Thorp Air Command - T18.net

Tony Bingelis, Firewall Foward...fuel flow test.

RB

Dick: Did not mean to mislead you. The fuel flow test in the book is not aircraft specific (T-18, RV, etc), but is very detailed on how to do one for a gravity or boost pump system. Page 175-177. He states to establish an "extreme climb angle." No exact number is given, so what is an "extreme climb angle?" I'll let the others chime in here with a number/numbers, but 30 degrees and above is a number I would use. BTW...EAA, I believe had Tony's books for 20% off. Not sure if is still valid ?

RB

I use about 15 degrees nose high for the fuel flow test. 30 Degrees would considered an aerobatic attitude. I doubt many Thorps can use more that 10 to 12 degrees nose high on a go-around or initial climb out after take-off. I don't really measure the attitude. Just put the tail in a ditch or something to get what you think would be an aggressive climb attitude.

Gary Green

Anyone ever put fuel injection on an 0-290GPU? I hear that some experimental systems are made that are good. Just bought an unconverted GPU and am making up a new engine and thinking of running fuel injection.

Brent Schultz
N6CM
Corona Airport

Did the test yesterday on MLM.

16 degrees nose up, 13 USGPH for the last gallon. (Failed.)

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In theory, theory and practice are the same. In practice, they are not.

Hi Dick,

Wouldn't you want the last gallon to flow the slowest?

Jim Mantyla :-)

remember the gravity feed "Rules",

1.) No sharp turns i.e. avoid 90 deg fittings, stick with 45 deg (AN823) or straight (AN816)
2.) 3/8 lines throughout, no reductions or increase in hose size. No bushings, reducers etc, all components should accept a #6 pipe thread or a #6 flared tube.
3.) #6 fittings only
4.) No check valves, fuel flow transducers etc.
5.) K.I.S.S.! The system should follow as direct a path from the tank to the carburetor as possible no sharp turns, loops etc.
6.) carefully size the lines, hoses such that they have the necessary flex component but at the same time have no excess length, as direct a path as possible.

The system should look as follows. All fittings are either AN816-6 or AN823-6

tank
fitting
hose (no solid line)
fitting
shut off valve
fitting
line or hose
fitting
gascolator
fitting
hose (no solid line)
fitting (AN822-6 90 deg may be necessary here)
carburetor

I can think of one particular Thorp right now that has "gravity feed issues". I took a peek inside and counted <4> 90 fittings before the fuel even made it through the firewall. Gravity feed DOES work but you have to build it right. Think about driving around the block (ignoring traffic rules of course), at every turn, you come to a near stop then turn. Now think about a race track ... don't really have to slow down to make that turn, fluids work the same way.

Hate to harp on this but if you have multiple 90's in your system you may consider a re-work or a fuel pump, it would not surprise me if your flow was less than desirable with min fuel.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

No wonder!

tank
bushing/finger strainer (3/8 to 1/4 NPT)
M-M fitting (1/4 NPT)
shut off valve (1/4 NPT)
fitting, 90, (NPT to Hose)
3/8 hose
Hard 3/8 line with compression fitting thru firewall
fitting 90 degree 3/8 comp to 1/4 NPT
bushing (3/8 to 1/4)
gascolator
bushing
fitting, 90, 1/4 NPT to dash 6
hose
fitting, AN822-6 90 deg
carburetor

Note that the 1/4 NPT fittings have a 9/32" thru hole!

_________________
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In theory, theory and practice are the same. In practice, they are not.

That will do it!! Let's hear those results when you clean it up ... that is unless you are going to install a fuel pump and "cheat" [;)]

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

No. I like gravity. It keeps me grounded.

I'd be surprised if my finger strainer was any different than what most folks have. (ie a coarse screen soldered into a 3/8 NPT brass bushing.) With a 1/4 NPT female outlet one has no choice but to wind in a 1/4 NPT male of some sort, so right off the bat you begin with a 9/32" restriction. Do people drill this first fitting out to 3/8? It appears to be doable.. there's lots of material.

_________________
_________
In theory, theory and practice are the same. In practice, they are not.

Good point Dick, the outlet on the tank is 1/4 NPT to begin with. Guess that's a necessary evil (along with the AN822 at the carb). Just remove all the other restrictions and see what you get. I wouldn't change the tank flange.

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

Dick,

The tap drill size for a 1/4NPT is 7/16". It will not leave much meat between the hole and the root of the thread.

Jim Mantyla

All this talk made me decide to test my system as per Lee's suggestion.
I made it almost all the way around the block before getting a ticket for having an airplane on the road - Who knew?!

you must have forgotten to fold the wings!

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

I'm taking no chances. 1/2" mini-shut off came yesterday. I'm going to plump as much 1/2" as I can to minimize losses.

Incidentally... almost all the airplanes I looked at in KD had valves coming right off the fuel tank. Perhaps this isn't as big a deal as implied? Hanging the valve off the tank sure simplifies the whole system.

_________________
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In theory, theory and practice are the same. In practice, they are not.