Variable Pitch / Constant Speed Variable Pitch / Constant Speed propellerspropellers

Len KlopperLen Klopper

Not SAGPA approvedNot SAGPA approved

The following is my attempt to assemble The following is my attempt to assemble information from all sources and to combine information from all sources and to combine it into a useful document. it into a useful document.

Please feel free to comment, change, fix, Please feel free to comment, change, fix, repudiate, teach by adding value to the repudiate, teach by adding value to the document for everyone’s benefit.document for everyone’s benefit.

Mail me to have the base document Mail me to have the base document changed – lenk@ehr.co.zachanged – lenk@ehr.co.za

Variable Pitch PropellersVariable Pitch Propellers

Four common types of propellerFour common types of propeller– Fixed pitch Fixed pitch – Ground adjustableGround adjustable– In flight adjustable In flight adjustable – Constant speedConstant speed

The last two are both examples of variable pitch The last two are both examples of variable pitch propellers. propellers.

History of Variable Pitch History of Variable Pitch PropellerPropeller

On 7 February 1922 Wallace Rupert Turnbull patented On 7 February 1922 Wallace Rupert Turnbull patented the Variable Pitch Propeller. Considered one of the the Variable Pitch Propeller. Considered one of the

most important developments in the history of aviation, most important developments in the history of aviation, this mechanism allowed for change in blade pitch to this mechanism allowed for change in blade pitch to

suit flying conditions and airplane weight. When suit flying conditions and airplane weight. When Turnbull was posthumously inducted into the Canadian Turnbull was posthumously inducted into the Canadian Aviation Hall of Fame in 1977, his citation read: "The Aviation Hall of Fame in 1977, his citation read: "The

patient application of his aeronautical theses to a patient application of his aeronautical theses to a number of problems unique to flight, and more number of problems unique to flight, and more

especially his invention of the successful variable pitch especially his invention of the successful variable pitch propeller, have been of outstanding benefit to aviation." propeller, have been of outstanding benefit to aviation."

Variable Pitch // Constant Speed Variable Pitch // Constant Speed PropellerPropeller

A A variable pitch propellervariable pitch propeller (VPP) or (VPP) or controllable pitch propellercontrollable pitch propeller (CPP) is a special  (CPP) is a special type of propeller with blades that can be rotated type of propeller with blades that can be rotated around their long axis to change their pitch – around their long axis to change their pitch – manual transmission in a car.manual transmission in a car.

A A constant speed propellerconstant speed propeller (CSP) is a type of  (CSP) is a type of propeller that can change its blade pitch propeller that can change its blade pitch automatically to take better advantage of the automatically to take better advantage of the power supplied by an engine in much the same power supplied by an engine in much the same way that an automatic transmission in a car way that an automatic transmission in a car takes better advantage of its power source. takes better advantage of its power source.

Basic MechanismBasic Mechanism

Airspeed // PitchAirspeed // Pitch

ControlControl

WARNING!WARNING!

Engine overspeed Danger!Engine overspeed Danger!– If no governor or governor settings inop. Watch If no governor or governor settings inop. Watch

MAP & Engine RPM closelyMAP & Engine RPM closely

Always set CLIMB pitch on final approach in Always set CLIMB pitch on final approach in case of a go-roundcase of a go-round

Keep Aircraft speed in mind when adjusting Keep Aircraft speed in mind when adjusting pitchpitch

TIPS!TIPS!

Excessive manifold pressure raises the cylinder Excessive manifold pressure raises the cylinder compression pressure, resulting in high stresses compression pressure, resulting in high stresses within the engine. Excessive pressure also within the engine. Excessive pressure also produces high engine temperatures. A produces high engine temperatures. A combination of high manifold pressure and low combination of high manifold pressure and low r.p.m. can induce damaging detonation. In order to r.p.m. can induce damaging detonation. In order to avoid these situations, the following sequence avoid these situations, the following sequence should be followed when making power changes.should be followed when making power changes.

When increasing power, increase the r.p.m. first, When increasing power, increase the r.p.m. first, and then the manifold pressure.and then the manifold pressure.

When decreasing power, decrease the manifold When decreasing power, decrease the manifold pressure first, and then decrease the r.p.m.pressure first, and then decrease the r.p.m.

Final tip!Final tip!

All power changes should be made All power changes should be made smoothly and slowly to avoid overboosting smoothly and slowly to avoid overboosting and/or overspeeding. and/or overspeeding.

Len Klopper