Avionics and Instruments Flashcards
What are the three types of aircraft instruments?
Primary Flight Instruments
Engine Instruments
Navigation Instruments
What types of instruments are Direct Sensing Instruments?
Analogue Instruments are often Direct Sensing
What types of instruments are Remote Sensing?
Digital Instruments
What are the main advantages of Digital instruments over Analogue?
Reliability
Accuracy
Flexibility
Cost
What are the Primary Flight Instruments
Attitude Indicator (AI)
Airspeed Indicator (ASI)
Altimeter (ALT)
Vertical Speed Indicator (VSI)
Horizontal Situation Indicator (HSI)
Turn and Slip Indicator (T&S)
How many primary flight instruments are there?
6
What is the classic ‘tee’ shape of primary instruments?
ASI, AI, ALT, HSI
What is a PFD?
Primary Flying Display
Power Lever or Thrust Lever?
Power Levers for Propellers
Thrust Lever for Jet Engine
What is Power?
The rate of doing work
Distance/Time
What is Torque?
The rotating force in the gearbox to turn the propeller.
What are the Control Instruments?
Power Instruments
Attitude Indicator
What are the Performance Instruments
ASI
ALT
VSI
HSI
T&S
What is the equation for performance?
Power + Attitude = Performance
What is Static Pressure?
Static presure is the ambient pressure
What is the AHRS?
Attitude Heading Reference System
What is the Indirect reading of the ASI
Pitch information
What is the indirect reading of the ALT?
Pitch
What is the indirect reading the HSI
Bank or Yaw
What is the indirect reading of the Turn Indicator
Bank or Yaw
What is the indirect reading of the Slip Indicator
Yaw
What is an ESI?
Electronic Standby Instrument
Where is the Tropopause at its coldest?
The Equator, due to its highest point 56 000 ft
What is Pressure Altitude?
The altitude indicated when the altimeter is set to 1013.25 hPa.
Standard Pressure Setting.
What is the Density Altitude?
DA is the pressure altitude adjusted to take into consideration the actual temperature of the air.
DA = Pressure Altitude + 120t (where t is the ISA temperature deviation)
What is another term for Static Pressure?
Ambient Pressure
From where is static pressure provided?
Static Vents
What is Alt Statik?
A backup system should the Static Port freeze of become blocked.
How does the Pitot Tube work?
Air in motion possesses energy and therefore exerts a pressure on any object in its path (the pitot tube and chamber)
As Airspeed increases the pressure air entering the pitot tube (ram air) increases.
What happens to Static Pressure as we climb?
It reduces.
What is the capsule within the Altimeter known as?
Aneroid Capsule.
What types of Altimeter are there?
Simple
Sensitive (multiple aneroid capsules)
Servo-assisted altimeter
Digital Display
Cabin Altimeter
What is PITHBLOT?
Errors of the Altimeters.
What is the P in PITHBLOT?
Pressure Error (Position Error) - Accuracy of static vents not reading pure static pressure.
What is the I in PITHBLOT?
Instrument Error - caused by irregularities during manufacture, residual error will be noted on a correction card.
What is the T in PITHBLOT?
Temperature Error - Arises when the atmospheric conditions differ from those assumed by standard atmosphere used to calibrate the altimeter.
What is the H in PITHBLOT?
Hysteresis Loss - Imperfect elastic response. Difficult to predict, most noticable in sharp climbs or descents.
What is the B in PITHBLOT
Blockages and Leaks - Uncommon occurences, can be caused by frozen pipework, insects, other obstructions.
What is the L in PITHBLOT?
Lag Error - Caused whenever height is changed rapidly, varies with the rate of change. Reduced by the fitting of a vibration system.
What is the O in PITHBLOT?
Orthographic Effect - Caused when a current of air meets a barrier of hills or mountains.
What is the T in PITHBLOT?
Transonic Jump - At high speeds, near Mach 1, if a shock wave passes over the static source, a rapid change in static pressure will occur. This gives an error in the altimeter indication for the duration of the disturbance.
What types of ASI are there?
Simple ASI
Sensitive ASI
Servo ASI
What is Dynamic Pressure?
Dynamic Pressure is the difference between Static pressure and Pitot Pressure
How is the Flap Operating Range described on the ASI?
A white arc.
The range within the arc represents normal speeds for take off or landing with flaps extended.
What types of ASI errors are there?
Instrument Error
Pressure Error
Compressibility Error
Density Error
What is CAS?
Calibrated Air Speed (CAS)
What is EAS?
EAS is Equivalent Air Speed
It is CAS corrected for compressibility error.
What is TAS?
True Air Speed (TAS)
What is Mach?
Mach is the ratio of true air speed to the local speed of sound.
What is the structure of a Machmeter?
A Machmeter is an aircraft pitot-static system flight instrument that shows the ratio of the true airspeed to the speed of sound.
An airspeed indicator with a linked altimeter aneroid capsule.
What are the components of a VSI?
A differential capsule contained within a case. With a calibrated leak.
How does an Instantaneous VSI work?
There are small weights that act as accelorometers to remove lag from the pressure changes.
What is the purpose of an Instantaneous VSI?
A IVSI removes the initial lag error when a climb or descent is started. They utilise accelerometers or accelerating weights.
What is an ADS?
Air Data System
What components comprise a basic ADS?
Probes and Sensors for pressure, temperature, angle of attack and side slip.
Transducers to convert sensor air data into electronic signal.
Air Data computers (ADC) to process the air data for aircraft systems and displays.
What is the role of a Transducer in an ADS?
The transducer converts sensor air data into electronic signals.
What are the roles of Probes and Sensors in an ADS?
The probes and sensors check pressure, temperature, angle of attack and sideslip.
What is the role of the Air Data Computer?
The ADC processes the data input from the sensors, aplies any necessary corrections and supplies output data in a digital form which can be converted into graphical presentations on the primary flight displays.
What are the advantages of the Air Data System?
The bulk and complexity of pitot/static pressure pipework is removed.
One ADC replaces the multiple analogue pressure instruments.
Eliminates analogue instrument error.
Increased accuracy and sensitivity.
Minimal time lag.
Digitised air data enables flexibility in presentation.
How can we get vertical position from air pressure?
Pressure varies with increases in height
What are the 6 degrees of freedom?
Six degrees of freedom (6DoF) refers to the freedomof movement of a rigid body in three-dimensional space. Specifically, the body is free to move forward/backward, up/down, left/right (translation in three perpendicular axes) combined with rotation about three perpendicular axes, often termed pitch, yaw, and rol
What are the three types of gyroscopes?
Spinning
Optical
Vibrating
What is Inertia?
The resistance of an object to any change in its state of motion.
What is momentum?
The product of an object’s mass and velocity.
What is angular velocity?
An objects speed of rotation or spin.
What is Moment of inertia?
The product of the moment arm about the spin axis that an object’s mass is said to act and the total mass of the object.
What is angular momentum?
The product of angular velocity and the moment of inertia which defines the amount of force needed to oppose rotation.
What is the conservation of angular momentum?
As angular momentum is the product of the moment of inertia and angular velocity, if one is decreased so the other will increase to conserve a spinning objects angular momentum.
What is the First Law of Gyrodynamics?
If a rotating body is free to move in any axis through its centre of mass then its spin axis will remain fixed in intertial space.
Rigidity
What is the Second Law of Gyrodynamics?
If a constant torque is applied about an axis perpendicular to an unconstrained, symmetrical object’s spin axis, then the spin axid will precess steadily about an axis mutually perpendicular to both the spin axis and torque axis.
Precession
What property do Displacement Gyroscopes utilise?
Gyroscopic Rigidity.
What is a rate gyroscope?
A rate gyroscope system is constrained with a single degree of freedom.
When the gyro experiences a rotation about the constrained axis, it will precess about an axis mutually perpendicular to the applied torque and its spin axis.
What are the classifications of spinning gyroscopes?
Rate Gyroscope
Rate-integrating Gyroscope
Displacement Gyroscope
What are the applications of displacement gyros?
Vertical - Attitude Indicator
Horizontal - Direction Indicator
What are the practical applications of a rate gyro?
Rate of Turn
What are the practical applications of the rate-integrating gyros?
Inertial Measurement units.
What is the definition of wander?
Wander is defined as any movement of the spin axis away from the reference frame in which it is set.
What are the causes of wander?
Real wander- caused by imperfections in the gyroscope mechanism.
Apparent wander- The rotation of the Earth or transportation of the gyroscope from one point on Earth to another can give an indication of apparent wander with regards to the Earth’s surface, even though the gyroscope’s actual orientation remains fixed in inertial space.
Into what components can wander be resolved into?
Drift and Topple
What is Drift when referring to gyros?
Drift is the wander of the spin axis in the horizontal plane.
What is Topple when referring to Gyros?
Topple is wander of the spin axis in the vertical plane.
What is the sagnac effect?
beam of light is split and the two beams are made to follow the same path but in opposite directions. On return to the point of entry the two light beams are allowed to exit the ring and undergo interference. The relative phases of the two exiting beams, and thus the position of the interference fringes, are shifted according to the angular velocity of the apparatus. In other words, when the interferometer is at rest with respect to a nonrotating frame, the light takes the same amount of time to traverse the ring in either direction. However, when the interferometer system is spun, one beam of light has a longer path to travel than the other in order to complete one circuit of the mechanical frame, and so takes longer, resulting in a phase difference between the two beams. This arrangement is also called a Sagnac interferometer. Georges Sagnac set up this experiment to prove the existence of the aether that Einstein’s theory of special relativity had discarded.
What are the benefits of a ring laser gyro?
An RLG is a gyro that is more sensitive and accurate.
There are no moving parts, no wander errors, no spin up time.
Resistant to shock, vibration and temperature changes.
They are small, durable and reliable.
What is a FOG?
Fibre Optic Gyro