Fuel pump or no fuel pump

[ghostflyer]

I am having trouble understanding why people are going to great lengths to remove their fuel pumps . They are even refitting their fuel lines with a larger diameter fuel line . I have a engine driven fuel pump, and a electrical fuel pump. Their failure rate is very low . If my aircraft is sitting out in the hot sun for some time after a long flight and is heat soaked in the engine compartment it will not start without the electric pump on. Yes you can prime it but it needs that constant flow of fuel. All,the Cessna models require a mechanical pump,and most a additional electrical pump. So please ,enlighten me .

[GAHorn]

I am having trouble understanding why people are going to great lengths to remove their fuel pumps . They are even refitting their fuel lines with a larger diameter fuel line . I have a engine driven fuel pump, and a electrical fuel pump. Their failure rate is very low . If my aircraft is sitting out in the hot sun for some time after a long flight and is heat soaked in the engine compartment it will not start without the electric pump on. Yes you can prime it but it needs that constant flow of fuel. All,the Cessna models require a mechanical pump,and most a additional electrical pump. So please ,enlighten me .

“All” the Cessna models do NOT require a fuel pump. Fuel injected models do by necessity as do low-wing models, ...but, In the case of the 170, only the ragwing requires a pump. It is NOT due to the need for larger plumbing. (The plumbing is the same size). The reason is the ROUTING of the plumbing.

CAR3 required that the fuel system provide 150% of the engine fuel-demand at takeoff/full-power, (there was also a psi minimum requirement, 4 psi, IIRC.)
The routing of the ragwing fuel system takes the fuel from the tank and runs it toward the engine via the forward doorpost. This means that at full-power/climb the fuel must travel UPHILL to the forward doorpost before getting down to the gascolator/engine, and that did not meet the requirement. So a fuel pump was installed to meet the requirement, along with a check-valve to prevent the pump from pressurizing itself and also to provide a by-pass route for fuel in the event of pump failure.

The 170A/B models re-routed the plumbing down the AFT doorpost...which solved the problem and removed the complexity of the pump/check-valve. The unmodified Ragwing has NO APPROVAL BASIS to remove the pump/ck-valve that I know of.

[edbooth]

Am I sensing that this conversation is comparing apples and oranges? Continental / Lycoming ?

[ghostflyer]

No, it’s not about the comparison of 2 engines but about a degrading [my opinion of course] of a aircraft system. I know of 2 cases where the owners are hell bent on the removal of their fuel pumps . You can still get fuel vaporisation without pump / pressure . Once I had to open the drain at the gaslator and carburettor and run it for about a minute to get cooler fuel. It was about 125 deg in the sun and the aircraft was just too hot to get into . There was a coiled up firehouse near the refuelling point so I unwound some hose and turned on the water to cool the aircraft . To my horror it spluttered and a weak flow came out . It was full of rusty water . I unscrewed the nozzle to clear it. After clearing the nozzle the aircraft had a bath . [and so did we] . After take off and climbing to about 3 thousand feet our wet clothes felt great with the cabin air blowing on them.

[GAHorn]

With thousands of hours in single cessnas without fuel pumps I’ve never had a fuel vapor problem. The ONLY vapor problems I”ve ever had were aircraft with fuel pumps. (Usually fuel injected models)
This may be a chicken-and-egg matter: Fuel pumps are installed on aircraft that might be more subject to fuel-delivery problems? ... and the pumps are intended to improve fuel delivery?

[DuaneShockey]

Ghostflyer wonders why people are removing fuel pumps. I will only speak to 170s, 170, 170A, 170B, not to all Cessna's. I bought my 170 (rag wing) in 1976 (and still have it). There was no fuel pump on it. It was illegal !! The equipment list requires it. It flew fine and I saw late the "required item" on the equipment list. Had I gone into a prolonged steep climb I might have caused an air pocket in the fuel line that would have caused engine storage. I had to buy an engine driven pump, check valve and bend steel fuel lines to complete the required system. The pump being on the starboard front of the engine required the fuel lines to cross under the prop and then aft between the oil pan and the sheetmetal shroud near the oil pan. Very prone to chaffing if not installed clear of those 2 parts. After years of flying legally, I feared that a malfunction of that system that might cause a leak that would spew fuel in very hot areas, just below the cylinders and spark plug leads, and near mufflers. I was able to get the FAA to authorize an electric fuel pump on my firewall in the engine compartment. This kept any potential fuel leaks aft of the rear cylinders. The fuel lines are not 3/8" in the 170 as one person mentioned in an earlier response to the original message. The 170 has 5/16s" lines. After I got the 337 approved from the FAA I assisted many other 170 owners to do the same by getting 337s approved. I was able to get the company who made the original check valve to supply me with 10 or more valves for our members. Since that time the FAA no longer wants to approve such. Too bad that a method of increasing safety is no longer acceptable. Duane Shockey

[DuaneShockey]

I am wondering who "ghostlflyer" is. Duane Shockey

[GAHorn]

.... The fuel lines are not 3/8" in the 170 as one person mentioned in an earlier response to the original message. The 170 has 5/16s" lines....

Duane, as an owner of a ragwing of so many years, especially as one so deeply involved in the mx of your 170 as we all know you are, I have to wonder about this statement.
The reason I question it is because I once believed the 170 had smaller 5/16” lines as well. But many many years ago when I posted that ... I was caught unawares by another member (who I also knew professionally as a very experienced AP/IA who also owned a 170/ragwing) and he corrected me by informing me how surprised he was that I’d posted such because he thought I knew better.... that 170/ragwings had the same size fuel lines as later models.... 3/8”.

I checked with others and the IPC and sure enough, the fittings are -6D on the main fuel lines, which are for 3/8” lines. (There are places in primer lines, etc. of course all the way down to -2 fittings, but the main lines/fittings all call for -6.)

Can we investigate this further and come up with a definitive answer from you ragwing owners? ...and also figure out why the IPC calls for 3/8” fittings?

(And I hate to “out” ghostflyer, but you’ve met him at conventions in Deming and Cody. David Nelson from the land of Oz led us in a rousing rendition of “Waltzing Matilda” at Cody, and came accompanied by a beautiful native girl who goes by “Roz”.

[ghostflyer]

My singing is getting so bad ,I might not be asked to sing again .[hint] . AND I am not going to practise .

[gobrien]

Since that time the FAA no longer wants to approve such. Too bad that a method of increasing safety is no longer acceptable. Duane Shockey

Hey Duane,

I am renovating a ragwing in Ireland (formerly N4180V). It will no longer be certified; it will go on the EI- register with an IAA permit to fly. It appears this aircraft previously had your electric pump 337 mod although after her incident with an airport sign, the engine was sold off by the insurance company so I'm having to start over with an early 172 O-300B. Anyway, as the FAA is not involved I can put back the electric pump mod, in fact I've bought the parts already. Before I do I would love to know did the FAA ever give any reason why they stopped allowing this mod on a 337? Especially was there a technical reason?

Thanks,

Gareth.

[hilltop170]

Duane-
With your electric pump mod, will the electric pump bypass fuel thru itself in case of failure? Or did you plumb-in a bypass/check valve to allow for bypass in case of failure?

[DuaneShockey]

George Horn in Tex, Gareth in Dublin Ire, David Nelson in Australia, I'll try to answer all questions here. I don't go on the forum as much as many of you do. If you want quick response, my e-mail address is in the directory. I will be checking my fuel lines at the tank outlet and in the belly at the shutoff valve to see if they are other than 5/16" --- I do have the -6 fittings in the engine compartment. The FAA made the decision after my 337 (field approval) was accomplished to not allow alterations to fuel systems across the board, the way I heard it. I guess that would have been for GA small aircraft of standard category ?? It was not a decision focused on the 170 ragwing situation. As I was told it was a "shotgun approach" to alleviate responsibility for the FAA. I believe electrical systems were another target. Yes, I did put a check valve in my system with the electric pump which caused for the fuel routing to be similar to that of the engine driven pump routing. But, with the electric pump on the firewall not needing the solid steel fuel lines coming aft from the pump that was on the engine originally. If someone has a 170 (ragwing) with 3/8" fuel lines from the tanks I would have to wonder if they replaced original 5/16' lines. Again, I will check my lines to see if I have been making false statements for years. DuaneShockey

[gobrien]

Thanks Duane!

Based on their shotgun approach, they would really hate my electrical system. I started with one of Bob Nuckoll's designs and modified from there so it doesn't even vaguely resemble the original!