Aerodynamics and Aircraft Control

Ailerons and Adverse Yaw

• Aileron drag (adverse yaw) is an undesirable effect caused by aileron displacement
• An upward moving aileron travels a greater distance, creating parasite drag that counteracts induced drag from the lowered aileron, minimising adverse yaw
• Frise ailerons minimize adverse yaw by extending the leading edge of the up aileron below the wing's lower surface, increasing parasite drag

Canard Configuration

• Aircraft with two lifting surfaces instead of a horizontal stabilizer are classified as canards virtually eliminating stalls.

Rudder Use

• The rudder overcomes adverse yaw at the beginning of a turn and starts the nose moving in the correct direction

Flap Types

• Slotted flaps increase the lift coefficient more than simple flaps
• Krueger flaps are hinged to the wing's leading edge and alter the wing profile when deployed

Boundary Layer

• The boundary layer is the region of air flowing adjacent to the aerofoil surface

Stall Strips

• Stall strips are installed on the wing's leading edge near the root to ensure progressive stalling from root to tip, maintaining aileron control throughout the stall

Aerodynamic Balance

• Aerodynamic balance is achieved by extending a portion of the flight control surface ahead of the hinge line, known as a horn balance or overhang
• Aerodynamic balance panels help pilots move controls more easily.

Mach Number

• Mach number is the ratio of true airspeed to the speed of sound
• Transonic speed is the most difficult flight realm, ranging from Mach 0.75 to 1.20
• Critical Mach number (Mcrit) is when airflow over the wings reaches Mach 1.0
• Sweeping wings back prevents drag rise and control issues in transonic flight

Shock Stall

The shock stall differs from an ordinary stall (the ordinary stall can occur at any speed); mainly because it occurs at a small angle of attack

Supersonic Aircraft

• Convergent-divergent inlet ducts (fixed or variable) are required on all supersonic aircraft

Active Load Control

• Active Load Control reduces wing bending and improves ride quality via hydraulic actuation of flight controls, enabling lighter or longer wings.
• A passive load alleviation method involves storing fuel in wing tanks

Mechanical Backup Systems

• Longitudinal control (pitch) is achieved by trim wheels mechanically moving the Trimmable Horizontal Stabilizer while keeping elevators at zero deflection
• Lateral control (roll) is achieved using rudder pedals connected to the rudder servo control

Structural Safety Factors

• A safety factor of 1.5 is applied to the prescribed limit load, which includes external loads on the structure

Design Limit Load

• Design Limit Load (DLL) is, the maximum anticipated load on the aircraft during its service life

Structural Classifications

• Primary structure is critical for aircraft safety
• Secondary structure failure causes significant damage but doesn't lead to aircraft loss
• Tertiary structure failure doesn't significantly affect aircraft operation

Strain Calculation

• Strain = change in length/original length

Fatigue Crack Formation

• Fatigue cracks in metals require local plastic stress
• Fatigue cracks in metals require tension stress
• Fatigue cracks in metals require cyclic(repeated or fluctuating) stress

Corrosion

• Corrosion requires an anode and a cathode
• Corrosion requires a metallic connector between them
• Corrosion requires an electrolyte like water

Bonding Straps

• Bonding straps are made from braided copper or aluminium with crimps
• The maximum permissible resistance for bonding straps is 0.003 Ω

Stringers and Longerons

• Stringers have a bulb to oppose bending loads
• Longerons are heavier than stringers and carry large structural loads in the fuselage

Aircraft Exits

• Aircraft with exits above 1.8 m (6 ft) must have slides

Aspirators

• Aspirators are cylindrical tubes with sliding or flapper doors that open with high-pressure gas and close when the gas stream stops

Additional Facts

• Seat pitch is the space between a point on one seat and the same point on the seat in front of it

Fuel Tanks

• Removable metal tanks must be supported by the airframe with padded straps to prevent movement
• Auxiliary tanks are emptied of usable fuel during flight by transferring to the main tank

Fuel System

• Suction valves enable fuel to be drawn from tanks if boost pumps fail; closed when booster pumps operate
• Transferring fuel from one tank to another is normally done when the aircraft is on the ground.
• Capacitance type fuel quantity indicators are used on most modern transport aircraft to measure the mass of the fuel
• Capacitance type fuel probes are connected in parallel, Indications remain the same regardless of aircraft attitude

Hydraulics

• Open circuit systems can only operate one subsystem at a time
• Closed centre circuits supply full pressure to control valves at all times
• A standpipe outlet feeds the engine-driven pump and allows the hand pump to be used even if the engine pump loses fluid
• Vane pumps are used when a large volume of fluid needs moved without high pressure

Aircraft Tyres

• Type III tyres are used for low-pressure service and flotation
• Type VII tyres are high-pressure tyres used on jet aircraft

Aircraft Wheel markings

• A red spot or triangle indicates the light part of the tyre
• If the wheel lacks a mark indicating the heavy spot, align the red spot on the tyre (the light point) with the valve fitting location on the wheel

Oxygen Systems

• A green plastic discharge indication disc on the fuselage skin shows cylinder discharge from over-pressure (when the disc is missing).
• Oxygen cylinders are considered empty at 50 psi
• If the pressure relief valve opens, that causes the green indicator disc to be blown out of the fuselage port, and a yellow indicator comes into view to show that the cylinder was discharged or the pressure relief valve is open
• Passenger oxygen systems use a solenoid to release mask doors
• The actuator must be reset by pushing upwards on the test stop button

Corrosion Treatment

• After corrosion removal, the surface can be treated with a 5% chromic acid solution to neutralise any remaining corrosion salts or Alodine treatment will also neutralise corrosion as well as forming a protective film on the surface of the metal

Pressurisation Systems

• If the outflow valve fails, the safety valve controls cabin pressurisation using a differential type control

Fire Protection Systems

• Fire wire systems are manufactured by Fenwal (single conductor) and Walter Kidde (dual conductor) companies for engine fire detection and overheating detection in bleed air systems
• Extinguishing containers have a thermal fuse that releases the agent if subjected to high temperatures
• Bottles emptied from high temperatures blow out a red indicator disc
• Bottles discharged normally blow out a yellow indicator disc

Freewheeling Diodes

• Freewheeling diode eliminates voltage spikes when the master switch is opened. It does so by feeding the induced EMF from a collapsing coil back into itself rather than back into the distribution system.

Battery Acid Spills

• Lead acid batteries require a solution of water and bicarbonate of soda
• Ni-Cad battery spills require a chromic acid solution as a neutralising agent
• Spills can be neutralised with a boric acid solution or vinegar

Reverse Current Cut-Out Relay

• The purpose of the reverse current cut-out relay is to automatically disconnect the battery from the generator when the generator voltage is less than the battery voltage

Tropopause

• As air heats, its density decreases. Decreased density causes air to rise; reduced pressure allows air to expand and cool as it rises

Aneroid Barometers

• The effect of a decrease in temperature on the U-shaped bracket is to cause the limbs to bend inwards, and by the angular position of the pins, a corresponding downward force is exerted on the capsule assembly to oppose the error-producing expansion

Pitot-Static Systems

• A small calibrated drain hole allows this moisture to escape without affecting the sensed pressure (pitot systems)
• Independent static vents are located on each side of the fuselage and interconnect via a common manifold to average and minimise dynamic pressure effects due to yawing or sideslip of the aircraft
• Normally an area around the fuselage-mounted static ports is free of paint
• The two screws in the unpainted area are for attachment of a test adaptor to allow testing of the static system. The screws must always be in position.

Non-Sensitive Altimeter

• Aneroid capsule with leak free case, the port is connected to static pressure
• A non-sensitive altimeter only has one pointer which makes one complete revolution for each 10 000ft in altitude
• Can also be used in pressurised A/C to show cabin altitude

Sensitive Altimeter

• Altimeters with two or three pointers or with a single pointer and a drum counter and a means to correct for local pressure deviations from International Standard Atmosphere (ISA) are sensitive altimeters.
• Static pressure outside the aircraft is conducted to the instrument case by tubing and hose.
• Turning the knob alters the barometric pressure setting display and the altitude reading
• Atmospheric pressure information relayed to pilots by air traffic control is part of the ‘Q’ code of communication. With all altimeters in a specific area set at the same barometric pressure setting

Altimeter Codes

• QFE (Field Elevation) code refers to setting the barometric pressure prevailing at an airfield to make the altimeter read zero feet when on the ground at that airfield
• The QNH (Above sea level) code refers to setting the barometric pressure to make the altimeter read airfield elevation above sea level on landing and take-off
• The QNE (Isobaric) code refers to the barometric setting on the altimeter of the ISA sea level value of 1013.25 millibars. The QNE code applies whenever an aircraft flies above the ‘transition altitude,’ which is an altitude set by traffic control authorities

Airspeed Indicator

• Indicated airspeed is a measure, displayed in knots (nautical miles per hour),
• Difference between the dynamic pressure (known as pitot pressure) and static pressure with regard to airflow.
• Airspeed indicator: airtight case connected to static pressure, capsule connected to pitot static pressure
• The calibration of the barber’s pole relates directly to the Vne (Max velocity) for that particular aircraft type.

Machmeter

• The altimeter mechanism is calibrated to QNE (Isobaric) and modifies the magnification of the airspeed capsules output.

Vertical Speed Indicator (VSI)

• The metering unit vents static pressure to the interior of the case through a calibrated leak. A capillary tube supplies static pressure to the inside of the capsule.

Instantaneous Vertical Speed Indicator (IVSI)

• An Instantaneous Vertical Speed Indicator (IVSI) consists of the same basic elements of a VSI, but in addition, they employ an accelerometer unit

Pitot-Static System Errors

• Pitot tube blockages prevent accurate airspeed indications, but have no effect on the altimeter or vertical speed indicator
• A pitot or a static line leak will cause errors in the indication of altitude and/or airspeed, and these errors compound if the aircraft is pressurised
• A pitot line leak would expose the airspeed indicator to cabin pressure, potentially adding to the ram air pressure and causing an overreading.
• To guard against cross connection, the pitot lines are usually a smaller diameter than the static lines, and/or the fittings are colour coded. Red identifies pitot lines, and green or blue identifies static lines.

Gyroscopic Systems

• When the spin axis of the rotor becomes aligned with the axis of the outer gimbal, that is, the inner and outer gimbals are aligned, the gimbals become locked. This condition, due to precession, tries to force the inner gimbal to rotate at the same speed as that of the rotor
• This physically prevents the inner gimbal and the outer gimbal from becoming aligned

Artificial Horizon

• Supplies pitch and roll attitude
• The gyro spin axis is maintained in a vertical position or horizontal plane of rotation relative to the Earth
• magnetic detecting element, called a flux valve, automatically maintains the alignment of the gyro to the Earth’s magnetic field by applying signals to a torque motor that precesses the outer gimbal

Compasses

• Power to supply this is usually fed through either screened cable or a twisted pair. Both types of cable minimise the magnetic field produced by current flow in the wire

Compass Errors

• Turning error
• Acceleration error
• Coefficient A refers to installation error and is corrected until the compass reads the corrected heading
• Coefficient B refers to deviation produced by soft and hard iron magnetism creating an imaginary magnet lying along the fore and aft axis of the aircraft fuselage.
• Coefficient Crefers to deviation produced by an imaginary magnet lying along the aircraft’s lateral axis or wingspan

Angle Of Attack (AoA) Indicators

• For a given aircraft, a stall always occurs at the same angle of attack regardless of airspeed
• To compensate for asymmetric airflows during turns or large crosswinds, two sensors are installed on either side of the fuselage
• As AoA increases, the stagnation point gradually moves down leading edge of wing

Temperature Indicators

Bimetallic:

• Bimetallic temperature indicator, The metals most used are brass and invar, which has avery low expansion coefficient

Thermocouples:

• K type (Chromel Alumel)-270 to 1260 C (-454 to 3200 F)
• J type (Iron Constantan)-210 to 760 C (-346 to 1400 F) - Commonly used in EGT indicating systems in piston engines
• T Type (Copper constantan)-270 to 3700 C (-454 to 7000 F) Commonly used in Cylinder Head Temperature (CHT) indicating systems in piston engines

Air Temperature

• The term describing the temperature increase is ram rise, and the name for the temperature indicated under such conditions is Ram Air Temperature (RAT)

Autopilot

• Series autopilot actuators move the flight surface without moving the controls
• Parallel autopilot actuators move flight surfaces and controls

Communication Types

• Simplex: One signal direction only
• Half duplex: Two way communication but only one direction at a time
• Full duplex: Both directions at the same time

Computerised Maintenance System (CMS)

• Class 1 Failures which have an operational consequence for the current flight are categorised as Class 1failures, and displayed as a warning in real time on the ECAM and available on the MCDU
• Class 2 failures are identified on the ECAM STATUS page
• Class 3 failures have neither operational nor safety consequences for the aircraft, and only available on the ground through the MCDU
• Software upload is a ground-only operation, whereas downloading can be accomplished in flight and on the ground
• After loading a Loadable Software Aircraft Part (LSAP), a Certificate of Release to Service must be issued by appropriately authorised line/base maintenance staff

Structural Monitoring

• Typical strain gauge resistances range from 30 Ω to 3 kΩ (unstressed)
• A single strain gauge is sensitive to strains only in a direction parallel to the mounted axis
• A Wheatstone bridge (strain gauge bridge) circuit indicates measured strain by the amount of imbalance of voltage due to resistance variations in the bridge
• Piezo Strain gauge produces positive voltages when they are deformed in one direction and negative voltages when deformed in the other direction
• Strain gauges can be either bonded or welded to the test surface

Modular Avionics Unit (MAU)

• Communication in the MAU is managed by the Network Interface Controller (NIC)
• The node with the highest priority (lowest arbitration ID) automatically gets bus access. The lower priority nodes must wait until the bus becomes available before trying to transmit again.

Automatic Flight Controls System (AFCS)

• The Input/Output Module (IOM) converts non-AFDX data coming from conventional LRUs into AFDX data used within the Avionics Data Communication Network (ADCN) and vice versa.

Cabin Intercommunication Data System (CIDS)

• CIDS Directors (DIR) are the central control and interface component of CIDS
• Each DIR has its own Onboard Replacement Module (OBRM) - The OBRM used to store the software for the current cabin layout and the properties of related equipment
• The main data links used by the directors are the CIDS bus and ARINC 429 bus
• The ARINC 429 is a simplex bus that uses a twisted, shielded pair which principally interfaces to onboard aircraft systems
  • Flight Attendant Panel (FAP)
  • Vacuum System Controller (VSC)
  • Environmental Conditioning System (ECS)
  • Smoke Detection Control Unit (SDCU)
  • Centralised Maintenance Computer (CMC)
  • In-Flight Entertainment system (IFE)
  • System Data Acquisition Concentrator (SDAC)
• • Decoder/Encoder Units - type-A (DEU-A), which is used on passenger-related systems, and type-B (DEU-B), which is dedicated to cabin-related systems and crew functions -- Decoder/Encoder Unit Type-A (DEU-A) data buses interface with the DIR to control passenger-related systems -Passenger Service Units (PSU) -PAX lighted signs (FSB/NS/RTS) -PAX-call lights -Loudspeakers
  • Cabin lighting -- Decoder/Encoder Units Type-B (DEU-B) data buses interface with the DIR to control cabin-crew-related systems -Area Call Panels (ACP) -Attendant Indication Panels (AIP) -Additional Attendant Panels (AAP) -Handsets -Emergency Power Supply Unit (EPSU) -Slide/door pressure sensors -Drain mast heating monitoring

Forward Attendant Panel (FAP)

• The Forward Attendant Panel (FAP) is connected to the DIRs through ARINC 429 data buses
• Programming and Test Panel (PTP); used for system indications, programming and testing of the CIDS. It consists of a display, keypad and Cabin Assignment Module (CAM). The CAM is a memory module which stores the cabin-related programmable information

CIDS Communications

• Passenger address and integrated pre-recorded announcement/boarding music
• Cabin interphone
• Service interphone
• Crew signalling and alerting

Communications and CIDS

• The cockpit handset is connected with the active DIR. The announcement is broadcasted by the loudspeakers by the DEU-A or to the headset via the IFE.
• The cabin attendant’s announcements are transmitted via DEU-Bs to the DIR by digital data and then broadcasted over all PA loudspeakers via DEU-As or passenger’s headsets via the In-Flight entertainment system (IFE)

No Smoking Signs

• controlled by the no-smoking on/auto/off switch in the cockpit
  • Come on manually when in ON position
  • Come on automatically when in AUTO position if the landing gear is down and locked or slats are extended and oil pressure is high
• Can update CIDS with new software to adapt to new cabin layout configuration

PVIS (Passenger Visual Information System)

• The main computer of the PVIS is the PVIS Processor Unit (Digital Interface Unit or DIU). The information is provided to the passengers via display units mounted either on cabin overhead panels or seat mounted
• The Processor Unit has data bus interfaces with:
  • Flight Management Guidance and Envelope Computer (FMGEC)
  • Passenger Entertainment System Video (PES Video)
  • Central Maintenance Computer (CMC)
  • Cabin and Passenger Management System (CPMS)
  • Multipurpose Disk Drive Unit (MDDU)
• The Processor Unit uses signals from above interfaced units to calculate:
  • The global position of the aircraft
  • The altitude of the aircraft
  • The distance to the destination
  • The outside air temperature
  • An estimate of the time until arrival at the destination
  • The total flight time
  • The local time at the destination

Automatic Dependent Surveillance (ADS)

• With ADS, an aircraft automatically transmits its position (and other data relevant to trajectory and weather) to the ATC via VDR, HFDR or SATCOM

Air Traffic Information Management System (ATIMS)

• ATIMS data is transmitted/received/processed by the following components:
  • Air Traffic Service Unit (ATSU)
  • Data Control and Display unit (DCDU)
  • Multifunction Control Display Unit (MCDU)
  • ATC MSG illuminated pushbutton switches
  • ATSU reset switch
• The ATSU is in charge of receiving ground messages (AOC and ATC), routing them to the right peripheral and acquiring messages or reports from these peripherals and sending them to the ground.
• The ATSU case (hardware) has minimal software and enables the uploading of the following software through the Multipurpose Disk Drive Unit (MDDU) or the portable data loader.
• Uplink and downlink messages are displayed on the Data Control and Display Unit (DCDU)

Aircraft Communications Addressing and Reporting System (ACARS)

• ACARS utilises the aircraft VHF radio system to transmit data between the aircraft and operators AOC facilities

This quiz covers key concepts in aerodynamics and aircraft control systems, including Frise ailerons, stall strips, canard configurations, aerodynamic balances, critical Mach number, wing sweep, shock stalls, Krueger flaps, and Air Traffic Service Unit roles.