'48 Fuel pump one way valve

How to keep the Cessna 170 flying and airworthy.

Moderators: GAHorn, Karl Towle, Bruce Fenstermacher

User avatar
showe
Posts: 19
Joined: Sat Sep 30, 2017 8:08 pm

Re: '48 Fuel pump one way valve

Post by showe »

Bruce, here’s the dimensions.
76CC4392-C0AD-45CB-A023-6768D7F4CBB2.jpeg
Gary, looks like Parker on the label to me.
448116D3-5F86-4CA6-B4DA-F9282B952558.jpeg
Shawn
1948 N4039V SN 18358
User avatar
mike.bernath
Posts: 24
Joined: Mon Mar 26, 2018 5:56 pm

Re: '48 Fuel pump one way valve

Post by mike.bernath »

This is interesting. Can somebody confirm which way the actual valve should be oriented? The valve/slug orientation is what I am after.
User avatar
3958v
Posts: 543
Joined: Tue Apr 23, 2002 12:00 am

Re: '48 Fuel pump one way valve

Post by 3958v »

The valve allows fuel to bypass the fuel pump and flow to the carb in the event of a fuel pump failure. It stops fuel from returning from the pressure side of the pump back to the suction side of the pump. In all but the most unusual situations the 48 will run without the pump but it is required equipment. Bill K
Polished 48 170 Cat 22 JD 620 & Pug
User avatar
mike.bernath
Posts: 24
Joined: Mon Mar 26, 2018 5:56 pm

Re: '48 Fuel pump one way valve

Post by mike.bernath »

Which way does the actual bullet/check plug orient? I understand the purpose of it. Thanks.
User avatar
GAHorn
Posts: 20967
Joined: Fri Apr 12, 2002 8:45 pm

Re: '48 Fuel pump one way valve

Post by GAHorn »

If it has an "arrow" pointing toward the carb that would be a "clue". One might also gently blow thru it with your mouth to see which way it allows flow (towards the carb.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
3958v
Posts: 543
Joined: Tue Apr 23, 2002 12:00 am

Re: '48 Fuel pump one way valve

Post by 3958v »

Georges recommendation to gently blow thru the valve is an important step. The pressure of the gravity of the fuel in the line needs to open the check valve or a fuel pump failure will soon result in an engine failure. Bill K
Polished 48 170 Cat 22 JD 620 & Pug
User avatar
n2582d
Posts: 2808
Joined: Mon Apr 29, 2002 4:58 am

Re: '48 Fuel pump one way valve

Post by n2582d »

n2582d wrote: ...Frankly, that copper fuel pressure line, restrictor or no restrictor, makes me a bit queasy. If the line breaks with no restrictor there is a stream of pressurized fuel in the vicinity of the red hot exhaust pipes. With a restrictor it's probably a fine mist of pressurized fuel. Too vivid of an imagination I guess. I have never heard of NTSB reports where this has been an issue. But I have had 1/8" fuel primer lines break. ...
Here's an accident report on a C-195 where a copper oil scavenge line failed. The Aussies are queasy about copper fuel lines too.
AWB 28-007.pdf
(25.62 KiB) Downloaded 354 times
Here's what John Schwaner says about copper tubing:
Most tubing-failures on aircraft are caused by fatigue. Tubing on aircraft vibrates. How well your tubing endures when subjected to load reversals, impulses, and vibration is called "fatigue strength". Of the three popular tubing types (3003-0, 6061-0, 5052-0), 5052-0 has the best fatigue strength. Originally aircraft used soft copper-tubing. There is even some of this still around. Although copper was strong enough, it was replaced with aluminum and stainless tube because of the high fatigue failures of copper. For lower pressures, 5052-0 became the tubing of choice because it has the best fatigue strength of any of the non heat-treat aluminum alloys. ... Copper tubing on older aircraft should be removed and replaced with 5052-0 before it breaks. There is no warning when copper tubing breaks. One cannot "inspect" it and declare it ok. Another limitation on the use of copper tubing in aircraft engine compartments is that copper strength decreases rapidly with temperature. Some experimental and light-sport aircraft have hydraulic and fuel lines built with 6061-0 or 3003-0-tubing. Low ultimate strength and low fatigue strength provide a narrow safety margin in dynamic (vibration or impulse) applications. Take extra care in clamping and preventing tube vibration. The aircraft industry's long experience with copper tubing failures proved the importance of fatigue strength. 5052-0 has higher strength and higher fatigue strength at a small price difference. Both 5052-0, 3003 have the same Cold Workability Rating of A (easy to work with). 6061-T6 has a far lower rating of C. "It hasn't failed yet," was the attitude at NASA that essentially led to both of the Space Shuttle disasters; the complacency arises from skirting the line and surviving. But the law of large numbers will eventually get you.
Of course for those wanting to maintain the antique look of copper tubing aluminum lines just don't cut it. It would be easy to anodize these lines a copper color. Any metallurgists out there know how anodizing affects fatigue strength in aluminum?
Gary
Post Reply