Let's face it, it wouldn't be the first time that fuel mismanagement in a police helicopter has resulted in a crash.
Why did it all go wrong when it did? 'Pressonitis'

JTobias

I couldn't agree more, and I will happily join you on that journey.

Wageslave

Certainly as far as the Mull Chinook is concerned, you clearly haven't got a clue what you are talking about!

I know I'll be slated for saying this by ignoramuses and holier than thou pricks, but I'm absolutely gutted for the guy. I certainly haven't ruled out the possibility that there is more to this than first meets the eye!

Enough of the personal abuse and inappropriate language, please. I haven't the time to edit your posts but if you have an issue with each other; take it outside.

How compatible with NVG was this cockpit?

SeniorPilot (Moderator)

Apologies for my language but whoever that guy is, he's not got the right to reply the way he did to my earlier post.

Tandem rotor - thanks

Joel

Jtobias, give me a call and I'd be your wing man on that little jaunt.

Sorry JT, I don't understand what you, as a pilot of both fixed and rotary aircraft, mean by;

Do you mean he simply didn't react in time, or something else happened that stopped him reacting in time? If your 206 flamed out for example, what might cause you not to have 'sufficient time' to react?

Silsoe,

Don't you start! Were mates now !

And why do you feel the need to quote my 'credentials' you can clearly see that I posted that only because I was challenged in the original reply to my first post - don't you start adding fuel!

Now, to answer you, I don't 'mean' anything - my whole post is basically asking for a steer as to what might have happened to have caused him to not react quickly enough - surely my post is in plain enough language for anyone to understand that - I'm asking!!

For instance is it possible that his hand wasn't on the collective for whatever reason or that the collective was locked with friction or the autopilot was engaged and it takes 1 second to disengage but the RRPM decays in under that time.

In my machine, if my engine fails (god forbid) I get an engine out tone, I get un commanded yaw and I drop the lever quick. But my machine also allows me something like two seconds in which to do it. Does the EC135 allow such a time frame?

However, if I had a passenger who panicked and grabbed my arm or I was switching my pitot heat on or changing frequency at the point my engine failed maybe those action could cause me to react more slowly and the RRPM might decay to an un-recoverable point. In this case whilst the manufacturer might consider in a calm cockpit with no other distraction there is traditionally sufficient time to lower the lever there are factors like those I've described that might cause there to be NOT sufficient time to react. It's not rocket science!

If there were warning captions illuminated, aural tones, and procedures that he had to follow etc that distracted him, plus pax that might have been talking to him or were panicked causing him to not instantly realise that he'd had a double flame out then he may not have had sufficient (as in humanly possible) time to process the information that his brain was dealing with and consequently not lowered the lever quickly enough.

None of us were in that cockpit so no one knows what happened but I'm asking for a steer from someone like you who flies twins and understands the systems and processes that might have lead to that. Finally, should the fuel transfer switches been on or off, because I don't think that's been answered.

The point is, I don't know, which is basically why I'm asking!!!!

Come on Silsoe! I'm relying on you for a sensible answer now that you've waded in!

Joel :ok:

Digital flight deck,

Thanks !

Joel :ok:

Helicopter certification standards must permit RRPM to be recoverable by a "reasonable" pilot and that generally means at least 2 seconds must be available. When flying an incredibly reliable twin, double engine failure possibilities seems so remote compared to being on the edge in the 206 all the time given the immediate consequence presented by the failure of one engine in a single engine machine.....

The recognition keys are the same in all machines, so it reacts just like yours to complete loss of power to the drive train, though apart from the yaw you mentioned, pitch movement is also a key factor. It is really here that individual machines behave individually, some pitch remarkably, some hardly move and have advanced mixing units to cope, some pitch up (rare), some pitch down (more common) and some even change depending on configuration : floats fitted, winch fitted, external tanks fitted or even emergency floats deployed.

I don't know one end of a 135 (or any other rotary device) from the other. But I have a small interest in this accident for personal reasons (no names no pack drill). I have a couple of questions about The Book:

What are the single engine failure checklist/action items on this aircraft, according to The Book?

There has been some discussion about the low fuel warnings and systems behaviour, flight time remaining from low fuel warning etc. What does The Book say about how the position of the transfer pump switches affects this scenario? The behaviour here must have been tested, explored and understood during certification.

I'm speaking strictly as a fixed wing pilot here. A single engine failure on a twin is routine. A single engine failure *following low fuel warnings* would ring my alarm bells good and proper, have Gimli flashing before my eyes, and have me thinking "oh sh!t I've stuffed up my fuel management" - would a prudent rotary pilot not be thinking *land immediately* in that scenario?

Re NVGs. If the unit was cleared to operate with them, and if the aircraft was "NVG serviceable" on the night, then given the dark lumpy areas up there, the crew would probably wearing them. We always did.

Also, if the above is true, then the cockpit would be completely NVG compatible.

As to why both Transfer pumps were off, with all the constant switching on and off as they illuminate in the cruise and hover, as some operators do, perhaps that's why in 15 years or so I never did. Just left them on to work when they were re-immersed in fuel.

I can't recall any incidents of premature pump replacement.

Thanks MG.

So how would the NVGs impact on looking up and back to identify the load shed? Any other possible distractions/restrictions that could be created by the goggs on the front of the helmet or by the restricted field of view; just stabs in the dark as we acknowledge that something out of left field has apparently been confirmed by this interim report.

When an experienced pilot crashes a fully functioning aircraft in broadly benign conditions there is commonly an issue of cognitive psychology in play. In other words, some 'software bug' of the human mind or perception from which none of us can ever be entirely immune. I remember a phrase from my psychology degree: 'we are free to construe but bound by our constructions'. In other words, you can make sense of things in any number of ways, but once you have made sense of things it can be inherently difficult to step back and identify mistaken assumptions. This can be a vicious trap in an emergency situation, where perception is narrowed and time is short.
In other words, it's worth considering whether the pilot became cognitively disoriented. That need not mean spatially disoriented. There are plenty of examples of crews intensely working a puzzling but irrelevant problem until CFIT, or becoming increasingly exasperated by 'spurious' cockpit warnings until the tragic moment when those alarms prove to have been functioning exactly as intended. The answer to 'But in that situation, every pilot knows to...' may lie in figuring 'What could possibly have somehow led him to doubt or be in denial that he was in that situation, just for long enough to no longer be within the recovery envelope'.

:D :D :D

Agree 100% RD

At the centre of this there will be a lack of cognitive processing space available at a critical time. What will be instructive is why. What will be certain is that it could have been me.

Yes they can get in the way at times. Can't comment on any other distractions they may or may not have suffered.

question for the 135 guys...

approx how long will 4Kg's of fuel last?

as in from the first engine flaming out, how long before the second one will quit?

RD quite right.
Maybe not much actually wrong just overcomplicated to death?
Needs two crew to manage this overcomplex cockpit scenario?


Under pressure the complexity of many pumps (with conditional performance), tanks, engines, goggles, several warning systems, alarms, horns, beeps, lights could lead to mental seizure.
and proceedures! (load shedding etc) (you wouldn't want to wast your time going through a drill in the 2 seconds you have to put a lever down)

2 minutes and 25 seconds (ish)

Ranger One:

Transfer pump switches are there for that purpose - I've not flown the 135 myself, but on the AS 350, you use the transfer pumps when you want to transfer fuel from one tank to another - nothing more, nothing less. Fuel boost pumps (and not all machines have them) must be on all the time. I would not necessarily read anything sinister from the fact that the transfer pumps were off in this case.

Fuel low warning lights typically come on early enough so that you don't have to land immediately, but as with cars, the prudent pilot doesn't trust them! For example, you have around 6 minutes on some helicopters, but call it three. But you should certainly land in a suitable time frame.

Talking of which, you are supposed to have 30 minutes on a battery when the gennies stop working. I wonder if this one was up to speed when running the electrics which are required to fly a machine such as this.

Not in the 135, the primepumps are normally on just for engine start.

skadi

Surely when your low on fuel and especially if the low fuel light has already illuminated your main focus would be your hand on the collective, looking for a suitable landing spot and you'd be primed to react immediately.

Years ago I stupidly pushed on in a 206 with the low fuel light on, as I could see the airport a few minutes away ( haven't we all at some time ) I halved the book time, climbed to 1500ft and glued my hand over the collective and kept a constant look out for a suitable landing spot, should the worst happen it was the longest 2/3 minutes of my life unfortunately for me the engine flamed out but I managed a perfect EOL just inside the Airport in question all with 5 POB, I was really lucky and it taught me never to press on like that again.

I find it hard to believe that an experienced guy like this, flying in the dark a few minutes away from safety wouldn't have done the same, there must be other factors contributing to this tragedy, he would have been wound up like a spring ready to react, his mind would have been finely tuned to every sound or reaction of the machine, Surely his mind would also be on the outcome of surviving an EOL landing in the dark with no fuel being the cause! ie losing his job or prosecution. Poor bugger

Should, Would, Could.
 

Sorry JT.

Quite plainly, perhaps he simply didn't expect a double failure.

His hand could have possibly been doing something else as the first engine failed, but the collective shouldn't have been locked by collective friction to that degree. Input to the controls would override the autopilot and when the second engine went, the hand should have been on the collective in an instant.

I believe the 206 has higher inertia blades, so I would imagine the timeframe is a lot shorter. For the 135, entering autorotation is an immediate action following a double failure.


I would imagine that most helicopter pilots' motor systems should have developed enough to be able to get the hand back on the collective immediately, whatever it had been doing at the time.

Mmm, doesn't this suggest that didn't react in time, rather than didn't have sufficient time. When the second engine failed, the time was always there and could have been used.

Quite true, but given the latest report, there are some pretty good leads as to what could have happened.

Given that there was 76 kg in the main tank, the transfer pumps should have still been on, well at least one of them at any given time due to the ac attitude. The supply tanks should have had 47 & 43 kgs in them and the prime pumps should have been off. The only reason for the prime pumps to be on in flight, should be when you get a low fuel pressure warning.

At some point around 22:00 that night (Bothwell task?), when the supply tanks became the only fuel source, the configuration of all the fuel pumps was altered.

However, regardless of the switchology, this doesn't get us away from all the warnings and indications that should have been there and should have been actioned upon. I would have thought that the decrease of supply tank levels down to nothing, should have risen some back hairs and early action could have been taken …. if indeed all the warnings and displays were there to take action on!

Ranger One;

Your answers will be found here http://helicopterindia.com/yahoo_sit...2.24193407.pdf
It's not up to date as far as amendments go, but will sufficiently answer the questions you have asked :ok:


Robdean; Totally agree :ok:

Given the timefacts from the report, I just roughly calculated the estimated fuelindication for the main tank.
They took off with around 300kg, after the 35 min first task and transfer to Dalkeith, the indication could have been around 100kg. So on the way westwards ( ~25 min ), the aft fuelpump fell dry and was switched off. When reaching Glasgow area, the trackcircles indicate the possibility of lowspeed/hover attitudes, which could have resulted in switching the fwd pump off, so the remaining 95ltr in the maintank now were unusable without switching the aft pump back on. And there is still the possibility of a false indication of the supplytank content.

skadi

Just to help clear up a few of the questions, misconceptions and speculations.

Some posters are jumping in with half knowledge or none on 135 type/helicopters/piloting/aviation experience at all.

A small handfull on here fly these aircraft night after night on police ops with thousands of hours on type, and no it doesn't make them or me infallible, but if those in the first category want answers to questions please don't then challenge in a personal manner the informed answer that those in the second category give.

The fuel system on the 135 has been explained in minute detail, with illustrations and text, please look back at the posts before before asking new questions that may confuse others and the press.

The overhead panel is laid out in a logical manner, NVS lighting does make it harder to read and the goggles certainly have to be lifted to the stowed position to read it and in that position with a taller pilot may in fact hinder the ability to identify the switches. In fact there is little clearance between the top of the helmet and the roof/panel structure at the best of times. Wearing spectacles for reading, with a helmet and goggles in that cockpit makes it very difficult to use the overhead panel.

A police aircraft cockpit is a real hotbed of noise and distraction. Those with private flying experience only will be very used to planning ahead, flying from A to land at B or perhaps even just flying around A many times before landing again. The Corporate pilots will be used to pretty much the same with the added pressure of satisfying the company and client. The airline pilots will be used to standard routes and someone else to load share. The military pilot will be used to a degree of planning and teamwork and regular training for the demanding roles and flying environment. The police pilot briefs such known factors as met /notams/ aircraft serviceability and fuel load at the start of the shift, after that it's take it as it comes, ie the TFO asks you to jump, you react straight away day or night, good or bad weather, you can be in flight with no planning at all within 2 minutes of someone answering the next phone call. You will have no advance knowledge of the destination or what lies between, the 3 of you need to exchange information with each other and the ground at very frequent and conflicting times. I've often taken off towards B, then whilst I'm asking ATC to give us clearance one of the TFOs is taking a higher priority task to C, whilst I the apologise to ATC and ask for clearance towards C, another radio asks us to drop everything and make our way towards D. This all has to be discussed, debated and prioritised in the cockpit whilst doing snap fuel calculations/weather apreciation and a huge dose CRM so that the 3 of you are still fuctioning as a team throughout the shift. Acrobat, diplomat, doormat is the police pilots motto for good reason. Having said that when asked how difficult it is to do the job I would answer, I use 5% of my military flying experience 95% of the time and was ready to use 95% of it 5% of the time.

Please don't condemn this pilot without absolute fact, the AAIB have said there was a fault with one of the displays, lets see how that pans out.

Re how long does 4kg last
 

If both supply tanks had the same amount of fuel at a given reference time and both engines have a similar rate of fuel burn and useable fuel is the same as fuel remaining for both tanks, then both engines will flame out at approximately the same time. It is the useable fuel in both supply tanks at a certain reference point in time that matters, not the relative fuel tank sizes.

It is the left supply tank low fuel warning that will illuminate approx 2mins 25 seconds before the corresponding right hand one at 32kg and 28kg respectively, if they are working correctly, not one engine flaming out 2' 25 before the other.

What is niggling me is the multiple intermittent low fuel warnings issued by the left hand tank sensor. That doesn't seem normal behaviour to me. The right hand one illuminated later and illuminated permanently. Why were the two behaving differently?

Shy........looking up back and left for load shed, 2nd eng runs down .............

that certainly 'fits'.

SkyRP,

If I'm reading your query right, my explanation is as follows.

Given that the Main tank transfer pump/s deliver fuel to the supply tanks at a rate greater than both engines at maximum power can suck it from both the supply tanks, the manufacturer believes and teaches that at the point where fuel transfer from the main tank ceases, the supply tanks will be full. From that starting point with engines sucking very similar flow rates from their respective supply tanks, the warnings will occur at different times, and the engines will flame out at different times. The supply tanks have the same manufactured capacity with the exception that one of them has a foam core inserted to take up the space that would otherwise be occuppied by fuel (4kg ish). It is my experience that this sequencial warning is what happens rather than simultaniously.

Just to summarise, the supply tanks should never have the same amount of fuel.

Good to hear from you art.

Thanks mate, tend to keep my powder dry these days because of the trolls. Safe flying.

Bertie Thruster;
Would that be necessary?

A Theory
 

So how about this for a scenario

Both transfer pumps off as can happen during police scenarios due to transit and hover.

You would normally be made aware of this by supply tank contents reducing with fuel still in the main tank. Next thing you get is the yellow fuel caption, the eventually the red low fuel caption. You would have to ignore all these inputs to let the supply tanks run dry and the engine flameout.

What about if the first indication you get is the reflow fuel caption. You know you haven't had the yellow caption, which you should have had and both supply tanks are indicating full. Logical conclusion maybe that the low fuel caption is spurious as the gauges have always been extremely accurate.

Then an engine fails. You still have supply tanks indicating full and 78kg in the main. Natural reaction over a city at night maybe - ok, no need to panic. I have rotor rpm and fuel. Remain cal get into single engine speed and make a decision about continuing to the heliport or going to the airport. 30 secs latter the second engine fails. You are very poorly placed.

What's interesting is that the AAIB report does not mention the yellow fuel caption coming on.

Also interesting is that the current problem with EC135 fuel probes, only highlighted after the accident, is indicated by the yellow fuel caption not coming on and the supply tanks over reading (sometime indicating full)

I'd also like to comment on the lack of autorotation theory. The final route of the aircraft was 180 out from its final resting orientation. It came over a high building attached to the rear of the pub.

What if autorotation was successfully entered albeit with rrpm on the low side. From 1000 at night over a city, there is very little time and few options to choose from. What if at the final stages you are faced with a large building. Crash into it of flare and use some collective. Survival instinct would be that you flare. You've now used our one shot of collective but you fall with no rrpm over the other side of the building.

So maybe this guy didn't just ignore all the warnings that he should have had and maybe he did get into autorotation. Maybe he was faced with a very confusing situation over a city at night.

Just trying to balance some of the very black and white and sometimesl informed views on here.

Fact

From the AAIB
Transfer pumps were off - they should not have been and this Pedro the supply tanks emptying
The yellow fuel caption coming is not mentioned.

From airbus helicopters
Current EC135 fuel probe issue
Yellow fuel caption may not come on
Supply tanks indications may over read.

Arrab,

tried to follow your thinking but a few phrases threw me off, by 'yellow fuel captions', do you mean amber low cautions? and by 'red fuel low caption', do you mean Red Fuel warning? This important, they are totally seperate systems, one cautions the pilot, the other warns with a gong. I say again, please re-read the previous excellent descriptions of the fuel system and then prepare a scenario. Also what is a reflow caption?

Senior pilot, my apologies if you felt I was out of line; I haven't the time to wade through 107 pages at the moment. To be fair it's the first post I've had deleted in 15 years here. I'll butt out now.

Arrab (first time caller!);

Ref the FUEL caption, there isn't any historical display information available from the CPDS, so we won't know if it or any captions came on or not.

As far as the fuel probe issue, you're nearly there, …
They don't say, "Yellow fuel caption may not come on", they say;

"Tests have confirmed that the affected fuel content probes generate erroneously high signals if contamination with water occurs. In each case an incorrect frequency is being transmitted to the indicating system. That leads to an erroneously high indication of fuel quantity and prevents the amber FUEL caution light from operating."
http://www.airbushelicopters.com/sit...18-Rev0-EN.pdf

Surely that 0.4 litres of fuel remaining in the no2 supply tank would have indicated a water contamination issue, as would the 95 litres left in the main (where the supply fuel came from).
No contamination issues are mentioned in the report, nor are the twist grip positions.

given all of the above info...

from the report, we are told he contacted ATC at 22:18 for clearance, and fell off radar at 22:22.19 (at 400ft).

given that from low fuel warnings you have at least 10 mins of flight time (or have I got this wrong?), he must have been looking at low fuel warnings before he contacted ATC?

do we take from this that he was unaware of the warnings?

I get the feeling that may be the case scuffers.
The CPDS and it's relevance in all of this will be a very interesting read.

No reason to - SBC1 & SBC2 are closed when either EPU connected or at least ONE GENERATOR.

SHED EMER only operates when GEN DISCON 1 AND GEN DISCON 2 active.