Single acting turbo prop operation - propeller control , Other Engineering

Single acting turbo prop operation:

Before moving on to double acting propellers the following diagram and explanations will help the student consolidate the information listed in the notes thus far and hopefully help towards the understanding of the operational sequence and control of a small turboprop aircraft.

Several things should be checked prior to starting the engine. Ensure the propeller is 'on the locks'. Pull the propeller through, listening for unusual noises. Check for control lever freedom of travel and position the speed lever to the low or taxi position. Place the power lever ahead of ground idle. The preferable position is in flight idle.


Actuate the start switch. Note the increase of RPM on the cockpit indicator as well as propeller rotation.

2220_single acting turbo prop operation.png

The engine will accelerate to 10 percent RPM. The EGT rise is the true indication of lightoff. If lightoff does not occur within 10 seconds after 10 percent, the start be aborted.
RPM will continue to increase, fuel and temperature will increase with temperature stabilising at the starting value. Horsepower, or torque will also begin to indicate.

As engine speed reaches 60 percent, the speed switch will send a signal to de-energise the ignition system. Horsepower has stabilised due to the fixed prop load, fuel will remain the same while temperature has decreases due to the increased air flow. The engine is now considered self-sustaining.

1427_single acting turbo prop operation1.png

The engine will continue to accelerate on its own until it reaches its onspeed condition. RPM will stabilise at 65 percent. Fuel flow and temperature will have reduced and stabilised. RPM is now a function of the underspeed governor.

474_single acting turbo prop operation2.png

The chart at Fig, illustrates the action of the underspeed governor and the reason for the reduction in fuel and temperature. Notice that the fuel required for acceleration is greater than that required at a stabilised onspeed condition, or 'required to run'. Acceleration fuel starts at 10 percent RPM when the fuel valve opens. From that point the acceleration schedule is a function of increasing P3 air. Increasing P3 air is indicative of engine rotational speed increasing. As the engine approaches its low speed setting, the underspeed governor begins to meter fuel to the engine. It will continue to cut back on fuel flow until the stabilised RPM is achieved or when power equals propeller load.

2191_single acting turbo prop operation3.png

When the engine has stabilised and all parameters are check, the propeller can be removed from the locks (Fig 63). This is necessary to allow the propeller to produce thrust which would otherwise be extremely difficult with the propeller fixed at a low blade angle. To accomplish this the power lever is moved toward reverse. By being in beta mode, blade angle is controlled by the propeller pitch control through the power lever. This will cause the propeller to move toward a reverse blade angle. This reverse blade angle is a greater load than the starting blade angle, so the operator will notice an increase in torque, fuel flow and temperature.

22_single acting turbo prop operation4.png

Posted Date: 9/14/2012 3:27:34 AM | Location : United States







Related Discussions:- Single acting turbo prop operation - propeller control , Assignment Help, Ask Question on Single acting turbo prop operation - propeller control , Get Answer, Expert's Help, Single acting turbo prop operation - propeller control Discussions

Write discussion on Single acting turbo prop operation - propeller control
Your posts are moderated
Related Questions
Combustion chamber injection system: Injecting a water or water/methanol mixture into the combustion chambers increases the mass flow through the turbine and the high volumetri

I am looking for a circuit similar to a schmitt trigger which use a varying capacitive input and provided a varying frequency output.

Analysis of truste,2D truss analysis using method of joint(cantilever & simply support)?

Steam enters in the turbine at 6 MPa and 450 deg C and expands at some intermediate pressure 60 % of steam is extracted and remainder expands to 10 kPa at this Investigate the effe

a hexagonal prism of 40mm side length of base and height 80mm is resting on HP on its base with two edges of base is parallel to horizontal plane. A square hall of equally inclined

Ask questioy 4 men #Minimum 100 words accepted#

(a) Discuss the requirements, specifications and special requirements for theĀ  design of arterial road networks and residential area street networks in a developing suburban region

why we need EJB

Speed control in Aircraft Engine: Because the APU is designed to run at a constant rpm, some means must be provided to control this speed. Such a control device is known as a

what is lloyd''s length