True single engine ceiling on P337?

[kevin]

I received this inquiry today:

Sir: I've always been under the impression that the Pressurized Skymaster would hold altitude at nearly 18,000 feet one only one engine.

Either the front or rear. Recently we had an experience while flying with the front engine off where it lost altitude from 8,000 feet. What is your experience in this matter? I think the book states that the ceiling using the rear engine is much higher than that. Rear engine seems to be developing the right amount of power and gets similar performance out of the prop.

Where would you look for a problem?

Any help is greatly appreciated.

Mark

[kevin]

Hmmm... Single engine service ceiling is 18 to 20K, can't remember exactly where. But I have never operated on one engine up there myself. Question: Did you have full power, full RPM on the engine that was operating? Was the other engine feathered? If yes, I am suprised, and suggest further investigation, beginning with me taking my airplane to 12,000 and reducing power on the front engine to simulated idle thrust, which would be about 1900 RPM.

I will also post an inquiry on our site, see what other folks experience is.

BTW, I am fairly certain that the aircraft will be unable to maintain pressurization on one engine at 18,000, but it should be able to maintain altitude, at least I thought it would...

Kevin

[Jerry De Santis]

I have a 1975 P337G skymaster. The Cessna POH states single engine operation is 18,500 feet either engine. Before the P337G, I hand a normal asp. 1972 337F skymaster. Don't remember the exact numbers but they are something in the range of 7200 feet for rear engine and 5000 feet for front engine in single engine condition. I did lose the front engine once on the 1972 plane when I was at 10,000 feet. I was able to stay at 8200 feet with rear engine.
Jerry
N34EC

[OSCARDEUCE]

WOW!!!!
18,000 feet!!!
I'm lucky to get 2000 in the O2!!!
Maybe I should put a couple of turbos on mine!!!
Tom

[kevin]

FYI, I took my '73 P337 to 12,500 today, and (after cooling it a bit), reduced power to the rear engine to idle. This gave me 1900 RPM on the rear engine, which the book says is the same thrust as feathered. Something seems wrong about that, maybe it would have eventually slowed down such that I needed to put some power back in to maintain 1900 RPM, but anyway...

I was easily able to maintain altitude with only climb power (31/2500) on the front engine, not even full power. I let the airplane coast down in speed for five minutes, and it had seemed to stabilize in level flight at blue line and climb power.

I chose to cage the rear engine rather than the front (which is your example) because the front is not quite as efficient as the rear, and I wanted worst case.

Gear and flaps were up.

If you were operating at only 8000 feet, something is VERY wrong. Were you getting full MP (35", if I remember right) at full RPM on the rear engine?

Perhaps someone else on the site will have a suggestion...

Kevin

[WebMaster]

If you had a non-turbo skymaster, 8000 would be logical, but time after time, the turbo skymaster has reported >14000. In fact, Brian bought the turbo pressurized skymaster so that in single engine operation he could clear the greenland icecap (11000 ft).
If the turbo was putting out power, you should have been able to maintain altitude.

[Bob Cook]

I would assume;

1) 75% power or greater. 31/2800 would be minimum.
2) I would consider trying full power to see what would happen.
3) You should be able to get 37" at test altitude otherwise your turbos or engine is not putting out.

Believe the book figure is based on full gross or 4800 lbs, therefore there is something wrong.

I have operated single engine at 13k ft in colorado without overstressing the engine. Think it was 31" and 2700 rpm.

bob

[WebMaster]

Thanks Bob
I knew that what he was saying didn't make sense.