Maximum climb angle

[Esser]

I need to do a fuel flow test before my final inspection at the maximum climb angle. What is everyone seeing for their max climb angle?

[jiott]

I don't know the actual Kitfox number, but it probably varies with your particular engine and GVW. I just used the FAA recommended angle of 25 degrees (better check this, my memory may be off).

[n85ae]

With IO-240B it's completely vertical, until I let off throttle, or the sky gets too
dark and full of stars and I lose track of the Earth ... :)

The 25 degree number seems reasonable.


I need to do a fuel flow test before my final inspection at the maximum climb angle. What is everyone seeing for their max climb angle?

[Hockeystud87]

With IO-240B it's completely vertical, until I let off throttle, or the sky gets too
dark and full of stars and I lose track of the Earth ... :)

The 25 degree number seems reasonable.

130 HP gets you unlimited vertical?

[airlina]

130 HP gets you unlimited vertical?

He's pulling you leg, Jeff's been known to do that.

[Hockeystud87]

He's pulling you leg, Jeff's been known to do that.

Thats not my leg.

[n85ae]

Not unlimited, at some point you run out of fuel ... Or lose directional control
due to lack of gravity.


130 HP gets you unlimited vertical?

[jonstark]

I need to do a fuel flow test before my final inspection at the maximum climb angle. What is everyone seeing for their max climb angle?

I just did my IV with Rotax 582 at 25.4 degrees and got 7.5 gph.
My DAR said that I should see 150% of take-off power fuel flow which would be 10.5 gph.

I asked John McBean and he replied with the following...




Do not have a published procedure..

Where did you get the 25.5 degrees ? Generally 15 Degrees if I remember the FAA guidelines..

Where is the 150% gravity feed requirement on a pump required system... or pressure system... It's not..

For a gravity feed system 150% is required.. for pump systems 125% for each pump system.. but technically you should have an aux pump.

Generally.. one can convert fuel to lbs.. and calculate 1/2 lb per horsepower. 582 is 65 hp.. so 32.5 lbs. fuel is 6.0 lb per gallon.. so 32.5 / 6 = 5.42 gallons * 125% = 6.775 gallons per hour..

Or.. HP / 12 = X 65 / 12 = 5.42 gph.

All that being said.. be sure the fuel system is clear of obstructions.. all going downhill and minimal bends.. there is also an approximate .02 psi of pressure at 30 mph on the pressure vent of the fuel tank.

Your only option would be to increase the inner diameter of the fuel line to increase the flow.

However, your 7.5 gph is adequate given the equation above. Hope that helps.


Fly Safe !!
John McBean
Ph 208.337.5111
www.kitfoxaircraft.com
"The Sky is not the Limit... It's a Playground"


John says I have a "boost pump required system".
The old build manual had no such requirement. When did that come about? Am I nuts not to have an electric boost pump?

jon

[jrevens]

Hi Jon,

To technically meet the letter of the law, according to 14CFR 23.955, you must have a minimum flow rate of 150% of full throttle fuel flow (at sea level would be the max. requirement) with a gravity system. With a fuel pump system the requirement is 125%. I believe Rotax says the 582 requires 8 gph at max. takeoff power? With a pump, that means you should have a minimum of 10 gph tested flow rate. 7.5 gph seems pretty low to me.

Not sure of the exact angle, but when I tested my 912 ULS installation, I got the mains up on a couple of car tire ramps. With 1 gal. in each wing tank, and 1 gal. in the header tank, I measured the flow rate at over 17 gals./hr. According to Rotax, the takeoff power requirement for my engine is 7.1 gal./hr.

[jiott]

John, where did you measure the fuel flow, right at the carbs, or just before or after the fuel pump? I measured right at the carbs at first and got around 7 gph. Then I measured just before the fuel pump and got a lot more. A fuel pump that is not operating has a lot of restriction to gravity flow thru it. It apparently is not zero, but may be just barely enough to keep the engine running at high power.

[jonstark]

I measured the fuel flow at the intake of the impulse pump. I have since then remeasured it with a deck angle of only 15+ degrees yielding similar results. The fuel shut-off valve is kinda tiny looking so will check flow before and after then at the outlet of the gascolator where the system goes from 5/16 in to 1/4 rubber tubing for the rest of the way.

I’ve decided to add a Facet non-shutoff pump. Parts on order.

Jon

[jrevens]

John, where did you measure the fuel flow, right at the carbs, or just before or after the fuel pump? I measured right at the carbs at first and got around 7 gph. Then I measured just before the fuel pump and got a lot more. A fuel pump that is not operating has a lot of restriction to gravity flow thru it. It apparently is not zero, but may be just barely enough to keep the engine running at high power.

Jim,

The flow rate I mentioned was right before the pump. I’m sure there is potentially considerable restriction through the pump. It was easy to disconnect at that point and direct that hose down into a measuring container, and I didn’t have a hose or tube in the hangar at that time to connect to the outlet. I’m thinking that many, if not most, people check it as I did, but it is not the best or a complete test of course. I would like to test after the pump sometime soon. Even if the flow rate is cut in half after the pump I will still have enough flow for full throttle “normal” operation, and that is measured without the benefit of tank pressurization from the vent tubes. Does anyone know what the actual flow restriction is in the latest pumps? Another thing to add to the equation is the recirculating line feeding back through an orifice at the point where the fuel line tees off to the carbs. That will probably decrease the potential flow rate to the carbs also.


Jon,

FWIW, I have 3/8” fuel line throughout my system with the exception of short lengths of 5/16” at each tank. I also have no flow sensors or additional pumps in the circuit, and all valves are full-flow ball valves.