From: Sky2high@aol.com
Message-ID: <1910d0fc.36281059@aol.com>
Date: Fri, 16 Oct 1998 23:34:49 EDT
To: lancair.list@olsusa.com
Subject: 3x0 fuel systems, an observation
Mime-Version: 1.0

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Since sending a description of my simple system (automatically keep the header
tank full) to this interchange, it has, subsequently,  been most interesting
to read about the many systems proposed and those operating ones described. 

My observation is that most contributors laid out systems that were un-
neccessarily complex  even though a claim was made that they were "simple".  I
have read about crossfeeds, fuel selectors, serialized pumps, direct wing
feeds, large fuel lines, tada, tada, tada...  The contributors' basis for
complexity was often obscure, but the theme that comes thru is: I WANT A
SYSTEM THAT, REGARDLESS OF FAILURE MODE, WILL ALLOW ME TO COMPLETE MY FLIGHT
AS PLANNED!  This is an unsafe goal.

As a long time subscriber to "Aviation Safety", it always amazes me to see the
large number of "pilot failed to manage fuel system properly" as the reason
for "prematurely terminated" flights.  High among these are failures to
position the "selector" valve properly (wrong tank, not in detent, off, etc.)
which led me to eliminate any thoughts about incorporating a "selector valve"
into the system.  A high number of "fuel exhaustion" problems reinforced my
desire for an accurate fuel use and quantity reporting system.  And, since
most problems are a result of a mental lapse, the fuel system had to be
simple, but automatic.  Note: the only flight in which  I relied on using the
manual system (fuel pump switches) to alter trim by wing fuel weight, I
managed to pump several gallons overboard via the header tank vent by not
devoting full attention to the filling process (this did provide useful
fuselage air flow data by tracing the blue stain). In addition to safety, I
have often heard of problems with interconnected wing tanks, such as non-level
parking draining fuel towards the low wing side, etc....

Lancair's design of the 3x0 fuel system is very simple and quite good.  It
only requires that you hold this truth to be self evident: KEEP THE HEADER
TANK FULL AND YOU WILL BE OK!  It doesn't matter whether you do this manually
or automatically, but if the header is full, you will have the proper reserve
(about 1 hour of flight) to find a place to land.  In a 320, that could easily
result in a range of 200 miles. If the fuel supply system is your concern,
always plan the flight path to be within 200 miles of a weather-usable landing
site from your present position.

The objective of any "major" problem should be to get to the ground quickly
and safely so that the problem can be fixed.  That's the way one breaks the
chain of cascading problems.

Since I keep my header full, the fuel transfer pumps are NOT connected to my
"essential bus" because if a have a serious electrical problem, I'm heading
for the nearest airport.

Scott Krueger
N92EX