Take off noise

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3 months 1 week ago #3024 by STEVE ELLS
Replied by STEVE ELLS on topic Take off noise
Hello Alain;

The Continental fuel injection system is designed to provide a specified fuel flow at each engine rpm.

The Continental fuel flow settings are adjusted to be rich during all power engine operations above approximately 1500 rpm (when the idle circuit adjustment affects the mixture), therefore if you pull the rpm back to lessen the noise, you will also be lessening the fuel flow to the engine.

The fuel flow to the cylinders is linear to the engine rpm in the Continental system, so if follows that if the fuel flow is rich at takeoff rpm it will be rich at a lesser rpm, such as 2500.

Engine rpms that are less than the full 2850 rpm will result in less power generated by the engine. The result of pulling the rpm back from 2850 will be less power generated by the engine which will cause a longer takeoff run.

I often pull the rpm on my engine back to 2500 (from the 2700 rpm full power setting) soon after takeoff to lessen prop generated noise and to reduce cabin noise.

One study recently printed in KitPlanes magazine that propellers generate equal to and in some cases more thrust when rpm are reduced from maximum

If you need to get off the ground quickly, or need to climb at a steep angle, leave the prop control forward until clear of obstacles.

Your mechanic needs to make sure the fuel pressures being delivered to the cylinders are correct. The previous Continental service bulletin that gives guidance in this is SB97-3G. Today that information has been included in Continental Manual M-0. If he/she does not have that manual try to "Google" it. There may be a free download floating around the internet. It's a very valuable tool for servicing Continental engines.

The only time you will not have the mixture full forward is when you're taking off from an airport that is over 5000 feet (1524 m) above sea level.

I don't know anything about the Skydemon software.

If you have more questions, please post them here on the forum.

Best,
Steve

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3 months 1 week ago #3021 by Alain Bosco
Take off noise was created by Alain Bosco
Hello

I am a happy owner of a Cessna U206G 1979. I buy it with a new engine and new 3 blade Mc Cauley prop.
It seems that I made a huge noise on take off. My prop turns at 2850 with full power on take off then I decrease at 25 / 25 to climb and 23 /23 on cruise.

My question 1 ...

1)
as I decrease at 2500 the noise is totally acceptable can I take off with 2600 without any influence on the capacity and performance ?

2) what do you advise about mixture ?

3) any expert on Skydemon Weigt and balance ?

Thanks

Alain
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