Power plant Flashcards
Describe the power plant
Powered by two four-cylinder liquid cooled turbo charged Thielert TAE-125-02-99 four stroke diesel engines each generating 135 hp at 2300 RPMs
Propeller
Driven by a reduction gearbox
FADEC
Full authority digital engine control
Operates two engine control units on each engine
Only one ECU is active at a time and the other remains at standby
Controls the engine fuel system propeller as well as the turbo charger system
Principles of diesel engine
Four strokes: induction, compression, power, exhaust
Rather than relying on a spark, a large compression ratios use so that the temperature becomes high enough to cause spontaneous combustion.
Timing controls when and where the fuel is injected into the motor
Glow plugs are used to preheat the cylinders
Lubrication systems - engine
Wet sump system
Engine driven pump provides flow of oil for the engine and turbo charger lubrication
Minimum oil - 4.8 quarts
Maximum oil - 6.3 quarts
Lubrication system - gearbox
Gearbox oil system has its own pump which supplies the gearbox and propeller pitch control system
Gearbox oil is checked via a site glass on the lower right side of the cowling
Lubrication system - gearbox
Gearbox oil system has its own pump which supplies the gearbox and propeller pitch control system
Gearbox oil is checked via a site glass on the lower right side of the cowling
Fuel injection system
- Fuel from the aircraft is delivered to the engine via a filter, located at the rear of the engine nacelle
- There is a sediment bowl located at the bottom of the filter with a drain.
- From the filter fuel is delivered to a low pressure pump which in turn delivers fuel to the engine high pressure pump.
- High pressure fuel is then delivered to a fuel injector located in each cylinder.
- Excess fuel is returned to the appropriate wing tank.
Engine turbo charger system
- The air intake system provides either filtered ram air or unfiltered warm air from within the engine, cowlings to the turbo charger
- pressurized air from the turbo charger is delivered via an intercooler to the engine and let manifold
- Turbo charger is controlled by a wastegate fitted in parallel to the exhaust system. The waste gate is controlled by the FADEC.
- If the air filter becomes blocked, the alternate source can be selected via the lever located under the instrument panel.
Engine cooling system
Liquid cooled
Coolant is a mixture of water and antifreeze, and his pumped around the passages within the engine by a belt driven pump.
Two circuits
1. Main circuit - includes a heat exchanger and a thermostat control valve.
2. Bypass circuit.
When coolant is hot the thermostat valve direct fluid through the heat exchanger
When the coolant is cold, the valve fluid through the bypass circuit straight back to the pump inlet
A sensor located in the valve provides a temperature signal to the ECU in the EIS display the coolant temperature
There is an expansion pressure relief valve to prevent over pressure
There is an overflow valve located below the engine nacelle
Propeller and propeller control system
Each engine is fitted with a three blade, constant speed, feather propeller
Both propellers rotate clockwise as viewed from the cockpit
Left engine is critical engine
Each blade is a wood, composite construction with fiber reinforced plastic coating in a stainless steel leading edge
Blade is controlled automatically by the ECU
Normal operations blade to a pitch oil pressure is used to drive blades towards fine pitch
The accumulator uses oil from the gearbox, and the accumulator is connected to electric valve operated by the engine master switch
Engine and propeller are controlled by a single power lever
Power demand set on the power lever are sensed by FADEC which schedules various engine and propeller parameters to ensure optimum power delivery and pitch angle
Power equals 100% power
Propeller controller
Equipped with an oil accumulator that has a shut off valve controlled by the engine master switch.
During normal engine operations, the valve is open, resulting in the accumulator being charged with oil at system pressure
Stored is used for unfettering as well as ensuring oil supply to the CSU
Start latch
During normal engine shut down with idle at 0% load centrifugal latch engages at 1300 RPM and prevents the blade from entering the feathered range
Start lock blade
Approximately 15°, which reduces engine low during start.
If ECU malfunctions and the proper blade angle gets stuck in the start lock position, the propeller will produce negative thrust and will over speed as soon as power is applied
Feathering
Occurs when the engine master switch to off
Accumulator valve closes storing the oil charge
Electrically operated governor valve allows oil to flow back from the propeller
In flight shut down must occur above 1300 RPM or the start lock will engage
