Message-ID: <3B34D200.9D7E03B@regandesigns.com>
Date: Sat, 23 Jun 2001 10:29:36 -0700
From: "Hamid A. Wasti" <hamid@regandesigns.com>
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To: lancair.list@olsusa.com
Subject: Re: 80, 78, 76, 72 Useable?
References: <5.1.0.14.2.20010623100150.042ec250@pop3.olsusa.com> <003601c0fc01$b07b2080$14e4de9e@colwell>
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Reply-To: lancair.list@olsusa.com

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It is very important to know the useable fuel in the tanks.  IT IS NOT THE SAME
AS THE FUEL TANK CAPACITY.  Even in certified airplanes, especially the
geriatric variety that some of us fly, it is not always the same as the
published "useable fuel" numbers.  I am one of the people who came close to
finding this out the hard way.

I had owned my previous Mooney for 2 years and knew everything about it, or so
I thought.  I had never flown any flights longer than about 3.5 hours (35-40
gallons of fuel), just because the need never arose.  I was flying from CA to
FL and the first leg was planned to use 45 of the 52 gallons in the tank.  I
knew it held 52 gallons because I had personally observed a little over 52
gallons being pumped into the tanks after they were emptied to replace the
quick drain valves.  I was aware that I was pushing the envelope and monitored
my progress closely to make sure that I was getting the ground speed I had
planned.  All was good until I got a wakeup call when the first tank dried up
prematurely over eastern Arizona in the middle of nowhere.  The nearest airport
was my planned fuel stop.  It made for some very stressful minutes of flying
till I landed at my destination.  The tank that had "dried up" still had 2
gallons of fuel in it.  The other tank had 4 (2 usable, I hoped).  The fuel
consumption was on the money, 45 gallons planned, 46 actually used.

When I got my current plane, before I made any flights that would dip into the
last 10 gallons (even for planned reserve), I intentionally ran each of the
tanks dry (on separate flights :-) to see how much useable fuel they held.
This useable figure is for straight and level flight only and I require another
4 gallons in one tank for landing.  And that is in a certified airplane.

A homebuilt would require at least that much testing.  Before running tanks dry
in the air, you must determine if your engine will restart in the air.
Certified planes have to be designed to restart when the fuel flow is
restored.  It may or may not be true for your plane.

Hamid

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