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29 Cards in this Set
- Front
- Back
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Briefly describe the engines on the DA42.
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-Thielert Diesel TAE 125-01 engines
-135 HP @ 2300 RPM at Sea Level -4 cylinders -4 stroke -Liquid cooled -Turbocharged -Reduction gear to propeller -Wet sump oil system |
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What are some characteristics of diesel engines?
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-Typically turbocharged, to ensure proper compression / temperatures in combustion chamber
-Diesel fuel (or Jet A) contains more energy than avgas, therefore more efficient, cleaner burning |
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Describe the common rail injection system.
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-Simply put, it's a high pressure reservoir of fuel which feeds the injectors
-Pressurized to 1800psi which assures optimal vaporization which results in a fine tuned engine, efficient and cleaner burning with more power. -Fuel from tanks passes through a filter -A low pressure fuel pump which supplies fuel to a high pressure fuel pump -High pressure pump supplies fuel to common rail injectors -The ECU interprets the rail pressure from the fuel rail pressure sensor, compares it to a target value, and adjusts rail pressure control valve to reach correct pressure -Injectors supply fuel directly into cylinders -Surplus fuel is returned to the main fuel system through a fuel cooler -At max power, engine burns approx 29 L/hr (7.6 GPH), and return fuel flow is 82 L/hr (22 GPH) |
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Where is the air intake for the engine?
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Lower right hand side of the cowling.
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Where is the alternate air intake for the engine?
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Aft of the normal air intake.
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Is there a loss of power with the alternate air on?
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Nothing is indicated in either the AFM or the AMM
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Does the alternate air block off the normal air intake entirely?
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Looks like it does based on AFM & AMM
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What is the purpose of the turbocharger on the engine?
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To ensure air is properly compressed for combustion.
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Describe how the turbocharger works.
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Exhaust gas feeds to a turbine, which is essentially a wheel in exhaust gas flow, attached to a shaft, with a wheel at other end (compressor) in engine air intake.
The compressor is downstream of the air intake and compresses the air for proper combustion. As a result, air temperature is increased significantly. |
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How the turbocharger regulate how much air compressed?
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Through a wastegate: It's a bypass for exhaust gases located behind the turbine. It's controlled by the ECU.
The more it's open, the less exhaust gas flows over the turbine, resulting in less compression. The more it's closed, the more the turbine spins resulting in more compression of the air from the air intake. |
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How does the ECU control the waste gate?
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The ECU controls the wastegate based on a manifold pressure sensor behind behind the compressor. The sensor allows the correct position of the waste gate to be determined and allows any excess exhaust gases to bypass the turbocharger thereby preventing excessive manifold pressures at low density altitudes.
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What is the purpose of the intercooler?
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Since the air temperature is increased as it's compressed via the compressor, it needs to be cooled. Cooling the makes it more dense so it provides more power. It also prevents detonation.
Intercooler intake is on the LH side of the engine. |
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How is the engine cooled?
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-It is liquid cooled using a water-based with antifreeze additive
-Uses a two circuit system for engine cooling; Main circuit to coolant heat exchanger; Second circuit a bypass for cold engine temperatures (below 88°C or 190°F) -Separate circuit for cabin heat exchanger -Coolant level sensor in expansion tank; activates “Coolant Level” caution on PFD |
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Describe the coolant flow.
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-Coolant flows through passages in crankcase and cylinder heads
-Leaves through thermostat valve into the coolant radiator -From radiator on to coolant pump then into the engine |
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How are the engine parameters controlled?
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-The ECUs Monitor, control and regulates all important parameters of the engine. Most notably: Manifold pressure, Injected fuel quantity & Propeller speed
-The ECUs receive input from sensors & compare signals with programmed characteristics -There are 2 ECU’s per engine, A & B: A is used for normal operation, B for backup -Because the ECUs are electronic, electric power is required to run the engines. |
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For normal operations, which ECU controls the engine?
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For normal operations, the SWAP switch is set to automatic, and ECU A controls the engine. If an internal error or the loss of a sensor signal occurs, the system automatically switches to the ECU B. If the cause of the problem was a sensor loss, the system switches back to ECU A. If the switch to ECU B does not happen automatically, a manual switch may be necessary.
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If the ECU swap switch has been set to B, how do you switch it back to ECU A?
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Once the switch has been set to ECU B, the ECU B will remain in control even if the ECU SWAP switch is returned to AUTOMATIC. To change back to ECU A, the power lever must be set to idle and the ECU TEST button is pressed until both ECU caution lights on the annunciator panel go off.
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How are the ECUs powered?
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Under normal operation, power is supplied to the ECUs from the alternator.
If both alternators fail, main aircraft battery can provide power for 30 minutes – after which, both engines quit!!! |
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How are the power levers connected to the ECUs?
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2 independent electrical connections to each ECU. This allows either ECU to control the engine.
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Why should the power levers be moved slowly?
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It avoids over speeding the propellers.
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If the ECU swap switch is set to automatic, which ECU is operating?
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Both ECUs are operating at all times, but only one will be active and controlling the engine.
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Why would an ECU swap occur automatically?
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-Each ECU monitors its condition and calculate its “health level” continuously. If the health of one ECU is not 100%, the system switches to the other ECU automatically. An Annunciation appears on the PFD.
-Any abnormality is sent to an “event log” which maintenance can view with a diagnostic tool |
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How is the ECU health level calculated?
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Health level drops if a sensor is lost. Resulting health levels vary based on importance of sensor, eg: crankshaft more important than gearbox oil temp.
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Where is the engine time stored?
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It is stored in the ECUs.
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What happens when the Engine master switch is switched to ON?
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It provides power for:
-Engine -Engine pre heat system (glow plugs) -Unfeathering accumulator -Enables starter to be engaged -Connects respective alternator to the excitation batteries |
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Briefly describe the engine lubrication system.
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It's a wet sump lubrication system with an maximum oil capacity of 6.3 quarts (6 L) and a minimum 4.8 quarts (4.5 L).
Approved Oil grades: Shell Helix Ultra 5W30 Synthetic API SL/CF Shell Helix Ultra 5W40 Synthetic API SL/CF Aero Shell Oil Diesel 10W40 (this is the one we use) |
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How does the engine lubrication system work?
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-The bottom of the crankcase makes up the sump for oil system. -The engine oil pump takes oil from sump, through a filter and oil thermostat to a cooler.
-The cooler is bypassed when temp is colder than 80°C. -The oil from the cooler (or bypassed thermostat valve) returns to the engine Oil separator: vents blow-by gases and any remaining oil mist overboard Tank: oil filter housing; also houses oil pressure sensor Engine nacelle drains: 1 from oil separator, one from engine coolant expansion tank |
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Where is the oil cooler located?
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Top rear of engine nacelle
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How does the alternate air for the engines work?
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-It serves both engines simultaneously. Only one lever for both engines.
-It allows air to be drawn in from the engine compartment instead of the normal air intake. -Lever is located under the instrument panel to the right of the center console. |
