Fuel drain drip

How to keep the Cessna 170 flying and airworthy.

Moderators: GAHorn, Karl Towle, Bruce Fenstermacher

Post Reply
MT_Don
Posts: 26
Joined: Sat Sep 03, 2016 3:12 pm

Fuel drain drip

Post by MT_Don »

Hi All,
I see the old threads on replacing the wing tank drain, suggested to do both. My question is exactly what is the part #? I cannot find it in the 1948 service manual. It appears, it should be a CAV170. Anyone know for sure?
Thanks, Don in MT
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

Re: Fuel drain drip

Post by Bruce Fenstermacher »

Interesting the IPC for the A and B model show a AN814-4D plug which is 7/16-20 NF thread, no quick drain. A CAV-170 which has 7/16-20 thread is used.

I found in the '48 IPC the drain called for is a CPP100-2. This drain apparently had 1/8" NPT thread. A CAV-110 would be used for this thread and that is what some member with '48 tanks used according to old threads. So you likely have 1/8" NPT thread and need a CAV-110.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
MT_Don
Posts: 26
Joined: Sat Sep 03, 2016 3:12 pm

Re: Fuel drain drip

Post by MT_Don »

Thanks Bruce. I saw that part CPP100 but could find no connection to newer. I'll see if I can view a stamp on the side CAV110, go from there. Don
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

Re: Fuel drain drip

Post by Bruce Fenstermacher »

The CAV-110 and the CAV-170 look the same. They just have the different thread. The size is usually stamped on a flat of the nut.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
User avatar
sfarringer
Posts: 309
Joined: Wed Jan 12, 2005 10:49 pm

Re: Fuel drain drip

Post by sfarringer »

My '48 does have 1/8 NPT for all fuel drain valves, and I know of at least 3 other '48's that also have this thread.
This conflicts with the charts that some fuel drain valve suppliers use, which claim that the fuel tanks have 7/16-20 threads (which is true for the 170A and 170B I believe).

Also, on my airplane, I need to use the flush valves, rather than the CAV-110, due to clearance with the door as it swings open. This may not be necessary on all '48's.
Ragwing S/N 18073
n3833v
Posts: 857
Joined: Tue Apr 23, 2002 6:02 pm

Re: Fuel drain drip

Post by n3833v »

Our 48 needed the short 1/8" pipe threaded for door clearance also.

John
John Hess
Past President 2018-2021
President 2016-2018, TIC170A
Vice President 2014-2016, TIC170A
Director 2005-2014, TIC170A
N3833V Flying for Fun
'67 XLH 900 Harley Sportster
EAA Chapter 390 Pres since 2006
K3KNT
MT_Don
Posts: 26
Joined: Sat Sep 03, 2016 3:12 pm

Re: Fuel drain drip

Post by MT_Don »

I was able to see the side stamp. It is a CAV-110. Thanks for all the inputs! Don :)
User avatar
n2582d
Posts: 2808
Joined: Mon Apr 29, 2002 4:58 am

Re: Fuel drain drip

Post by n2582d »

Like the stab attach angle slots or the bend in the upper door hinges we could go on another quixotic quest to determine when Cessna switched from 1/8” NPT threads to 7/16-20 threads for the sump drains. The ‘48 C-170 IPC calls for p/n CPP100-2 on the right wing on fig. 7-4 and next to the gascolator on fig. 38-36. Cessna inadvertently left it off the left wing illustration on fig. 3 but later corrected this oversight in the revision page. The Curtis Cessna single engine application chart crosses this with their CCA-2100 or CCA-2800, both of which are 7/16-20 threaded valves. Cessna published AK150-82E and later SK150-69, both of which call for installing Cessna sump drain valves p/n S2106-2 which again is a 7/16-20 threaded valve as seen in this Saf-Air cross-reference chart. It’s clear that Cessna or the aftermarket suppliers such as Curtis or Saf-Air are unaware that at least some of the ‘48 170 tanks have a 1/8” NPT drain port. I found the most useful reference chart for locating a flush 1/8” NPT valve to be on McFarlane’s website.
Gary
Post Reply