Liters), Total Useable Fuel (Liters), Un-usable Fuel (Liters)....and any Cautions or other Warnings about Aircraft Attitude and Fuel related Caution and Warning Lights?

Is it safe to assume the AAIB would have mentioned any damage to a fuel cell that would resulted in the leakage of fuel from that Cell?

Is it safe to assume there was no spilled fuel as the AAIB did not mention that?

If we assume intact fuel tanks and fuel lines....thus no spillage.....what does the Drained Fuel Amount reported by the AAIB tell us?

A Mile and a Half from Base....a low fuel level....decelerating for a landing.....nose up pitch attitude....and something happened.....What?

I will ask one more question....and the experienced folks will understand why i ask it.

Was the Pilot's Collective Lever bent upwards....indicating a maximum physical effort pull on the Collective Lever being made?

[STANDTO]

quote:

"Once removed from the building, approximately 95 litres of fuel were drained from the fuel tank system."

I'm presuming that from the way the rescue services were operating, there was no fuel deposition in the building? If so, that doesn't seem to be a whole lot of juice? 75 kilos? Is that not lights and bells territory?

[toptobottom]

Is that not lights and bells territory?

You're getting warm (http://www.pprune.org/8193456-post769.html)

[FrustratedFormerFlie]

Ok, come with me for a moment.
Total or marked reduction in power, drop the collective. No brainier. Instinct to captain of this experience.
I get intermittent partial power loss (fuel pump problem? Low fuel - sucking alternat slugs of fuel/air?). Oh no, this can't be happening. But power comes back, so I pull for height - even if only to buy time if it deteriorates further. Power never fully restored, rotor rpm reducing fast. Boats burned.

I must emphasise that I know NOTHING. This is all pure pprune speculation, and those with deep type knowledge may be able to comment on possibility of such a partial/intermittent power loss scenario which, at v low level, urban, night, single crew, could suggest to a highly experienced captain that pull and hope looked a better bet than precautionary dump the collective and ar.

[SilsoeSid]

Arkroyal
Sid
Not sure what you mean by the angle of the aircraft when fuel was taken.

It was taken after the helo was removed from the building, so probably substantially level.

How far was there to go to the helipad, and at what distance would one expects to commence a speed reducing flare?

I'm sure that when the ac was removed from the building and placed on the road, one of the first things that I saw happen was the fuel sample being taken. Given the angle of the ac on the strops, this would certainly be an 80+ kts attitude. With the fuel sample point being where I think it is, near to the fwd transfer pump, I would assume that the fuel in the forward part of the main tank wasn't drainable. With the fwd transfer pump u/s above 80kts, the fuel unusable is 59kgs.

This link shows a video of the recovery and at around 30 seconds it seems to me that the sample is being taken with the ac still on the strops at that angle;

Vid - The Independent (http://www.independent.co.uk/news/uk/home-news/glasgow-helicopter-crash-death-toll-rises-to-nine-8976647.html)

Is this the fuel sample being taken?

http://i52.photobucket.com/albums/g11/silsoesid/fuelsample_zpsd00c9780.png


In conclusion, in addition to the 76kg litres drained (95 litres @ sg0.8) I suggest that there was at least another 60 litres in the system. 136 kgs would still give at least another 10 minutes before a night time MLA of 90kgs, which in itself would still leave another 25-ish minutes until the tanks are dry. So all in all over half an hour remaining before it ran out of fuel.

[Sanus]

"Be interesting to know where the rotor brake lever position was".

If the rotor brake had been inadvertently deployed there would be very obvious overheating indications all around the rotor brake calipers and vicinity. Probably a fire as well. You can't miss it.

[c53204]

This may seem a long shot and not appreciated by some, but if the pilot cut fuel, could he then apply the rotor brake - intentionally?

[booke23]

"Does the EC135 have a rotor brake?"

It does, but surely any rotor brake in a certified helicopter would be nowhere near powerful enough to actually cause an incident like this.

Besides, on the EC135 I believe the rotor brake disc is mounted to the tail rotor shaft, so even if it did manage to jam somehow, the tail rotor shaft would break long before the engines were overcome.

[Sven Sixtoo]

Sanus

Agreed. You do not need a fully applied rotor brake or anything like it to cause a fire. There will be people on here who know / recollect far more than I do, but how about the Merlin Mk1 that went in the Sound of Raasay?

And, I have very personal experience of the results of cocking up the rotor brake action sequence. The result is unmistakeable.

[SilsoeSid]

Rotor brake applied intentionally ..... wouldn't the other person in the front fight to release it?

People, when you're thinking up your theories, don't forget, there were 3 people on board!

[rotorspeed]

If the rotor brake was deployed after the engines were stopped and RRPM had reduced with collective say not being lowered, there would be no fire. Extremely unlikely,of course. But then so is everything else.

[west lakes]

Rotor brake applied intentionally ..... wouldn't the other person in the front fight to release it?Sorry folks you are now on a Hamster Wheel, the rotor brake has already been discussed and discounted!!

[whitefriars]

No one seems to have taken into account that the Pilot may have been taken ill? He could have had a blackout or a sudden heart attack.Have the PM's been done yet?

[Sven Sixtoo]

I throw this in for one of the EC135 operators / engineers to comment, as I can't readily lay my hands on a LP fuel system schematic.

In the Sea King, we had a vaguely similar fuel system, in that all the working bits were in the collector tank (I suspect equivalent to the supply tank). Now one of the things that could go wrong was that if the pipework between the back and the front (where the collector tank was) became disconnected inside the tank, then the collector tank could be at the same level as the main tanks. In a Sea King, which held 6000 lbs of fuel (american aircraft) and had a minimum when I started of 85 lbs / side, the result of a pipe disconnect downstream of the transfer pumps and a leaky collector tank inlet valve would be absolutely nil, just as long as you didn't manoeuvre the aircraft hard at a low fuel state. There was, when I became the MTP for the RAF SAR fleet in the mid-90s, no check at all for these two pre-existing failures, and no cockpit indication direct or indirect that they were present.

Where I am headed with this boring old duffer's discourse on an unrelated and otherwise quite dissimilar type is:

What mechanical failures could cause the EC135 supply tank to be near empty, when the lack of failure indications could give the pilot the impression that it should be full? Are any of those failures of a type that could lie dormant for long periods? Could such mechanical failures (splits in feed pipes within the tank system, for example) be hidden from a post-crash inspection by the gross disruption of the lower fuselage?

I lack the knowledge to offer an opinion in respect of the EC135, but I have seen several dormant faults of this type on the Sea King once we went looking for them.

Sven

[FrustratedFormerFlie]

Yes. Bodies released and captains funeral past, god rest him. I think if there was anything there, reference might have been made?

[Whirlybird]

No one seems to have taken into account that the Pilot may have been taken ill? He could have had a blackout or a sudden heart attack.Have the PM's been done yet?

Even if the pilot had been incapacitated, the rotors wouldn't stop. It's pretty hard to think of ANY scenario in which the rotors would stop turning in that short a time, even if you wanted them to. :confused::confused::confused:

[DOUBLE BOGEY]

As a relatively experienced commercial pilot I am not sure of the relevance of my experience to handling a complete power loss in flight. Paradoxically, a relatively inexperienced FI(H) is probably going to react better than me !!

I have not had to handle such an event in 15k. How many of us have had such an experience. I would suggest very few.

I believe, with near max pitch, the rotor would decay very quickly to a residual value.

[SilsoeSid]

I would suggest that they were slowing/had slowed down to <80kts during the pre-landing stage in order to arm the floatation gear.

[henra]

Pub User, Shortfinals, indeed, and I would expect any pilot, and this one in particular, to have the lever on the floor until rotor RPM was restored. Even a fully stalled rotor should still have some rotation as long as the lever was down. Surely this points towards a major mechanical failure of the transmission. Very odd.


I'm afraid this is a widely spread misconception.

A stalled rotor has a drag coefficient > 0,4 /@AoA 20°). This will even overwhelm turning engines.
For comparison in a full flare Cd will be between 0,1 and 0,2.
Without engines turning a fully developped Rotor stall will stop the rotor in very few seconds (<<10s).
Once stalled above a certain degree there is simply no way to restore RRPM and once RoD builds up, AoA (and thus stall) will progressively increase. As a result the drag will increase steeply and stop the rotor in a frighteningly short time.
Much shorter than a MGB failure will achieve (the latter one will most likekly separate before achieving similar rates of RPM reduction).


Edit:
The big question is: Why did it stall in the first place?

[FrustratedFormerFlie]

I'm wondering whether the situation served up was so full of conflicts as to give no clear indication of appropriate response. Is this terminal - dump, AR? Is this transient - heave, think and hope? Just a very few seconds of the latter response could have cut off the retreat to the former.

[chopjock]

Whirly
Even if the pilot had been incapacitated, the rotors wouldn't stop. It's pretty hard to think of ANY scenario in which the rotors would stop turning in that short a time, even if you wanted them to

I could think of one scenario, if the ac had auto pilot activated and ran out of usable fuel whilst the pilot was in capacitated, what would happen?

engines stop, AP keeps pitch on until rotors stop...

[Manchester]

Ppruners are usually very ready to castigate the general media and their commentators for misleading and inaccurate reporting, but what about the professional media:

Glasgow helicopter crash not due to engine failure, AAIB reveals - News - Shephard (http://www.shephardmedia.com/news/rotorhub/glasgow-helicopter-crash-not-due-engine-failure-aa/)

“Glasgow helicopter crash not due to engine failure, AAIB reveals”

The AAIB reveals no such thing. It says there was “... no evidence of major mechanical disruption to either engine...”. That explicitly does not rule out engine failure, say by flame-out for a fuel-supply or FADEC reason, I think the most common causes for engine failures.

Can we please now have some of the bile usually reserved for the BBC and the daily papers?

[Grenville Fortescue]

Even if the fuel supply stopped, this does not explain the aggressive decay in rrpm - unless the response to a double engine failure was to pull maximum pitch!

Stunning that there are some who believe that "Even a fully stalled rotor should still have some rotation as long as the lever was down." As henra has said, there is a "point of no return" for every helicopter in terms of rrpm afterwhich recovery is no longer possible. You should know the minimum rrpm for the type you fly or, if you can't remember, simply do not allow your rrpm to decay beyond the bottom of the green.

In my mind I was speculating that we might have read about a catastrophic main gearbox failure but now I have no idea as to what may have happened. So many details (on the surface) don't seem to add up.

[SilsoeSid]

Google maps, just across from the pub is the 2Canvas shop. In addition to a couple of cameras around the junction, on top of the lampost facing The Victoria, is that a CCTV camera?

[Sven Sixtoo]

Grenville

I think what we are fishing for is that in most (all?) serviceable and reasonably modern multi-engine helicopters, there is nothing you can do with the controls that will significantly droop the Nr unless the engines are set so as to permit Nr droop.

In the Sea King, the highest matched torque I ever saw in flight in the real aircraft (we did appalling things to the sim) was 135%, which is 12% over the gearbox transient limit. The Nr and both engines were perfectly happy (it was dark, in the mountains, going down rather fast, before NVG and I was the co-pilot staring rather hard at the engine gauges - the captain was a bit busy Aviating). I find it difficult to believe that a 35-yr-younger design wouldn't do better. And personal experience tells me that the rotor brake has no chance against the engines. So I'm assuming that, regardless of how the controls were handled, if the transmission was serviceable and the engines were running at governed Nf/Nr, the rotor would have been turning. Ergo, as the rotors were stopped at impact the engines must have been below governed Nf/Nr, and quite likely stopped, whether because wound back, shut down or for some other reason.

[high spirits]

Does it rule out that the engines were shut down deliberately(as in drills for tail rotor drive failure). Main gear box and mechanical failure of engines ruled out. Makes no mention of tail rotor/fenestron though...??

[Grenville Fortescue]

I think what we are fishing for is that in most (all?) serviceable and reasonalby modern multi-engine helicopters, there is nothing you can do with the controls that will significantly droop the Nr unless the engines are set so as to permit Nr droop.



So is there such a setting on the EC135 which will configure the engines in such a manner so as to permit a catasprophic droop in Nr?

[Sven Sixtoo]

Sorry, you will need one of the type professionals to answer that.

[booke23]

"In my mind I was speculating that we might have read about a catastrophic main gearbox failure"

I was fully expecting the same.

The AAIB report specifically states the main rotor and tail rotor were not rotating at impact. Witness reports indicate "misfiring" sounds.....presumably engine surges. So presumably the engines were running very shortly before the accident.

How do you go from engines running to rotor stopped in such a short time frame.......you'd need both engines to stop more or less at the same time (pretty unlikely) and for the pilot to grossly mishandle the collective (even more unlikely). It beats me.

I really hope we don't end up with a final report where the cause "could not positively be determined".

[Sven Sixtoo]

High Spirits

AAIB say "No evidence of mechanical failure".

Now I am quite aware that absence of evidence does not equal evidence of absence. But AAIB are the most conservative of bodies in their statements. I may be wrong, but given that they say that they can't find anything broken, I would bet a lot of money that they can prove that the fenestron would have been going round if the main rotor had been going round.

Further to that, a quick check of the report shows that they have explicitly said so:

providing drive from the
No 2 engine power turbine to the main rotor and to the
fenestron drive shaft.

And that, of course, only says that the fenestron drive shaft could have been going round, not the fenestron itself. However, given the "no mechanical failure" statement, we can be confident that the fenestron would have been turning if drive had been provided.

[HeliComparator]

It's a pity there is no mention of the position of the engine control switches and/or throttles.

[Sven Sixtoo]

Indeed, which may either be significant to other matters or may be that they are mangled beyond recognition.

[chopjock]

How do we know for sure that one engine was not already out and the pilot was expediting the trip home, perhaps on AP and then when the second engine quit the AP just tried to continue the flight?

[FrustratedFormerFlie]

One of the smallest spaces on any aircraft is the one between the pilots ears. We've spent decades reducing the capacity of that space to be the root of disaster, but what we can do little to do is to increase the capacity of that space to respond to chaos.

The one man we would wish we could consult is no longer available to us.

I think we are all glad not to have been where he was.

But I wish I could have observed what he saw, in a sim.

[Torque Tonight]

Grenville, I think you misinterpreted my comments. I did not suggest that a stalled rotor should be recoverable. I said that I believe a stalled rotor with the collective fully down may still have some small rotation. The AAIB have stated that there was zero rotation, so even if there had been a double engine failure and a completely mishandled entry into autorotation (which I would not expect from this pilot) this doesn't quite add up. No rotation suggests to me a mechanical failure in the transmission. As the AAIB are indicating against that, I am quite puzzled by this accident.

[jimjim1]

henra said
and stop the rotor in a frighteningly short time.

In support of that I noticed the following.

Regarding a different EC135 incident[1] the NTSB report said:

1741:48, the main rotor RPM had decreased to 73 percent.
...
a rapid increase in main rotor rpm, to about 125 percent, which occurred at 1741:53
...
At 1741:56, the pilot transmitted, "mayday mayday, our engines are out, we're going down."


125% is 3 times the Knietic Energy of 73% (square law)

It seems that aerodynamic forces can change the rotor speed very rapidly (at least upwards).

With the same input force (or is it power, or are they the same thing?) it would go from 0% to 73% (or the reverse) in about a second and a half.

[1] NTSB Report Untitled Page (http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20001211X11617&ntsbno=NYC99FA032&akey=1)

[Self Loading Freight]

Yes, I'm most surprised that the engine control positions haven't been mentioned yet. I'm of the understanding that this information is of primary importance in incidents where there's no obvious, gross mechanical failure, even more so in the case where there's no flight data recorder, and one - if not the - first thing to be noted when the investigators get access.

Also, I'd appreciate some informed info on the basic physics. If the rotors had stopped by the time the helicopter impacted, then what had happened to their rotational energy such that the helicopter itself wasn't rotating? Is there anything other than a managed reduction in speed that could do this?

[Quick Start]

Try this
The pilot used ALT ACQUIRE on the auto pilot at a fairly low level, he was close to the helipad I think.
He was distracted and did not apply power (only 3 axis autopilot).
Helo slowed and then decended and entered vortex ring. Pilot (brain scrambled)
applied full collective. Over pitch etc etc.
Can you stall the blades with both engines working?
He might have shut down the engines before impact. Feds did not say if 'speed select levers' shut off.

[P3 Bellows]

It's a pity there is no mention of the position of the engine control switches and/or throttles


I think the fact the AAIB have not stated the position of the throttles and fuel switches will prove to be quite telling.

[MightyGem]

I suggest that there was at least another 60 litres in the system.
Where do you get that from Sid?

Re the rotor brake, a unit once did start a 135 up with the rotor brake applied but I don't think it stopped the donkeys and the blades still turned.
The engines start and the blades do turn if the rotor brake is left on. I know.:O

the AP just tried to continue the flight?
If by AP you mean the Auto Pilot, the AP doesn't work the collective.

To the poster who asked about AVGAS in one of the tanks, yes, it was a stupid question.

[henra]

Grenville, I think you misinterpreted my comments. I did not suggest that a stalled rotor should be recoverable. I said that I believe a stalled rotor with the collective fully down may still have some small rotation.



No.
Once fully stalled, the position of the collective makes little difference.
It may reduce the AoA temporarily by 5°.
Once much above 10°, AoA will increase quickly, once RPM decays and Rate of Descent builds.
If you arrive at AoA >12-13° with lever full down, it's game over. Watch the Rotor stop in about 5s from there. (In a low inertia rotor system, a high inertia one may expand that towards 10s).


Edit:
After having read @Grenville's comment I think me too misunderstood the point you were trying to make. See my comment to @Grenville.

[Sven Sixtoo]

Chopjock

Because that (given the facts of a call to enter the zone at 2218 and catastrophe at 2222) WOULD have been grounds for a PAN call at least when the first engine failed and the pilot being incapacitated or some similar catastrophe when the second engine failed.

Also, no sane helicopter pilot given 1 minute or so warning of complete power loss (ie first engine stopping) fails to do everything necessary to cope with the imminent event. Which, with one spectacular exception in my 37 years knowledge, has never previously involved a twin simply running out of fuel.

Now, if you are postulating two entirely independent failures, I am willing to discuss the odds. Would you like to play poker?

[Bladecrack]

How do we know for sure that one engine was not already out and the pilot was expediting the trip home, perhaps on AP and then when the second engine quit the AP just tried to continue the flight?

Chopjock - in normal flight on the 135 the AP is always engaged, (helpful yellow caption if you forget) however I doubt few of us would engage the upper modes e.g. HDG, ALT etc. and sit on our hands in the event of ending up in a OEI configuration for whatever reason, even less likely 1 or 2 miles from base.

[mercurydancer]

There was a comment from the AAIB that the lifting of the helicopter from the site and other factors regarding the aircraft being disturbed in situ meant that the extent of the examination of the aircraft was limited.

[SASless]

How do we know for sure that one engine was not already out and the pilot was expediting the trip home, perhaps on AP and then when the second engine quit the AP just tried to continue the flight?

Well....what is the question?

In your scenario....What does the Pilot do?

How long could you sit there like a Knot on a Log before you punched off the Autopilot?

You 135 Pilots out there.....if your last and final engine quits...thus taking the "only" generator with it....do you simultaneously lose the Autopilot system?

Would not every Helicopter Pilot's default position be to lower the Collective upon the second engine failing....regardless of the Status of the AutoPilot?

Apologies to Blade Crack....we posted at the same time.

[Grenville Fortescue]

Grenville, I think you misinterpreted my comments. I did not suggest that a stalled rotor should be recoverable. I said that I believe a stalled rotor with the collective fully down may still have some small rotation. The AAIB have stated that there was zero rotation, so even if there had been a double engine failure and a completely mishandled entry into autorotation (which I would not expect from this pilot) this doesn't quite add up. No rotation suggests to me a mechanical failure in the transmission. As the AAIB are indicating against that, I am quite puzzled by this accident.

TT, okay have understood you now, apologies for not catching your drift earlier.

Yes I agree. Even a "stopped" disc would have some small rotational movement created by the upward airflow. That this disaster is puzzling is without question.

The AAIB have stated that the aircraft impacted the building at "a high rate of descent" and when "neither the main rotor nor the fenestron tail rotor were rotating."

This means that between the "popping" sounds reported by eyewitnesses (and recorded in the bulletin) and sometime prior to impacting the building (a handful of seconds presumably) the drivetrain came to a complete and sudden stop, almost as though it struck something, which we know it didn't, and which is why I was expecting to read about a catastrophic mechanical failure.

[Sky Sports]

I am in no way implying this is what happened, and I am content to wait the year or however long it takes for the AAIB to do their usual thorough job, but heres a scenario for the seasoned 135 chaps to comment on. How do you get yourself out of this one?

We are transitting back to base, I say we, you are the handling pilot and I'm sat next to you. I develop a very sudden and massive panic attack, (never had one before, no idea why it's happening, could be stress, but there you go, it's happening). All I know is, I want this flight to end now and I want to be back on the ground right now.
In my blind panic to get back on the ground, I reach over and flick the engine switches to off. Immediately followed by pulling the rotor brake on. My actions are irrational, but thats a panic attack for you.
As soon as you try to correct either the eng switches or the R/B, I push down on the collective to speed up my return to the percieved safety of the ground.

How long would it take for us to reach the ground from 700(ish)'?
Supposing you manage select one engine switch back to flight, (before I turned it off again), would the relight on a hot engine go with a 'pop', similar to a 'misfiring' engine?

Once again, not saying this is what happened.

[chopjock]

MightyGem
If by AP you mean the Auto Pilot, the AP doesn't work the collective.

So I presume then the AP maintains alt by use of cyclic fwd and aft. So in my scenario then,second engine stops then aft cyclic would be applied by AP in order to try and maintain alt?
Then what, if no pilot action?

[Bladecrack]

We are transitting back to base, I say we, you are the handling pilot and I'm sat next to you. I develop a very sudden and massive panic attack, (never had one before, no idea why it's happening, could be stress, but there you go, it's happening). All I know is, I want this flight to end now and I want to be back on the ground right now.
In my blind panic to get back on the ground, I reach over and flick the engine switches to off. Immediately followed by pulling the rotor brake on. My actions are irrational, but thats a panic attack for you.
As soon as you try to correct either the eng switches or the R/B, I push down on the collective to speed up my return to the percieved safety of the ground.


:hmm: Anyone touching my engine switches, or any other switches for that matter without my say so would rapidly receive a knuckle sandwhich style reminder of their error of their ways.

Its all getting a bit tedious again :ugh:

[awblain]

Rotor rpm increasing from 73 to 125 per cent does indeed correspond to a kinetic energy increase of almost 3.

However, the power available to a windmill goes as the airspeed through the disk to the third power, and so the ability to pick up speed is very sensitive to the airflow conditions.

With the right blade angle of attack, a ~2m/s change in the flow speed through the disc could power the rotor as much as the ~1 MW from the engines. (Power ~ disc area * rho * v^3)

The kinetic energy of the rotor is also not large compared with the power flowing through it. A 200-kg rotor, 10-m in diameter has something like 2MJ of energy at 200rpm (~20 radians/s). But, it's driven by about a MW of power, so in the right/wrong conditions, it could stop in a few seconds.

Edit: The energy in the turning rotor's overestimated here.
Moment of inertia for 200kg, 5-m radius, turning at 200rpm is about (1/3)*200*25~1500 kg m-squared. At 20 radians/s, energy is only 750*400J~0.3MJ.

[rotorspeed]

Chopjock

If you had an engine failure on a twin, in VFR conditions, close to base, you would not be on autopilot.

[The Ancient Geek]

The AAIB report is clear that the engines and gearbox have not yet been dismantled or examined in detail. All we know is that they could be rotated when externally inspected. The detailed stripdown examination could still reveal surprises. For example a bearing could sieze when overheated but still be free when cold.

[henra]

Yes I agree. Even a "stopped" disc would have some small rotational movement created by the upward airflow.


Fair enough.
Stopped doesn't necessarily mean exactly 0 RRPM, although even that might be possible.
Even AAIB probably didn't mean this litteraly. But it doesn't make any appreciable difference if you arrive with 50 RRPM or 0. (<1% in Lift).

[Grenville Fortescue]

Essentially this is an AFCS malfunction whereby the software receives no signal from the collective jack as to what position it is in. So the software goes looking for it, and demands inputs of huge magnitude at a very swift rate. It is absolute mayhem in the cockpit ( Been there!) as the collective hydraulic jack goes from maximum to minimum unpteen times per second.



:eek:



The kinetic energy of the rotor is also not large compared with the power flowing through it. A 200-kg rotor, 10-m in diameter has something like 2MJ of energy at 200rpm (~20 radians/s). But, it's driven by about a MW of power, so in the right/wrong conditions, it could stop in a few seconds.

Thanks for this. Also, there must be some amount of pitch in order to bring Nr to zero.

Based on awblain's explanation, rapid loss of Nr is possible if power is absent meaning that in order to achieve the AAIB's initial findings of a high speed impact with nil apparent Nr we are looking at a total power failure followed by sustained pitch on the main rotor? :confused:

[choppereng]

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

[Camper Van Basten]

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.

[SilsoeSid]

Sven Sixtoo
High Spirits

AAIB say "No evidence of mechanical failure".

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.

[Jet Ranger]

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?



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

[Camper Van Basten]

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

:p

[SilsoeSid]

MG
Quote:
I suggest that there was at least another 60 litres in the system.
Where do you get that from Sid?


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.

[henra]

Based on awblain's explanation, rapid loss of Nr is possible if power is absent meaning that in order to achieve the AAIB's initial findings of a high speed impact with nil apparent Nr we are looking at a total power failure followed by sustained pitch on the main rotor? :confused:



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

[Jet Ranger]

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

...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...

[steveo67]

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.

[Thomas coupling]

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. :\

[henra]

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.

[cenzo]

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.

[Pub User]

and tries in vain to salvage the decaying Nr by chopping the remaining engine and .............

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

[Pub User]

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.

[SilsoeSid]

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 (http://www.expressandstar.com/news/2013/12/04/glasgow-pub-tragedy-prompts-west-midlands-helicopter-checks/)

[henra]

ever closer towards its point of no return (what is it in the 135? 82%?).



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.

[Stu B]

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.

[SilsoeSid]

TCThe duff engine drives the Nr out of its governed range thus enabling the pilot to select the correct engine for shut down.

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

[DX Wombat]

Any radio hams out there - listening in?
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

[yellowbird135]

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.

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???

[skyrangerpro]

AAIB said "Radar contact with the helicopter was lost at 2222 hrs.
Around this time, the helicopter was seen and heard
by a witness who described hearing a noise like a loud
“misfiring car”, followed by silence. He then saw the
helicopter descend rapidly."

This looks key. AAIB have had a week to interview numerous witnesses. They chose to quote only one in the entire report, perhaps because of the high confidence in that witness or because he was representative of the collective witness statements.

Sound: Notice the abrupt transition from "misfiring car" to "silence"

Visual: "He then saw the helicopter descend rapidly". He heard it before he saw it, in fact he may not even have seen it before the descent. How clearly could he see it in the dark at all, lit by just normal navigation lights? No one has mentioned a searchlight at anytime.

So what event creates a sound like a misfiring car, then silence then instant vertical descent with no auto-rotation and rotors arrested so quickly that there is no residual rotation just a few seconds later on impact? The answer lies therein.

[Lemain]

...at the time of the impact but that neither the main rotor nor the fenestron tail rotor were rotating.

....the helicopter struck the flat roof of the single story building with a high rate of
descent and low/negligible forward speed.



If the rotor is not rotating there is no gyroscopic stability. No/negligible (forward) velocity, the report says. Wind was a few knots. If still in the air, the a/c would topple. Now suppose that before impact the rotor was rotating very slowly. A slowly moving rotor blade would probably the first contact with a hard object which would bounce off, make a heck of a din, gather speed and the a/c could topple 'end over end' across hard objects making a tortured noise like a massive lawn scarifier over a stone path. I wonder if they need to widen the search a little for another point of first impact where a blade hit?

[ShyTorque]

It's pretty hard to think of ANY scenario in which the rotors would stop turning in that short a time, even if you wanted them to.

Well, Whirly, I can. Some are now coming round to my earlier suggestion that a possible fenestron problem of some sort may have occurred and that it may have precipitated certain actions that could fit the available evidence already on record, including the stopped rotors. It should be remembered (some obviously haven't so far) that there may be tail rotor failures other than a "straightforward" drive failure.

I wrote the word in italics for a reason. For example, the drive and fenestron may remain working, but control of the blade pitch might not.

A few questions for those suitably qualified on type: What form does the EC135's tail rotor pitch control mechanism take (as in from yaw pedal to the fenestron itself? Is it cable, more than one cable, a push/pull rod, hydraulic or a combination of one or more? Is maximum positive pitch runaway practiced in the EC135 simulator?

More is known about generic helicopter tail rotor drive shaft failures than is known about tail rotor control failures. In-flight diagnosis may be very difficult in the face of confusing and rapidly divergent aircraft behaviour. Simulators may not realistically replicate actual aircraft behaviour, btw, it's known as "off model", where the simulator response is a mere "best guess".

[SilsoeSid]

yellowbird135
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.
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???

No guesses, they were just stating facts. They drained 95 litres from the fuel tank.

By the way, considering the 135 has 3 fuel tanks …. !

http://img30.imageshack.us/img30/3640/135tank02.jpg

[Mark_Hughes70]

Just one to throw into the ring for discussion as the idea of the rotors coming to a stop has me thinking more on the transmission. Loss of fuel, he could auto rotate although at the height he was at i believe it would not be achievable. I vaguely remember an incident on the Lynx freewheel actuator that caused loss of drive but if memory serves this would result in a twist on the intermediate drive shafts of which at first pass isn't shown on the pictures ? Thoughts…

Helicopter Crashes Caused by Freewheel Disengagements (http://www.meaforensic.com/forensic-engineering-expert-witness/blog/bid/80872/Helicopter-Crashes-Caused-by-Freewheel-Disengagements)

[charlieDontSurf]

Some pages ago someone summed up different scenarios, and at the end added "Sabotage, or another cause starting with an S".
I didn't understand what that could stand for, but I certainly got a chill after reading the AAIB press release today...

[cattletruck]

Perhaps the pilot lost all cockpit indicators through some serious electrical fault and had assumed last known state or single engine ops and was initially unaware that he had actually lost both engines.

Funnily enough, this exact time last week my car battery literally exploded causing the instrument cluster to flicker into reset mode continually. It turned out to be the voltage regulator had failed on the alternator which pumped high voltage in the sealed battery causing the electrolyte to boil and divest its pent up pressure in a mater of minutes spraying acid all over nearby components.

Obviously helicopter's electrical systems with their extra complexity are built to significantly higher standards, but by being so close to returning to base after a few hours out perhaps made the occurrence of a double engine failure even harder to believe before it was too late.

I flew a JetBanger with a weak battery (started with external power) when the generator failed in flight. Lost radios, fuel pressure and even the enunciator (PTT did nothing). First indication was a slight twitch in the tail, also observed on the Tq dial (about 1%), which was caused by the two electric fuel pumps on their way out. Maneuvering limits were observed for a safe RTB.

[earth2mars]

In reference to the fuel system diagram in post #1026.......

If BOTH transfer pumps failed would that not leave about 95 liters of Unusable fuel in the lower Main fuel Cell??

Therfore... NO Fuel in the two aft SUPPLY fuel cells!

[fatmanmedia]

reading this thread one idea that i have not seen is the idea of complete electrical system failure.

No Batt, No gens, no power at all.

Would not explain why none of the "witnesses" seen any lights and would it also explain the engines sputtering as there is no fuel being pumped in to the engines?

I'm not a Roterhead, just a fixed wing pilot.

Could that be the case?

[helimutt]

fatmanmedia, that is so unlikely im pretty sure you can discount it completely. A 'total' electrical failure????

[Spanish Waltzer]

AAIB preliminary report indicated no mechanical failure in engines or drivetrain and fuel still in system. No fleet grounding or mandated inspections either immediately or after preliminary inspection. My belief is that AAIB have a pretty clear understanding of the sequence of events and my money, sadly, is on human 'factors' being key.

[widow18]

I may be the only remaining member of this forum who hasn't had a go yet, so here is my question.
In a prior life flying EMS in the BK117, a not too dissimilar aircraft, at about 1.5 NM from the pad at night I would be starting to slow things down, so I would not be in cruise. In an earlier post there was mention of arming floats, my question is if the approach was over water (river) to the pad and arming floats for that landing was SOP, what is close to the Floats Arm Switch on the panel/collective?
Obviously, if floats not required, this post is like many others and a waste of electrons.

[STANDTO]

what is the float fit like on a 135?

Bit of a last chance saloon, but would inflated floats reduce the impact energy if deployed prior to contact with the ground?

[Jet Ranger]

Still Possible Fuel Starvation
In reference to the fuel system diagram in post #1026.......

If BOTH transfer pumps failed would that not leave about 95 liters of Unusable fuel in the lower Main fuel Cell??

Therfore... NO Fuel in the two aft SUPPLY fuel cells!


@earth2mars

Not possible! SUPPLY tanks are always full (44 kg and 40 kg) and do not need XFER pumps to supply the engines ("the engine driven fuel pumps alone provides enough suction capacity to draw fuel from supply tank via supply lines...")

Sometimes you land with 4kg in MAIN tank (or 0 kg ... and F.XFER pump CAD caution light ON) with 40 kg in one and 36 kg in another supply tank. If the average fuel flow is 3-3.5 kg/min, it´s enough fuel for 21-25 min...and FUEL LOW is still not ON.

When FUEL LOW warning light is ON, you have to land in 10 minutes.

[awblain]

If the rotor was stopped, then there's no gyroscopic stabilization, and it would be possible for the aircraft to have been "tumbling" as witnesses suggested.

While eyewitnesses are not necessarily able to assess or report the true motion in 3D, the helicopter "tumbling" is not ruled out as it would be by the presence of angular momentum with the rotors turning.

Turning at 20 radians/s the 200kg 10-m-diameter rotor has an angular momentum of order 100,000 kg m^2 s^-1, requiring a huge torque of order a million Newton-metres to make it turn end-over-end at a radian per second.

With the rotor stopped, the whole helicopter has a moment of inertia of only a few 1000 kg m^2, turning quickly in any axis when a torque of only ~10,000 Newton-meters was applied.

[RVDT]

Not possible! SUPPLY tanks are always full (44 kg and 40 kg) and do not need XFER pumps to supply the engines

So what feeds the SUPPLY Tanks then? XFER pumps no? :ugh:

[Whirlybird]

Thomas Coupling wrote: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 instinctively 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.

I'm far from an expert on the 135, but this sounds plausible to me. Or, at any rate, something along these lines - ie, something goes wrong, tired pilot makes mistake, then he tries to sort it out but too late. In other words, it's beginning to look as though this tragic accident was due to a combination of unexpected malfunction combined with human error.

I realise this probably leaves us with an almost infinite number of possible scenarios, limited only by our collective knowledge of helicopter aerodynamics and human factors. Well, we have several months....

[Prawn2king4]

Shy Torque:

Your post mirrored my thinking. I remember when I was flying 330’s; the aircraft was on the ground and the engines at ground idle when something sheared on the TR pitch assembly and the tail rotor went to full pitch setting – can’t remember which way. The force was sufficient to yaw the fuselage, even though on the ground at a low power setting.
Many discussions in the crew room on how to cope with that failure in the air – and no positive answer, particularly if the aircraft was at low airspeed at the time.
Only way to stop the yaw is autorotation – and pull collective to slow the NR ……….?

[rotorspeed]

Spanish Waltzer

Sadly I agree, and have thought so ever since TC's post #545. Suspect charlieDontSurf feels the same. But I really hope we're wrong.

[DOUBLE BOGEY]

Prawn2King4 - with a tail rotor hardcover to full pitch autorotation will make things much worse. In this situation, at low speed, you need as much torque on the rotor to counteract the maximum anti torque from the TR.

As the TR is at maximum pitch, AUW, MR torque, density Altitude and wind direction against the anti torque moment are all relevant but combined, may not be enough to overcome the anti torque moment being generated and a yawing spin may be inevitable.

Turning the engines off removes all the MR torque and the yaw rate would dramatically increase and most likely result in an uncontrolled crash.