ATPL(A) 022 InstrumentationRevision notes and practice questions

022 InstrumentationFree sample, 10 questions

1. 1How is a peripheral device, such as a printer or an additional hard drive, connected directly to a computer?

   1. Through the central processing unit.
   2. Via the read-only memory.
   3. Via the internal bus(ses).
   4. Via the external bus(ses).
   Show the answer

   Answer D. Inside the computer, the CPU, memory and controllers communicate over the internal (system) bus. Peripherals such as printers or extra hard drives are attached through ports and interfaces on the external bus, for example USB, SATA or FireWire. They are not wired directly to the CPU or to the read-only memory, and the internal bus is reserved for the core components.

2. 2Which statement about fuel mass units is correct?

   1. 1 t = 450 lb.
   2. 1 t = 2200 lb.
   3. 1000 lb = 2200 kg.
   4. 1000 lb = 4500 kg.
   Show the answer

   Answer B. One tonne is 1000 kg and one kilogram is about 2.2046 lb, so 1 t = 1000 × 2.2046 ≈ 2205 lb, rounded to 2200 lb. In the other direction 1000 lb is only about 454 kg, so the options giving 2200 kg or 4500 kg for 1000 lb invert the conversion. The 450 lb option confuses the tonne with the roughly 454 kg that corresponds to 1000 lb.

3. 3Below the tropopause in the standard atmosphere, when climbing at a constant Mach number...

   1. TAS increases.
   2. TAS decreases.
   3. CAS increases.
   4. CAS remains constant.
   Show the answer

   Answer B. TAS equals the Mach number times the local speed of sound, and the speed of sound falls as the temperature decreases with altitude in the troposphere. At constant Mach the TAS therefore decreases during the climb. CAS falls even faster because the density decreases, so it neither increases nor stays constant.

4. 4With a magnetic variation of 20°W, the magnetic heading of an object is...

   1. 115° when the true heading is 095°
   2. 175° when the compass heading is 195°
   3. 175° when the true heading is 195°
   4. 115° when the compass heading is 095°
   Show the answer

   Answer A. With westerly variation, magnetic north lies west of true north, so magnetic headings are greater than true headings: MH = TH + 20° = 095° + 20° = 115°. Subtracting the variation, as in 195° − 20° = 175°, would apply an easterly variation. The options using a compass heading confuse variation with deviation.

5. 5Complete the following sentence: a gyroscope with a vertical spin axis can (1) ______, and a gyroscope with a horizontal spin axis can (2) ______.

   1. (1) only topple;
      (2) drift and topple
   2. (1) drift and topple;
      (2) only drift
   3. (1) drift and topple;
      (2) also drift and topple
   4. (1) only topple;
      (2) only drift
   Show the answer

   Answer A. Drift is a movement of the spin axis in the horizontal plane and topple a movement in the vertical plane. A vertical spin axis, as in an artificial horizon, has no azimuth direction to lose, so it can only topple. A horizontal spin axis, as in a directional gyro, can wander in azimuth (drift) and tilt (topple).

6. 6By convention, is there a difference between an INS and an IRS?

   1. There is NO actual difference between an INS and an IRS, they are just different abbreviations used by different system manufacturers.
   2. Yes, the INS requires electrical power for its operation, while the IRS is completely independent of the electrical power.
   3. Yes, the INS is an older system based on a stabilised platform and mechanical gyros, while the IRS is a more modern, fixed system based on ring laser gyros or fibre optic gyros.
   4. Yes, the IRS is an older system based on a stabilised platform and mechanical gyros, while the INS is a more modern, fixed system based on ring laser gyros or fibre optic gyros.
   Show the answer

   Answer C. By convention, INS refers to the older design with a gimballed platform stabilised by mechanical gyros, while IRS refers to the modern strapdown system using ring laser or fibre optic gyros fixed to the airframe. Both need electrical power. The option that reverses the two describes the same distinction the wrong way round.

7. 7The purpose of the autopilot Control Wheel Steering (CWS) mode is...

   1. to capture and hold the altitude selected with the control wheel on the mode control panel.
   2. to control the nose wheel steering during low visibility take-off and landing.
   3. To allow the pilot to manually manoeuvre the aircraft through the autopilot computer and actuators using the control wheel.
   4. to control the nose wheel steering during automatic landing.
   Show the answer

   Answer C. In CWS the autopilot stays engaged, but its pitch and roll channels follow the forces the pilot applies to the control wheel, measured by force transducers, and drive the servos accordingly. When the wheel is released the autopilot holds the attitude reached. Despite the word steering, CWS has nothing to do with the nose wheel.

8. 8With the autopilot engaged, the automatic pitch trim serves to...

   1. relieve the autopilot servo motor and return the aircraft in-trim when disconnecting the autopilot.
   2. correct altitude deviations in altitude hold mode.
   3. synchronise the longitudinal loop.
   4. block the elevator and pilot the aircraft only via the trim tab actuator or the horizontal stabiliser.
   Show the answer

   Answer A. While the autopilot holds attitude, the pitch trim moves the stabiliser or trim tab so that the elevator servo does not carry a sustained load. The elevator stays close to neutral, so when the autopilot is disconnected the aircraft is in trim and does not pitch suddenly. Altitude corrections in ALT hold are made with the elevator, not the trim.

9. 9With a modern thrust computer, during a steady climb...

   1. N1 and N2 remain constant.
   2. N1 is automatically adjusted as aircraft climbs and N2 remains constant.
   3. N2 is automatically adjusted as aircraft climbs and N1 remains constant.
   4. N1 is automatically adjusted as aircraft climbs.
   Show the answer

   Answer D. As the aircraft climbs, air density and temperature change, so the thrust computer continuously recomputes the climb N1 (or EPR) limit and the autothrust or FADEC adjusts the engines to it. N2 is not a controlled parameter: it simply follows from the N1 setting, so it is neither held constant nor set separately.

10. 10One CDU fails in flight. What happens to the associated FMS?

    1. Can be used by inserting data via datalink.
    2. It is lost, and its FMC must be switched off for the rest of the flight.
    3. Can be used by inserting data VOR/LOC receiver.
    4. Either FMS can be programmed by using either CDU.
    Show the answer

    Answer D. In a dual installation the two flight management computers are cross-connected, and each CDU can address either computer. When one CDU fails, the crew simply uses the remaining one to program both FMS, and the system keeps operating normally. The computer itself has not failed, so there is no reason to switch it off.