For governor maintenance and operation instruction please refer “Installation and Operation Manual”.


When good operating practices are observed the governor assembly will require complete overhaul only at regular engine overhaul time. Engine oil changes at frequent periods will greatly extend the useful life of the governor and engine. The propeller and engine manufacturers lubrication and service instructions are important in maintaining satisfactory propeller, engine, and governor operation.
Tightness and security of all external screws, nuts and levers must be checked as a part of each routine engine check. Normal periodic overhaul requires that the piston engine governor be completely disassembled at engine overhaul time. Propeller governor overhaul is a major repair and must be performed by a qualified governor shop or the unit has to be returned to the factory for exchange. All factory overhauled governors are zero time units and carry the same warranty as a new unit.


Overhaul consists of the following basic steps:
  • Disassembly,
  • cleaning of parts and examining visually and dimensionally for  unserviceable parts,
  • reassemble using overhaul kit,
  • test.

Overhaul kits contain parts that are always replaced at each overhaul. Visual and dimensional inspection may reveal flaws that require parts replacement such as wear, rust pits etc.


See at section DOCUMENTS Operation and installation Manual P-ROV-514/01, page 701 or look here:



7.1.1 Excessive transfer bearing leakage Engines with excessive transfer bearing leakage can experience propeller surging since the governor may not be able to get enough oil pressure to the propeller. Solution : Perform a transfer bearing leakage test per engine manufacturer’s instructions. If test indicate a high rate of leakage (even through it may still be on the high side of “acceptable” tolerance), this maybe the cause. Install the suspect governor on a known “good” aircraft. If problem disappears, engine work may be indicated.

7.1.2 Malfunctioning magnetos

7.1.3 Dirty engine oil Contaminants in dirty engine oil can cause blockage of close tolerance passages in governor, leading to erratic operation. Solution : Flush the governor in order to cleaning out contaminated oil.

7.1.4 Excessive “play” in aircraft propeller control linkage Excessive “play” in the linkage between the governor and the cockpit control often leads to erratic operation. Specifically, if the propeller RPM is suddenly changing and holding a new setting of its own, this could indicate loose linkage. Solution : Trace linkage and locate unsecured sections and tighten-up as needed. Please note that although linkage may appear to allow full governor control while the engine is off, it may not in the air. Engine vibration and “stretch” of the mount during operation can often aggravate the condition. Therefore, it is important the entire length of linkage be properly secured, even if the ends alone are tight.

7.1.5 Excessive propeller friction (NOTE : This is rarely the cause of RPM malfunction.) Propeller may be overly-resistant to pitch movement. This can be caused by either excessively shimming of the propeller blades, or internal corrosion or part failure, causing binding. Solution : Check amount of propeller blade “play” as defined in the propeller manufacturer’s operating manuals.


7.2.1 Internal oil leakage Governor unable to reach sufficient control pressure. Solution : Contact propeller governor service center for governor internal leak test.

7.2.2 Extremely high temperature Extremely high temperature changes oil viscosity. The governor may not reach sufficient control pressure. Solution : Check oil temperature. Correct cause of high temperature.

7.2.3 Governor wear Excessive wear of internal parts. Solution : Contact governor service center for bench test.


7.3.1 Pollution of engine oil Excessive dirt in the engine oil pollution can cause governor seizure. Solution : Overhaul the governor.


7.4.1 Engine drive vibration Excessive engine vibrations can cause governor drive failure. Solution : Overhaul the engine and the governor.