DA 42 Twin Star

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DA 42 Twin Star

• Aircraft Systems
• Part I

2
Outline

• Airframe
• Flight Controls
• Landing Gear

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Airframe

• Fuselage
• Semi-monocoque molded construction
• Carbon Fiber Reinforced Plastic (CFRP)
  half-shells for skin (includes vertical
  stabilizer)
• Glass Fiber Reinforced Plastic (GFRP) frames and
  webs for strength and stiffness
• Center wing bolted to fuselage
• Mountings for wings, engines/nacelles and landing
  gear
• 28 6 length

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Airframe

• Wings
• Front Rear spar top shell and bottom shell
• Principally sandwich construction aluminum fuel
  tank in each wing
• 44 wingspan
• Horizontal Stabilizer
• Top bottom shells of GFRP front and rear spars

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Airframe

• Lightning Protection
• Necessary due to composite construction
• All metal components are bonded to the lightning
  conductors
• Aluminum alloy tubes (nose to tail, wingtip to
  wingtip) and strips / braids

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Lightning Protection Diagram
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Flight Controls

• Ailerons
• Flaps
• Elevator
• Elevator Trim
• Rudder
• Rudder Trim

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Flight Controls
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Ailerons

• GFRP/CFRP Sandwich
• Operated through control rods
• 4 hinges secured by a roll pin
• Aerodynamic balance
• Located on outboard bottom of aileron
• Must be checked for debris before flight

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Ailerons 4 Roll Pins Flaps 10 Roll Pins If
pin slips upwards, ok If pin slips downwards,
needs maintenance
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Flaps

• GFRP/CFRP Sandwich
• 2 section construction
• Outer
• 6 hinges connects to wing
• Inner
• 4 hinges connects to center wing
• Fail-safe construction

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Flaps

• Electrically operated 3 settings
• UP (cruise), APP (approach), LDG (landing)
• 0, 20, 42 respectively
• Flap Position Indicator

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Flap Control System Diagrams
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Elevator

• GFRP top bottom shells
• Operated through steel push rods
• Trim tab at trailing edge
• Variable elevator stop
• Electrically operated
• Linear actuator
• Acts as a moveable stop
• Limits elevator up movement
• When both engines exceed 20 and
• Flaps are set to landing

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Elevator Control System
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Variable Elevator Backstop
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Elevator Trim

• Mechanical electrical systems
• Trim tab actuator through trailing edge of
  elevator
• Two actuating levers
• Left
• Connects to long flexible cable that is adjusted
  by the pilot
• Right
• Friction damper
• Prevents fluttering if mechanical failure of trim
  cable

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Trim Tab Actuator Assembly
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Elevator Trim Actuators
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Rudder

• Operated through cables from rudder pedal
  assembly
• Two hinges
• Upper hinge
• One bolt
• Lower hinge
• Is available for visual inspection

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Rudder Trim

• Controlled with black trim wheel in center
  console
• Flexible cable
• Connects hand wheel to trim actuator assembly
• Two operating rods
• Connect actuator assembly to the trim tab control
  horn

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Rudder Control System Diagrams
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Questions?

• What is the purpose of the elevator stick
  limiter?
• How does it work?

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Landing Gear

• Outline
• General
• Steering
• Hydraulic Supply Control
• Extension Retraction
• Emergency Extension
• Indicating System
• Safety Features
• Brakes

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Landing Gear

• General
• Fully retractable
• Hydraulically operated electrically powered
• Dampers compress quickly, but expand slowly
• Main Gear
• Tubular strut with trailing link at the bottom
• Wheel attaches to the trailing link
• Gas/Oil filled damper attaches to rear of tubular
  steel strut and the trailing link

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Main Gear Micro switches
Up lock switch
Down lock switch
Squat switch
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Landing Gear

• Nose Gear
• Steel strut with gas/oil damper to absorb shock
• Steering obtained by rudder control system via a
  steering linkage
• Steering stops attached to gear leg limit nose
  wheel travel to 30
• Spring assembly attached to tubular steel strut
  centers gear when deflected

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Nose Gear Micro switches
Up lock switch
Down lock switch
Full-pressure switch
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Full Pressure Switch -- Aft wall of nose gear bay
Forward
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Nose Gear Assembly
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Hydraulic Supply Control

• Hydraulic Control Block
• Heart of hydraulic system
• Electric motor
• Hydraulic pump pressure switch
• Hydraulic reservoir
• Hydraulic accumulator
• Located rear of aft cockpit bulkhead, left side

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Landing Gear Operation

• System is always pressurized
• Electrically operated valves provide required
  hydraulic pressure to move actuators on each gear
  leg
• Main gear retracts inboard into center wing
• Nose gear retracts forward into nose
• Hydraulic pressure on actuators keep gear
  retracted

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Retraction Differential Pressure
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Retraction Full Pressure
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Normal Extension
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Emergency Extension

• Up to 156 KIAS
• 110 KIAS in cold air
• Emergency extension lever
• Releases hydraulic pressure to reservoir
• May take 20 seconds
• Training different due to breaker pull

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Emergency Extension
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Emergency Extension

• NOTE Failure of electrical system causes gear to
  automatically extend!
• AFM Notes gear may slowly extend

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Gear Indicating System

• On instrument panel, next to gear selector switch

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Safety Features

• Squat Switch
• Left main gear leg
• Right main gear leg
• Gear Warning Horn
• Sounds with gear retracted
• Either power lever below 25 or
• Flap position in LDG

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Questions?

• For you
• How could you test the function of the gear
  warning horn while in-flight?
• What will happen if the gear handle is selected
  UP while on the ground?
• What is the emergency extension method for the
  landing gear?

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Brakes

• Two sets of master cylinders
• Pilot copilot
• Fluid reservoirs
• Behind copilots rudder pedals
• Operated with toes of rudder pedals
• Each pedal operated the brakes for that main
  wheel
• Parking brake
• Pull down and pump 3 times

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• Copilots master cylinder fails -gt Pilot side
  still works
• Pilots master cylinder fail -gt No brakes work
• Parking brake valve works as one-way valve when
  engaged only works when toe brakes pumped 3-4
  times to pressurize