Because Owning And Flying Your Beechcraft Can Be Done Safely AND For Less Money!



  Check Your Fuel Caps



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.


Click HERE for a SAIB from the FAA on water contamination of fuel

Click HERE for an ABS Video on Fuel System Maintenance



Below is a May 2019 pirep from Bonanza owner, Bill J., regarding his replacement parts find for his Shaw 416-50 caps:


"I got tired of worrying about my worn out fuel caps on my M35. Bonanzas from J35 - mid-N35, use Shaw Aero 416-50 "non-indexing" caps - no notches. But being the ultimate CSOB, I also got tired of buying other people’s junk on eBay advertised as "working condition" only to find the levers were worn out.


I collected part numbers, a parts diagram, and combined them, along with quotes for many of the parts from Preferred Airparts. The levers themselves, have 4 different part numbers, the pins that hold them onto the shaft, 3 p’n’s. Thankfully most of the parts are available. All are listed.


Alan at Preferred Airparts was quite helpful, sending pictures of some items to verify they were what we thought, and his pricing is reasonable to boot.


I bought new levers, new pins, new friction "plates" and new shims for 3 caps for around $70.


Hopefully this info will help others rehab worn cap levers or corroded shafts. April Showers should bring May Flowers, no engine failures…



Click HERE for Bill's summary outline of part numbers.



Here is an image showing McMaster-Carr sourcing for the bead links and holder

Courtesy of Bonanza owner, Tom R.






Buy Flurosilicone Fuel Cap Kits from Gallagher Aviation, LLC.




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, you decide!


See the whole article on this B58 engine failure HERE



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 towbars!


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 Fluoro-Silicone units:


This is why you need to look at your O-Rings carefully AND OFTEN!

Especially if they are the 1940s technology nitrile rubber versions.







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


Resin Fuel Cap Washers & Flurosilicone O-Rings

from McPeck Aviation


High performance resin fuel cap washers.  Replace the worn metal washers under the Shaw fuel cap tab. Ultra low friction for improved opening and closing of the fuel cap.  Resists wear and eliminates metal on metal chaffing of the fuel cap components.

Similar products are offered for $115.75/pair on Spruce .  McPeck's sell for $29/pair. Available in black or white.

Below is the complete O-Ring & Washer Kit (includes materials for TWO Shaw Caps) available from McPeck Aviation for $56.

Flurosilicone O-Rings only @ $13.50/cap

Click the PayPal logo below to make a proper payment to McPeck Aviation for your

Resin Fuel Cap Washers or the Complete O-Ring & Washer Kit.





Contact Adam McPeck for additional info or to place an order

by clicking the box below




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




Gabb Cap Disassembly & Repair of Rounded Corners by Bonanza owner Mark J.



Below is a narrative by Bonanza owner Mark J. in which he outlined in his BeechTalk post how he dealt with the rounded corner issue of the locking tab in his Gabb fuel caps:


I just did both my GABB caps. Rotate the tab and push the hinge pin out of the tab and the cap comes apart. I used a belt sander to flatten the bottom and front of the tab. Leave a small radius on the nose so it rolls and lifts nicely. I used a thin AN washer to shim up the amount of material removed from the tab, so that when it snaps down, the lower section is pulled up tight to make a good seal.


There is no adjustment bolt/nut, so the locking tension is a function of height of the tab in the closed position. If you remove material from the bottom of the tab to square it up, you will need to use a thin washer as a shim.


Easy job. I bead blasted and painted and used new flurosilicone blue o-rings. The tabs were limp and stuck up, now they sit flush and snap down with some authority. I also lubed the washers, shaft and spring contact surfaces with DC-4 and they operate butter smooth.



Step #1


To disassemble, lift the tab and rotate. Then squeeze the cap together which will give you some clearance for the pin to be removed. Then with a pick or flat blade push the pin out then grab the other end with a needle nose and slide the pin out. My pins came out easily. Now you can remove the tab. Once the tab is off, just pull the cap apart into its respective pieces.





Step #2


The tab shaft had some mild corrosion, probably from water sitting in the shaft. You can see the portion of the shaft that is still shinny, and that is where the small o-ring rides.




Step #3


Some light polishing with a scotchbrite pad and it looks like new. Notice the two gates! The block on the top cap piece must be positioned inside those gates. Those are the tab "twisting stops".




Step #4


The middle plate is keyed, and only seats on the top cap piece one way.

Note the shiny portion near the center. The spring seats there and I used some DC-4 there as a lube. Any light grease would work but I had the tube out for the O-Rings anyway.




Step #5


Here the cap bottom, spring and center plate are stacked and ready to go.




Step #6


I polished the washer with a scotchbrite pad.




Step #7


I bead blasted the top of the cap only. The cap is plated and I did not want to damage the plating, so I taped it off. I painted with rattle can flat white. Here you can see the small o-ring, lubed with DC-4 and pressed in the recessed boss.




Step #8


Then, I lubed both sides of the washer with DC-4 and placed in over the O-ring. You can see that there is another recessed area just for this washer. The "Thin" AN washer has a smaller O.D. and I though it best to place the factory washer in first.




Step #9


Next, I lubed and placed my shim washer (MCS1450-6B14-010) over the factory washer. I tested it on the plane without the shim washer and although it locked down, I could move the cap with some effort. The shim took all the play out and and snugged it right up.




Step #10


Not a very good pic of the bottom of the tab, but you just want to remove enough material from the bottom and front of the tab which contacts the washer when in use to take out some of the ware that enlarged the nose radius. There needs to be a small rounded edge so the tab releases, but flat enough so it has a snap action and folds down flush in the cap. I used a stand belt sander and worked slowly as I did not want to remove too much material. Only remove material from the bottom and front of the tab, holding it square. Don't file or sand on the radius, which you are trying to shorten. Painted and ready to go.




Step #11


The tab, snapped down and locked flush. No more limp taps for me!




Step #12


Lube and install the large O-Ring and your done!





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.





Check out an innovative "Thermos" style fuel cap rebuild pirep from Deb owner, Adam Y. HERE



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.