The International Cessna 170 Association

Hello! I'm new to the forum and new to C170 ownership. After owning a Luscombe and a C-140, I was suddenly overcome with dreams of flying both of my kids around at the same time and purchased a 1948 metallized 170. It is missing some early logs--and I'm sure you can see where this is going...

Since taking possession of the plane (it is tied down currently), there has been a lot of water in the fuel. And the fuel caps and filler necks have seen better days. However, these are not the factory gas caps and, bigger problem, there does not seem to be a 337 for the caps and the logbook from the metallization is lost.

I've spent a lot of time beating myself up for being in this situation, I really do know better, but now I'm just in problem solving mode. This plane has successfully gone through decades of annuals with these caps on, but the filler necks and caps need attention. I'm throwing myself at the mercy of this group and your expertise.

1) The cap number is Shaw Aero Devices #416-50. The issue is for the life of me I can't figure out what filler neck is supposed to accompany this. Does anyone have any idea how I could figure this out? There is no documentation in the log.

2) Long-term, how should I go about sorting the paperwork for this? I've heard that getting a 337 is a year-long process.

I want this to be the last plane I ever own (or so I say!) so I would like to get this right.

Below are photos of the caps and filler neck.

Have you ordered the aircraft records from Oklahoma?

Headline 2007: PARKER HANNIFIN ACQUIRES AEROSPACE EQUIPMENT MANUFACTURER SHAW AERO DEVICES, INC.

You probably knew that. I did a quick search of Parker for #416-50 and didn't get any hits.

Looking at the pictures it is difficult to see the filler neck. Why do you believe it does not match the cap? Those caps work by expanding the o-ring when the tab is turned and sealing against the side of the neck.You didn't show a picture of the top but I assume there is a quarter turn tab/handle that pushes in flat when the cap is tight. Have you tried new o-rings?

Of course none of my drivel addresses the legality of it all.

Good luck.

I don't know if the metallizing STC covered that change or not.

But, I suspect that it actually is a better fuel cap arrangement than the original '48 C170, which is very prone to water leaks. I can see why some previous owner would have wanted to make a change.

Of course, the seals and sealing surfaces around the perimeter of the cap and at the center stem need to be kept in good condition. That cap design appears to have been original equipment on numerous airplanes which were higher value than the 170.

First, welcome to the Forum!
I'd agree with Cessnut that your first step needs to be getting any paperwork that the FAA may have on your plane. Here's the place to get that. Hopefully the tank modification will be part of the STC.

The FAA database shows five STC's for metalizing the C-170 wings;
SA4-226
SA4-7
SA1-13
SA235SO
SA4-11

As these STC's were issued decades ago, I would be amazed if you were able to locate any of these STC holders. It might be possible to contact the appropriate ACO of whichever STC you have for your metalized wing to obtain whatever documentation they have on the conversion.

In addition to those Supplemental Type Certificates, there are two companies listed in the TCDS that offered the option of metalized wings for the C-170. Item 612 was by Birtcraft Engineering Co. and item 614 was offered by Met-Co-Aire. I believe the latter is still in business selling wingtips.

-Regarding the Shaw cap, I tried to find the Cessna part number cross reference. C156001-0102, -0106, or -0108 might be possible numbers.

-Air Safety Support International has the attached bulletin on these Shaw caps: Cessna also issued several Service Letters on what I believe are these caps:There's a guy who sells fluorosilicone o-rings for these caps online here. You can get them a lot cheaper at Aircraft Spruce. The American Bonanza Society recommends replacing these o-rings annually. Viton o-rings, p/n M83248/1-232 and M83248/1-010, would be superior to fluorosilicone o-rings. Search "umbrella valve" here for information on replacing the umbrella valve on your cap, assuming it has one. Although it doesn't specifically apply to this cap, Neal Wright has a lot of information on this umbrella valve here.

Thank you for the replies! I'm going to do some detective work and pursue this. Stay tuned!

Just a word of caution. If you are getting water in your fuel be extremely careful as the drains for getting that water out are not 100% effective. You can get water in the outer tank and there are no drains in those tanks. I had the same issue when I first got my plane and had an emergency landing as a result so please use extreme caution and take what ever steps needed to prevent water entry. Bill K

Here’s a pic taken at the Branson Convention in 2008 of Chief Production Test Pilot Mort Brown (100 year-old B-day the following week) standing beside Duane Shockey’s ‘48 C-170.

Notice that Duane has some water-resistant wing-covers over his fuel cap areas. The “ragwing” is notorious for allowing water into the tanks from rain and washing. Some folks put an upside-down tin cans over their caps….but here’s Duane’s more-elegant solution:

Just for fun….here’s Mort “back in the day”….(w/genuine aviator sunglasses instead)

The late John Frank of the Cessna Pilot's Association writes the following in Tech Notes 003,

... any operator who is continuing to use flush style fuel caps on a Cessna aircraft with bladder fuel tanks is both a fool and a person who will knowingly jeopardize lives. The combination of the flush style fuel caps that are prone to leak and the fuel bladders that can develop wrinkles that will keep contamination from getting to the sump drain is deadly.

Hyperbole perhaps, but it does stress the importance of preventing water from entering the fuel tanks.
AD 84-10-01 does not apply to your plane, but it does apply to other Cessnas with your Shaw flush style fuel caps. It calls for, among other things, following the fuel cap testing procedures in Cessna Service Bulletin SE 82-34. (It's noteworthy that this AD also applies to the C-190/195 which has fuel caps virtually identical to the stock 1948 C-170 fuel caps.)

The second item which that AD addresses is fuel drains. Cessna published SEB92-26 which called for additional fuel drains on several SE models. Within this Bulletin was Service Kit SK170-10 which gave instructions for adding a drain to the outer right tank on the '48 C-170.

Gary, this is all very useful (and sobering). I seriously appreciate this information.

n2582d wrote:The late John Frank of the Cessna Pilot's Association writes the following in Tech Notes 003,

... any operator who is continuing to use flush style fuel caps on a Cessna aircraft with bladder fuel tanks is both a fool and a person who will knowingly jeopardize lives. The combination of the flush style fuel caps that are prone to leak and the fuel bladders that can develop wrinkles that will keep contamination from getting to the sump drain is deadly.

Hyperbole perhaps, but it does stress the importance of preventing water from entering the fuel tanks.
AD 84-10-01 does not apply to your plane, but it does apply to other Cessnas with your Shaw flush style fuel caps. It calls for, among other things, following the fuel cap testing procedures in Cessna Service Bulletin SE 82-34. (It's noteworthy that this AD also applies to the C-190/195 which has fuel caps virtually identical to the stock 1948 C-170 fuel caps.)

The second item which that AD addresses is fuel drains. Cessna published SEB92-26 which called for additional fuel drains on several SE models. Within this Bulletin was Service Kit SK170-10 which gave instructions for adding a drain to the outer right tank on the '48 C-170.