Mailing List flyrotary@lancaironline.net Message #17820
From: Jim Sower <canarder@frontiernet.net>
Subject: Re: [FlyRotary] Re: Vapor Lock
Date: Wed, 23 Feb 2005 23:34:05 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>


Paul wrote:
Re: [FlyRotary] Re: Vapor Lock
Thanks for the info, Tracy.  My only concern is this....if the Facet pump was not involved, might it be better to have it back in the system so that if I have a future problem, I could turn the Facet pump on to pressurize the sump tank with fresh fuel?  Ed seems to be comfortable with this, and has had to use it.
I would keep the Facet in.  Upstream from the sump?
       Of course, on the other hand, if the Facet even partially contributed to  the vapor lock issue, I don't want it in my system.  I need to talk to Herb Sanders one more time, as he was concerned that because the Facet will not allow back flow, it might be a major contributor to the vapor lock issue.
It could get you into a little trouble.  It will get you OUT OF a LOT.
I'm feeling like my system is fairly simple as it now stands. Gravity feed, only the two required EFI pumps, a vented sump tank, and a simple Andair fuel selector valve. 
If you get vapor in the sump, it's going to push fuel back toward the selector too, isn't it?  The Facet can pressurize the HP pump inlet.  That trumps just about everything else.  Keep it in.
I do not need to transfer fuel from one tank to another, or anything like that. I can also select "both" on the fuel selector,
If you're almost home and have "Both" selected, and one tank runs dry, what do you end up with in the fuel line?  I believe mostly air.  Late in the trip (traffic pattern?) where trouble shooting time is at a premium.  Use L or R.  Not B.
and balance fuel consumption automatically,
It does NOT balance.  One tank nearly always transfers faster than the other.
or just switch to left or right tank if needed. Paul Conner
It works with sump and Facet.  Suppose it needs them BOTH.  Leave it that way ... Jim S.
 
----- Original Message -----
Sent: Wednesday, February 23, 2005 1:12 PM
Subject: [FlyRotary] Re: Vapor Lock

Paul, one last thought on the vapor lock thing.  Very glad you have found that it was the problem.  There is nothing worse than not knowing. 
 
It is quite possible that changing EITHER of the two variables (in-line Facet or vent on the header/sump tank) will make the system work.  Just because you remove one and it works does not mean you have found the root cause.  Earlier I used the "strikes" analogy, and we don't know how many of these it takes to make an "out".
 
  From your background I'm sure you know that it is frequently a combination of things that can cause a failure.  Removing one of them may 'fix' the problem now but add in other variables like fuel vapor pressure, altitude, etc, and the problem could come back.  The goal is to make the system as tolerant of all factors as possible.  Happily, this frequently means making it simple too!
 
One other thought on simplicity.  I have never landed without power (in my rotary powered plane) but I have come close several times in the early days.  The only thing that prevented it was having a fairly simple system and knowing it very well.  This helped diagnose the problem and fix or compensate for it before running out of altitude and ideas.
 
Tracy


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