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Tsb Report: As350 Eng Failure Due To Air In Fuel System


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An engine re-light system does not always work, I can attest to that with my one and only real life auto. The stainless steel air line to the fuel control broke/cracked under the hex nut and the poor ol engine decelled, and there I was staring at the auto relight light with nothing happening, but my shorts filling up. Luckily I managed to auto onto a frozen pond and did no damage to Lois,s base machine, ( Norman Wells ), but a wise lesson to all, that auto re-light is NOT the be all to end all some pilots seem to think it is.

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Many of us did not know the air was NOT being bled out of the system and with a flow thru system the theory was that you were not getting the contaminants out of the system by bleeding with the pumps on. This is a two fold issue:


-Air is not being purged out of system as was explained, thus need to drain pump on.


-When you have updated check valves then you run risk of fuel being bled down out of lines back to tank thus air entering when aircraft is sitting shutdown.


Glad there was such thorough investigation into this crash which has brought to light a difficiency in the system.

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Thanks for posting Dick, very interesting read.


I too have met a handful of experienced pilots who suggested draining the fuel filters with no boost pump pressure.


If you read the bottom of that report you can see that the Frenchies don't necessarily agree with the TSB's findings and are doing more investigating. Slightly unsettling that there doesn't seem to be a firm conclusion to this report or solution to the problem.


"2. After routine fuel filter maintenance, the fuel system bleeding procedure does not

ensure the system is completely purged of air, thereby increasing the risk of an engine



That's also a little unsettling.



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