Ring Laser Gyro, Inertial Navigation System and Air Data Instrument Definitions Flashcards

1
Q

Describe the principle of operation of a gyro stable platform?

A
  • The platform houses the accelerometers and so isolates them from vibration, turbulence, and attitude changes.
  • Remote vertical gyros keep this platform aligned in azimuth and with true north during the aircraft’s travels, thus maintaining the accelerometers in a fixed orientation throughout the flight.
  • Alignment occurs during the initial synchronising procedure and is known as “gyro compassing” and must be complete before any flight plan can be entered.
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2
Q

How is the stable platform held in alignment with the global (earth) frame?

A

Achieved by mounting the platform using gimbals (frames) which allow the platform freedom in all three axes. (FIG 20-1).

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3
Q

What is the purpose of an accelerometer?

A
  • Provide displacements of the aircraft in all those planes by measuring accelerations experienced by the aircraft both positive and negative.
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4
Q

How many accelerometers does the Gyro Stable Platform house? What is the minimum needed and what are their movements?

A
  • Three
  • Minimum of two –> one for north-south movement and another for east-west movement and possibly one for vertical movement.
  • The vertical movement can be eliminated with altitude data being gained from the Air Data Computer.
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5
Q

What is the basic function of the gyro stable platform?

A

To maintain the accelerometers level regardless of the aircraft’s attitude.

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6
Q

What is the product of the first integration of the N-S accelerometer in an INS?

A

Velocity along the local meridian.

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7
Q

What is the product of the second integration of an accelerometer output?

A

Distance.

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8
Q

What is the INS? How does it achieve this?

A
  • The INS is a self-contained long range navigation system that provides a continuous and accurate fix of aircraft position.
  • It achieves this by employing GREAT CIRCLE NAVIGATION to provide very accurate steering commands to the AFDS to steer the aircraft via a series of waypoints to its destination, it superseded the hyperbolic systems.
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9
Q

Describe the inputs and outputs of the INS?

A
  • This system, through its own computer, is coupled directly with the AFDS computer to steer and navigate the aircraft.
  • It also utilises the CDU of the FMS, receives inputs from the ADC and displays information on the EFIS.
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10
Q

What is the definition of CAS and EAS?

A
  • Calibrated Airspeed - IAS corrected for position and instrument errors
  • Equivalent Airspeed - CAS corrected for compressibility error.
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11
Q

What is the definition of mach number?

A

Is the ratio of the speed of an aircraft to the local speed of sound in the same atmospheric conditions.

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12
Q

What is the definition of the local speed of sound?

A

The speed of sound at a given altitude.

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13
Q

What is the definition of VMO and MCRIT?

A
  • Maximum operating speed, same as VNE on the ASI and NZ.

- Critical Mach number. The free-stream Mach number when a local Mach number reaches Mach 1.

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14
Q

Explain the principle of operation of a ring laser gyro

A
  • 2 coherent lasers are transmitted through a bore in a triangular/square block in different directions
  • All corners have a mirror (three mirrors) with one mirror being semi-transparent which allows both lasers to enter to sense phase.
  • Coherent light has sine wave properties.
  • The rotation of the block changes path and wavelength so the frequency can be measured.
  • When angular acceleration occurs, a phase difference in the light can be detected.
  • This change in phase and therefore frequency can be computed to detect angular acceleration over a measured time.
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