Constant Speed Propeller Training

Constant Speed Propeller Differences Trainig

I have flown multi engine variable pitch props for many hours but single engine is different.  At failure for example it won’t feather but instead goes fine.

Last night’s flight was my differences training for using Constant Speed Propellers.  In a Mooney M20 our 1hr 30 minute flight took us from Aberdeen to Fife and back over the Cairngorms to Aberdeen.  The Mooney is certainly a fast machine!

Key Points 

1.       The throttle controls manifold pressure (MP) and pitch of the prop. Increasing throttle increases the manifold pressure (the pressure of the flow of fuelto the engine) and the prop tries to turn faster.

2.       The prop controller then resists faster RPM by coarsening  the blades. This increased pitch and angle of attack of the blades causes more thrust, but also causes more drag, resisting an increase in RPM

So the throttle controls the MP/engine torque/prop pitch, and the prop knob regulates engine/prop RPM.

On Start Up  - High RPM (Prop Controller

Power Checks – Run Up to 1800 rpm and follow check list

Pull back Prop Controller 3 x and observe:

1.       RPM Drop

2.       Manifold Px Drop

3.       Oil Pressure Rise (check)

T/O High RPM Cowl Flaps Open

500’ agl Rev  up ; Throttle back 25MP aand 2500rpm

Climbing – Increase RPM then MP

Cruise Set Power as Required (Check placards)

Descending – leave prop where it is and reduce MP 1” for every 100’ per minute

PFL and FL extend glide range by moving prop controller fully back

Cowl Flaps:

Open  - T/O, Climb and Cct

Closed  - Cruise ;Descent

Note high MP reduces Engine Wear (low RPM)

 

In review of the controllable pitch propeller:

• the RPM control (blue knob) sets prop/engine RPM

• the throttle (black knob) controls prop pitch/manifold pressure unlike a fixed-pitch prop, produces max RPM/power for takeoff

• loss of oil pressure causes fine pitch to stops (high RPM)

• lower cruise RPM causes less noise, smoother through turbulence

• idle throttle causes fine pitch, high drag "plate" airbrake

• higher MP with same RPM causes more torque and p-factor

• oversquare settings are inefficient and overtorque the engine

 

Dundee from the Mooney

Largo - Fife