DA42 Twin Star

Aircraft Systems
Part II
 Outline
n Airframe n Propeller
n Flight Controls n Electrical System
n Stall Warning
n Landing gear
n Heating & Ventilation
n Engines and n Ice Protection System
associated systems
n Performance Charts
n Fire Protection n Operating Limitations
n Fuel
Engines
 Engine & Associated Systems
n General
n Diesel Engines
n Common Rail Injection
n Induction System and Turbocharging
n Cooling
n Engine Control Unit (ECU)
n Power Levers
n Master Switch
n Lubrication
n Alternate Air
 General
n 2 Thielert Diesel TAE
125-01 engines
n 135 HP @ 2300 RPM at
Sea Level
n 4 cylinders
n 4 stroke
n Liquid cooled
n Turbocharged
n Reduction gear to
propeller
n Wet sump oil system
 Diesel Engines
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
Common Rail Injection
 Induction System and Turbocharging
n Not principally different from conventional gasoline
engine
n Induction air intake on lower side of engine cowling
n Alternate air source aft of air intake
 Induction System and
Turbocharging
n Turbocharger
n To ensure air properly compressed for combustion
n Exhaust manifold collects exhaust from cylinders, feeds to
turbine
n Runs compressor
n Compressor
n Downstream of air intake
n Compresses intake air for proper combustion
n Air temperature is increased significantly
 Induction System and
Turbocharging
n Wastegate
n A bypass for exhaust gases, located behind turbine
n Controlled by Engine Control Unit (ECU)
n Positions
n Open: Less air flow through turbine (less compression)
n Close: More flow through turbine (more compression)
n Position adjusted to control manifold pressure intake
to engine
 Induction System and Turbocharging

n Compressed air is
cooled with an
Intercooler
n Intercooler intake on
left side of engine
n Cooler air more
dense, more power
developed
Intercooler
 Engine Cooling System

n Water-based with antifreeze additive

n Two circuit system for engine cooling
n Main circuit to coolant heat exchanger
n Second circuit a bypass for cold engine temperatures
n Below 88°C or 190°F
n Separate circuit for cabin heat exchanger
n Coolant temperature displayed on MFD
n Coolant level sensor in expansion tank;
activates “Coolant Level” caution on PFD
Engine Cooling System
 Engine Control Unit
n The heart of the FADEC System
n Monitors, controls and regulates all important
parameters
n Receives input from sensors & compares signals
with programmed characteristics
n 2 ECU’s per engine, A & B
n A is used for normal operation, B for backup
n ECU SWAP switch & ECU TEST switch
n Power supply
n ELECTRICAL POWER REQUIRED TO RUN ENGINES
Engine Control Unit
 Power Levers
n One per engine
n Selects % power
n Should be moved slowly
n Avoids over speeding the propellers
n 2 independent electrical connections to
ECU
n Provides signals to ECU A & ECU B
n Allows either ECU to run engine
 ECU Redundancy
n Two separate, independent ECUs (per engine)
n Both ECU’s operational at all times, but only
one active (ECU A normally)
n Each ECU monitors its condition, and calculate
its “health level” continuously
n If the health of one ECU is not 100%, the system
switches to the other ECU automatically
n Annunciation on PFD
n Any abnormality is sent to an “event log” which
maintenance can view with a diagnostic tool
 Engine Master Switch
n Provides power for:
n Engine
n Engine pre heat system (glow plugs)
n Unfeathering accumulator
n Enables starter to be engaged
n Connects respective alternator to the excitation batteries

Engine shut down by selecting Engine Master OFF

 Lubrication (Oil) System
n Separate systems for engine oil and propeller
gearbox oil
n Wet sump lubrication
n Oil capacity 6.3 quarts (6 L)
n Minimum 4.8 quarts (4.5 L)
n Approved Oil grades:
n Shell Helix Ultra 5W30 Synthetic API SL/CF
n Shell Helix Ultra 5W40 Synthetic API SL/CF
n Aero Shell Oil Diesel 10W40
Lubrication
(Oil) System
 Alternate Air
n Allows air to be drawn
from the engine
compartment
n Serves both engines
simultaneously
n Lever located under
instrument panel to the
right of the center
console
 Questions?
n For you:
n How does a common rail injection system
work?
n What is the purpose of the Engine Control
Unit (ECU)? How many ECU’s are there?
Fire Protection
 Fire Protection
n Overheat detectors
n Installed in engine nacelles
n Bi Metal switch
n Switch closes at 250°C / 480°F
n Warning on PFD
n ‘LH/RH ENG FIRE’
n Aural alert through intercom
n Operating gear warning TEST switch will
cause this warning to operate
Fire Protection
 Questions?

For you:
At what temperature does the overheat sensor
activate the warning on the PFD?
Aircraft Fuel System
 Aircraft Fuel System

n Components
n Distribution
n Auxiliary Fuel Tank
 Main Fuel Tanks
n Approved Fuel Grade: JET A
n 2 aluminum tanks, 3 chambers joined by hoses
n 25 USG (useable) per tank
n 50 USG total
n 1.0 USG unusable per tank
n NOTE: 1 U.S Gallon of JET-A = 7.01 lbs (@ 15°
C)
Fuel Tanks

Fuel System
 Components
n Fuel Selector
n 1 per engine / tank
n ON, X-FEED, OFF
n Safety guard prevents inadvertent selection of OFF
n Do NOT shut down engine with selector
 Components
n Indicating System
n Only outer and inner chambers have fuel quantity
probes
n Low Level sensors
n Float based
n Operate at 3-4 USG
n Fuel Cooler
n One for each fuel return system
n Air flows in through a NACA duct on the lower
surface of the engine nacelle, across fuel cooler
n Outlet is on rear face of nacelle.
Fuel Distribution
Normal Operation
Fuel Distribution - Crossfeed
 Auxiliary Tank (Optional)
n Provides
n 13.2 USG extra useable per side
n 76.4 USG total useable
n Tank
n Located in rear of engine nacelle
n Welded aluminium construction
n Baffles
n Prevent rapid fluid movement
n Separate filler cap
n Located at the top of the engine nacelle
Auxiliary Tank (Optional)
 Questions?
n For You:
n Why is a fuel cooler necessary on this
aircraft?
n If the LH engine failed inflight, how could
the fuel in the left tank be accessed?
Propellers
 Propellers
n Structure
n Constant Speed Unit (CSU)
n Pressure accumulator
n Feathering & Unfeathering
Propellers
 Propellers
nGeneral
nMade from wood, covered with GFRP
nAcrylic Lacquer painted finish
nMTV-6-A-C-F/CF187-129
nConstant speed, fully feathering
nErosion Protection on leading edges
nOutboard:
nBonded stainless steel sheath
nInboard:
nSelf adhesive rubber strip
 Propellers
n Gearbox
n Ratio of 1.69:1
(engine RPM to prop
RPM)
n Separate oil system
n ‘combi’ pump attached
to gearbox provides
pressure to constant
speed unit
n Overload clutch
 Constant Speed Unit
n Constant Speed Unit (CSU)
n Governor
n Electrically controlled 3 way valve
n Controls oil pressure in the propeller pitch change mechanism
n Propeller pitch change mechanism
n In propeller hub
n Piston that moves in reaction to oil pressure
n Movement of piston adjusts pitch of blades
n Increasing oil pressure
n Moves blades towards fine pitch
n Oil from gearbox system
Constant Speed Unit
Propeller RPM V Load
Propeller Schematic
 Propellers
n Accumulator
n Nitrogen & oil
n 290 PSI when engine is
running
n Used for:
n Unfeathering
n Maintaining RPM as engine
slows down
n Feathering
n Turn off engine master switch
n Unfeathering
n Turn engine master switch on
n Coarse pitch stop
n Prevents propeller from
feathering below 1300 RPM
 Questions?
n For You:
n Explain how the FADEC system is able to
adjust propeller RPM
n How does the unfeathering accumulator
work?
n Upon a normal engine shut-down, will the
propeller feather? Why or why not?