Long High angle climbs

[TroyBranch]

Have any of you tried continuous high angle climbs, like 70mph indicated for long periods of time less than half fuel solo?

My usual routine would be climb hard and I found that after a minute or so in the climb the engine would not be quite as smooth so I just pulled the throttle a touch. That always fixed it. I figured it was just the modified carb set up on the 340 that was causing that. Pulling mixture did not help and just rose EGTs to a level that I would not except.

Yesterday I figured I would leave the throttle in and see what happened. Full rich and continuous climb I would start to see a slight decay in fuel flow from high 12's to low 12's and roughness would start. (Flying above 5000ft) Drop the noes a touch, it would stop, pull the throttle a touch it would stop. Level flight it would flow over 13gph and smooth the whole time.

Two people on board, full throttle smooth the entire time in the climb as I just cant get those really high climb angles.

I think it is a combination of two things, the carb does not like the high angle attitude as the float is not doing a proper job and with lower fuel in the wing, it cannot provide enough head pressure for the fuel demand. I did a flow test before first flight but I know I could never set the plane up as high as angle it can do solo. Who new it could climb so steep

Have anyone else tried this? Just wondering if I should be hunting for an underlying issue.

Thanks

[aeroaddict]

How long is a 'long period of time' in your climb. I climb hard at times but I wouldn't guess for more than a minute or two.

I usually fly frequently and can try to duplicate your observations.

What carb do you have on your plane?

[TroyBranch]

I would say a minute or two as well. With my 1/4 tanks on the last flight when I tested it only took about 60 sec to start getting less smooth climbing at 70. Once passing through 6000ft from a 3500ft take off it got rough, pull the throttle a touch and dropped the nose a touch and smooth again. I plan to review the logs when I get time. I just filled it up and I will try the same thing with full fuel, I don't recall an issue with full fuel as I could not climb at such a steep angle.

The engine was shipped in 2016. The engines before had a carb that would just not run smooth at full throttle I thought. I think they made changes to the design to solve that. I was told that before I started building so my memory has no detail of it.

[aeroaddict]

I believe you are correct in regards to the carb issues on earlier models.

I recieved my motor in late 2018 and it has the Avstar -4PA carb. Which tanks do you have; extended or standard?

I'll probably fly tomorrow but I have half fuel on board.

[Daveembry]

Troy,

Check out this Mike Busch article. I remembered reading it years ago where he talks about partially shutting the throttle. Specifically, it’s on page 3 (ironically on the same page as a Cubcrafters ad! Haha)

https://resources.savvyaviation.com/...ugh-engine.pdf

I would say a minute or two as well. With my 1/4 tanks on the last flight when I tested it only took about 60 sec to start getting less smooth climbing at 70. Once passing through 6000ft from a 3500ft take off it got rough, pull the throttle a touch and dropped the nose a touch and smooth again. I plan to review the logs when I get time. I just filled it up and I will try the same thing with full fuel, I don't recall an issue with full fuel as I could not climb at such a steep angle.

The engine was shipped in 2016. The engines before had a carb that would just not run smooth at full throttle I thought. I think they made changes to the design to solve that. I was told that before I started building so my memory has no detail of it.

[aeroaddict]

Interesting, thanks. Next time I fly, I'll climb the plane like a home sick angel and see what happens.

[aeroaddict]

Flew this morning.

OAT 60F, 1/3 fuel, DA 2300, climbed 68mph, full rich at WOT for 2 mins. No issues, no loss or degradation in power. EGT/CHT all within limits.

[TroyBranch]

Thanks for doing that. I guess I now need to figure out what is going on....

I will try at full fuel and see if it makes a difference.

Do you remember your fuel flow?

Flew this morning.

OAT 60F, 1/3 fuel, DA 2300, climbed 68mph, full rich at WOT for 2 mins. No issues, no loss or degradation in power. EGT/CHT all within limits.

[aeroaddict]

Fuel flow? I'm pretty sure the fuel was flowing. That turn thingy below the accelerator knob said 'both'

While I have the Skyview HDX system, I kept the plane light and simple and do not have the red cube.

[TroyBranch]

Are you saying I should just remove the red cube to solve my issue.

In all seriousness that could be something.....just need someone with the red cube to do the same test.

I really think there is a flow restriction issue, why else would flow gradually drop and engine start to not run smooth.

I need to do this full fuel test.