A governor is defined as a mechanical device which is used to sense the speed of a motive device and maintain its speed using mechanical feedback. McCauley uses this type of control system device to hydraulically control a propeller. In fact, McCauley has developed a full line of control system components to control the propeller on both single and twin reciprocating engine applications.

McCauley's control system family is divided into two major and distinct product groups. The first is constant speed governors which are designed to deliver engine oil to the propeller to increase pitch. The second is feathering governors which are designed to deliver engine oil to the propeller to decrease pitch.


Constant Speed-Undampened & Dampened
Constant speed governors were the original unit developed to maintain a constant speed on the propeller as the name implies. The single engine aircraft benefited a great deal from the development of the constant speed propeller. The governor uses oil from the engine to hydraulically maintain a set speed setting. The constant speed governing system decreased takeoff roll and improves climb rates and cruise speeds.
McCauley manufactures two different type styles of constant speed governors. The two types are defined as dampened and un-dampened. The basic undampened model is identified by the alphanumeric callout C290D3(X)/T(X). The dampened version is identical to undampened version except for the flyweight assembly. The basic dampened model is identified by the alphanumeric callout DC2901(X)/T(X). The dampened version uses a spring loaded flyweight assembly designed to filter out unwanted vibrations that could interfere with the smooth operation of the pilot valve on certain makes and models of engines. Both dampened and undampened constant speed governors feature a retained flyweight assembly which insures smooth, even rotation, free from fluctuations.

Feathering Governors
Feathering governors were developed to maintain a constant speed on the feathering propeller as the name implies. The basic feathering governor model is identified by the alphanumeric callout of DCF290D(X)/T(X). Twin engine aircraft benefit from the safety of the use of the feathering propeller control system. The feathering governor uses oil from the engine to hydraulically maintain a given speed setting and allows the pilot to feather the propeller in the event of a loss of power or other engine problem. Feathering the propeller eliminates drag that would be caused by a wind-milling, non-feathered propeller. This gives the pilot the ability to fly the aircraft with one engine to the nearest airport for repairs.

Feathering Governor Options

Unfeathering
Using the basic feathering governor (DCF) many options can be added to increase safety and comfort of the passengers. Some feathering governors have been designed to include the option of unfeathering. The basic unfeathering governor model is identified by the alphanumeric callout of DCFU290D(X)/T(X). The unfeathering option allows the pilot to unfeather the propeller if desired after it has already been feathered. The unfeathering systems includes a McCauley unfeathering accumulator which provides high pressure oil to the propeller to "push" the propellers blades out of the feathered position by using stored oil to move the propeller piston.

Synchrophasing
Synchrophasing governors use an electromagnet in the head of the governor to automatically adjust, or 'fine-tune" flyweight position to increase the speed of the slower propeller to match the speed of the faster propeller. This is referred to as "synchronizing" the propellers. The system often also incorporates a feature that allows the pilot to "phase" the propellers. Phasing is means of re-clocking the propellers blades on one propeller in relation tot the blades of the other. The ability to phase often allows the pilot to move much of the propeller vibration to unoccupied sections of the aircraft, thereby reducing the annoying "beat" of the propellers and providing additional comfort to the passengers.

Tachometer
Feathering, unfeathering and synchrophasing governors can be equipped with a tachometer pickup. A tach pickup takes it data directly from the flyweight assembly within the governor and transmits it to the aircraft avionics system. This information is used to create the engine/propeller RPM readout in the aircraft cockpit.

Features and Benefits
All McCauley constant speed and feathering governors are built to the same quality and reliable standards that the aircraft industry has come to expect. All exterior governor components are double-coated with both anodize plating and tough polyurethane paint to insure protection from corrosion. The externally adjustable pressure relief valve is double sealed to eliminate unwanted external oil leaks. McCauley uses viton o-ring seals to insure a leak tight seal at high oil temperatures. Tight tolerance, balanced, retained flyweight assemblies insure smooth operation and quick response to changes in rpm. All McCauley governor designs are lightweight and compact, often providing a 25% weight reduction over the competition. Manufactured under very strict, ISO9000 certification standards, McCauley governors are compatible with all engine manufacturers utilizing an AND20010 mounting pad.

 

Governor Tech Guide