Propeller Speed Select And Feathering Control; Propeller Settings - Thrush Aircraft S2RHG-T65 TURBO THRUSH Maintenance Manual

THRUSH AIRCRAFT, INC – MODEL S2RHG-T65 TURBO THRUSH
In all forward configurations, which includes low idle, takeoff, climb, and cruise, the
power lever control performs only one function - the function of scheduling fuel. When
the cockpit power lever is advanced, the cam follower pin (Fig. 4-3, #11) moves forward
and pushes the FCU arm (Fig. 4-3, #10) forward to schedule more fuel.
The extension of the cam follower pin rides in the track of the beta control cam (Fig. 4-3,
#2). In all forward configurations the path taken by the cam follower pin exactly
matches the cam track. Therefore, the beta control cam does not move; the push-pull
control cable is inoperative; the top end of the propeller reversing lever does not move;
and the fuel governor reset arm remains on the maximum stop on the CSU.
In beta after touchdown the power lever has two functions. It schedules the blade angle
directly, and it resets the Nf governor down. After the blades have passed zero pitch,
the power lever begins its third function in reverse. That function is to schedule the fuel
flow as well.
After touchdown the aircraft operator presses the override button which is located on
the power lever and moves it rearward. The cam follower pin loses contact with the
FCU actuating lever, and the FCU will stay at flight idle (69% Ng), because the high idle
roller (Fig. 4-7) will prevent any further lowering of gas generator speed. As the cam
follower pin moves rearward, it picks up the cam track of the beta control cam and starts
to move it rearward. This action pulls the push-pull control cable as well. This action
also pulls the propeller reversing lever and the fuel governor-interconnecting rod.
The FCU remains at flight idle while the blades fine out until the cam follower pin picks
up on the dead band adjustment screw (Fig. 4-7). This moves the FCU reversing lever,
which starts to schedule more fuel in reverse. From this instant the cockpit power lever
is performing three functions. The functions are scheduling the blade angle directly,
scheduling the fuel flow, and setting the Nf governor down. The action continues up to
maximum reverse blade angle.

PROPELLER SPEED SELECT AND FEATHERING CONTROL

The cockpit propeller lever has two functions:
A. The first function is to select the propeller RPM in takeoff, climb, and cruise
configurations.
B. The second function is to feather the propeller when it is required.
The cockpit propeller lever is connected to the speed select lever on the CSU.
The first function is performed by varying the speeder spring pressure by rotating the
propeller speed select lever (Fig. 4-2, #9) toward the propeller speed max stop (Fig. 4-2,
#10). The second function is performed by rotating the propeller speed select lever
(Fig. 4-2, #9) toward the feathering stop. This action will cause the override rod to pull
the pilot valve plunger upward, therefore allowing servo oil to be dumped from the
propeller servo piston. This action will cause the propeller blades to travel to the feather
position, by action of the feather-return spring pressure acting on the propeller servo
piston.
A. Maximum RPM . . . 1,700 RPM
4-16
AIRCRAFT MAINTENANCE MANUAL

PROPELLER SETTINGS

Effective: 5/05/04