Mailing List flyrotary@lancaironline.net Message #17813
From: Tracy Crook <lors01@msn.com>
Subject: Re: [FlyRotary] Re: Vapor Lock
Date: Wed, 23 Feb 2005 22:20:11 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Re: [FlyRotary] Re: Vapor Lock
I agree, it's a tough call on the Facet pump with the sump tank.  But then if you eliminated the sump tank.......  : ) 
 Your Andair valve is a good (but pricey) solution.   And I see the fuel transfer requirement as no more onerous than the requirement to switch tanks.  This is a cherries & nectarines issue.  Both taste great.
 
I'll have to think about that "auto leveling" a bit but at first blush, I'm not sure it would work in all situations.  Have you tried it?
 
Tracy
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.
       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. 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.  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, and balance fuel consumption automatically, or just switch to left or right tank if needed. Paul Conner
 
----- 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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