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Police helicopter crashes onto Glasgow pub

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Police helicopter crashes onto Glasgow pub

Old 17th Jan 2014, 18:49
  #1781 (permalink)  
 
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Due to the shape of the tanks Engine 2 will stop after approximately 23 minutes and then engine 1 after 27 minutes.
Apologies for my maths if wrong but having followed this thread, and its offshoots, I thought the average fuel burn could be as low as 180Kg to 220Kg per hour depending on Tq setting. I will use 200KG as a middle ground.

that means 3.33Kg per minute being burnt or 1.67KG per engine per minute. with a 4KG difference between the two tanks that would give you 2.4 Minutes. If you also factor in that once OEI the working donk will be at a higher Tq then the fuel burn will also increase reducing this time even further. So in fact if you think that you have 4 minutes to silence it may come as an even greater surprise when No. 2 stops within half that time!

There has also been a lot of questions on how two engines can be lost at the same time. Unless I have missed something we do not know that is what happened and If fuel starvation for whatever reason was the cause then the above scenario of Two followed by one would be more likely.

If after No.2 stopping you run through the drills establish OEI check for other problems fire etc and then assess and address the problem you could find yourself working the overhead panel ultimately. Making the emergency shed bus then checking pump circuit breakers switch config. etc. If whilst doing this and left hand is holding flip cards or working above your head on panel when No.1 stops allowing for Pilot intervention time the Nr may well have been below recoverable before the lever was lowered. Even if only close to it the only way to increase Nr is to accelerate (not easy with not a lot of height below you) or load the disc (hard to flare when already probably at 60Knts or so OEI and still trying to asses the situation). This will leave you with a slow forward speed no Nr situation ending up with all on board as pax.

There is very little rotation at all once blades are fully stalled as anyone who has seen the video of the R22 falling completely level with only a couple of RRPM on till it impacted can tell you. The 135 is a low inertia system and if the lever is not lowered quickly or fully pulled up to early without any drive the system will effectively stop.

Just the rambling thoughts of an idiot who will now duck for cover.
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Old 17th Jan 2014, 19:54
  #1782 (permalink)  
 
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PieChaser, Mechta, & MaxTakeoff - good informative posts there guys

tests by Bond and two other EC135 operators in Europe found possible similar supply-tank fuel gauging errors that overestimated the fuel on board.
That is the statement that concerns me most...

Dipping the tanks.

I've searched the thread and not spotted this being discussed. My experience has been that despite gauges, calculations and paperwork one should always dip the tanks regularly to see how much is actually in there.

OK fixed wing not rotary but on annual we always drained the tanks and "started again".
SGC - a question for an engineer to answer, its not something the pilot can do.
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Old 17th Jan 2014, 20:13
  #1783 (permalink)  
 
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Skadi - thanks for the link
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Old 17th Jan 2014, 20:34
  #1784 (permalink)  
 
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Here's a scenario:

Fuel gauges showing a modest amount of fuel in tanks, but just from sphincter sensations you knew you couldn't have a great deal on board. Then two red fuel low level lights unexpectedly illuminate. Next thing that happens is that, inexplicably one engine runs down. What would you suspect may be the cause?

In that scenario, would you be running through flip cards or working through the overhead panel? Indeed is there a memory drill for a simple engine run down?

Anyone ever heard of (T)DODAR? Where 'T' stands for time?

Experienced pilots can frequently 'skip' steps that a robot, or inexperienced pilot would be obliged to perform. SOMETIMES being human is a good thing. SOMETIMES being human is not!

Personally, I'd be sh1tt1ng myself, looking for an IMMEDIATE (and I MEAN immediate) landing. I would also be mentally preparing myself to dump the lever at the slightest cough from the running engine.

Finally, where do the witness statements of 'fireworks' or 'sparks' fit into this scenario?

I have no real answers. Just throwing it out there for debate, that's all.

Last edited by Tandemrotor; 17th Jan 2014 at 21:05.
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Old 17th Jan 2014, 20:59
  #1785 (permalink)  
 
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Then two red fuel low level lights unexpectedly illuminate.
Tandem - LOW FUEL 2 comes on first, followed a few minutes later by LOW FUEL 1.

Any experienced 135 pilot would notice IMHO if the fuel level looked significantly wrong after 1.6hrs airborne.

looking for an IMMEDIATE (and I MEAN immediate) landing. I would also be mentally preparing myself to dump the lever at the slightest cough from the running engine.
Same here
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Old 17th Jan 2014, 21:02
  #1786 (permalink)  
 
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Bladecrack, thanks.

I think you get my point?
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Old 17th Jan 2014, 21:10
  #1787 (permalink)  
 
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I think the word immediate is incorrect in context because this has a specific meaning in the helicopter world like: Land NOW immediately. Further flight is not recommended. IE: MGB no oil, Double engine failure etc etc.. But I know where you are coming from.
Because there (normally) is a time gap between 1st and 2nd engine failure due to fuel starvation, there is time to set yourself up for a : LASAP.

Question: Was he flying over/about to fly over the river prior to landing at base or HAD he flown over the river prior to finals to the base?

Because if he had the river between himself and the base in sight and then the No1 stopped he would have been manouevring for a LASAP with the river as a potential obstacle. Now let's say the No2 stopped as he was commencing the crossing of the river (at a decent height because he only had one engine running), he may have thought he could have extended the flight path to clear the river by bleeding off some Nr...........never made it
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Old 17th Jan 2014, 21:30
  #1788 (permalink)  
 
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Tandem - a lot of people seem to opine on here that twin pilots fly along scratching their ass daydreaming about their next holiday...

IMHO that is certainly not the case for UK HEMS pilots, and I would be certain the same applies for police pilots, (I spent the best part of 10 years flying & instructing on singles before flying twins) as on task we tend to be very focused and constantly updating the mental picture, i.e. weather, obstacles, ETA, ETE, fuel, hospitals, IFR diversions etc.

I often fly in remote rural areas where we can be out of radio contact with both ATC & AMB CTRL for significant periods, so we very much rely on each other as a crew, and to give the paramedics credit, the most experienced ones are extremely capable navigators as they know the patch intimately (sometimes down to individual buildings) and will also be thinking about fuel, obstacles, ETA etc. when not talking/thinking medical. Anything unusual, e.g. vibes, cautions, warnings, gongs, strange noises etc. will be spotted and announced pretty sharpish by the front seat TCM in my experience.

As for:

Finally, where do the witness statements of 'fireworks' or 'sparks' fit into this scenario?
That I would like to know too, and I would not discount the witness statements out of hand.
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Old 17th Jan 2014, 21:42
  #1789 (permalink)  
 
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Tandem - a lot of people seem to opine on here that twin pilots fly along scratching their ass daydreaming about their next holiday
But that would make them fixed wing pilots, not rotary!
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Old 17th Jan 2014, 21:49
  #1790 (permalink)  
 
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But that would make them fixed wing pilots, not rotary!
Indeed sir!
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Old 18th Jan 2014, 08:18
  #1791 (permalink)  
 
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Suppose the probes and the sensors had bacterial growth retaining water on them, this would cause the fuel probes to misread and the red lights to not come on either.

When I enquired in this thread about the sensing mode of the red light sensor in the supply tank which activates the red light for 'very low fuel', what was described was something along the lines of a mass flow (MAF) sensor in a car. I.e. Its resistance changes with temperature. In that case, if there was a build up of bacteria sludge on tank components, then this sensor could just as easily be affected, also causing either no or a slow response from it.

Page 44 of the UH-72 Lakota flight manual, which can be read online, gives a good description. Yes, I know its not an EC-135, but the principle is likely to be much the same.

UH-72 Lakota Helicopter Flight Manual - Department Of Defense - Google Books
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Old 18th Jan 2014, 09:30
  #1792 (permalink)  
 
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The capacitance gauges and amber warning sensor are within two concentric tubes. With the presence of a small amount of water they will fail together, hence the AD.
The red low warning sensors are located in a completely different place, and are of a thermal type so not as susceptible to contamination.
It would be highly unlikely that two types of sensors in 4 different locations would fail at the same time.

Last edited by PieChaser; 18th Jan 2014 at 09:34. Reason: Dyslexic
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Old 18th Jan 2014, 09:54
  #1793 (permalink)  
 
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Fuel gauges showing a modest amount of fuel in tanks, but just from sphincter sensations you knew you couldn't have a great deal on board. Then two red fuel low level lights unexpectedly illuminate
If you knew you were low on fuel the lights should not be a surprise they would only surprise you if you thought you had enough.

If you thought the gauges were wrong and believed your sphincter and stopwatch then you should already be considering actions when the red lights come on confirming your beliefs. If you believe the gauges to be true and the lights come on suddenly surprising you then you should be carrying out the actions following their illumination. In both cases once the red low fuel lights come on on the CWP you should be carrying out the actions as laid down. The most important one being get on the ground within the prescribed time.

Lets half the time in the air and give ourselves 4-5 minutes for a cruise. 4 Minutes at a 120 cruise will take me just over 9 miles. I may have some height and take a cruise descent maybe getting 130Kts (I am light after all I have little fuel) so range is somewhere around nine to ten miles from the point I was at when the lights came on and I still have 4-5 minutes to land after this transit if I really need them.

My first thought on seeing the red low fuel lights would be believe them as independent systems very closely followed by my second thought of get somewhere to land and away from a built up area were I over one. Once turned on track and heading to open ground I would carry out the drills remaining such as switch and CB Config. in the hope that I can correct a mistake I may have made earlier and get some fuel back where I want it. If in fact that is not the case I am still heading away from the built up area and towards a landing site. In this situation I would then not have anything to do if my No.2 stopped as I would already have covered it whilst trying to get to a suitable landing site switches checked emergency master made etc. and my hands would be on the controls ready for the second stoppage.

a lot of people seem to opine on here that twin pilots fly along scratching their ass daydreaming about their next holiday
I don't think that is the case but as humans we pilots do make mistakes and under perform at times due to many reasons hence the human factors section of our learning process when gaining a CPL/ATPL. After all if we performed perfectly in every situation and role at work then the leading reason aircraft would crash would be due to major mechanical failure however pilot error is always the top reason for crashes across all types of aircraft. If we can not accept that we make mistakes and learn from them but instead keep looking for an answer that says we the pilot did all we could but it was not our fault then we are depriving ourselves of an opportunity to prevent further accidents and incidents.

The big question to answer is were the red low fuel lights on at impact?

If they were then irregardless of the cause be it pump/fuel system failure or incorrect system operation by the pilot why was the aircraft still over a built up area after 8 to 10 minutes of warning that the engines were going to suffer fuel starvation. What area was the A/C over ten minutes earlier when the lights came on? was it better than the centre of a city.

In all of this one thing that should be remembered is that this talk of fuel may be a complete red herring and have no bearing on the cause of the crash and we await the final report to hopefully answer our questions. In the meantime honest and open discussion of subjects as a result of this incident can lead to improved safety and system awareness from us the pilots who are charged with the safe keeping of our pax and those we fly over.

Tandem, Bladecrack and others my quoting of posts does not mean I disagree with you it is purely to further promote discussion and thought on the various subjects related to this crash and I hope I have not caused any offence. If I have I apologise in advance.
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Old 18th Jan 2014, 12:51
  #1794 (permalink)  
 
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The red low warning sensors are located in a completely different place, and are of a thermal type so not as susceptible to contamination.
From the diagram of the EC135 fuel system below, it looks as if the red light low warning sensors are adjacent to, if not actually attached to the outside of the capacitance probes. I struggle to see how if there was any sort of bacterial sludge build-up on them, this could fail to retain liquid (fuel and/or water) for at least a short period after the main fuel level in the supply tank had dropped, thus delaying the sensor's indication of the fuel level having dropped.

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Old 18th Jan 2014, 12:53
  #1795 (permalink)  
 
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Max Takeoff

No problem. People get too easily offended here sometimes!

You said talk of fuel problems may be a red herring, and that is certainly my position. I say that for a number of reasons. Not least due to the scenarios I have given in a couple of posts recently.

I have no idea of your background, but I accept it could be significant and relevant. But where I would strongly disagree with you is the idea that a highly experienced helicopter pilot would, after a flame out of one engine in the relevant circumstances, attempt to calculate, and then fly, his aircraft towards a guesstimated tanks dry figure. That makes the hairs on the back of my neck stand up. I can only imagine the response I gave earlier. Immediate landing would be essential, and in the meantime I would be anticipating entering autorotation at any moment.

That last point in particular doesn't seem to tie in with lack of RRPM at touchdown?

What about the 'sparks' and 'fireworks' described by witnesses? The 'misfiring' noises? The extremely low level flight? Much does not seem to fit?

We might do well to look more carefully at other possibilities? As I tried to outline in post #1835. As I said, the clues may be there.

Regards
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Old 18th Jan 2014, 13:08
  #1796 (permalink)  
 
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Tandem,

apologies if I did not make it clear in my post the calculation of flight time is from the first RED low warning light illuminating. This would allow me to head to a suitable landing area and even then I have halved the flight time from that allowed to be on the ground. Once the first engine stops (should you still be in the air) you have indeed left it all too late in my opinion.

MT
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Old 18th Jan 2014, 13:26
  #1797 (permalink)  
 
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With that I can certainly agree. As I suspect would virtually everyone with relevant experience. In any event, once the first engine flames out, the situation, and immediate action required is completely and utterly unambiguous. Which in a sense is yet another reason why fuel starvation (without contamination) seems an unlikely scenario?

Even with the numerous possible 'issues' in the fuel system. The red lights are your safety net. That is precisely what they were designed for.

You asked whether it would be possible to tell whether the red fuel lights were on at impact? Without recording equipment on board, it is my understanding that would depend on whether the bulbs were damaged or not. As I believe it is only possible to determine the energised nature of a filament at the moment at which it fractures?
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Old 18th Jan 2014, 13:47
  #1798 (permalink)  
 
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As long as the bulb has not been totally destroyed and lost by direct impact or fire then a filament can be analysed to determine if it was illuminated when the airframe impacted. If it was illuminated (hot) it will show signs of stretching.
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Old 18th Jan 2014, 13:57
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Max, surely that only applies if it has been damaged.

A broken filament will tell you if it was on or off at the time of breaking, but if still intact then it tells us nothing.
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Old 18th Jan 2014, 14:05
  #1800 (permalink)  

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A stretched filament indictes it was lit when impact occurs.
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