Single-engine Endurance and Performance

[Ernie Martin]

A question and then the reason behind it.

In a normally aspirated Skymaster, with 2/3 load, on a day 20 deg F warmer than a standard day, if one engine fails at a cruise altitude of 5,000 feet, can you maintain altitude for an extended period, say, two hours, and what is the performance?

I fly out of Miami, mostly over water. Based on the POH data*, I have been under the impression (and still believe) that, despite the higher temperature, the single-engine aircraft would maintain 5,000 ft altitude without difficulty, at a speed of ~ 110 - 120 MPH (depending on which engine) at 25/25 or a speed in the 90 - 100 MPH range at reduced power (say 24/23).

Someone with Skymaster experience told me otherwise. He thinks that even 25/25 will not maintain altitude, and you have to put the aircraft in a gradual descent (say, 75 ft/min) to maintain 90 - 100 MPH. Meaning that you've got around one hour before you run out of altitude. And he voiced concern, assuming you could keep it airborn longer (for instance, if the load is even smaller), that the engine would run for hours at 25/25 without overheating.

I am hoping to test this using the simulated engine-out procedure, if and when I have such a load without finnicky passengers, but in the interim it would help if you have any opinion or experience on this.

Ernie Martin

______________________
* Where single-engine ceiling is ~ 6,000 ft and there is positive climb rate below that (higher for the rear engine).

[hharney]

My opinion is based on limited single engine work, just enough to know how the aircraft will handle. I have shut down an engine several times but this was for practice and can't say what the loads were exactly but here's a good attempt at remembering.

Out in the mountain states years ago with 2JF dad and I practiced the SE stuff several times. I can remember being at around 10K MSL but don't remember the temperature. I would guess that it was at least standard or maybe less. For load the mains were full, not sure on the aux's but it's a good chance that they were full too. Myself at 200 lbs and dad at 265 lbs. We maintained 10K for some time but it was a little sluggish. The rear was better than the front. I lost a cylinder over Lake Michigan several years ago and pulled the front back to minimal and flew it for about an hour with no problems. I would say that I was at 6500 ft. I did not know what had happened to the engine while in flight but I watched my vitals and limped into the airport. Cylinder separated from the base.

At 5,000 ft and 2/3 load I would estimate that you could maintain altitude. You didn't mention that your experienced source had actual factual info on this or if it was just an opinion based on POH.

[Ernie Martin]

The source was basing it on recollections of practices/simulations and conversations he had with others, not on a specific incident.

Ernie

[Cole5Oh5]

Follow the POH
Feather the engine that doesn't work, because if you feather the engine that was working, you got a lousy glider.
Close the cowl flap doors on the engine that isn't working.
Open the cowl flap doors on the engine that does work.
Go to max throttle, lean for performance. At full load, or pretty close to it, you can maintain altitude, at least at 5K, even on a warm day.
keep in mind, however, that you don't want to do this for very long, and you'll be down to blue line or pretty close to it, which is why it is there.
I was able to maintain altitude for a short period of time, on the front engine, but it was an emergency, and we headed for an airport right smartly.

[Cole5Oh5]

you wanted to do it at 25/25, or reduced power.
Not the wise thing to do. POH says max power. Do that, you can stay up.

[Ernie Martin]

The issue of power and extended endurance is precisely the question. These engines are not rated for extended operation at full (i.e., take-off) power. If your closest landing is 1 or 2 hours away, you want to go to full cruise power, which is the top of the green band or 25/25. I believe that the engines are designed to operate at this power for extended periods. Can we start with that? Do you all agree or disagree? Then, will it maintain 5,000 ft at 2/3 load on a warm day?

I think this aircraft -- and all twins -- are designed to do that. Am I wrong?

In a single-engine aircraft, you have to promptly find a landing spot if the engine quits. Are we saying that our second engine simply extends briefly (5 - 15 minutes) the time we have to pick a landing spot?

Ernie

[skymstr02]

Originally Posted by Cole5Oh5

you wanted to do it at 25/25, or reduced power.
Not the wise thing to do. POH says max power. Do that, you can stay up.

Thats max continuous power (25/25), not full power.

On my O-2, I am able to maintain 4K, configured single engine, rear engine operating, near full gross wt.

And what the hell is blue line on a center line thrust airplane?