The Artificial HorizonNavigation — Instrumentation — DGCA CPL practice questions
Question 1 of 9
An artificial horizon utilizes (i)............ to show (ii)........ in (iii)....... and (iv).............
All 9 questions — The Artificial Horizon
Navigation — Instrumentation · DGCA CPL. The correct option is marked on each.
Q1. An artificial horizon utilizes (i)............ to show (ii)........ in (iii)....... and (iv).............
- A.(i) an earth gyro — (ii) position — (iii) latitude — (iv) longitude
- B.(i) a space gyro — (ii) attitude — (iii) degrees — (iv) minutes
- C.(i) an earth gyro — (ii) latitude — (iii) pitch — (iv) roll
- D.(i) an earth gyro — (ii) attitude — (iii) pitch — (iv) roll✓
Why: The AH uses an earth gyro (spin axis tied to the earth's vertical by gravity). It shows attitude (not position or latitude) in both pitch and roll. See Section 1 and Section 2 . — "Earth gyro" = spin axis tied to earth's vertical by gravity. "Space gyro" = spin axis fixed relative to inertial space. The AH is an earth gyro.
Q2. During the take-off run an air driven artificial horizon will usually indicate:
- A.nose up and incorrect left bank
- B.a false descending turn to the right
- C.increased nose-up attitude and right wing low✓
- D.a false climbing turn to the left
Why: During the take-off run (linear acceleration), a British air-driven AH (anticlockwise rotor spin) shows a false nose-UP and right wing DOWN indication. Pitch error: lateral vanes lag → port slot opens → reaction precessed → nose-up. Roll error: bottom-heavy rotor housing lags → precessed → base moves starboard → right wing down. See Section 7 . — The question specifies "air driven" and implies British-style (anticlockwise rotor). The mnemonics: "ACCELERATION = Nose-Up + Right-Wing-Down."
Q3. The indication on the right shows: [image shows 30° bank to port, horizon bar above gull-wing]
- A.a climbing turn to the right
- B.nose up and left wing down
- C.30° starboard bank, nose up
- D.30° port bank, nose below horizon✓
Why: On an AH display, when the gull-wing (aircraft symbol) tilts to the right relative to the horizon bar, the aircraft is banked to port (left). When the horizon bar is above the gull-wing (nose), the aircraft is nose-down. See Section 3 . — Remember — on the AH, the gull-wing follows the aircraft. If the left wing appears lower (gull-wing left side down), the aircraft's left wing is down = port bank.
Q4. False nose-up attitude displayed on air driven artificial horizon during the take-off run is caused by:
- A.the high pendulosity of the rotor
- B.the lag of the lateral pendulous vanes✓
- C.the linear acceleration cut-out
- D.incorrect rotor speed
Why: During acceleration, the lateral pendulous vanes lag backwards (due to inertia). This uncovers the starboard slot and covers the port slot, creating an unbalanced reaction that is precessed to produce a false nose-up indication. See Section 7 . — Pitch error = lateral vanes lag. Roll error = pendulous (bottom-heavy) rotor housing lags. Two distinct mechanisms for two distinct errors.
Q5. The rotor axis of an electrical horizon is tied to the earth's vertical by:
- A.four pendulous vanes
- B.the roll cut-out
- C.the low centre of gravity of the rotor housing
- D.two mercury level switches and two torque motors✓
Why: The electric AH uses mercury / levelling switches (one for pitch, one for roll) and torque motors to tie the rotor axis to the earth's vertical. See Section 11 . — Air-driven = pendulous vanes. Electric = mercury switches + torque motors. A clean distinction that is frequently tested.
Q6. False right wing low attitude shown on an air driven artificial horizon during an acceleration is caused by:
- A.the lag of the base of the rotor housing✓
- B.the longitudinal pendulous vanes
- C.the roll cut-out
- D.high rotor speed
Why: The rotor housing is bottom-heavy (pendulous). During acceleration, inertia causes the weighted base to try to lag behind. This force is precessed (90° in direction of rotor spin), moving the base to starboard → gyro axis tilts → right wing down indication. See Section 7 . — Pitch error (Q4) = lateral vanes. Roll error (this Q) = heavy base of rotor housing. Learn to distinguish the two mechanisms.
Q7. Inside an artificial horizon:
- A.the inner gimbal ring is pivoted laterally inside the outer gimbal ring and the outer gimbal ring is pivoted longitudinally inside the case✓
- B.the inner gimbal ring is tied to the vertical by a control system
- C.the rotor axis is kept level by a calibrated spring attached to the outer gimbal ring and the instrument case
- D.there is only one gimbal ring
Why: This describes the correct gimbal arrangement for the AH. The inner gimbal pivots laterally (about the lateral/pitch axis YY), the outer gimbal pivots longitudinally (about the longitudinal/roll axis ZZ inside the case). See Section 3 . — In the AH, the gimbal arrangement allows complete freedom in pitch and roll. The rotor axis stays vertical while the instrument case (attached to aircraft) moves around it.
Q8. When an adjustable aircraft datum is fitted to an artificial horizon in light aircraft:
- A.it should be checked at regular intervals
- B.it should be set to the central position and left there✓
- C.it should be rendered inoperative
- D.it should be set to 15°
Why: In light aircraft, AIC 14/1969 strongly recommends that the datum be set before flight and thereafter left alone. For aircraft over 6,000 lb MTOW, EASA requires it be rendered inoperative. Note: option (c) applies to heavier aircraft. See Section 14 . — The question specifically says "light aircraft." For heavy aircraft (>6,000 lb), render inoperative. For light aircraft — set before flight, leave it alone.
Q9. An electrically driven artificial horizon has less errors during the take-off run because:
- A.it is less pendulous, has a higher rotor speed and a linear acceleration cut-out✓
- B.the mercury level switches are more sensitive than the pendulous vanes fitted to air driven types
- C.the roll cut-out speed is activated
- D.it is less aperiodic than the air driven types
Why: Three factors reduce acceleration errors in the electric AH: (1) less bottom-heaviness (less pendulous rotor housing) reduces roll error; (2) higher rotor speed increases rigidity reducing all precession; (3) linear acceleration (pitch) cut-out at 0.18g prevents false erection. See Section 12 . — All three factors in (a) work together. The cut-out prevents false erection; less pendulosity reduces the mechanical cause of roll error; higher speed reduces the effect of any residual error.