Because Owning And Flying Your Beechcraft Can Be Done Safely AND For Less Money!
  O-Ring PN Sources & Fluorosilicone Options

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

 

Here is a conventional nitrile rubber Fuel Cap O-Ring (the larger outer one) after a short while in service, typically a year or less, in my experience:

 

 


 

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.....

 

 


 

Here is a Bonanza that is definitely in need of fuel cap o-rings. This Bo owner couldn't get his

flurosilicone o-rings fast enough after he saw this on his flight

 

 

Why wait for this to happen to you?

 


 

Here is a P35 Bonanza fuel selector that is definitely in need of the center shaft o-ring. The owner reported leaks when selecting the right tank.

 

 

This looks like a great opportunity for a flurosilicone o-ring (with your A&P's approval of course)!

Why wait for this to happen to you?

 


 

See more on fuel caps at CSOBeech HERE

 

See a Shaw 531 Fuel Cap O-Ring Change Article written by BeechTalker, David M. HERE

 

Thanks for the contribution David

 


 

There is some confusion about the big o-ring for the GABB 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 pops out of the slot. The -338 seems 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

 

 

 


 

O-Ring Cross Reference HERE (circa 1995 - use at your own risk)

 


 

Listings of my favorite B55 & Other O-Rings

 

(Check your parts catalog to be sure they will work for your SN)

 

Military Nitrile Rubber O-Rings

 

 

 

 

 

 

 

 

 

 

  • * There is some confusion about the big o-ring for the GABB 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 pops out of the slot. The -338 seems like a better fit. Just a watch out that you double check what's being used in this application!

 

 

  • MS29513-010 (4) = B55 Fuel Selector Shaft w/Separate Aux Tanks (See Narrative HERE)

 

 

O-Ring Reference Guide PDF HERE

 


 

Buna-N (Nitrile) O-Rings


Description:
Standard Nitrile is also known as Buna-N. Excellent resistance to petroleum-based oils and fuels, water and alcohols. Nitrile also has good resistance to acids and bases, except those with a strong oxidizing effect.

 

Limitations: Avoid highly polar solvents (Acetone, MEK, etc.) and direct exposure to ozone and sunlight.

 

Chemistry: Copolymer of butadiene and acrylonitrile. By varying the acrylonitrile content, elastomers with improved oil/fuel swell or with improved low-temperature performance can be achieved. Specialty versions of carboxylated high-acrylonitrile butadiene copolymers (XNBR) provide improved abrasion resistance. And hydrogenated versions of these copolymers (HNBR) provide improve chemical and ozone resistance elastomers.

 

Trade Names: CHEMIGUM , HYCAR , PARACRIL , PERBUNAN

 

ASTM D1418 Designation: NBR, XNBR, HNBR

 

ASTM D2000/SAE J200 Type, Class: BF, BG, BK, CH

 

Temperature Range: –55 to 120C (–65 to 248F)

 

Typical Uses: Ion Implant, PVD

 

Compound# Color Hardness
Shore A
Tensile
Mpa (Psi)
Elongation % 22Hr C/S
@ 100C
Low Temp High Temp
B1000 Black 70 15.0 (2,150) 400 10 –40C(–40F) 120C(248F)

 

 


 

 

Fluorosilicone O-Ring Options*

 

 

 

/3 = 60 Durometer Available from Genuine Aircraft Hardware (List Price $4.50/each WOW)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $0.50/each)

 

 

/3 = 60 Durometer Available from Genuine Aircraft Hardware (List Price $28.00/each WOW)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $6.96/each)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $4.25/each)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $2.75/each)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $8.25/each)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $1.00/each)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $0.50/each)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $0.50/each)

 

  • M25988/1-010 (4) = B55 Fuel Selector Shaft w/Separate Aux Tanks (See Narrative HERE)

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $0.50/each)

 

 

/1 = 70 Durometer Available from O-Rings, Inc. HERE (List Price $2.50/each)

 

See a failing Bonanza fuel selector o-ring HERE

 

Remember: Failing O-rings in your fuel selector are a prime source of air entering the fuel supply and creating all sorts of mysterious runability issues in your engine at possibly the worst possible times!

 

*Fluorosilicone o-rings, whether 60 or 70 Durometer, have less tear resistance than the military Nitrile rings being crossed. They may or may not be appropriate for your particular application. Notice the tensile strength and elongation spec differences in these two materials. Be sure your mechanic approves return to service.

 

O-Ring Reference Guide PDF HERE

 

Baron Fuel System Parts Catalog Extract HERE

 


 

Here is an image of where o-rings/seals are in the basic Bonanza fuel selector are located and why they leak in this area.

 

 

Bonanza owner and A&P, Bob B. adds this about the fuel selector o-rings/seals:

 

These fittings call for a 'special' o-ring correctly called a boss seal. It is an MS29512-4 or MS28778-4 ( probably a dash 4 but do not quote me.) The dash number indicates fitting size not the same as normal o-ring sizing nor is it the same material as the usual/standard o-ring although it looks similar. When a standard o-ring MS28775  for most usage or MS29513 for fuel are substituted, they will leak after awhile for no apparent reason. Or The nut may be a little loose or even too tight creating undesirable extrusion. In either case, remove the fitting, replace the o-ring with a correct 'seal'.

 

Remember: Confirm all part numbers with your parts catalog for your serial number airframe!

 


 

 

 

NEWS FLASH 6/21/2009:

 

The GROUP BUY on these super long lasting Fluro Silicone O-Rings from Genuine Aircraft Hardware and O-Rings, Inc. resulted in participation to convert 108 fuel caps! Great participation folks!

 

Stay tuned for more Group Buys from CSOBeech.com

 

Baron Owner & IA, Stuart S., pirep on Fluoro Silicone: "Mine are like new and they were installed in 1996."

 

Fluorosilicone O-Rings

 

 

Description: Combines excellent low-temperature performance of silicone with improved
chemical resistance. Very good resistance to military and aerospace fuels. Excellent performance
in oxygen plasma environments.

 

Limitations: Avoid polar solvents, hydro-carbon fluids and phosphate ester brake fluids.
Susceptible to hydrolysis by acids and bases. Limited abrasion resistance.

 

Chemistry: Methyl disiloxane with CF3 groups (Methyl-trifluoropropyl siloxane)
(CH 3 )(CH 2 CH 2 CF 3 ) –SiO.

 

Trade Names: SILASTIC LS , FSE

 

ASTM D1418 Designation: FVMQ

 

ASTM D2000/SAE J200 Type, Class: FK

 

Temperature Range: –60 to 180C (–76 to 356F)

 

Typical Uses: Dry Etch, Resist Stripping

 

Compound # Color Hardness
Shore A
Tensile
Mpa (Psi)
Elongation % 70Hr C/S
@ 200C
Low Temp High Temp
F1006 Blue 40 7.6 (1,100) 410 20 –60C (–76F) 180C (356F)
F1003 Blue 60          
F1001 Blue 70 7.5 (1,090) 230 15 –60C (–76F) 180C (356F)
F1002 Blue 75          
F1004 Blue 80 6.8 (990) 177 11 –60C (–76F) 180C (356F)

 

 

Fluoro Silicone PNs Available at Genuine Aircraft Hardware & O-Rings, Inc.

 

 

 

 

 

 

Pirep 8/20/2012:

 

Reported to be available from East Coast Aircraft Supply in Melbourne, FL

 

800-330-3945

M25988/1-338 $5.25

M25988/1-010 $.40 ea (min order 10)

 


 

 

No O-rings for this "Old School" Fuel Cap for very early Bonanza airframes. Rumor has it these puppies are quite pricey!

 

 

 

Here are some pics of the real "McCoy" NOS early Bonanza fuel caps that a certain someone offered for sale recently at a phenomenal price of $50! Now this is a very good reason to join and PARTICIPATE in Beechcraft internet forums....The complete Beech PN is: 35-921526-14

Rumor has it the rubber seal alone is over $200

 

 

 

 

  • Baron IO-470 Alternator Belt - NAPA # 7315

 

  • Flap Decal 20 Degree 35-000066 Placement Instructions HERE

 

 

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