Fuel odour in cabin

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dselder1962
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Fuel odour in cabin

Post by dselder1962 »

I know I have read about this in a couple of threads, but can't find the exact one I am looking for.
I have a new 42-VI, and there seems to be an odour of fuel in the cabin. I notice it occasionally, but on a recent trip my wife and son in the back said it was quite strong.
No fuel testers or anything are kept in the cabin.
I remember seeing one comment that said to be suspicious of an overflow from the aux tanks and that could remain around the air intake but we have had that checked (as well as the lines and switches for fuel in the cabin) and no source yet found.
Any ideas on where to look?
David
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Colin
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Re: Fuel odour in cabin

Post by Colin »

I will be very curious what you find. I have been chasing that issue since I got the plane almost two years ago. The mechanics know that there is an issue with fuel overflow running down the wing and the low-point of the wing is right in front of the fresh air intake. So I think it is a common complaint and that is the *usual* answer.

At one point I tried to check and address that by spraying orange mist air freshener in that fresh air port. I *did* smell the citrus, but even though the wing was totally dry, I could still smell a little fuel. I am pretty sure that mine has to do with the fuel hoses and connectors, and something to do with a tiny tiny leak into the space under the seats. In a strange break with good engineering, that space is used as a plenum for all of the fresh air into the cockpit. So any single drop of fuel that winds up in there (or near the fresh air intake) is sprayed through the cockpit.

Jet fuel is much nastier than 110LL. The latter often got on my hands as I pre-flighted and it was never an issue. If I happen to get three drops on my shoe while sumping the DA42, I know it.
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Re: Fuel odour in cabin

Post by CFIDave »

The only time I've experienced JetA smell in the cabin of a DA42 was in a rental aircraft that had the fuel sumping/tester stored in the nose baggage compartment. As a result, when I got my own DA42-VI I "double bagged" the tester within a sealed jar to make sure no fumes leaked into the fuselage interior. You can smell extremely tiny amounts of JetA.

In my experience, the fresh air intake under the wing has never generated a JetA fuel smell, but HAS resulted in JetA *exhaust* smells entering the cabin whenever holding the stick all the way back to demonstrate a full stall. This applies to both DA42 and DA62 aircraft, and is due to reversed airflow around the wing and engine nacelles during full stalls.
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Re: Fuel odour in cabin

Post by dselder1962 »

Colin/Dave,
Thanks for replying.
So far no luck:
We got advice from Diamond:
Please check following items:
- LH and RH low pressure fuel pumps and all connections/valves for leakage
- LH and RH fuel filter body and its hoses for leakage
- LH and RH fuel selector valve and its hoses for leakage
Please let us know your results,
Mit freundlichen Grüßen/ Best Regards

So the LAME (has done the factory training) replied:

We have the following observations regarding the fuel smell on
The aircraft had been stored with its cabin closed for nearly a week in a hangar prior to us looking at the aircraft. No visible fuel drips or stains were observed prior to it being moved. The aircraft was close to full fuel on mains and aux tanks. The left aux tank was approx. 20mm lower than the right with some signs of venting / streaking aft of the vent, indicating that had occurred in flight. Opening the cabin there was more of a plastic type smell (maybe resin) with a hint of Jet fuel but difficult to be certain.
There was no fuel sampling / cleaning equipment in the cabin compartment.
All cabin equipment was removed and cabin closed for 24 hours. Nil fuel smell was detected. There was no de-icing fluid smell evident.
We inspected the airframe in areas you have listed below with no seepage or weeps evident. Vent holes all appeared to be clear. Nil defects were observed to cause this smell to enter the cabin.

To which, Diamond to their credit has replied:

thank you for your detailed info of troubleshooting and investigation about fuel smell.
You can try another check on the low pressure fuel pumps: connect ground power to aircraft, turn on the fuel pumps and check again –it could be that the leak occurs only when pumps are operated.

If you do not find any leakage or trouble on my explained areas as below ( low fuel pr. Pumps, selector valve and so on ) we would recommend to remove LH and RH Aux tank maintenance covers and check this area for fuel leakage.
We had one case, that when the aux tanks was full and the aircraft turns very fast on ground the fuel swaps over via the filling port and fuel flows down on the outer skin of the aux tank.

Please let us know your results, if you need further info please let us know.

So that will happen this coming week, and I will keep you all in the loop.

(For the record, I don't keep anything smelly in the cabin: everything is kept in sealed Tupperware, sealed and in the nose baggage area.)

Best wishes
David
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Re: Fuel odour in cabin

Post by dselder1962 »

CFIDave wrote: In my experience, the fresh air intake under the wing has never generated a JetA fuel smell, but HAS resulted in JetA *exhaust* smells entering the cabin whenever holding the stick all the way back to demonstrate a full stall. This applies to both DA42 and DA62 aircraft, and is due to reversed airflow around the wing and engine nacelles during full stalls.
Dave
No, this odour was in level flight with the family on board. They complained more than I have noticed in the front. Though my son in the front did say after that he could smell something.
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Re: Fuel odour in cabin

Post by FTEJerez »

Hi David,

I recommend you read this thread: viewtopic.php?f=9&t=5783
In our case, it was the low-pressure hoses as described in the thread - the leak was extremely difficult to detect - I recommend you check the P/N as indicated.
Furthermore, we have now established a procedure where if fumes are detected (not an issue since we changed the hoses on the entire fleet), we try all possible combinations on the ventilation system (cold, heat, defrost, AC) to determine which side is leaking (as each engine provides heating for different areas).
On other occasions, we've had reports of fumes due to the expansion of the fuel in the fuel tank: aircraft topped up in the early morning, sitting in the tarmac with the sun hitting it, fuel expands into the vent system, leaks under the wing and runs into the seal between the wing and the engine nacelle, eventually infiltrating.

Hope this helps.

Cheers,
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Re: Fuel odour in cabin

Post by Valera »

I had a similar problem. Check leaks under the pressure of the right fuel filter in the 90th position. The cause of the seal's destruction.
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Re: Fuel odour in cabin

Post by dselder1962 »

Well we think we have found the issue.
As suggested by the factory: You can try another check on the low pressure fuel pumps: connect ground power to aircraft, turn on the fuel pumps and check again –it could be that the leak occurs only when pumps are operated.
The LAME told me they checked this and there was a tiny drop of fuel about every 5 seconds. This then ran down to collect as a small puddle.
So we are awaiting new o-rings which will fix the problem; so glad I am not going mad with asking myself am I imagining the smell.
Will update after the “fix” is done. Fingers crossed.
David
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