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Title: Flight Controls Note Part 2
Description: EASA PART 66 MODULE 11 FLIGHT CONTROLS NOTE PART 2

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3/15/2014

HIGH SPEED FLIGHT

SPEED OF SOUND
MODERN AIRCRAFT ARE CAPABLE AT CRUISING AT SPEEDS
AROUND 87% OF THE SPEED OF SOUND
...

THE SPEED AT WHICH SOUND WAVES TRAVEL WILL VARY WITH
A CHANGES IN TEMPERATURE
...

ON A DAY WITH A TEMPERATURE OF 150C, AT SEA LEVEL, THE
SOUND WILL TRAVEL AT 761 MPH, THE SPEED DECREASING
WITH ALTITUDE AS THE TEMPERATURE DROPS
...

SOUND WAVES WILL CAUSE A CONTINUOUS SERIES OF
PULSES OR PRESSURE WAVES RADIATING OUT FROM THE
POINT OF ORIGIN
...


SPEED OF SOUND

POINT OF ORIGIN

2

3/15/2014

SPEED OF SOUND
SOUND WAVES RADIATE OUT
FROM THE POINT OF ORIGIN

EQUAL IN ALL DIRECTIONS

SUBSONIC FLIGHT
WHEN THE AIRCRAFT BEGINS TO MOVE THROUGH THE AIR AT
SUBSONIC SPEEDS THE PRESSURE WAVES STILL RADIATE OUT
FROM THE AIRCRAFT
...

AS THE PRESSURE WAVES ARE CLOSER TOGETHER IN FRONT OF
THE AIRCRAFT, THE SOUND OF THE AIRCRAFT COMING
TOWARDS YOU WOULD SEEM LOUDER THAN WHEN IT HAS
PASSED YOU
...


3

3/15/2014

SUBSONIC FLIGHT
PRESSURE WAVE

DIRECTION OF
FLIGHT

SOUND RADIATES OUT FROM THE AIRCRAFT

SUBSONIC FLIGHT
SOUND WAVES ARE CLOSER
TOGETHER IN FRONT

SOUND WAVES ARE SPREAD OUT
BEHIND

THE SOUND WAVES TRAVEL FASTER THAN THE AIRCRAFT

4

3/15/2014

SUBSONIC FLIGHT

THE AIRCRAFT WOULD SOUND LOUDER COMING TOWARDS YOU AND QUIETER AS IT HAS
PASSES
...
IT IS TERMED
INCOMPRESSIBLE
...

AT SUPERSONIC SPEEDS THE AIRFLOW OVER THE
AEROFOIL SLOWS DOWN AND COMPRESSES AS IT FLOWS
OVER THE AEROFOIL
...


5

3/15/2014

TRANSONIC FLIGHT
DURING THE TRANSONIC STAGE SOME OF THE AIR
FLOWING OVER THE AIRCRAFT WILL BECOME
SUPERSONIC, WHILE THE REST WILL REMAIN SUBSONIC
...

THEY CONTINUE TO ACCUMULATE AND FORM A BOW
(SHOCK) WAVE IN FRONT OF THE AIRCRAFT
...


SUBSONIC FLOW
SUBSONIC AIRFLOW THROUGH A VENTURI

CONVERGING

DIVERGING

INCREASING VELOCITY

DECREASING VELOCITY

DECREASING PRESSURE

INCREASING PRESSURE

CONSTANT DENSITY

CONSTANT DENSITY

6

3/15/2014

SUPERSONIC FLOW
SUPERSONIC AIRFLOW THROUGH A VENTURI

CONVERGING

DIVERGING

DECREASING VELOCITY

INCREASING VELOCITY

INCREASING PRESSURE

DECREASING PRESSURE

INCREASING DENSITY

DECREASING DENSITY

TRANSONIC FLIGHT
BOW WAVE

PRESSURE WAVE

DIRECTION OF
FLIGHT

7

3/15/2014

TRANSONIC FLIGHT
PRESSURE WAVES TRAVELLING AT THE
SAME SPEED OF THE AIRCRAFT

TRANSONIC FLIGHT
BOW WAVE CONTINUES TO BUILD

THERE IS NO SOUND AS THE AIRCRAFT APPROACHES

8

3/15/2014

TRANSONIC FLIGHT

BOW WAVE

PRESSURE WAVES BUILDING UP ON AN AIRCAFT AEROFOIL

SUPERSONIC FLIGHT
ONCE THE AIRCRAFT IS SUPERSONIC ALL PARTS ARE
CONSIDERED TO BE ABOVE THE SPEED OF SOUND AND IT
WILL BE TRAVELLING FASTER THAN THE SOUND WAVES IT
GENERATES
...

THE SHAPE OF THIS CONE CHANGES AS THE SPEED OF THE
AIRCRAFT CHANGES
...


9

3/15/2014

SUPERSONIC FLIGHT
PRESSURE WAVE

DIRECTION OF
FLIGHT

SUPERSONIC FLIGHT

AIRCRAFT TRAVELLING FASTER THAN THE PRESSURE WAVES

10

3/15/2014

SUPERSONIC FLIGHT

PRESSURE WAVES BUILDING BEHIND THE AIRCARFT

SUPERSONIC FLIGHT

THE NUMBER OF PRESSURE WAVES PRODUCED IS INFINITE

11

3/15/2014

SUPERSONIC FLIGHT
MACH CONE

THE PRESSURE WAVES PRODUCE A MACH CONE

SUPERSONIC FLIGHT

MACH CONE

THE FASTER THE AIRCRAFT FLIES THE SHALLOWER THE MACH CONE BECOMES

12

3/15/2014

MACH NUMBER
THE MACH NUMBER IS A RATIO OF THE TRUE AIRSPEED OF THE
AIRCRAFT AND THE LOCAL SPEED OF SOUND AT A GIVEN
ALTITUDE
...
TWICE THE SPEED IS MACH 2 AND
HALF THE SPEED OF SOUND IS TRAVELLING AT MACH 0
...


SUBSONIC FLOW - MACH NUMBERS BELOW 0
...
75 TO 1
...
2 TO 5
...
0

CRITICAL MACH NUMBER
THE AIR FLOWING OVER THE TOP OF A WING IS FASTEST
AT THE THICKEST PART OF THE CHORD
...

AS THE AIRCRAFT INCREASES SPEED THIS AIR WILL TRAVEL
AT MACH 1, EVEN THOUGH THE REST OF THE AIRCRAFT IS
STILL AT SUBSONIC SPEEDS
...
THIS SPEED IS CALLED ‘THE
CRITICAL MACH NUMBER’
...

A THICK WING WILL WILL CAUSE THE AIRFLOW TO SPEED UP
OVER THE CAMBER AND REACH MACH 1 MORE QUICKLY
THAN A THIN WING
...

IN THE TRANSONIC RANGE, AN AIRCRAFT WITH A THIN
WING CAN FLY FASTER THAN AN AIRCRAFT WITH A THICK
WING, BEFORE ANY ADVERSE EFFECTS ARE FELT
...

THE EFFECTS INCLUDE VIBRATION, BUFFETING, AN
INCREASE IN DRAG, A DECREASE IN LIFT AND MOVEMENT
OF THE CENTRE OF PRESSURE
...
IT IS
REFERRED TO AS ‘SHOCK STALL’

14

3/15/2014

SHOCK WAVE
IF THE AEROFOILS ANGLE OF ATTACK WAS ZERO THE SHOCK
WAVE WOULD FORM EQUALLY ON THE UPPER AND LOWER
SURFACES
...

THE INITIAL SHOCK WAVE TO FORM IS CALLED ‘THE
INCIPIENT SHOCK WAVE’
THE WAVE EXTENDS OUTWARDS AT RIGHT ANGLES TO THE
AEROFOIL SURFACES AND IS CALLED THE ‘NORMAL SHOCK
WAVE’
...
77

15

3/15/2014

SHOCK WAVE
THE SHOCK WAVE CAUSES THE AIFLOW OVER THE UPPER
SURFACE TO DECELERATE TO SUBSONIC SPEED,
RESULTING IN AN INCREASE IN PRESSURE
...

THE AIRFLOW BECOMES TURBULENT AND THERE IS A
RAPID INCREASE IN DRAG AND A LOSS OF LIFT
...

SEVERE BUFFETING IS LIKELY AND COULD LEAD TO A
‘SHOCK STALL’
...
82

16

3/15/2014

SHOCK WAVE

SUPERSONIC FLOW

NORMAL SHOCK WAVE

SHOCK INDUCED
SEPARATION

AT MACH 0
...

AS THE AIRCRAFT’S SPEED INCREASES THE SHOCK WAVE
MOVES AFT
...

AS THE AIRCRAFT REACHES THE UPPER TRANSONIC RANGE
BOTH SHOCK WAVES MOVE AFT AND ATTACH AT THE
TRAILING EDGE
...

THE ADVERSE TRANSONIC EFFECTS WILL BE ELIMINATED
...
05

EFFECTS OF MACH NUMBER ON LIFT
MAXIMUM LIFT IS UP TO M 0
...
5

1
...
5

MACH NUMBER
LIFT DRASTICALLY DROPS AS THE CRITICAL MACH NUMBER IS APPROACHED

18

3/15/2014

EFFECTS OF MACH NUMBER ON DRAG
DRAG INCREASES DRASTICALLY UP TO M 0
...
5
MACH NUMBER

1
...
5

DRAG STARTS TO
INCREASE AT M
0
...

IN ADDITION THE INCREASED PRESSURE ON THE
LEADING EDGES WILL GENERATE HIGHER
TEMPERATURES
...


21

3/15/2014

AERODYNAMIC HEATING
THE HEATING OF THE AIRCRAFT WILL CAUSE ITS SKINS AND
VARIOUS MATERIALS TO EXPAND AT DIFFERENT RATES
...

THE MAXIMUM TEMPERATURE WOULD BE FELT ON THE
AIRCRAFT’S NOSE AND WOULD BE IN THE REGION OF 1750C
...

SENSORS ON THE CONCORDE WILL REDUCE THE SPEED TO MACH
1
...


AREA RULE
THIS IS USED FOR THE DESIGN OF HIGH SPEED AIRCRAFT
AND USES THE THEORY THAT IF THE CROSS-SECTIONAL
AREA DOES NOT HAVE LARGE CHANGES, THE DRAG WILL
BE KEPT TO A MINIMUM
...

ALTERNATELY THE FUSELAGE CROSS SECTIONAL AREA
COULD BE INCREASED WITH THE USE OF ENLARGED
SECTIONS IN FRONT AND BEHIND THE WINGS
...

THE SMOOTHER
PATTERN OF THE
AREA RULE
AIRCRAFT
...
5
...
IF THE AIR ENTERING THE ENGINE IS ABOVE 0
...

IF THE AIRCRAFT WAS TO CRUISE BETWEEN MACH 0
...
0, A DIVERGENT DUCT CAN BE USED
...
5
HOWEVER BECAUSE OF THE CHANGES IN THE PROPERTIES OF
THE AIR AT THE SPEED OF SOUND, IF THE AIRCRAFT IS TO FLY
ABOVE MACH 1 THEN A CONVERGING DUCT WILL BE
REQUIRED TO SLOW THE AIR DOWN
...
0
...
0
...

ONE WAY OF ACHIEVING THIS IS BY THE USE OF SWEPT-BACK
WINGS
...

SWEEPBACK NOT ONLY DELAYS THE EFFECTS OF THE SHOCK
WAVE BUT ALSO REDUCES THE SEVERITY OF THE SHOCK STALL
SHOULD IT OCCUR
...
8

0
...
9

0
...
0

CRITICAL MACH NUMBER

27

3/15/2014

EFFECTS OF SWEEPBACK
ASPECT RATIO = 3
CD
STRAIGHT WING
300 SWEEPBACK
450 SWEEPBACK

0
...
0

1
...
4

1
...
8

2
...
2

MACH NUMBER

MACH TRIM
AS THE AIRCRAFT APPROACHES THE CRITICAL MACH NUMBER
THE CENTER OF PRESSURE MOVES, THE WING STARTS TO
GENERATE LESS LIFT WITH MORE DRAG
...

(ALSO KNOWN AS TUCK UNDER)
THE MACH TRIM SYSTEM AUTOMATICALLY COUNTERACTS
THIS BY VARYING THE TAIL PLANE ANGLE IN RELATION TO THE
AIRSPEED TO MAINTAIN A STRAIGHT AND LEVEL ATTITUDE
...
68 TO 0
...


28

3/15/2014

FLIGHT CONTROL SYSTEMS

FLIGHT CONTROL OPERATION
ON LIGHT AIRCRAFT FLIGHT CONTROL OPERATION IS NORMALLY
ACTUATED BY A SYSTEM OF CABLES, PULLEYS, FIXED AND
ADJUSTABLE CONTROL RODS BELLCRANKS LEVERS AND TORQUE
TUBES
...

ON LARGER MORE COMPLEX AIRCRAFT THIS SYSTEM IS
SUPPLEMENTED BY A SYSTEM OF HYDRAULICALLY OPERATED SERVO
JACKS WHICH ACTUATE THE CONTROLS
...

ATA Chapter 27

29

3/15/2014

FLIGHT CONTROL OPERATION
THIS RELIEVES PILOT LOADS AND ASSISTS WITH THE ACTUATION OF
THE CONTROL
...

THE LINKAGE OPERATES A SERVO VALVE WITHIN THE JACK WHICH
DIRECTS HYDRAULIC FLUID TO ONE SIDE OR THE OTHER OF THE
ACTUATOR, TO EXTEND OR RETRACT IT
...

THIS INCREASES THE CONTROL LOADS BUT THEY REMAIN WITHIN
THE PILOTS CAPABILITIES
...

THE AERODYNAMIC LOADS ON THE CONTROL SYSTEMS WOULD BE
TOO HIGH FOR THE PILOT TO OVERCOME MANUALLY
...

AS A SAFETY FACTOR THE FLYING CONTROLS WILL NORMALLY HAVE
DUAL HYDRAULIC SYSTEM OPERATION
...

THE PILOT CAN CONTROL PITCH AND ROLL BY ONE OF
THE FOLLOWING CONTROL INPUT DEVICES:
CONTROL COLUMN
...

SIDE STICK
...

THEY ALLOW FOR BIGGER MOVEMENTS OF THE CONTROLS
NEEDED BY THESE TYPE OF AIRCRAFT
...


CONTROL
YOKE ASSY

32

3/15/2014

WHEEL AND CONTROL COLUMN (BOEING)

33

3/15/2014

SIDE STICK CONTROL (AIRBUS)
THE SIDE STICK CONTROLLER IS GENERALLY USED TO
CONTROL FLY BY WIRE AIRCRAFT
...


A320 Cockpit

34

3/15/2014

FLIGHT CONTROLS

ALL OF THE THE CONTROL STICKS HAVE CONTROL
SWITCHES ON THE HAND GRIPS
...

INTERCOM AND RADIO COMMUNICATION SWITCHES
...
)

CONTROL RODS
CONTROL ROD BODYS ARE NORMALLY MANUFACTURED
FROM LIGHT ALLOY OR STEEL WITH STEEL EYE OR FORK
ENDS
...

ADJUSTABLE RODS ARE USED FOR RIGGING PURPOSES
...


35

3/15/2014

CONTROL RODS
THE ENDS ARE LOCKED TO THE BODYS USING TAB WASHERS, DOUBLE
LOCKNUTS OR LOCKING WIRE
...

CONTROL RODS DO NOT HAVE THIS PROBLEM
...

CONTROL RODS CONNECT AT INTERVALS TO BELLCRANKS AND
QUADRANT ASSEMBLIES
...
THEY ARE
MANUFACTURED FROM EITHER CORROSION RESISTANT
OR GALVANISED STEEL AND MAY BE COVERED IN A
PLASTIC SHEATH
...

THE CABLES DIFFER IN SIZE DEPENDING ON THEIR
WORKING LOADS
...


37

3/15/2014

CONTROL CABLES

1 X 7 NONFLEXIBLE

1X19 NONFLEXIBLE

7X7 FLEXIBLE

7 X 19 EXTRA
FLEXIBLE

THE CABLE IS DETERMINED BY THE NUMBER OF STRANDS
IT CONTAINS AND THE NUMBER OF WIRES IN EACH
STRAND
...


CONTROL CABLES
THE FLEXIBLE AND EXTRA FLEXIBLE ARE USED THE MOST
FREQUENTLY ON AIRCRAFT
...

FLEXIBLE CABLES ARE USED WHERE THE CABLE CHANGES
DIRECTION AROUND A PULLEY
...

SMALLER DIAMETER CABLES MAY BE USED ON TRIM
SYSTEMS BUT DEPENDS ON THE MANUFACTURERS
REQUIREMENTS
...

THEY ARE INSPECTED FOR CONDITION AT REGULAR
INTERVALS
...

CABLES ARE NORMALLY GIVEN A LIFE AND ARE REPLACED
WHEN THEY BECOME DEFECTIVE OR LIFE EXPIRED
...


CABLE END FITTINGS
THREADED END FITTING FOR CHAINS

FLAT END-FITTING FOR FORK ENDS
...


THREADED END FITTING FOR TURN BUCKLES

39

3/15/2014

CONTROL CABLES
SOME OLDER CABLES USE THIMBLE EYE FITTINGS
...

IT IS THEN PASSED BACK INTO THE SLEEVE
...


40

3/15/2014

41

3/15/2014

CABLE FRAYING

42

3/15/2014

TURNBUCKLES
TURNBUCKLES ARE USED TO ADJUST THE TENSION OF THE
CABLE IN ACCORDANCE WITH THE AMM
...
THE
ENDS ARE HELD STATIONARY WHILST THE BARREL IS ADJUSTED
...

LOCKING CLIPS MAY BE USED
...


45

3/15/2014

FAIRLEADS
FAIRLEADS ALSO SUPPORT CABLES OVER LONG RUNS

FAIRLEAD

SUPPORT BRACKET
CABLE

THEY ARE NOT USED TO CHANGE THE DIRECTION OF THE
CABLE AND IT SHOULD NOT BE ALLOWED TO DEFLECT THE
CABLE
...

THEY ARE MADE OUT OF THERMOSETTING PHENOLIC
PLASTIC REINFORCED FABRIC OR ALUMINIUM
...

EACH PULLEY IS FITTED WITH AN INTEGRAL CABLE GUARD
TO PREVENT THE CABLE FROM SLIPPING OUT OF THE
PULLEY GROOVE WHEN THE CABLE TENSION DECREASES
...

THERE WILL BE A CHART IN THE MAINTENANCE MANUAL
SHOWING TENSION SETTINGS AGAINST TEMPERATURE
...

THE SETTING WILL RELATE TO A POINTER AND SCALE ON
THE REGULATOR BODY WHICH IS ADJUSTED TO THE SET
TEMPERATURE
...


PITCH CONTROLS
CONTROL SURFACE
CABLE TENSION REGULATOR
CONTROL YOKE - PUSH PULL

TORQUE TUBE

BELLCRANK
CABLE RUNS

PULLEYS

THE CABLE TENSION REGULATOR KEEPS A CONSTANT
TENSION ON THE CABLE REGARDLESS OF TEMPERATURE
...

• HYDRAULIC PRESSURE IS SUPPLIED FROM AT LEAST 2
SYSTEMS FOR REDUNDANCY
• MAY ALSO BE ASSISTED BY BALANCE PANELS AND
BALANCE TABS
...
F
...
U
...

• AS THE PISTON EXTENDS OR RETRACTS, ITS OUTPUT TO THE
CONTROL SURFACE IS PROPORTIONAL TO THE PILOTS INPUT
...

• THE MOVEMENT OF THE OUTPUT SYSTEM CANCELS THE
INPUT ONCE THE DESIRED CONTROL SURFACE POSITION HAS
BEEN REACHED
...
IT REMOVES THE SUPPLY ONCE THE CORRECT POSITION IS ACHIEVED

57

3/15/2014

POWERED FLYING CONTROLS
THE PFCU CAN BE TANDEM, DUAL OR TRIPLICATE
...

THERE MUST ALSO BE AN IDLE CIRCUIT MADE THROUGH
THE FAILED PFCU TO ALLOW THE FLUID TO CIRCULATE,
THROUGH THE FAILED SYSTEM, SO THAT IT HAS NO
EFFECT ON THE GOOD SYSTEM
...


TANDEM ACTUATOR

58

3/15/2014

Dual Assy PFCU

59

3/15/2014

DUPLICATE OR TRIPLICATE PFCU
TYPE 1
DUAL OR TRIPLICATE PFCU`S HAVE THEIR ACTUATORS
MOUNTED SIDE BY SIDE
...

HYDRAULIC PRESSURE IS PROVIDE BY AN ELECTRICALLY
DRIVEN RADIAL TYPE PUMP WITH A SLIP RING
ASSEMBLY
...

AN INPUT WILL CAUSE THE SLIP RING TO MOVE TO AN
ECCENTRIC POSITION
...

THIS TYPE OF PFCU WILL BE DUPLICATED AND EACH MAY
DRIVE A DUPLICATE AND INDEPENDENT CONTROL SURFACE
...
FURTHER INPUTS
ARE ABSORBED BY SPRING UNITS WHICH ALLOW THE OTHER
PFCU’S TO CONTINUE OPERATING
...


SELF CONTAINED PFCU

62

3/15/2014

INPUT SYSTEMS
GENERALLY THE INPUT SYSTEMS ARE PRIMARILY EITHER
CABLE OR ROD, WITH RELATED QUADRANTS BELLCRANKS,
PULLEYS AND FAIRLEADS
...

THE CABLE SYSTEMS MEET AT A COMMON INPUT TO THE
CONTROLS AND MAY BE INTERCONNECTED THROUGH
TORQUE TUBES (OR A CHAIN) AT THE CONTROL COLUMN
AND TO THE LINKAGES TO THE PFCU
...

FLIGHT CONTROLS ARE LEAST EFFECTIVE AT LOW SPEED DUE TO
REDUCED AERODYNAMIC EFFECTS
...

ONE PROBLEM IS OVER SENSITIVE CONTROLS WHICH COULD
LEAD TO THE LOSS OF CONTROL OR OVER STRESSING OF THE
AIRFRAME
...


66

3/15/2014

HIGH SPEED AILERONS
NORMAL AILERONS ARE SITUATED INBOARD OF THE WING
TIPS FOR MAXIMUM EFFECTIVENESS AT LOW SPEED
...

AT HIGH SPEED THE HYDRAULIC VALVES WHICH FEED THE
OUTER AILERONS ARE ISOLATED AND THE AILERONS ARE
LOCKED INTO THE NEUTRAL POSITION
...


HIGH SPEED AILERONS
PRESSURE TRANSDUCERS SENSE AIRSPEED SIGNALLED
FROM THE PITOT SYSTEM TO ISOLATED THE OUTER
AILERONS WHEN A PRE-DETERMINED AIR SPEED IS
REACHED
...

ON SOME AIRCRAFT BOTH SETS OF AILERONS WILL
OPERATE AT LOW SPEED, OTHERS WILL SWITCH BETWEEN
EITHER THE LOW OR HIGH SPEED AILERONS
...
THE FASTER AN AIRCRAFT FLIES
THE LESS MOVEMENT IS REQUIRED AT THE CONTROL SURFACE
...
IF A CONTROL ROD IS OPERATED BY A LEVER, THE
SHORTER THE LEVER THE LESS THE ROD MOVES
...

IN EFFECT THIS WILL MAINTAIN A CONSTANT RANGE OF
MOVEMENT AT THE PILOTS CONTROLS BUT REDUCE THE
RANGE OF MOVEMENT AT THE CONTROL SURFACE
...


68

3/15/2014

FLAP CONTROLS
ON SMALL AIRCRAFT FLAPS ARE OPERATED USING
HYDRAULIC JACKS WHICH ACTUATE A SINGLE FLAP ON
EACH MAINPLANE
...

SOME AIRCRAFT USE LINEAR ACTUATORS EACH
CONTROLLED BY A SERVO VALVE
...


SMALL AIRCRAFT FLAP CONTROLS
DEPLOYMENT IS INITIATED BY A COCKPIT LEVER WHICH IS
MECHANICALLY CONNECTED TO THE SERVO VALVES BY A
DUPLICATED SYSTEM OF CABLES, BELLCRANKS, QUADRANTS
AND CONTROL RODS
...

THE ACTUATOR RAM IS ATTACHED TO THE AIRFRAME
STRUCTURE ALLOWING THE ACTUATOR BODY TO MOVE
...


69

3/15/2014

Small Aircraft Hydraulic System

Flap Actuator

70

3/15/2014

SMALL AIRCRAFT FLAP CONTROLS
OPERATING THE SELECTOR LEVER FROM THE FLAPS UP
POSITION COMPRESSES A SPRING STRUT
...

THIS INPUT TO THE SPRING UNIT IS PROGRESSIVELY
RELEASED AS THE ACTUATORS RESPOND TO THEIR
CONTROLLED RATE OF DEPLOYMENT
...


SMALL AIRCRAFT FLAP CONTROLS
THERE ARE ALSO INTERNAL MECHANICAL LOCKS WHICH
ENGAGE WHEN THE FLAPS ARE FULLY UP
...

THE FLAP SECTIONS ARE INTERCONNECTED BY LINKS WHICH
PREVENT THE FLAPS DEPLOYING ASYMMETRICALLY
...
THIS SHOWS THE POSITION OF EACH SET
OF F LAPS
...


71

3/15/2014

FLAP CONTROLS SAFETY ASPECTS
• System cables are duplicated in case one cable breaks
...

• Should an actuator become hydraulically locked or its
control signal lost the interconnecting links will lock
the controls in alignment
...
It could be through accumulator
charge pressure where operation could be limited
...

• Some aircraft have an electric motor as back up if the main
system fails
...

• The screw jacks drive the flaps through linkages and trolleys
(carriages) along flap tracks
...
(B727 and B737 located in wheel well)
• A gearbox driven by hydraulic motors
• When the flaps reach the selected deployed position
micro switches on the gear driven selector drum arrest
the flaps
...


74

3/15/2014

B727 Flap Power Drive Unit

Flap Drive Unit

75

3/15/2014

76

3/15/2014

77

3/15/2014

FLAP TRANSMISSION SYSTEM
TORQUE SHAFTS CONNECT THE DRIVE UNIT TO THE SCREW
JACKS
...

FLAP TROLLEYS RUN ALONG TRACKS THAT ARE ATTACHED
TO THE WINGS TRAILING EDGES AND ARE MOVED UP AND
DOWN BY THE SCREW JACKS
...

• Movement of the flap selector lever energises the
appropriate solenoid selector valve to allow
pressurised fluid to pass to the hydraulic motor
...

• When the flaps reach the selected setting the solenoid
selector valve is de-energised by operation of the
selector drum microswitches
...

TO PREVENT THIS FROM OCCURRING ASYMMETRY
PROTECTION CIRCUITS ARE INCORPORATED IN THE CONTROL
SYSTEM
...
C
...

THE TRANSMITTERS ARE PAIRED AND IF THE SIGNALS BECOME
OUT OF PHASE WITH EACH OTHER THE FLAPS ARE ISOLATED
AND LOCKED
...
82M

85

3/15/2014

Flap Maintenance (Hydraulic Torque Tube
System)
• Lubrication on screwjack, hinge, flap tracks, carriages,
torque tube
• Check for rubbing or chaffing with fixed structure
• Leak check on transmission and gearboxes
...

• Check conditions of leading edge anti abrasion coating,
reapply as necessary
• Flap spitting adjustment
• Corrosion inspection of flap tracks and attachment
area (every 10 years for 727 and 737)
• Duplicate inspection

LEADING EDGE FLAP LEVER
LEADING EDGE FLAP LEVER AND
QUADRANT

86

3/15/2014

FLAP OPERATION LEVERS
FLAP QUADRANT

FLAP LEVER
ROTARY TRANSDUCER

TYPICAL LARGE AIRCRAFT FLAP DRIVE

87

3/15/2014

Typical Electrical-Hydraulic Flap System (Airbus)

LEADING EDGE FLAP CONTROL
• A leading edge flap system include variable camber
and kreugar flaps
• B747 have as many as 28 flaps on the wing
...

• Krueger on some aircraft operated by linear hydraulic
actuator to single stage fixed position (B727 and B737)
• Krueger flaps normally located inboard near the wing
roots

88

3/15/2014

PNEUMATIC LEADING EDGE FLAP CONTROL
B747 uses penumatic system for the LE flap controls
...

Flap lever selections drive the primary mode
Each power unit will have two drive motors
Primary motor is pneumatically driven
...


LEADING EDGE FLAP CONTROL
Rotary variable differential transducer (RVDT) senses the
lever movement and sends a signal to a flap control unit
...

There will be a transducer for each of the flap lever
settings
...

The electric motors will also have limit switches that
stops the flaps when the selected flap setting is reached
...

Pneumatic operation is more rapid than electric
...

OR BY THE AUTOMATIC FLIGHT CONTROL SYSTEM
...

SPOILERS ARE NORMALLY ELECTRICALLY CONTROLLED
AND HYDRAULICALLY ACTUATED
...

SPOILER CONTROL UNITS RECEIVE THESE SIGNALS AND
SEND THE PROCESSED SIGNALS TO THE SPOILER
ACTUATORS
...

ELECTRO HYDRAULIC VALVES CONTROL THE FLOW OF
HYDRAULIC FLUID TO THE ACTUATOR IN RESPONSE TO THE
SPOILER CONTROL UNIT COMMANDS
...

A ROTARY TRANSDUCER SENDS A FEEDBACK SIGNAL TO THE
SPOILER CONTROL UNIT WHICH IS ALSO PROPORTIONAL TO
THE DEFLECTION OF THE CONTROL SURFACE
...

IN SOME SYSTEMS OPERATING THE AILERON WILL ALSO
DEPLOY THE SPOILERS
Title: Flight Controls Note Part 2
Description: EASA PART 66 MODULE 11 FLIGHT CONTROLS NOTE PART 2