Operational ceiling

[Farmboy]

Since I operate at sea level and really get over 3000 feet, thought I’d ask you guys with all the mileage.
In my Stromberg equipped no – lean C90 powered PA – 11…

What would be it’s operational ceiling, where you could still land and take off with an average load and typical runway length?

Pb


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[cubdriver2]

Pete my J4 is similar to what your flying, stroker with a Stromberg. Every thousand feet makes a difference. The same takeoff at my 1400' pond I can do at Island Bobs and I'm off 150' sooner. Twitchell Lk at 2100' adds 100' to what I do at my 1400' pond level or almost 250' longer then the Island. All at close to 70F, gets worse as temp and humidity go up. I got it up to over 10K once but it took awhile the last 3000'

Glenn

[JP]

A couple of years ago on a nice summer evening of larking about I got to thinking about density altitude (note: I live in Maine. The other day we had a density altitude of -3,700 at 470 ft msl). A friend had an instructor that used to ease the throttle back a bit on students for a takeoff to simulate density altitude. He would tell the student that this is what it's like to take off from a high density airport, etc. I decided to experiment with the Cub and see at what point the airplane would not have the power to take off. Actual density that day was about 1000 so I had a tiny bit of help in the simulation.

So, I made some takeoffs, reducing power each time around. I was pleased to discover that she would take off out of the grass and climb slowly with a good deal of power removed. I can't remember the exact rpm's but it was about 1700. You had to fly the wing a bit but it would climb out and the ground roll wasn't as long as one would think once she got trundling along.

On the reverse end of the spectrum a full power take off on an average day with the VGs doing their thing lets you dial the airspeed back by increasing the pitch angle quite a ways before you even get near the hints of a T&D stall. On steep turns you can also dial back quite a bit in slow flight before the inboard wing starts to notify you that you are getting close. With the VGs it really talks before it quits. Its nice to know where the edges are should one need to use the capability in a given situation. Plus, its just good fun to do.

[aktango58]

Using less throttle is a good indication, but in true higher altitude situations the lower density will also reduce the lift your wing produces at any given speed, so you will need the plane flying faster, which will take more room.

Bottom line, when you head to Johnson Creek, you might want to be able to adjust the mixture a little bit.

You are experimental, put a mixture on that thing- if the extra control won't confuse you like it does Glenn

Good morning Glenn!

[Farmboy]

Thanks George. That’s a bit of what I was getting at. Ability to lean, ability to get in and out of all those great spots running rich and low power.


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[aktango58]

All the training in the world with low power doesn't set you up for departing sea level and landing at Mile high! (MY opinion here).

In our type of flying we are feeling the plane, looking outside, and making judgement calls faster than any computer built. Our minds are alert and sending information to our hands and feet as we make an approach... much coming from our eyes.

Admittedly, I fly low altitude most of the time. Us guys in Southeast Alaska have a hard time heading into the Brooks Range and other places where the 'low' strips are at 3,000' msl; we are used to our base being at sea level- and our DA below. Our eyes tell us we are just off the ground, so the plane will do x... but in reality we might be up at 5,000 msl and it takes a bunch more real estate to turn, climb, approach and land.

When I would head north to fly my friends in for sheep camp, it would take me about 15 landings to get my eyes calibrated for working base camp at 3,000 msl. I had over 6,000 hours total time, almost 1,000 hours in that plane, but would require a couple of days flying before I was willing to set down on some of the 500' strips for the sheep guys.

The speed at which the ground is going under the plane on approach is faster- this messes with your mind, you will want to slow it down- then you feel a stall. For the first few landings you will need to be eyes on the airspeed until you can ignore the speed difference and go back to the feel only.

Your flare and touchdown also change. Your groundspeed is faster, so your drift will be further. Less control due to lower density so more movement to get same results. You might find yourself dropping in a little harder, as your little power blast will also give less effect. Your overshoots will be magnified due to the faster groundspeed...

Solution? Go to altitude and practice, practice practice! The more you fly high, the easier it is to adjust.

On the other hand, watch these guys come from high altitude try to spot land down here at sea level! They think they are in a stall because they are flying so slow, so drop the nose and overshoot. Also their planes jump so fast into the air it scares them!

Practice!

I have a couple of high spots here if you want to come up.

[Waldo M]

Take this with a big grain of salt, but here are the numbers from Piper. I don't know if there was a mixture control installed on the test aircraft or what prop they were using.

We replaced the A-65-8 with a C-90-8 on our PA-11 two years ago. In anticipation of moving to Idaho, we did install a mixture control on the Stromberg carb. I'm expecting to have to lean for takeoff at high elevations. I haven't flown it over 9500' MSL yet.

When I was kid, much lighter, and with the A-65, I got the airplane to 13,500 MSL on a trip out west once. It didn't have a mixture control then.

[mvivion]

My 11 is equipped with a C-90-8, which is equipped with a Marvel Schebler carb. Best thing that ever happened to a C 90.

I installed a mixture control right after I bought the plane. I’ve had the plane to 12000 feet, and it’s based at 4500 msl. At 12 K, it didn’t feel like it was out of climb yet.

It performs well, even at altitude.

MTV

[Waldo M]

That's good to hear, MVIVION.

[Ruffair]

Pete my J4 is similar to what your flying, stroker with a Stromberg. Every thousand feet makes a difference. The same takeoff at my 1400' pond I can do at Island Bobs and I'm off 150' sooner. Twitchell Lk at 2100' adds 100' to what I do at my 1400' pond level or almost 250' longer then the Island. All at close to 70F, gets worse as temp and humidity go up. I got it up to over 10K once but it took awhile the last 3000'

Glenn

what the Hay......?

I thought the Stroker mod actually requires a M/S carb....

thats what we put on the Stroker in the J3.

I couldn’t be wrong...... Not after I spent all that money...!

B. S.

We flew south from Spearfish, chasing sunset, climbed to 10.5 to get the tailwind, and she was not out of power yet. Don’t know how high it will go.....!

[salex]

Good thread that encourages thinking.

I am the new owner of a now-overweight PA-11 with a 0-200 in it. (It is on a serious diet from useless stuff) I was back seat passenger first in 1977 as a skinny college kid when it was still light and had the C-90 in it. We flew over the full length of Castle Peak in the Alaska Wrangell Range south of Mount Blackburn at approx 11,000 ft. The last 1000 feet of climb took a while with the two of us adults in it, but we could have gone more. She won't do that now. Too fat. I am working hard to get empty weight back under 800 lbs.

The benefit of our altitude up here is that it is cool (cold?) air even if thin. Your stateside temps at altitude would make me nervous.