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Occasionally, we get questions regarding installation of a Top Prop STC in conjunction with another STC. There are many STCs available today for a wide variety of aircraft equipment. The responsibility for determining that the STC is compatible with previously installed modifications on a particular airplane rests with the installer (the mechanic with Inspection Authorization who completes the installation). A FAA statement to this effect is usually given in the STC document under the Limitations and Conditions section.
Generally speaking, the installation of STC’d interior equipment is considered to be compatible with the installation of a Top Prop conversion kit. Examples of such equipment include:
Airframe modifications are also generally compatible with the installation of a Top Prop propeller conversion kit. Examples of such equipment include:
A previously installed STC which approves engine modifications that change the power or vibrational characteristics of the engine is generally not compatible with a Top Prop propeller conversion. Examples of engine modifications not compatible with a Top Prop conversion include:
Modifiers who offer engine conversions or modifications sometimes work with Hartzell to have a Top Prop propeller approved with their engine modification STC.
Contact the holder of the powerplant STC to see if a particular Top Prop propeller model is listed on the engine modification STC.
If there is any question whether an STC is compatible with your modified airplane, consult your local FAA Flight Standards office. They are the final authority.
