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Title: Flight Controls Note Part 4
Description: EASA PART 66 MODULE 11 FLIGHT CONTROLS NOTE PART 4
Description: EASA PART 66 MODULE 11 FLIGHT CONTROLS NOTE PART 4
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4/15/2014
STALL WARNING AND PROTECTION
IF THE ANGLE OF ATTACK OF AN AIRCRAFT WING
INCREASES TO THE STAGNATION IT WILL STALL
...
AS THE AIRFLOW BECOMES MORE TURBULENT IT STARTS
TO IMPACT AGAINST THE AIRFRAME AND CAUSE
BUFFETING
...
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STALL WARNING AND PROTECTION
MANY AIRCRAFT DESIGNS DO NOT HAVE INHERENT
WARNINGS AND THEREFORE REQUIRE A WARNING
SYSTEM WHICH CAN DETECT AND ALERT THE PILOT OF
AN IMPENDING STALL
...
2
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PNEUMATIC STALL WARNING
THIS SYSTEM IS COMMON ON LIGHT AIRCRAFT
...
IT IS COVERED BY A SEALED,
ADJUSTABLE PLATE, THAT ACTS AS PART OF THE LEADING
EDGE
...
THE PLENUM CHAMBER IS CONNECTED BY A TUBE TO A REED
HORN ASSEMBLY MOUNTED IN THE COCKPIT
...
AS THE AIR PRESSURE AT THE SLOT REDUCES THE AIR IS
DRAWN IN TO THE PLENUM CHAMBER AND THROUGH
THE REED HORN ASSEMBLY
...
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WARNING HORN
HORN
SEAL
SCREEN
ADJUSTABLE PLATE
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ELECTRONIC STALL WARNING
• THIS SYSTEM IS USED ON LARGER AIRCRAFT (AND SOME
SMALL AND MEDIUM SIZE GENERAL AVIATION AIRCRAFT –
EG: KINGAIR)
• THIS IS A SIMPLE SYSTEM THAT USES A VANE OPERATED
MICRO SWITCH TRANSDUCER TO ACTIVATE THE WARNING
ALARM
...
• THE OPERATING VANE IS AT THE STAGNATION POINT
DURING NORMAL FLIGHT AND IS SENSITIVE TO AIR LOADS
...
AT A POINT JUST PRIOR TO A STALL CONDITION THE
LOADS ACTING ON THE VANE OVERCOME A SPRING
WHICH DEFLECTS THE VANE
...
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LEADING EDGE
ELECTRICAL SUPPLY
LIFT TRANSDUCER
OPERATING VANE
GASKETS
GASKET
TRANSDUCER MOUNTING PLATE
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Stall Protection System
• Stall Warning - As with the previous system this tells
the pilot that he is approaching a stall condition
...
e
...
• Auto Ignition – Automatically activate engine ignition
system to prevent engine stall/flameout
• Flap/Slat/Krueger Flap Modulation - monitoring of flap
and slat position and delay the initiation of stall
warning
...
They may be mounted on the main-planes or side
of the fuselage
...
• Stall Warning Computer - Receives signals from the
sensors and initiates warnings or control movements
...
An
electrically driven, out of balance rotor, which shakes
the control column when a stall warning condition, is
detected
...
It may usually be over-ridden by higher than normal
pilot force
...
• Test - A pre-flight test facility is built into the system
...
To prevent this an
input to the computer from mach switches or the air data
computer may be included to give a stall warning at high
mach numbers
...
THESE ARE:
AUTO IGNITION - ESPECIALLY ON REAR ENGINED
AIRCRAFT WHERE THE TURBULENT AIRFLOW
GENERATED WHEN AN AEROFOIL STALLS MAY FLAME
OUT THE ENGINE
...
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ANGLE OF ATTACK SENSOR/ INCIDENCE PROBES
INCIDENCE PROBES ARE MOUNTED IN THE CLEAR AIRFLOW ON
THE FORWARD FUSELAGE
...
THE INCIDENCE PROBES MAY HAVE INTEGRAL HEATERS WHICH
PROTECT THEM FROM ICING CONDITIONS
...
INCIDENCE PROBES DETECT THE DIRECTION OF THE AIRFLOW IN
RELATION TO THE AIRCRAFT DATUM AND TRANSMITS THIS
INFORMATION BY POTENTIOMETERS TO THE STALL WARNING
COMPUTER
...
WHEN THE ANGLE OF INCIDENCE INCREASES, A DIFFERENTIAL
PRESSURE IS FELT ACROSS THE PROBE SLOTS, WHICH CAUSES
A PADDLE WHEEL INSIDE THE PROBE TO ROTATE UNTIL THE
PRESSURES ARE EQUAL
...
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INCIDENCE PROBE
Potentiometer
Slots
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Angle of Attack Sensor
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Angle of Attack
Sensor
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ANGLE OF ATTACK INDICATOR
PROBE
GAUGE
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STICK SHAKER
THIS IS NORMALLY THE MAIN STALL WARNING DEVICE
...
AN ELECTRICALLY DRIVEN, OUT OF BALANCE MOTOR
MOUNTED ON THE CONTROL COLUMN, ROTATES AND
VIGOROUSLY SHAKES THE COLUMN
...
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STICK SHAKER
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Typical Stick
Shaker Installation
(B747)
21
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Nitrogen system
• Nitrogen is stored at 1,500 psi in a reservoir
• Supply to a pressure reducing valve and nonreturn valve to a low-pressure reservoir
• Low-pressure nitrogen is fed to solenoid valve A
and from there through solenoid B to a control
ram
• Dump valve can be operated from the center
console
• Dump pressure from the system to prevent
operation of the stick pusher
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STICK PUSHER
THIS IS A HYDRAULIC OR PNEUMATIC ACTUATOR LOCATED IN
THE ELEVATOR CONTROL SYSTEM WHICH AUTOMATICALLY
INPUTS A NOSE DOWN PUSH TO THE CONTROLS WHEN A
STALL IS SENSED
...
PART OF THE CONTROL CIRCUIT MAY BE FOR IT TO
AUTOMATICALLY OPERATE IF NO CAUTION IS TAKEN BY THE
PILOT WHEN THE STICK SHAKER OPERATES
...
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STALL PROTECTION SYSTEM
TO PREVENT UNWANTED OPERATION OF THE SYSTEM
ON THE GROUND, A CIRCUIT THROUGH THE WEIGHT ON
WHEELS DISARMS THE STALL WARNING SYSTEM
...
SPEEDS AT OR ABOVE THE CRITICAL MACH NUMBER
MAY CAUSE A HIGH SPEED STALL OR THE ENGINES TO
FLAME OUT
...
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Fly By Wire/ Electrical Flight
Controls
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Fly BY Wire (FBW) Overview
• A320 onwards for Airbus
• B777 onwards for Boeing
• Uses electrical signal to PFCU for control surface
movement
• Position transducer converts control input into
electrical signal
• A series of flight computers (usually duplicated
for redundancy) interpret the pilots command
• Computers will send the electrical signals to PFCU
• Signals can be digital or analog or the
combination
• Some aircraft uses Fly By Optical Wire System
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• Principle of FBW
– Control system receive input command by electrical signals
– PFCU (or PCU) are electro-hydraulic design converting
electrical signals into movement of a hydraulic ram
• Principles of FBOW
– Signals are converted to lights pulse and transmitted by
optical cables (fibreoptic cable)
– Data processing computers will be more or less the same
with FBW, the main difference will the the method of data
transmission
– Transmitter will modulate the data into light source
– A receiver will demodulate (decode) the data for the flight
computers to process the signal
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ADVANTAGES OF FBOW OVER FBW
• Increased amount of information can be
passed
• Increased speed of transmission
• Lighter in weight
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BENEFITS OF THE FLY-BY-WIRE SYSTEM
•
•
•
•
•
•
A more efficient structure design
Increased fuel economy
A smaller vertical fin
A smaller horizontal stabiliser
Reduced weight
Improved controls and protections
...
”
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ACTIVE CONTROL TECHNOLOGY
• Using a combination of control surfaces at the
same time to improve manoeuvrability and
reducing structural stress
• Had been in use in the past but FBW system
allow increase in usage
• Eg: Lockheed Tristar (L1011) partially
deploying spoilers near wing tip to shift the lift
closer to the wing root
• Allow the wing to be made lighter
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ACTIVE CONTROL TECHNOLOGY
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ACTIVE CONTROL TECHNOLOGY
• Foreplanes which can only move together to give pitch
control
...
• Flaperons which are control surfaces that act as flaps
and/or ailerons depending on the pilots selection
...
• Thrust vectoring, mainly used on combat aircraft, but the
advantages gained with short take off and landing will
mean that some form of vectoring system will be
developed for commercial aircraft in the future
Title: Flight Controls Note Part 4
Description: EASA PART 66 MODULE 11 FLIGHT CONTROLS NOTE PART 4
Description: EASA PART 66 MODULE 11 FLIGHT CONTROLS NOTE PART 4