The Ragwingl 170 Fuel Pump Question, once more...

[boydkl]

in October 2014 48RagwingPilot commented that he could not find any instance where anyone had obtained a field approval (337) for removal of the fuel pump on a C170.
After several hours of my own searching the postings for the last few years, it appears that a C170 which has an engine driven fuel pump in its Type Certificate Data Sheet must have one installed, in order to be compliant.
Or a 337 must be used to get approval to replace the engine driven fuel pump wwith an electric one.(but I didn't see where anyone had done that)
I see that a 337 was approved by the Seattle FSDO to remove the engine driven fuel pump AND reroute the fuel lines for 48RagwingPilot in 2015.
WoW ! CONGRATULATIONS!!!
I Just want to be sure I didn't miss anything. Thanks

[GAHorn]

You didn't miss anything!

The ragwing REQUIRES A FUEL PUMP AND CHECK VALVE to be legal. There is no alternative presently. (One airplane did obtain approval on a one time basis but no others are applicable. Forget about the electric pump idea.)

The reason for the pump is: The certification rule of the airplane required that the gravity system provide 150% of the required fuel flow at the most DIS-advantageous attitude which required the MOST fuel flow.. which happens to be steep climbing flight with maximum power.
The ragwing fuel system routes the fuel lines from the wing tanks to the FORWARD doorposts then down to the gascolator. This means that during takeoff/climb...the fuel...by gravity...must run UP HILL to the forward door post. The pump is required to provide the necessary fuel flow to overcome that up-hill travel.

The check-valve is a 1/4 psi valve which prevents the pump from feeding it's own pressure back to it's inlet.... while allowing fuel to by-pass the pump by gravity should the pump fail.
(By the way... the valves in many 170s are mis-assembled. They were built with a small spring inside them to assure positive check-action against back-flow.... but the spring is to be REMOVED when the check valve is installed in a C-170. These spring-removal instructions are often lost or overlooked and as time as passed on.... mechanics are not familiar with the system or the Service Letter instructions.

The pumps are available and not as expensive as one might think. The check valves are sometimes scarce, but they rarely fail and substitutes are available.

The modification to which you referred re-routes the fuel lines down the aft doorposts ... like the A and B models have.

[Bruce Fenstermacher]

I believe, but am not sure, the member Duane Shockey of CA has approval for either no pump or an electric pump. I could be mistaken. Any, Duane is a great guy and I wouldn't hesitate to give him a call and ask. Tell him I told you to call. Duane doesn't do the forums or much electronic communication so the phone is best. He's listed in the directory.

[boydkl]

Thank You for the quick response!
I think the person who ask me has decided to get rid of the electric auto pump and get an engine pump etc. in order to make it original and compliant.

[n2582d]

... (By the way... the valves in many 170s are mis-assembled. They were built with a small spring inside them to assure positive check-action against back-flow.... but the spring is to be REMOVED when the check valve is installed in a C-170. These spring-removal instructions are often lost or overlooked and as time as passed on.... mechanics are not familiar with the system or the Service Letter instructions. ...

George, Do you have a copy of this Service Letter? I've never seen it. Is it a Continental, Cessna, Parker, or AC Service Letter? Any chance of including it in the Maintenance Library?

[GAHorn]

I believe, but am not sure, the member Duane Shockey of CA has approval for either no pump or an electric pump. I could be mistaken. Any, Duane is a great guy and I wouldn't hesitate to give him a call and ask. Tell him I told you to call. Duane doesn't do the forums or much electronic communication so the phone is best. He's listed in the directory.

Duane is indeed the person who knows the most about this subject... and it was Duane... who informed me that no other ragwing will be allowed to perform the electric pump mod he has. Perhaps he'll chime in and remind us the reason for that matter.

[GAHorn]

... (By the way... the valves in many 170s are mis-assembled. They were built with a small spring inside them to assure positive check-action against back-flow.... but the spring is to be REMOVED when the check valve is installed in a C-170. These spring-removal instructions are often lost or overlooked and as time as passed on.... mechanics are not familiar with the system or the Service Letter instructions. ...

George, Do you have a copy of this Service Letter? I've never seen it. Is it a Continental, Cessna, Parker, or AC Service Letter? Any chance of including it in the Maintenance Library?

Here's a re-print of the email I received from Cessna Engineering... (He never sent the screen-print)

Subject: RE: Check Valve PN:475-GG-1/4D Follow-Up - Model 170 (1948)
Date: Wed, 18 Feb 2009 07:49:38 -0600
From: BKRodeman@cessna.textron.com
To: gahorn146ys@hotmail.com
No problem George. I have been called much worse.


Thanks for the info. We are on it.

By the way did you know that the engineering dwg. from 1948 tells the installer to remove the spring from the check valve at installation???


I will try to send you a screen grab of the print when I get a chance. I thought that was interesting.


Boyd

Subsequent to that email exchange I did receive another email in which Boyd stated a new/superceded part number is soon available: S4176-1
He indicated the new part will be mfr'd WITHOUT the spring. However my recent search does not find that number.