Instrumentation: Air Data and Gyros
Instrumentations
Instrumentations
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Flashcards
Gyro: What does the Ring laser Gyro measure?
The Ring Laser Gyro detects angular rates by measuring frequency differences
Gyro: What is the reason that the Ring Laser Gyro (RLG) is dithered (Bildbearbeitung)
The ring Laser gyro has to be dithered to overcome the ,,Lock in" effect
Gyro: What is the ,,Lock in" effect of a Ring laser gyro?
,,Lock in" effect means that the RLG (Ring Laser Gyro) is not able to measure very small angular rates when the gyro is not dithered.
Gyro: Lock in Effect?
Problem of a ring laser gyros => the two opposed light beams inside the ring laser will synchronize each other at small input angular seed and will produce a result a dead zone = Laser is not able to measure turns in the range of 0.1 Grad per hour without any support ==>====> the Ring Laser Gyro (RLG) is dithered (Bildbearbeitung)
Gyro: Why is it necessary that the accelerometers inside an INS/IRS work with a servo feedback system?
Accelerometers are constructed with a servo feedback system to increase accuracy and linearity
Gyro: MEMS ?
Micro Electro Mechanical Sensor (MEMS): theay are constructed without mechanical gimbals, operate at high accuracy and have a long lifetime => built like microchips => tiny, typical dimensions are explicitly less than 1mm or less
Gyro: MEMS Rate Sensor
Micro Electro Mechanical Sensor: These sensors produce a signal output proportional to the rate of rotation
Gyro: MEMS Magnetometer
Micro Electro Mechanical Sensor => to measure a magnetic field by using the Hall Effect => can measure either constant or crying magnetic fields => operate in a wide temperature range => thin piece of a conductor is placed in a magnetic field
=> Lorenz force acts 90 degrees to its direction = determining a charge separationan => electric field E (Hall field ) occurs
Gyro: Where do you use MEMS?
Micro Electro Mechanical Sensor do you use in AHRS ==> Accuracy of max. +7- 2 degree fr heading measurement, max. +/- 2.5 degree for pitch and roll measurement
Gyro: Which kind of MEMS sensors are in use for aircraft purposes?
For aircraft purposes MEMS are in use as angular rate sensor, accelerometers and magnetometer
Gyro: Which important effect is used in case of MEMS sensors which measure angular rates?
The important effect when a MEMS is constructed for measuring angular rate is the Coriolis Effect
Gyro: Describe teh principle of teh Hall effect which can be found in a MEMS magentometer ?
When an electron current flows through a MEMS Hall effect sensor the Lorentz force acts in such a way that a charge separation occurs
Gyro: Local vertical
After completed alignment, the platform has not to be adjusted perpendicular to a plump lien at a given position on earth
Gyro: Earth Rate ?
Earth Rate (ER): Rotation of the earth => split the rotation vector of the earth int the components of the INS coordinated axis
=>North component = QN = Q * cos (Winkel)
=> Vertical component = Q D = - Q * cos (Winkel)
Gyro: Earth Transport Rate = ETR
ETR = the motion of the earth => INS loses its original orientation => the INS has to generate signals to the torquer to compensate for the rotation of the axes due to Earth Transport Rate
Gyro: Intitial Alignenmt, what is this and two phases
After switching on the pilot has to enter the position of the aircrafts => Two phases 1. Coarse alignment 2. The fine alignment
Gyro: The Coarse Alignment; What means levelling ?
teh platform is oriented to the used coordinated system => oriented in a way that the axes are pointing to the north, east and down direction (NED)
=> Alignment until N and E measure a min output and the vertical accelerometer measures the maximum = levelling
Gyro: By the alignment phse (Intitial Alignment), how must the aircraft be?
The aircraft has to be stationary on ground, because the accelerometers which have sensitivity
Gyro: Fine Alignment; What is this?
The second phase => is reached by mathematical filtering of the small signals which are affected by noise => Kalman filter => the earth rate is taken into account to optimize teh dynamic of the platform axis control
==> A NAV lamp illuminated = ready to measure all movements, calculate the actual position and can perform the Dead Reckoning navigation
Gyro: What happend by teh IRS (INS) when the electrical power shuts down?
the electrical power has to remain uninterrupted for the rest of the flight => INS would lose all of its dara = can't be aligned again during flight
Gyro: What happens at high altitudes during alignment?
a platform has problem with an alignment at high altitude in the range of >75 degrees
Gyro: Quick Alignment?
During quick align the system doesn't teach for the truth north, it takes the last known value
Gyro: The earth itself is an accelerated coordinated system. What is one effecr which has to be compensated ?
On effect is the Coriolis Effect: Northern hemisphere Abweichung nach rechts, South: nach links
The measurement of the static pressure is subject to the following errors, among others: Position...
and manoeuvre induced errors.
The eye reference point (or position) is:
the position (or point) where the eye of the pilot must be during flight
The "Bourdon tube" is primarily used to measure:
pressure
Why are high vibrations used in some mechanical transmission systems?
to cause the bearings (Lage) to float (Schwimmer) and reduce mechanical lag (Nacheilung)
Application of analogue displays is particularly suitable when:
comparing of measurements (indications) is a priority
Different pressure sensors are used according to the intensity of the pressure measured (low, medium or high). Classify the following sensors by order of increasing pressure for which they are suitable:
1) bellows type
2) Bourdon tube type
3) capsule type
3, 1, 2
The altimeter ususally has a bimetallic temperature compensation. Why does a temperature error still remain? Because the bimetallic compensator:
does not compensate for outside air temperature effect on the pressure/altitude relation.
Why are jewelled bearings (Lage, Peilung) used in some mechanical transmission systems?
to reduce the rate of wear (Abnutzung)
The position error of the static vent on which the altimeter is
connected varies substantially with the...
Mach number of the aircraft.
When flying in warm air (warmer than standard atmosphere),
indicated altitude is:
lower than the true altitude
Which system can be used to drive the pointer in an electro-mechanical instrument?
A torque synchro.
In case of accidental blockageof an aircraft's left static pressure port (ice, birds):
the altimeter overreads the altitude in case of a sideslip to the left and displays the correct information during symmetric flight.
Which indicators will be found in a basic T:
1. airspeed
2. attitude
3. vertical speed
4. altimeter
5. heading
6. turn and BANK
1 2 4 5
In an analogue display, the movement of the indicator is:
directly related to the change in value of data being measured
Which part is the essential difference between a servo altimeter and a normal pressure altimeter?
The linkage from pressure sensor to indicator.
How is information transfered in a typical mechanical transmission system?
by gears and shafts
The purpose of the vibrating device of an altimeter is to:
reduce the effect of friction (Reibung) in the linkages
