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

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