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REFLECTOR: Copy of: N19DW Accident, Probable Cause




---------- Forwarded Message ----------

From:   Donald R. WHITE, 104401,2262
TO:     Duane Swing, INTERNET:velocity@metrolink.net
DATE:   6/24/99 9:39 AM

RE:     Copy of: N19DW Accident, Probable Cause

We, Duane, myself and the NTSB, have developed a STRONG PROBABLE CAUSE for
the accident.
By testing,I showed that the left tank fuel cap was NOT air tight when in
the locked position. We believe the airflow over the left fuel cap in
flight was evacuating air from the tank at a rate greater than the vent
line was allowing air in. This condition produced a vacuum in the left
tank, sufficient to prevent fuel from the left tank from flowing by gravity
into the sump tank. Therefore when the fuel was all used from the right
tank and the sump tank, the engine then suffered fuel exhaustion. 
The NTSB is submitting this theory to their engineering department for
evaluation. 
About a week prior to the accident I repaced the original plastic fuel caps
with a set of the new metal ones. I installed them in the as received
condition and noticed they the lock lever closed with much less pressure
than the old locks. After two short flights I checked caps for any fuel
leakage, but did not find any. However I did notice a more than normal
difference in fuel levels between left and right tanks upon landing after
short flights. In my experience a difference of 5 gallons between tank
levels is normal however this time the difference was about 10 gallons.
Sight tube showed about 5 gallons in right tank and 15 gallons in left
tank. I wondered about it, but felt even if one tank ran dry, fuel would
continue from other tank. (The left fuel cap air leak obviously could cause
this unusal fuel imbalance.)
My presnt RECOMMENDATIONS:
1)Carefully check your fuel caps for tight seal, proper adjustment and
proper installation. Keep a little Vasoline on the O-rings to assist in
sealing.
2)MOST IMPORTANT, monitor fuel tank levels during flight , and if an
unusual imbalance is seen,  ASSUME FUEL IN FULLEST TANK IS UNUSEABLE until
system is checked.
3) I will install the low fuel level warning on the sump tank. If I had
that warning , could have made it to nearest airport before fuel
exhaustion. 
4) Will install a finger screen around fuel outlet in sump tank as that is
the only fuel line in whole system not already protected by a screen. The
chance of dirt or flakes large enough in sump tank to block that outlet are
of course extremely remote

Was amazed at how little dirt was found in bottom of sump tank, in line
filter, and servo screen. A hole was cut in the sump tank to check for
possible blockage.Guess we did a really good job of cleaning system prior
to assembly. Our in line filter was the original with about 115hours on it.
However still recommend you check and/or change your inline filter within
25 hours of first flight.

Looks like aircraft will be declared a total loss by the insurance company.


Questions and or comments welcome. See you at Oshkosh without N19DW
Don White