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PROP EXTENSIONS(From CP36, Page 3, April, 1983)
As described In CP 30, page
5, the 6" prop extension has continued to provide trouble free operations. We have
sufficient time on these extensions on two Long-EZs here at RAF to feel confident in
recommending the 6" extension as well as the 3" extension.
Note that we have only tested these on Lycoming engines. Due to
the smaller crankshaft diameter of the Continental engines and the lack of data, we cannot
recommend anything but the thoroughly tested 3" extensions for Continental engines.
The 6" extension does reduce the noise level in the pilots
seat by as much as 3 decibels (OBA scale). However it also increases cylinder head and oil
temperatures slightly. The worst case is a new or recently overhauled engine, in a new
airplane. It is possible that engine temperatures could go out of acceptable limits during
the first few hours of operations, especially during ground testing. We have noticed on an
engine with hundreds of hours, that if we are forced to run the engines standing still on
the ground for extended periods of time, in excess of 30 minutes or so, the cylinder head
temperature can climb right to the red line. Using a 3" extension this will not
To summarize: We recommend both the 3" and 6" prop
extension for the Lycoming engines and only the 3" extensions for Continentals. You,
the builder must decide which to use in your application.