I’m posting this as a separate topic because in the visit it came to my attention that the Illustrated Part Catalog (IPC) did not specify a pump at all.
Looking thru the IPC I found the individual listings for “lines” to and from the pump and check valve..... So clearly the IPC recognizes the existence of the pump.... (page 62/63)
The “engine installation” (Fig. 34) shows the routing of the lines and location of the associated check-valve...and provides the Part Number for that check valve (and a discussion in these forums also provides the superseded part number S-XXXX).... but the “engine installation” does not show the pump itself.
This is a troubling oversight in my view and MAY be a reason that ‘48 170 Owners are sometimes surprised to find they’ve been operating and IA’s often OVERLOOK the need for the pump, check-valve, and associated plumbing on these models. The need for the pump and check valve for the “straight” 170 is documented in the Type Certificate Data Sheet (TCDS) under ‘Required Equipment”, Item 104.
WHY the pump is not listed in the IPC under “Engine Installation” may be due to the orientation of the “view” of the engine which shows only it’s left/port side. That illustration does show most of the lines and the check valve (pg 62, Fig 34, Items 33/34) but FAILS to show or mention the pump part number or model number.
Looking at the TCM IPC X-30014 also fails to mention or illustrate the pump. Under “Accessories” other items such as starter, generator, alternator, etc. are addressed....BUT NOT THE PUMP. Why? I suspect because it is not an Engine Part...it is an AIRFRAME item...peculiar only to THIS airframe.
All this revolves around the Fuel System design of the ‘48 170 which is a derivative of the 120/140 airplanes and the fuel lines routing from the fuel tanks passes through the FORWARD doorposts. This means that when the engine fuel-supply requirements are at the MOST... such as in a rejected-takeoff / go-around... or in an obstacle clearance-climb... the fuel must travel UP-HILL to reach the FWD doorposts before descending down-hill to the gascolator and carburetor. This routing reduces fuel-pressure (“head-pressure”) below certification requirements (CAR3).
The PUMP is intended to guarantee sufficient fuel supply to maintain the required fuel-flow during that high angle-of-attack and high-fuel-demand of the engine.
The CHECK-VALVE is in the system to provide an alternate route for fuel via gravity-flow should the pump fail in-flight.
Later A and B models of this airplane solved this issue by routing the fuel lines down the AFT doorposts to improve gravity-flow of the fuel. Since the later airplane does not require a pump, some operators might be under the misimpression that the pump was no longer needed.... without understanding the differences in fuel routing of those later models.
If you own a ‘48 170 there is no approved method of removing that pump and check valve and associated lines other than to gain approval for complete re-routing of the fuel system supply lines. Field Approvals are difficult. So how and where do you find that pump?
A call to Aircraft Spruce customer service provided the answer. It is Spruce Item 05-02557 and Tempest PN: 40585
(This pump was originally an AC mfr’d part, PN: 9867. Don’t know why Cessna couldn’t see fit to list it.)
NOTE THIS IN YOUR IPC’S!
From another post discussing “Bruce’s Sleuthing”, brought me to search for availability of the check valve and found the MSC source no longer available. Using a bit more searching I found that (of all places) Amazon offers it but also says “out of stock”. Finally Success ( in steel): at Grainger! For $462... https://www.grainger.com/product/PARKER ... alve-20JR5
The various identification/part-nos are : Item #20JR52, Mfr. Model #453-1/4S2-6, UNSPSC #40141608
