Cruise rpm

by Ed Midgley in General Tech Discussion 9 years ago

I have a 914 with a fixed pitch ground adjustable prop. At altitude I have to cruise it at 5600rpm to get the same speed I get at 5450rpm at lower altitudes. The plane is a light sport and I can't install a constant speed prop.
Anyone have an opinion on cruising at 5600rpm as far as engine damage goes. I've been running it this way for over 200hrs.
Thanks'
Ed

Re: Cruise rpm

by James Ott » 9 years ago

James Ott

22 334 392

If you are going to ignore the manufacturer's specifications then you are on your own with nothing to complain about if problems occur or you don't make TBO. I personally would not do it on an expensive engine like this. I can't imagine 100 rpm making that much difference in cruise speed.

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Re: Cruise rpm

by Ed Midgley » 9 years ago

Ed Midgley

4 35 77

I understand what you're saying. It actually gains about four kts. The extra 100rpm is a small percentage of the total rpm. It's hard to believe that 5500 is ok and an extra 100 will wreck the engine.
Ed

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Re: Cruise rpm

by andrew owen » 9 years ago

andrew owen

13 17 3

Your speed will be the same or faster at altitude, it's just the air is thinner so your ASI will under read. Think back to your flight training.

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Cruise rpm

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