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Cruise rpm

in General Tech Discussion 10 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 » 10 years ago

    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 » 10 years ago

    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 » 10 years ago

    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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