48 fuel pressure

[n3833v]

Mine is 18691 and has a pump that didn't work for about 4 years till I figured out it wasn't working. I was

John

[GAHorn]

Poncho73 wrote:
My pump was removed sometime in the 70's.

your serial number better be 18250 or higher.

Tom,
Why sn 18250? Per TCDS all 48 170's have a fuel pump.
Just curious
Thx,
Dan

SN 18727 was the last straight-170 "ragwing", according to my information. SNs 18728 and 18729 were 170A-model prototypes, which re-routed the fuel tank supply lines down the aft doorpost (instead of the 170's fwd doorpost), which relieved the requirement for a fuel pump.

From time to time this discussion comes up and some 170 owners have inquired:
1- as to how the mechanical fuel pump can be removed permanently. (Ans: It is required equipment without another approval basis.)
2-where to obtain the STC to replace the mechanical pump with an electric pump. (Ans: Only a few were approved for this and the STC is not available to subsequent airplanes. Duane Shockey has the electric pump and is probably the most knowledgeable about that topic.)
3-where/which/what part no. is the check valve to be used and where to obtain it. (Ans: the original unit may not be available but a suitable substitute (per AC23-27) is the ACS 10630 available from Spruce: http://www.aircraftspruce.com/catalog/a ... ckkey=6903

It was only a couple years ago that the "single engine line fuel engineer" at Cessna called me to inquire as to "why" the check valve was required and where to obtain it?" No kidding. Turned out he was working on the Columbia aircraft for Cessna. It seems that Cessna deliberately disposed of all their drawings regarding the system after the 1986 shutdown of the single engine line and none of the "old timers" were around to explain it to him.
He assured me that Cessna would be re-supplying this check valve, but when he called me back the following year the price hovered around $600 each.

NOTE: Anyone needing this valve should also know that the original valve was mfr'd by Parker with an internal spring to create a "cracking pressure" limit. The installation instructions of the check valve specified the valve was to be disassembled and the spring removed before installation. (If the spring is not removed then fuel may not flow adequately in the event of fuel pump failure.) This removal was generally performed by Cessna when they supplied replacement valves but owners often were unaware of it when they sourced (original PN) Parker #475-GG-1/4D valves from other sources than Cessna. (And keep in-mind that current Cessna employees know nothing about this matter. Even if you were able to obtain NOS check valves, the device will likely still contain the spring which is to be removed.)

[T. C. Downey]

IAW type certificate 799

In addition to the pertinent required basic equipment specified in CAR 3, the following items of equipment must be installed:
Landplane: Items 1(a), 103, 104, 201(a), 202(a), 204(a), 402(a). Skiplane: Items 1(a), 103, 104, 204(a), 208(a), 402(a), and (e) or (d).

Engine and Engine Accessories - Fuel and Oil Systems

104. Fuel pump (Continental No. 40585)

The 18250 number was a typepo

[Poncho73]

My pump was removed sometime in the 70's.

your serial number better be 18250 or higher.

18527

[T. C. Downey]

My pump was removed sometime in the 70's.

your serial number better be 18250 or higher.

18527

not high enough to not require a pump.

[Poncho73]

I went through the old US logs and I can't find any details regarding when and why the pump was removed. It has no check valve in the fuel system either. When the engine was overhauled in 1980 there was no fuel pump, the engine was overhauled again in 2001....no fuel pump either. The best I can estimate it has flown 2200 hours without a fuel pump or check valve....over to you George. FYI I searched my spares box this afternoon and I found an old Parker check valve and dusty old fuel pump...here we go..

[T. C. Downey]

FYI I searched my spares box this afternoon and I found an old Parker check valve and dusty old fuel pump...here we go..

Shake the check valve see if you can hear the ball rattle.
Fuel pump can checked for operation simply be submerse it in fuel and work the lever see if it pumps.
is there any fuel lines there too? it requires 3 special lines.

[Poncho73]

FYI I searched my spares box this afternoon and I found an old Parker check valve and dusty old fuel pump...here we go..

Shake the check valve see if you can hear the ball rattle.
Fuel pump can checked for operation simply be submerse it in fuel and work the lever see if it pumps.
is there any fuel lines there too? it requires 3 special lines.

Everything is there, including the 3 special lines. As I ponder the thought, is there really any need for these to go back in? I mean other than meeting the TC spec, from a functional stand point I can't see the need for a reinstall. If I sell I would need to reinstall. Your thoughts...I'm looking for the practical answer not requirements answer.

[T. C. Downey]

I'm looking for the practical answer not requirements answer.

I flew 2623V for a long time with out one installed, never had a problem.

[Poncho73]

I'm looking for the practical answer not requirements answer.

I flew 2623V for a long time with out one installed, never had a problem.

My finding exactly, I believe the aircraft has at least 2200hrs of operation without one. The fuel flow checks I have done seem to confirm my feelings. Notwithstanding all of this I'm continuing to check with a few other people for there thoughts, thanks

[GAHorn]

I'm looking for the practical answer not requirements answer.

I flew 2623V for a long time with out one installed, never had a problem.

My finding exactly, I believe the aircraft has at least 2200hrs of operation without one. The fuel flow checks I have done seem to confirm my feelings. Notwithstanding all of this I'm continuing to check with a few other people for there thoughts, thanks

The rules for certification of the aircraft required that fuel must be delivered to the engine at 150% of the rate req'd at the most disadvantageous attitude. A fuel pressure spec was also req'd which I believe was 4" water column, but don't quote me on these specs as it's been awhile....the point is that the specifications req'd were not met with the fuel system design which at takeoff/climb meant the fuel must travel up-hill to the forward doorpost.
I seem to recall that most operators who deleted the pump claim they've experienced no ill effects, however I also have stuck in my memory a couple of accident reports in which the engine partially failed during balked-landing/go-around events.

The possibility of injury to myself and others and the associated sense of responsibility would convince me what to do.

It's a simple and not overly-expensive matter to comply with the design of the aircraft and if it were me, I'd have the pump and check valve installed. The plumbing is easily fabricated common hardware and listed in the IPC.

[T. C. Downey]

Until you can show the certification requirements for fuel flow, (which I have never been able to find) it will remain a OWT in my opinion. and the accident data site does not show any accidents cause by low fuel flow in the 170.

[Poncho73]

Until you can show the certification requirements for fuel flow, (which I have never been able to find) it will remain a OWT in my opinion. and the accident data site does not show any accidents cause by low fuel flow in the 170.

Yes, I doubt Cessna did any instrumented aircraft testing for fuel flow on a 48 170...LOL. The fuel flow theory is likely just that, a theory. The fuel pump was likely an old school requirement. There is no way that engine, within a normal flight envelope, needs a fuel pump. Regardless I will respect the requirement and will dig out the parts. Thanks

[GAHorn]

Here's one source of data: "For gravity-flow fuel systems, the fuel flow rate must be 150
percent of the takeoff fuel consumption of the engine."

From: https://www.faa.gov/regulations_policie ... a_ch14.pdf

The basis is FAR 23.955 — Fuel flow.
(a) General. The ability of the fuel system to provide fuel at the rates specified in this section and at a pressure sufficient for proper engine operation must be shown in the attitude that is most critical with respect to fuel feed and quantity of unusable fuel. These conditions may be simulated in a suitable mockup. In addition—

(1) The quantity of fuel in the tank may not exceed the amount established as the unusable fuel supply for that tank under §23.959(a) plus that quantity necessary to show compliance with this section.

(2) If there is a fuel flowmeter, it must be blocked during the flow test and the fuel must flow through the meter or its bypass.

(3) If there is a flowmeter without a bypass, it must not have any probable failure mode that would restrict fuel flow below the level required for this fuel demonstration.

(4) The fuel flow must include that flow necessary for vapor return flow, jet pump drive flow, and for all other purposes for which fuel is used.

(b) Gravity systems. The fuel flow rate for gravity systems (main and reserve supply) must be 150 percent of the takeoff fuel consumption of the engine.
...etc etc etc.

As for fuel problems after takeoff, this is a '48 ragwing fatal accident (pump status unknown...I doubt the NTSB even knows about the requirement):

NTSB Identification: ANC07FA037
14 CFR Part 91: General Aviation
Accident occurred Friday, May 04, 2007 in Wasilla, AK
Aircraft: Cessna 170, registration: N4217V
Injuries: 1 Fatal.

On May 4, 2007, about 1548 Alaska daylight time, a ... Cessna 170 airplane, N4217V, sustained substantial damage when it collided with trees during a forced landing after takeoff from the Wolf Lake Airport, Wasilla, Alaska. ....A witness reported that he saw the airplane depart on runway 19 at Wolf Lake. The airplane climbed to about 200 feet, and the witness heard the engine lose power. The pilot made a right turn toward the north, and descended toward a residential area adjacent to the airport. The airplane collided with several trees, and then the ground, next to a residence....

[3958v]

George if Iwas a betting man I would put my money on water in the fuel before a fuel pump issue. But not saying it could not have been a whole lot of other problems I just think water in the fuel is probably a more likly senario.