Avionics MCQs – Gyroscopes – 1

1 - Question

What is the purpose of a gyro in an inertial navigation system?
a) Space-stabilize the accelerometer
b) Angle of rotation
c) Measure rotation rate
d) Calculate velocity
Explanation: The purpose of gyroscope or gyro in an inertial navigation system is to space stabilize the accelerometers. In gimballed platforms, the gyros measure the rotation of the platform, which is angularly isolated from the vehicle’s motion.

2 - Question

What is the range of an order of angular rate magnitude that gyros used in military planes need?
a) 8
b) 8.5
c) 7.1
d) 3
Explanation: A gyroscope on a military aircraft must sense angular rates as low as 0.005 deg/hr and as high as 400deg/sec, a range of 8.5 orders of magnitude. Strapdown gyros in civil aircraft need only sense an 8 order of magnitude range of angular rates.

3 - Question

Why are unfloated instruments with ball bearings not suitable for air navigation?
a) Weight restrictions
b) High drift rate
c) Low drift rate
d) Power restrictions
Explanation: Gyroscopes are used as heading references. The spinning wheel, large angle, unfloated instruments with ball bearings that have drift rates on the order of 50deg/hr . and hence are useless for navigation.

4 - Question

Which of the following is false with respect to SDF floated gyros?
a) Wheel is floated at neutral buoyancy
b) Used in launch vehicles
c) Three gimbals are used
d) Magnetic pickoff used to sense rotation
Explanation: In SDF floated gyros or single degree of freedom floated gyros, a spinning wheels were mounted inside a single gimbal that was floated at neutral buoyancy. A magnetic pickoff was used to sense rotation and they were primarily used in space launch vehicles.

5 - Question

Which of the following spinning wheel gyro has an accuracy of 0.001 deg/hr?
a) Floated TDF gyro
b) Electrostatically suspended TDF gyro
c) Floated SDF gyro
d) Unfloated ball bearing gyro
Explanation: In electrostatically suspended TDF gyro, the spinning wheel is suspended electrostatically hence reducing friction and achieving 0.001 deg/hr accuracy but at costs orders of magnitude higher than the floated TDF gyros.

6 - Question

The input, output and spin axes of a gyro are always perpendicular to each other.
a) True
b) False
Explanation: The input, output and spin axes of a gyro are always perpendicular to each other regardless of the motion of the gyro or the platform in which it is fixed. If a gyro is used for heading reference, then the gyro’s spin axes are mounted perpendicular horizontally to the platform.

7 - Question

Which of the following is false with respect to spinning rotor gyros?
a) Mechanically complex
b) High probability of failure
c) Low run up time
d) High power consumption
Explanation: The major disadvantage of spinning wheel or spinning rotor gyros is that they are mechanically complex and have a high probability of failure due to the moving components. They also require high powers and have high run up time. Run up time is the time taken for the gyro to start spinning at the required RPM after engine start.

8 - Question

What is the basic principle under which MEMS gyro work?
a) Sagnag effect
b) Coriolis effect
c) Angular momentum conservation
d) Mass conservation
Explanation: MEMS Micro Electro Mechanical System gyro exploit the effects of Coriolis force. Coriolis force is experienced when a vibrating mass is subjected to a rate of rotation about an axis in the plane of vibration.

9 - Question

Which part of the insects acts as gyros?
a) Wings
b) Halteres
c) Thorax
d) Legs
Explanation: Every flying object needs to maintain its orientation and insects that fly use halteres. Halteres work in the same principle as MEMS gyro, the vibrate and use Coriolis force to know their orientation.

10 - Question

Which of the following is false with respect to MEMS gyro?
a) Low failure rate
b) Low cost
c) High maintenance
d) Less power consumption