Maximum Sustainable Climb Angle

Hi All,

I'm on final approach to completion of my 7A. I was reading on Bret's post about fuel flow testing and one of the tests was to test flow at 5 degrees higher (if I remember correctly) than the maximum sustainable climb angle. One little problem is that my bird has yet to fly. So no hard data on the maximum climb angle........here's what I have.....

IO-360 Angle Valve (200HP)
Catto 3 blade cruise prop
I'm expecting empty weight to be around 1100 lbs (no paint, all fairings and interior installed - basically final form without paint)

What would be a guesstimate for starters of a maximum sustainable climb angle for this configuration? I'm assuming that the angle would be a little lower with a fixed pitch prop. I'm also assuming that I need to perform fuel flow testing prior to first flight. Correct?

Much Thanks!

I tested at 15 degrees

Ben

I bottomed the tail on the ground and still passed the test with flying colors. Did the test when living in ABQ. Don't just test based on what a catto prop will do. Don't worry test it hard. You'll be impressed and build confidence in your work by testing beyond minimums.

Sounds logical to me! I really don't think I'll have any problems but will test it that way. Thanks for your input!

Just yesterday I was perusing some of my Dynon Skyview datalogs to look at my climb angle and rate of climb on a recent departure. My longtime average for a Vy climb looks like 17 degrees pitch, and the max I've hit was 20 degrees briefly. At Vy and solo weight in my airplane that equates to 1600-1700 and 2100 fpm respectively.

The high climb rate I saw was in Lubbock on Tuesday of last week, the wind was straight down the runway at 14 knots and at 800 feet it was 53 knots. I translated all that additional airspeed into additional climb to get up quickly and out of the way of a SWA jet turning onto the runway behind me.

Hey Greg!

We've got to find some good use for all of that West Texas wind!

Are you flying a fixed pitch propeller?

airguy said:

Just yesterday I was perusing some of my Dynon Skyview datalogs to look at my climb angle and rate of climb on a recent departure. My longtime average for a Vy climb looks like 17 degrees pitch, and the max I've hit was 20 degrees briefly. At Vy and solo weight in my airplane that equates to 1600-1700 and 2100 fpm respectively.

The high climb rate I saw was in Lubbock on Tuesday of last week, the wind was straight down the runway at 14 knots and at 800 feet it was 53 knots. I translated all that additional airspeed into additional climb to get up quickly and out of the way of a SWA jet turning onto the runway behind me.

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Isn't that number actually climb angle, not climb pitch?

If you add the angle of attack of the wing the deck angle (of your longerons) will be higher.

drone_pilot said:

Hey Greg!

We've got to find some good use for all of that West Texas wind!

Are you flying a fixed pitch propeller?

Click to expand...

IO360 and Whirlwind composite constant speed.

az_gila said:

Isn't that number actually climb angle, not climb pitch?

If you add the angle of attack of the wing the deck angle (of your longerons) will be higher.

Click to expand...

It's the pitch angle indicated by the Dynon ADAHRS system, and looking back at it just now it indicates +1.6 degrees sitting on the ground on the gear, and was calibrated 0 degrees with the longerons level, so subtract 1.6 degrees from my indication for the actual aircraft pitch with respect to the gear, or not for respect to the longeron. But to answer your question, that's actual aircraft pitch with respect to local gravity, not a climb gradient. For the purpose of this discussion, with respect to fuel flow in a climb attitude, actual aircraft pitch is what you want. Climb gradient is irrelevant to the fuel pump trying to push uphill to the engine, climb pitch is all it knows.

On an injected engine, where are you tapping into the fuel line to test flow?

I used 25 deg for the test. At 70 kts, 195 hp O-375, and a 3 blade catto, the view outside feels very much like this, but I've been having too much fun to actually check the pitch angle...

airguy said:

IO360 and Whirlwind composite constant speed.



It's the pitch angle indicated by the Dynon ADAHRS system, and looking back at it just now it indicates +1.6 degrees sitting on the ground on the gear, and was calibrated 0 degrees with the longerons level, so subtract 1.6 degrees from my indication for the actual aircraft pitch with respect to the gear, or not for respect to the longeron. But to answer your question, that's actual aircraft pitch with respect to local gravity, not a climb gradient. For the purpose of this discussion, with respect to fuel flow in a climb attitude, actual aircraft pitch is what you want. Climb gradient is irrelevant to the fuel pump trying to push uphill to the engine, climb pitch is all it knows.

Click to expand...

Thanks.... a quick measure and calculation on my -6A gives just about 15 degrees longeron angle if I lower the tail so the tie down loop hits the ground.

Sounds just about perfect for the needed electric pump fuel flow test at climb angle.

drone_pilot said:

On an injected engine, where are you tapping into the fuel line to test flow?

Click to expand...

You'll need to pull the line where it connects to the fuel servo and check the flow at that point, and at the same height above level ground as the servo.