Leaking fuel hoses

[Steve D]

Aart - Strange answer from AMO. He tells me the factory parts are replaceable every 5 years. If however you have "Silicon Pipes", then it is on condition.

Apparently I don't have "Silicon Pipes" whatever they are.

[FTEJerez]

DA42 NG Maintenance Manual, Time Limits (Chapter 5)
Fuel hoses interconnecting the individual fuel tank chambers, and fuel hoses connecting fuel tank chambers to filler assemblies: Replacement time: 8 yrs ± 60 days

DA42 TDI MM, Time Limits
Fuel hoses interconnecting the individual fuel tank chambers, and fuel hoses connecting fuel tank chambers to filler assemblies. Replacement time: 8 yrs ± 60 days

Those were the only references I could find regarding time limits on fuel lines on the aircraft (which are the ones we are referring to), not the fuel line on the engine.

[Aart]

Sorry, my mistake. I thought we were talking about the hoses/lines on the engine itself. Indeed, the hoses you referred to have an different replacement interval. Just had mine done last yr.

[CFIDave]

On all aircraft that were manufactured in 2013 (4 of them) we have found evidence of leaks in the fuel line that connects the main fuel tank to the fuel selector valve assy.

I have a DA42-VI built in 2013 that was delivered right after all of yours (I got to wait in line for an anxious 6 months for mine to be built), but I have yet to experience any symptoms of fuel leaks.
Are there any particular phases of flight when fumes are more apparent in the cockpit?

[FTEJerez]

Hi Dave,

Sorry for the late reply but I've been busy with another Diamond issue ("cooling system problems" post).
Regarding your question, the initial reports were limited to inflight occurences, typically with high banking angles or assymentric training. We believe the accelerations and the hydrostatic pressure of the fuel (high bank angles) would cause the fuel to dampen the line (typically unpressurized) - this in turn would contaminate the area where the defrost and cabin heat air is heated, causing fumes to enter the cockpit if any of these was selected.
Later, the problem was intendified at engine startup, with an immediate smell of fuel on the ground. It would be possible to identify the leaking line if the appropriate heating was selected (since defrost and cabin heat are supplied by different engines).
I suggest you put your bare hand over the line and see if it's moist. That should be more than enough to determine if there is a leak.

Update from Diamond: they have requested us to return all leaking fuel lines for investigation, but have yet failed to clarify why (and why the IPC was chnged whithout any published information).

Let me know if you have any questions or comments!

[CFIDave]

Thanks for the reply.

I've smelled JetA fumes when flying other DA42s, but this was due to someone storing a fuel tester in the front baggage compartment without sufficiently enclosing/sealing it in another container. Fortunately I've been unable to smell ANY JetA fumes when flying our DA42-VI. Guess I'll need to try flying some high bank angles as you suggest.

We do temporarily smell diesel exhaust (not JetA) when practicing and holding full stalls, which I'm thinking causes irregular flow of external engine exhaust into the under-wing air supply NACA duct.

[klang]

Aart,
fully agree to your points. My DA42 is 2017, original 1.7 Thielert, replaced with Technify 2.0.
EASA and AMM require hoses to replaced with new at 5 years intervals. Has been c/w and I never had a trace of fuel smell in the cabin.
I inspected the hoses that came out. They all looked good (almost like new). It is costly and hurts but didn't`t want to take chances.

[FTEJerez]

Dave,
Agree on the exhaust fumes while practicing stalls. We observe the same phenomenon (and it gets worse when using the air conditioning unit, as the inlet is underneath).

Karl,
I'm still unable to find any EASA AD relating to a change in the fuel hoses. Could you please point me in the right direction?

Thanks!

[klang]

Daniel,
it is not an AD. The approved DA42 AMM, 05-10-00, "Time Limits and Maintenance Checks", Art 4 "Component Time Limits, Sect. B. "Airplane Life-Limited Components" - "Replacement Times, items 73-79", stipulates replacement of Fuel, Coolant and Oil hoses at calendar times 5 yrs +- 60 days.
In my opinion, LLP time limits are compulsory, to be c/w

[FTEJerez]

Karl,
Thanks for that. I was getting confused as people kept saying EASA. As per my knowledge, this is a Diamond only requirement. In fact, our DA42's equipped with the Austro engines don't have such requirements (items 73-79 don't exist in the maintenance manual).
Thanks!