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From: Jerry Hey <jerryhey@earthlink.net>
Subject: Re: [FlyRotary] Leaking fuel hose 
Date: Wed, 3 Aug 2005 08:24:50 -0500
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

John,  That is a mystery but a good determined effort on your part to  
locate the problem.  Any chance, in checking for spark, that a plug  
could have arced to the fuel line?  jerry


On Aug 3, 2005, at 8:06 AM, John Slade wrote:

> Here's a nasty failure mode to watch out for.
>
> After fitting a new fuel pressure sensor I turned on the pump to  
> check for leaks. The sensor fitting was good, but there was a  
> slight smell of fuel which I traced to the regulator. There was a  
> very slow drip which stopped after a few seconds. I stripped and  
> rebuilt the regulator. Next pre-flight I pressurized the system and  
> checked for leaks with a flashlight. The main return hose from the  
> rail (steel braided teflon 1000PSI) was a little wet. I removed the  
> cowl and turned on the pump. No leaks. I removed the hoses from the  
> regulator and pressurized the entire rail & hoses to 100 PSI. The  
> pressure held for more than 10 minutes. I put it all back together,  
> re-installed the cowl and tried again. No leaks. I left it  
> overnight, then did another check with the pump on. I had a steady  
> drip from one hose that stopped after a few seconds. I ran the  
> engine and did some taxiing, then checked again. No leaks.
>
> Next day I did another preflight check with a flashlight. Again the  
> hose was a little wet, but the leak went away after a few seconds  
> and the hose dried out. After removing the cowl there were no signs  
> of a leak. Last night I checked again. This time I had a jet of  
> fuel from the middle of the return hose. I removed the braided  
> teflon hose to find a dark spot at the point of the leak. The hose  
> had not been rubbing on anything and was not abraded. The damage  
> looks a lot like the result of an electrical arc, but there's  
> nothing for it to short to anywhere near.
>
> My theory is that this hose carried cranking amps at some time or  
> other. I'd swear I've never cranked the engine with the ground  
> strap off, but this is the only way I can imagine that his damage  
> occurred.
>
> Anyone have a better theory?
>
> John (checking my other hoses)
> <cz995.jpg>
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