http://www.airbushelicopters.com/sit...uel_system.pdf

There are two pumps and two pipes in parallel circuit. I'd expect the pump capacities vs pipe bores and fuel demand to have been considered for all the possible failure conditions...that's first year mech eng stuff. Looks like a perfectly sound system to me, assuming that there is a strainer/filter before the tanks, which there is bound to be.

Bearing in mind this threads title, doesn't all this fuel system talk need to be on a different thread?

Pie Chaser
I very much doubt that is even possible. Unless you are saying there is a known failure mode that would have produced such a tragedy from that precise amount? That would be tantamount to criminal negligence were that not widely publicised beforehand. Non of our EC135 contributors (or BO105-similar system?) has yet offered such an explanation?

I suspect the final determination may be a little more prosaic? But that's just my opinion!

It's not the January Bulletin you mean by 'a report coming out very shortly' is it?

http://www.aaib.gov.uk/cms_resources...l%201-2014.pdf

There are two pumps and two pipes in parallel circuit
 

Thanks for the link. There is only one red pipe from the main tank prior to splitting into two before entering the supply tanks.

That is NOT two independent supplys. A rupture of the red pipe will result in loss of feed to BOTH supply tanks.

Robin, I think that's a simplified schematic as the positioning of NRVs was discussed earlier in this thread by those with knowledge of type. There have to be flex couplings if solid pipes are used and bulkhead mounts, so I think we can assume a lot has been left out of the schematic for clarity.

However, the truth is that this accident was unexpected (aren't all?). We have an experienced and well-respected pilot and a major operator with a good safety record, crewed/manned by responsible people rather than a couple of champagne Charlies or "A-Listers" in the back making whoopee. The weather was excellent, viz good. This accident was never meant to happen so we can expect the unexpected.

The schematic is simple yet portrays the system well.
Transfer hoses come from the trans pumps and are connected to each other, and in turn to the supply tanks. It seems to me that if there is a leak or failure anywhere in the flexible transfer hose, the fuel will end up being circulated within the main tank and perhaps not be able to top up the supply tanks fast enough to prevent them emptying.

The check valve is integral to the transfer pump unit.

But of course, if this was to have happened the engines wouldn't have stopped at the same time and the fuel warnings and gauge would have indicated something to the crew.(therefore this part of the thread is imho better off being in the 135 thread)

Sid

We do not know that both engines stopped at the same time.

Sid -- I'd bet that's the sort of defect they would have been looking for in any case would have been found by now, with a directive to check/repair all a/c in service. The only directive we are aware of is a fuel indication issue - i.e. an instrumentation issue, not a safety issue per se.

Chop;It's a statement of fact based on the system, not a speculation. That's why there's an 'if' :rolleyes:

Back to the big question, how do you get to a point a metre above a roof in a vertical descent with the transmission system stationary? We do not know if this incident had anything whatsoever to do with fuel, and personally I still don't think it is.

Training
 

Having read most of the posts regarding this tragic accident there seems to be a great deal of poor understanding of the fuel system.

May respectfully suggest that all crew go on a FACTORY training course ensuring that they fully and correctly understand the systems they are operating.

...... Or you could tell us where we are all going wrong :rolleyes:

Not a Clue
 

From the posts you all seem unable to have a consistent and accurate understanding.

So You have it? I'm waiting for explanation!

skadi

You tell me please
 

How do you opertate the transfer pumps ( with a low fuel level ) transiting from hover to cruise and back to hover.?

Please read my post #1429.

skadi

How about keeping system issues to the 135 thread?

p.s. I think Robin is talking check valves ;)

Not nrv valves Transfer pumps.

Gone to 135 posts. Out.

irony...
 

SS - The irony of your post is staggering - the first accident in the AAIB report, you point to, is a double engine stoppage of a twin cause by fuel exhaustion - given that that may also be the case here (and other complete power loss events) it is tempting to conclude that the mathematical assumptions concerning the safety of TWIN ENGINED helicopters is FLAWED - is the rarety of full power loss in twins actually 10^-9 per hour ?