Helmet fire, That all sounds very sensible and plausible.

My understanding is that the main tank has a ledge over the top of the supply tanks, and so while the fuel level is above the pump supply pipe entry into the supply tanks, they will be kept full by gravity until the main tank level drops below. Then you have two full supply tanks worth of fuel accessible, so the Glasgow aircraft sounds a bit more generous for unpumped fuel than the US accident you note. But it would certainly account for the events, and for pressing on with that cognitive gotcha.

The pumps left on, or operating automatically would have prevented it?

I really see no advantage to the pilot having to manage those main tank pumps in flight. Lights can come on to indicate they're drawing vapor and turned off or that they've failed. I can see the advantage of having to make a conscious switch to a reserve tank at a set time in a simpler system, but not here.

If the capacitive (and warm wire) fuel meters are prone to organic goo (and nothing says they were here), would silver coated pressure sensors at the bottom of the tanks, or ultrasonic column sounders work better? Not that it seems to be a problem with the generation of the warnings, but perhaps their display and appreciation.

AoF Thanks for the response.

AWb,

The purpose of the open channel between the supply tanks and the main tank is to allow 'spill back' of excess fuel that is being pumped from the main tank to the supply tanks.
Just one of the two transfer pumps operating in the main tank will transfer fuel to the supply tanks at a rate greater than both engines at full power can consume. A simple way of keeping the supply tanks full until the contents of the main tank are exhausted.
Of course it works both ways as you suggest and a more extreme nose up attitude can gravity feed fuel from the main into the supply tanks at certain levels.
ie....you lose both transfer pumps but fuel remains in the main tank, allow the engines to use some of the now reducing amount of fuel from the supply tanks then pull nose up to get some of the main tank fuel into the space now in the supply tanks (taught during type conversion).

Does anyone please, pretty please, have proper engineering drawings of the fuel tanks? We are being told so many different things about an assembly which is vital to the whole investigation. No more words, please. No more Micky Mouse diagrams. Let's have real engineering drawings that tell us what is really there. Else how can future pilots understand the situation they are in?

Henry, best try googling for what you're after, try EC135 engineering manual, operation manual, flight manual etc, good luck. The diagrams posted some while back on here are the best that are generally available unless you're a bona-fide paying customer of the manufacturer with a need to have something better.

It's a fairly simple system if and it's a big IF, you've attended the manufacturers conversion to type and had many hours reading the manuals and a few years discussing faults as they occur with the engineers. Trying to explain it to those who are new on here from a standing start is akin to platting fog......

Art - Positive displacement pumps? Greater than 100pc bleed? Greater than 100pc wasted energy? Even Obelix would need magic potion!

...and thanks for your kind reply above, yes tried all that and got simplified press-oriented pics.

At least we've bust the phantom page :ok:

I should add, I've spent much time in front of a white board drawing the system and explaining it to Observers/TFOs along with all the other systems so it seems simple to me, the units I've worked at have such training as a compulsory requirement at the end of each shift briefing so that all flight crew are conversant with what the emergency captions really mean, rather than just repeat what the emergency drill cards say without knowledge.

In fact the Chief Pilot often requires pilots under test to brief systems to TFOs in his presence as a real test of the pilots understanding.

Yes Henry, 100% inefficient in some regards.

I do think a redesign of at least the switches will come of this. The Engine main switches used to be unguarded until the inevitable happened. The collective throttles used to both have the same grip, now they have different textures from each other. The throttles now also have guards.

AOF/FO2/SS, Anyone care to answer;with 400kg ,was the a/c at MTOW on t/o...?
At the end of the first part of the sortie ,the a/c was within 10 miles of Edinburgh Airport...why not drop in for a top-up rrr/f,5-10 mins,as most of the other tasks seemed to be non-urgent,or casual,would have allowed more free time..

Old Jungly saying, Never pass- up free fuel....

TR

Have you ever considered reading a post before quoting it and ranting about it?

I know that:

that's why I said:

Do you see the link?

No, that's why I said:

rather than "three technically qualified people" or "three licensed people".

I don't need to make a case for 'many'; I didn't say 'many', I said three pairs. The OED defines 'many' as 'a large number'.

I'm not, I said that it didn't make sense to me, I don't have an issue to fudge.

Nor did I say that they had to be, I merely suggested that they might be keen on staying alive and knowledgeable about whether warnings and lights were a good thing.

In all of the years that I spent doing the job (no longer doing it, AoF) I never disagreed with that; that's why I suggested that they might question decisions as part of a team, not make them as PIC.

I hope that's a bit clearer for you now, if you're going to pick fights, try to have a reason.

double flame out in 1999:
 

got a hint to a German police bo105 which had a double flame out after take off as main tank pumps were never switched on. Successful autorotation but landed in a shallow part of the Elbe river. Busy day with stressful task continuing into night, view on caution lights was blocked due to a gaffa-taped filter for NVG ops which went loose. It was a temp fix to get the ac aloft for a search mission of a missing child.
By any chance, could the view onto the cad in the ec135 have been blocked accidently with some equipment, a map or whatever (- if it was working correctly)? Pilots admitted they had simply forgotten about the main tank pump which I understand was to be switched on after starting the engines with only prime pumps on. Then they simply could not see the caution coming on, and they were not aware of it. P1 flying with NVG's and P2 operating the searchlight - all eyes focused to the outside of the cockpit.

Flight Time - main tank
 

Flight Time

"The fuel half page displays the fuel level in main tank and supply tanks digitally and in a graphic. For reliable values use only the digital data.
At fuel half page fuel flow of both engines can be displayed as well as the remaining flight time. Remaining flight time is calculated by fuel level in main tank. It is not reliable, if the fuel transfer pumps are not working. This fuel management System is optional an not installed in all liveries."

The TFO's know more about the systems than the Chief Pilot?:E

250kg in the main

Rantanplane,

Good point, there is a Velcro held placard panel on the upper part of the instrument panel (sun hood) that can and does fall down and obscure the CAD & part of the warning panel. However, any cautions that appear would still illuminate the master caution light in front of the pilot and the audio would still alert the crew.

There is always the possibility that any cautions were automatically & immediately cancelled, habitually. If the CAD was indeed obscured by this panel, perhaps no real check of the indications or fuel was made as it wasn't realised that the panel was obscuring the warnings, cautions & fuel indication and as such everything 'appeared normal'.

It usually makes a noise when it falls down, but it's a noisy environment.

http://adradvocacy.files.wordpress.c...135t3panel.jpg

thanks for the info and pic. I know about the master caution and audio warning. (won't help me according all my former girlfriends, wife and ..mother..do AH64's have a lot of audio warnings?? ah now there is a clue for a different topic.. )


I am also wondering about the fuel consumption with prime pumps on.
Is that exactly the same or can it be slightly higher? What I mean is if perhaps the pilot had less time to sort things out than he was aware of.
Also flying slowly or close to hovering ´- to sort things out - needs more fuel.
details and devils

Catch 21,
To answer your earlier question - if sat in the hover, the Fwd Tx pump caution can come on as early as 130kgs in the main - and the pump has to have had no fuel to pump for 2 minutes before the caption appears. The explanation as to why has been covered earlier in this thread.

Sycamore,
As it was a T2+, I would not have expected it to be at MAUM with 400Kgs of fuel. The explanation as to why has been covered earlier in this thread.

Reely 340,
The transfer pumps do have a non return valve fitted - as has been covered many times before in this thread - as has the fact that the pilot of a police aircraft does not get ordered around from task to task. The aircraft's presence is requested - I have never yet, in 14 years had a TFO accept tasking whilst airborne without asking first. It was one of the main reasons that it was decided to use pilots that were not police officers in UK police aviation.

40 odd, thank you. So as early as 130kg in the main tank the fwd pump can be exposed in a prolonged hover. The caution is the same caution as that given if the pump is switched off so it is up to the pilot to diagnose that reason for the caution using the standard checklist procedure?

That is correct.

Sycamore,

"AOF/FO2/SS, Anyone care to answer;with 400kg ,was the a/c at MTOW on t/o...?
At the end of the first part of the sortie ,the a/c was within 10 miles of Edinburgh Airport...why not drop in for a top-up rrr/f,5-10 mins,as most of the other tasks seemed to be non-urgent,or casual,would have allowed more free time..

Old Jungly saying, Never pass- up free fuel...."

The reason that police aircraft don't routinely dispatch with fuel to MTOW is for 2 reasons. Firstly, you just never know when with little notice you'll be expected to take something/someone with you on the next task, ie negotiator, dog handler, special branch or just a visitor (police) etc, so many units allow payload capacity to carry one extra pax. The second reason is that this single aircraft is crewed by pilots and TFOs of different weights so the unit management will have decided on a 'standard' fuel load for that unit to allow for the heaviest shift/crew combination. This fuel load can and is adjusted upward according to the situation during the shift and according to the task.

To explain further, the aircraft sits on the pad ready to go at 400kgs fuel, a task is accepted to fly some distance to a missing person search, the crew decide to put in more fuel to MTOW to complete the task. Just as you take off the misper is found, you now have too much weight for the next crew to take the aircraft if another task doesn't come in by the end of the shift and they're not going to be happy, nor is the boss. There is no way to defuel the 135. It's a balancing act as to having the aircraft back to it's 'standard' at the end of the shift or leaving a note explaining why the aircraft in the hangar is over weight for the mornings crew.

Some might suggest taking off anyway and burning the fuel......not a popular way of getting rid of the public purse. As for going in to Edinburgh Airport, I've not checked to see if it was open, or if the police have an account with them. Do they charge a landing fee, and how much more expensive is their fuel. These sound like very petty reasons not to use it, but management will want an explanation as to why you've landed them with a bill if not authorised in advance as part of the 'system' and not in an emergency. You've already seen at least one police pilot explain that he always went back to base for fuel, he didn't say wether he ever had to turn down requests for further tasking because of this.

This taken from a UK website, can't verify its contents, but certainly the police may have a deal to mitigate this cost, but equally may be a reason bosses wouldn't be happy with their pilots dropping in for extra fuel just in case.


“This aerodrome has a serious issue with its landing, security, and handling fees. Expect over £220 in fees for a Cessna 172.
This is an extremely serious issue that needs to be addressed.
The airport bosses must not be allowed to grow fat.
”