%

61-11-00
Propeller
AMM

Section 61-20 % Propeller Control - Lycoming Engine
1. General
%  The DA 40 with the Lycoming engine installed has a constant speed propeller and a Woodward or mt porpeller governor. The governor controls the engine speed by changing the propeller blade angle (pitch).
% This Section gives the basic data about the propeller governor. For more data about the Woodward % governor refer to the propeller manufacturer‘s manual or the Woodward governor manual. For more % data about the MT-P420-10 governor refer to the mt-Propeller governor manual.
2. Description and Operation
The DA 40 has an mt-Propeller constant speed propeller. The propeller uses oil pressure to increase the blade angle (pitch). In normal flight the centrifugal twisting moment (CTM) of the blade and the return spring cause the blade to move towards fine pitch.
Figure 1 shows a schematic diagram of the propeller governor. The propeller governor connects to the engine oil supply. The oil goes to a gear-pump in the governor. The gear pump increases the oil pressure to 270 - 340 psi (19 - 23 bar). A relief-valve controls the maximum oil pressure.
The governor has a pilot-valve. The outlet from the pilot-valve connects to the propeller. The inlet to the pilot-valve can connect to the oil pump, or it can connect to an oil return line back to the engine sump, or it can be closed off.
The governor has a control lever. The control lever pushes against the speeder spring and the spring pushes against the pilot-valve. When the governor is turning, flyweights pull the pilot-valve upwards, against the force of the speeder spring.
In normal flight the governor will be in one of the following conditions:
A. On-Speed Condition
When the engine runs at the selected speed, the governor operates as follows:
) The propeller blades are at the correct pitch to absorb the power from the engine.
) The centrifugal force of the governor flyweights balances the speeder spring force.
) The pilot-valve closes the connection to the oil-pump and it closes the connection to the oil return line.
) Oil cannot flow out of the propeller and the propeller blades stay at the same pitch.
) Oil from the oil-pump flows through the relief valve and returns to the pump inlet.
Doc # 6.02.01 Page 1
Rev. 4 09 Jan 2003

61-20-00
AMM

ON SPEED

Oil From
Oil To
Propeller
Propeller
UNDER SPEED OVER SPEED
Figure 1: Propeller Governor Schematic Diagram
Page 2 Doc # 6.02.01 09 Jan 2003 Rev. 4
61-20-00
Propeller
AMM

B. Under-Speed Condition
When the engine speed is less than the selected speed, then the governor operates as follows: ) The speeder spring force is greater than the force from the flyweights and the spring pushes the pilot-valve down. ) The pilot-valve connects the propeller to the oil-return. ) The oil flows from the propeller and the centrifugal twisting moment of the blades turn the blades towards fine pitch. This decreases the load on the engine. ) The engine speed increases until the flyweights move the pilot-valve to close the oil return connection and the force from the governor flyweights balance the force from the spring.
C. Over-Speed Condition
When the engine speed is more than the selected speed, then the governor operates as follows: ) The speeder spring force is less than the force from the flyweights, and the flyweights pull the pilot-valve up. ) The pilot-valve connects the propeller to the oil pump. ) Oil flows into the propeller from the oil pump. ) The propeller blades move towards coarse pitch. This increases the load on the engine. ) The engine speed decreases until the spring moves the pilot-valve to close the oil pump connection and the force from the governor flyweights balances the force from the speeder spring.
　
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