Fuel spewing out of your fuel cap is not what you want to see happening
just after takeoff or ANYTIME in flight! And certainly NOT in an IMC situation
Be sure to note how the fuel cap is placed in
the sealing ring of the airframe. If you see it cocked in any unusual
way.....check it out for proper seating. This will be a clue to the pilot doing
a proper pre-flight, especially after allowing line personell to fuel your bird.
The least of your CSOB worries is
the lost 100LL fuel.
HERE for a SAIB from
the FAA on water contamination of fuel
I will admit, this has happened to me once. It
happened as a result of one end link of the little chain on the cap getting
caught in the sealing lip. The cap, for all cursory visual clues, looked
properly closed. It was NOT!
Being a CSOB, I almost always self serve my
fuel and even if the FBO fuels me I will always be standing behind the line guy
to check the fuel loading and be ready to seal the caps. I can count on one hand
the number of times I have allowed FBO line services to fuel my bird without me
physically being present at the time of fueling.
Just after lift off from my favorite CSOB
northern tundra fuel stop in
KCLI, at maybe
400 AGL, my commercial ME pilot buddy in the right seat notices fuel streaming
from the right wing aux tank cap and says: "OH NO, Fuel leak!"
I tell him it's OK and say out loud two-times:
"Fly the Airplane". I fly a normal pattern at ~800 AGL and land uneventfully.
When my buddy and I landed (fortunately severe clear VMC prevailed) I was able
to see the chain link and how it had gotten wedged up under the cap and sealing
ring of the airframe.
From that moment forward I now always
purposefully clear the chain of any kinks and see it drop down and away from the
metal sealing surface of the fuel opening in the airframe.
Also, keeping your fuel cap O-rings in great
shape is good fuel cap leak prevention. Just look at what happened to this
really nice B58 Baron from water contamination of the fuel past a poorly
maintained cap and o-ring:
The right engine sputtered to a stop just
after takeoff. Here is the fuel cap center shaft from the above splashed Baron,
See the whole article on this B58
See the O-Ring page
HERE for some
popular fuel cap O-ring PNs. While you're there, give some thought to upgrading
to the long life Blue
Fluoro-Silicone O-rings listed there.
Baron Owner & IA, Stuart S.,
posted this pirep on his Fluoro Silicone o-rings: "Mine are like new and they were installed in 1996."
Here's a little tip for when your plane has
been hangared outside after a big rain has come through. A little while after
the rain storm, look inside the tops of your fuel caps. If I see water pooled
there behind the locking tab, to me that's indicative of decent inner
O-ring sealing condition on the rotating shaft of the locking tab. If I don't
see any water pooled behind the tab, I'm going to get a little concerned and do
an extra special sump job. This won't,
however, tell you anything about the big O-ring condition. A visual inspection
for cracking and checking of the outer O-ring can be a good way to determine
fitness for use.
Fuel Cap Tip #2: In addition to your normal
pre-flight fuel sumping routine, be sure to add an extra look and focus on
sumping when hangared outside after a rain storm or after washing your plane.
This is one of the greatest opportunities for water to enter the fuel tanks
through poor O-rings or bad fuel cap sealing/mating surfaces.
Fuel Cap Tip #3: After fueling and just prior
to getting in the plane for startup, I make just one last purposefully SLOW walk
to each fuel cap and make that last check for proper sealing of the caps and I
also make a scan under the airplane for any evidence of leaks, chocks AND
Fuel Cap Tip #4: This is what can happen if
you try to snug up the cap sealing force on the closure tab shaft and you run
out of threads on the center shaft or corrosion is built up on the nut and shaft
Don't ask me how I know!!! You don't want to
be on a trip and have this happen to you as you will be AOG!
My caps are all fine and have been for over 4
years but I still carry a spare in my little "AOG box" that I got from a Beech
lister way back when. You might consider carrying one or vow never to mess with
your caps while on a trip or just before a big trip.
Here are pics of my O-Ring swap out to
This is why you need to look at your O-Rings carefully AND
Especially if they are the 1940s technology nitrile rubber
Below is a picture of my
flurosilicone fuel cap O-ring taken on 12/13/14 (yeah, that's a cool date) which
has nearly 6 years TIS! You and your A&P decide which you want to use.....
See a Shaw 531 Fuel Cap O-Ring
Change Article written by
BeechTalker, David M. HERE
Thanks for the contribution David
Here are some pics (courtesy of
V35 owner, Dale B.) of clamping a Gabb Cap for the center shaft o-ring change:
Here are some pics of a Gabb cap
used on a P35 Bonanza (courtesy of
P35 owner, Jeff B.). There is some confusion about the big o-ring for the cap as
to whether it is a -338 or a -339. The IPC calls out a -339, however, folks
report that the -339 is somewhat loose and the -338 looks like a better fit.
Just a watch out that you double check what's being used in this application!
Here is a pic of a Gabb cap
where the owner reports a good fit using a -338 o-ring
No O-rings for this "Old School" Fuel Cap for
very early Bonanza airframes. Rumor has it these puppies are quite pricey! Click
on the pics to go to Spruce for pricing.
As always, if you have no idea what an O-ring
is or what a good one is supposed to look like or what a bad one looks like,
close this browser page and ask your A&P licensed mechanic to have a look at
your fuel caps and let you know if they need to be changed.