What if my engine is not running within the desired RPM range?
Have your tachometer checked annually. Mechanical tachometers are notoriously inaccurate and subject to drift over their lifetime. If your engine and propeller combination has one or more yellow arcs or red restricted arcs within the normal operating range - common to a lot of four-cylinder Lycomings - then it is vital that the tach accurately guides you out of these trouble spots. These limitations are in place because of vibration characteristics of the engine and propeller combination and can lead to long term trouble if routinely ignored.
If you have a fixed-pitch propeller, check the propeller pitch. The pitch is generally stamped on the propeller near the center of the hub. Check to see if your pitch to insure it is the correct pitch for your engine/aircraft. (Call us we will be glad to help with this.) "Rule of Thumb" for every inch you change your fixed pitch propeller pitch you will effect your static RPM by 25 RPM and your cruise RPM by 50 RPM. If the pitch is correct and your tachometer is accurate, have the propeller checked out by a certified propeller shop.
If you have a constant speed propeller, depending on where you are not meeting your desired RPMs (static or cruise), the low pitch angles may need to be set. To determine this, you will have to pull the propeller and have the pitch angles checked by a certified propeller shop. If your propeller appears to be functioning properly, the RPM issue could be caused by your governor.
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