1. The reason for using quadruplex actuation system is _______
a) precise movement
b) to counteract heavy air loads on the control surfaces
c) quick reaction to the control stick movement
d) as a fail safe mechanism
Explanation: A quadruplex actuation system consists of four independent actuators whose output drives the power control unit. The fail-safe mechanism of the quadruplex system is that when one fails three can override it. All four actuators have totally independent power and control electronics.
2. In a typical quadruplex actuator system, how is the failure of an actuator identified?
a) By comparing it with the signal of the three good ones
b) By comparing it with a simulation model
c) Using in-lane fault detection
d) Using reflectometry
Explanation: A typical quadruplex system uses signal processing based FDI( Fault Detection and Isolation) system. It identifies the failed actuator by comparing its control signal with the other three good ones. A model-based FDI system is generally used in triplex architecture.
3. What are control laws?
a) Algorithms relating pilots stick and control surface
b) Laws that govern aerodynamics forces
c) Laws that govern flight motion
d) Laws used to predict range and endurance
Explanation: The term ‘control laws’ is used to define the algorithms relating the control surface demand to the pilot’s stick command and the various motion sensor signals and the aircraft height, speed and Mach number.
4. What is θi in pitch rate command law?
a) Tailplane demand angle
b) Pilot input angle
c) Gain in loop
d) Pitch rate gearing
Explanation: Pitch rate command law is given by
ηD = K(θi − Gqq)
where ηD is the tailplane demand angle; θi is the pilot’s input command; q is the pitch rate; K is the forward loop gain, and Gq is the pitch rate gearing.
5. What is false true with respect to K in the pitch rate command law?
a) Value of K is infinite
b) Value of K is constant with height and altitude
c) Value of K changes with height and altitude
d) Value of k is constant with altitude and airspeed
Explanation: As the altitude and airspeed are varied, the magnitude of hinge moment in the control surface varies. This raises the need to vary gain K with change in flight conditions.
6. Derivative of a control system provides _________
a) Low steady state error
b) Gain proportional to error
c) Reduced overshoot
d) Infinite gain
Explanation: Derivative of error control provides a phase advance characteristic to
compensate for the lags in the system, for instance, actuator response, and hence improve the loop stability. This increases the damping of the aircraft response and reduces the overshoot to a minimum when responding to an input or disturbance.
7. Integral of a control system provides __________
a) Low steady state error
b) Gain proportional to error
c) Reduced overshoot
d) infinite gain
Explanation: Integral of error control eliminates steady-state errors and reduces the following lag. The integral of error term increases the loop gain at low frequencies up to theoretically infinite gain at dc so that there are zero steady-state errors due to out of trim external moments or forces acting on the aircraft.
8. Phase advance control is also known as __________
a) Proportional error controller
b) Derivative error controller
c) Integral error controller
d) One plus derivative error controller
Explanation: A phase advance controller is usually known as phase advance controller with a transfer function.
The control term is filtered to limit the increase in gain at high frequencies and smooth the differentiation process which amplifies any noise present in the error signal.
9. What is the MTBF of a solid state rate gyro?
a) 1,000 to 5,000 hrs
b) 5,000 to 10,000 hrs
c) 10,000 to 50,000 hrs
d) 50,000 to 100,000 hrs
Explanation: Solid state rate gyros are very reliable sensors with an MTBF in the region of 50,000 to 100,000 hours – ‘fit and forget’ devices. Also, they are mounted internally and suffer less damage from the environment.
10. What are the shortcomings of using an angle of incidence indicator for feedback sensor?
a) Damage from bird strikes and local airflow disturbance
b) Damage from ice formation and local airflow disturbance
c) Ground and impact damage from landing
d) Works only in subsonic ranges
Explanation: Although the angle of incidence indicator can provide motion feedback sensor information the major shortcomings of using them are damage from bird strike as they are mounted external to an aircraft and effect of the local airflow around the fuselage cause variations in measured values.