Overview and general propeller operation. The Cessna 350 Corvalis is equipped with the McCauley C444 constant speed propeller (D3A36C444). This propeller was implemented in production during 2006. The Cessna 400 Corvalis TT is equipped with the McCauley C447 constant speed propeller (D3A36C447) effective February 2010. Both of these propeller models are available as an STC kit that can be installed on all 300/350/400 Corvalis aircraft. All 350/400 aircraft are also delivered with a McCauley constant speed governor installed. These aircraft were originally certified with a Hartzell constant speed propeller. The two main differences between the McCauley and the Hartzell are that the McCauley utilizes a single piece hub for added structural integrity (the Hartzell uses a split, 2 piece hub) and the McCauley is filled with red-dyed oil for superior internal corrosion protection and lubrication (the Hartzell is grease filled). The McCauley propeller was certified as “equal to or better than” the performance of the Hartzell, so no changes are necessary to the POH regarding performance and field length. Cessna 350 Corvalis with a McCauley constant speed propeller. A constant speed propeller is defined as a single-acting unit in which hydraulic pressure works against the forces of springs and the natural centrifugal moment of the rotating blade to provide the correct pitch for engine load. Hydraulic pressure causes the blades to move toward high pitch (decreasing rpm).The springs and centrifugal moments urge blades toward low pitch (increasing rpm). The source of hydraulic pressure for operation is oil from the engine lubricating system, controlled by the engine driven governor. Pressure is supplied to the forward side of the propeller piston through the engine shaft flange. Increasing the engine speed will cause oil to be forced into the cylinder to move the piston with a corresponding increase in pitch. Conversely a decrease of engine speed will result in oil leaving the cylinder, with a decrease in pitch. Flow of oil through the governor and propeller does not interfere with engine lubrication. A complete reduction of hydraulic pressure in flight, either by a failure in the system causing loss of oil, or by manipulation of controls to require maximum rpm, will cause springs to automatically move the blades to low or minimum pitch position. Control Input From Governor Pilot Control Propeller Blade Lever Pitch Range Speeder Spring Pressurized Oil Cavity Dampened Flyweight Assembly Pilot Valve Constant Speed Propeller Pressure Relief Valve Engine Flange Drive Rotation Gear Pump Oil to Sump Cutaway view of oil passages through a typical McCauley non-feathering, constant speed propeller and its governor. Why Red Oil? McCauley uses red-dyed lubricating oil in its C444 and C447 propellers. The oil is dyed red to aid in troubleshooting to distinguish propeller oil from engine oil. The propeller oil is completely independent of the engine oil. Engine oil and propeller oil are compatible with one another. Any mixing of the two would have no harmful effects. It is not necessary to “check the oil” between overhauls. Commonly Referenced Field Service Information The C444 and C447 propellers have no service issues, but below are a few general service items that are commonly used by aircraft owner’s/operator’s. SB137AD Per SB137AD, McCauley recommends overhauls on its C444 and C447 to be carried out every 2400 hours or 72 calendar months (whichever occurs first). Also included in SB137AD is information about the necessary pre-service inspections of controllable pitch propellers, along with other McCauley products, which have been in long-term storage. SB227B SB227B discusses the correct installation procedures for McCauley constant speed propellers and fixed pitch propellers. The proper torque for McCauley C444 and C447 propellers installed on their respective aircraft is 50-45 ft-lbs (lubricated torque only). SB177B SB177B details the necessary and required inspection criteria for McCauley propellers following a suspected lightning strike. If a lightning strike is suspected, the necessary action steps are provided using this SB. SL1995-4B SL1995-4B discusses the proper techniques used to evaluate and repair typical wear and tear experienced by propellers under normal usage. Specific instructions are given to aid the mechanic in performing an acceptable repair. NOTE: The above service information can be accessed at www.mccauley.textron.com. The website also contains much additional information including product information, propeller educational materials, STC information, the McCauley Application Guide (MAG), and information regarding technical training available at our Wichita, KS training facility.