Mailing List flyrotary@lancaironline.net Message #17835
From: Paul <sqpilot@bellsouth.net>
Subject: Re: [FlyRotary] Re: Vapor Lock
Date: Thu, 24 Feb 2005 06:57:38 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
 
----- Original Message -----
From: Jim Sower
Sent: Wednesday, February 23, 2005 11:34 PM
Subject: [FlyRotary] Re: Vapor Lock

CUT

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.
Answer: I have a long range canard aircraft with a 70 gallon fuel capacity. I have NEVER landed with less than 1/4 tanks, (usually have 1/2 tanks upon landing) and plan to continue this practice. My LongEZ was also a long distance aircraft with plenty of fuel capacity. NEVER landed with tanks less than 1/4 full. My canard is capable of 9 or 10 hours of flight. My bladder isn't.  No John Denver scenario for me.  Fuel management has always been high priority for me. I don't like arriving somewhere and having to shoot another missed approach low on fuel. Nope. No thanks.
and balance fuel consumption automatically,
It does NOT balance.  One tank nearly always transfers faster than the other.
 
Answer:  My LongEZ was very similar, Main strake tanks, fuel selector L R and Both. I used Both 90 % of the time.  I have been using Both on this canard as well (I only have 9.5 hours), but so far, fuel consumption HAS been equal. (Or at least no difference that I can visually measure).
CUT
 
----- 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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