Chapter 13,8
Module 13 – Aircraft aerodynamics, structures and systems
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Module 13 – Aircraft aerodynamics, structures and systems
The main pilotage instruments can be divided into 3 categories:
• Static instruments (altimeter, airspeed indicator and vertical speed indicator)
• Gyroscopic instruments (artificial horizon, turn and back indicator, directional gyro)
• Magnetic instruments (magnetic compass and gyrocompass).
Instrument systems - classification
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Module 13 – Aircraft aerodynamics, structures and systems
The static instrument are called static instruments because their main device is a metallic aneroid capsule with very thin walls.
• The capsule measure the difference in pressure.
• The static instruments receive pressure from:
1. A static source (positioned in a point where it isn't affected by the aircraft motion)
2. A dynamic pressure (positioned in a point where it is affected by the aircraft motion)
Static instruments
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Module 13 – Aircraft aerodynamics, structures and systems
• The altimeter is an aneroid barometer, whose measurements of the atmospheric pressure are converted in altitude parameters
• The altimeter is made up of a watertight box, connected with the outside through the static source. Inside this box there is the
capsule that is hermetically sealed
Altimeter
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Module 13 – Aircraft aerodynamics, structures and systems
The barometric surfaces of reference, utilized in aviation, are:
• The airport surface (QFE)
• The sea surface (QNH)
• The isobaric standard surface (QNE)
For example if, in the setting window, the pressure value of the isobaric standard surface (1013millibar) is introduced, the altitude indications are called “flight levels”. This setting of the altimeter is called QNE. This setting is used during cruise.
Altimeter
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Module 13 – Aircraft aerodynamics, structures and systems
• The air speed indicator is the instrument that measures the aircraft speed in relation to the air mass around it. It is made up of a
watertight box, connected with the outside through the static source.
• Inside the box there is the capsule, which is connected to the outside through the dynamic source
• The expansion of the capsule is bigger as the dynamic pressure, and thus the aircraft speed, is greater. During the flight the dynamic pressure is greater than the static one
Air speed indicator
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The different colorings identify and delimit fields of the operational speed of the aircraft. The utilized standard colors are:
• White
• Green
• Yellow
• Red.
The most significant errors of the air speed indicator are:
• The error of position
• The error of compressibility
• The error of density
The error of compressibility becomes important when the speed is so high to compress air molecules inside the static source. The CAS
corrected by this error is called EAS (Equivalent Air Speed).
The TAS is the EAS (Equivalent Air Speed) corrected by the error of density
Air speed indicator
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• The gyroscope is a rigid body that is put in rotation at high speed.
The gyroscope is made of a rotating disk (the rotor), which, due to physical laws of conservation, tends to maintain its rotation axis (or spin axis) oriented in a fixed direction
Gyroscopic principle
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• The turn and slip indicator is made up of a gyroscope with 2°of freedom. It is limited to rotate around its vertical axis (Z). The
rotational axis of the gyroscope (X) is horizontal and it is parallel to aircraft transversal axis
• A gravity slip and skid indicator is a very simple instrument that uses both the centripetal and centrifugal forces.
• The turn and bank indicator has also a gravity slip and skid indicator
Turn and slip indicator
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• The directional gyro, or heading indicator is made up of a gyroscope with 3° of freedom and with a horizontal spin axis.
• It is important to remember that the directional gyro moves gradually away from the indications of the compass, due to the apparent precession, the Earth’s rotation and the construction imperfections.
• These gaps can reach a maximum of 15° per hour, and so they must be manually corrected by the pilot every 15-20 flight minutes.
The maximum drift rate directional gyro is typical 1 degree per minute, with an accuracy of 2°.
• The rose is instinctive
Directional gyro
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• Errors are lines exit from the South magnetic Pole and enter in the North Pole
• The variation error is caused by the fact that the magnetic compass provides indication in relation to the North magnetic pole, which doesn’t coincide with the North geographic pole. The variation is greater at Poles
• Also the magnetic inclination error especially happens when the magnetic compass is near to the magnetic poles.
• The deviation error is caused by the airborne presence of ferrous parts and electromagnetic equipment that can divert the flow lines of the Earth’s magnetic field. This error can be compensated thought some compensator magnets. These residual errors, which can be not compensated by the magnets, are typically written on a small table, placed near the compass, as a value to add or to subtract from the indication read on the instrument. It’s important to remember that the values of residual deviation must not exceed 3°.
Errors
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Module 13 – Aircraft aerodynamics, structures and systems
FDR and CVR
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• In accordance with JAR-OPS 1, a commercial transport airplane must carry a FDR, which uses a digital method of recording and storing flight data.
• The parameters, which must be recorded, vary according to the maximum certificated take-off mass and to the age of the aircraft.
All parameters of all aircraft system must be recorded with a
common reference time scale. The data must be obtained from the various airplane sources, which will have accurate correlation with the information displayed to the flight crew.
• FDR is contained in a shockproof box that is able to sustain extremely high impact forces and high temperatures.
FDR
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• In accordance with EU-OPS 1, a commercial transport aircraft must carry a CVR that must be able to record 4 channels of audio data:
All radio voice communications transmitted from or received by the flight crew members
• The audio environment of the cockpit, including the cockpit conversation
• Voice communications, done through the airplane interphone system between the cockpit and the cabin
• All voice signals or other audio signals related to the identification of navigation or approach aids
CVR
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Module 13 – Aircraft aerodynamics, structures and systems
• The fuel level is measured using the change in electrical capacitance of a capacitor
• The capacitance of the capacitor depends on the dielectric value existing between the two armatures of the capacitor. An increase in fuel level would increase in capacitance.
Capacitance probe
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• Another type of fuel quantity indicator used in the more modern applications measures the fuel level in the tank by utilizing the emission and reception of sound pulsed-signal by an ultra-sound sensor installed in the bottom of the tank
Ultra-sound system
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• Another device that uses the change in electrical resistance as a function of temperature is the bulb thermometer. It is generally
used to measure the operating temperature of fluids inside engines.
• In these devices the probe consists of a container that encloses an electrical filament, which is placed inside the fluid whose
temperature must be taken
• The selection of the material of the filament (nickel or platinum) depends on the maximum operating temperature envisaged for the thermometer. Nickel is generally used for temperatures up to 300°
C, while platinum is suitable for maximum temperatures of 600° C.
Bulb thermometer
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LIGHTS
Module 13,9
Module 13 – Aircraft aerodynamics, structures and systems
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Module 13 – Aircraft aerodynamics, structures and systems
• Aircraft lighting may be divided into different groups:
o External lights: exterior lights provide illumination of the ground during landing and taxi operations and make the aircraft visible in flight.
o Internal lights: min power 3W
Passenger compartment lights
Cargo and service compartment lights
o Emergency lights: emergency lights provide interior and exterior illumination of exits and exit paths during emergency evacuation
Lights
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Module 13 – Aircraft aerodynamics, structures and systems
• Navigation lights are an essential system and control is obtained through a relay activated switch in the flight deck. Normal power supply for such lights is 28 V AC from a protected bus such as the essential or standby bus
• Navigation lights include a single lamp:
1. Red light on left wing 110°
2. Green light on right wing 110°
3. White light on thetail 140°
Navigation lights
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Module 13 – Aircraft aerodynamics, structures and systems
• The larger aircraft can be also equipped with some additional strobe lights, located on the trailing edge of the wings and on the tail.
• The strobe lights are activated both during the day and the night, in order to encourage the identification of the aircraft both in flight and on ground, especially in the case in which it occupies the runway
Strobe lights
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Module 13 – Aircraft aerodynamics, structures and systems
• The anti-collision lights system (also called anti-collision beacon lights) mainly consists of one or more red lights, according to the aircraft dimensions. They are flashing rotating lights, which are usually mounted on the top of the fuselage or of the tail.
• The minimum light intensity is 100 candles (the output is 400 candles)
• Anti-collision lights are activated when the engines are started up during night flights and daylight hours
Anti-collision lights
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Module 13 – Aircraft aerodynamics, structures and systems
• Landing lights are white and they are installed on the aircraft in order to illuminate the runway during landings and takes-offs
• The landing lights are generally of the PAR 200-300 W type.
• Some systems use retractable landing lamps.
• The fixed part is switched on when the aircraft is authorized to entry in the runway, and it is switched off at 10000 ft
Landing lights
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Module 13 – Aircraft aerodynamics, structures and systems
• Runway turnoff lights are white lamps, positioned to illuminate laterally the taxi-ways and the runways for an angle of 50°.
• These lights are used during the take-off run, during the landing and during the taxi phase
• During the departure, the runway turnoff lights are switched on at the beginning of the taxi, and they remain activated until 10000 ft.
Runway turnoff lights
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Module 13 – Aircraft aerodynamics, structures and systems
• Generally, the airliners are also equipped with some logo lights that illuminate the company's logo
• The logo lights remain activated during the night, during the ground operations and during the flight below 10000 ft.
Logo lights
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Module 13 – Aircraft aerodynamics, structures and systems
• The taxi lights are designed to provide the illumination on the
ground during the taxing phase or when the aircraft is towed on the airport surface
• The taxi lights don’t provide the same degree of illumination of the landing lights
• On aircraft with a tri-cycle landing gear, the taxi lights are often mounted on the non-steerable part of the nose landing gear
• Moreover some aircraft can be equipped with additional taxi lights located on the lower surface of the aircraft nose
Taxi light
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Module 13 – Aircraft aerodynamics, structures and systems
In the passenger cabin a large variety of lights can be installed.
The most of the passenger cabin lights are:
• Controlled by the flight crew and flight assistants
• Made of fluorescent tubes, connected to some
transformers to control the voltage
• COCKPIT: some incandescent floodlights with a large
luminous beam that are
installed on the cockpit ceiling Internal light – Passenger lights
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