Control LawsNavigation — Instrumentation — DGCA CPL practice questions
Question 1 of 6
In a Boeing 737-400, the minimum speed protection activates at approximately:
All 6 questions — Control Laws
Navigation — Instrumentation · DGCA CPL. The correct option is marked on each.
Q1. In a Boeing 737-400, the minimum speed protection activates at approximately:
- A.1.2 VS for current configuration
- B.1.3 VS for current configuration✓
- C.VMC (minimum control speed)
- D.VREF for current configuration
Why: The AFS minimum speed is based on angle of attack and is approximately 1.3 VS for the current flap configuration, sensed by AoA vanes on either side of the forward fuselage. See Section 2 . — The AFS commands a speed 5 kt above the minimum, and the under-speed symbol disappears only when 15 kt above minimum is selected.
Q2. In a fly-by-wire aircraft with bank angle protection, if the pilot releases the sidestick after a roll manoeuvre, the aircraft will return to a bank angle of:
- A.0° (wings level)
- B.15°
- C.33°✓
- D.45°
Why: After a roll manoeuvre, if the pilot releases the stick, the aircraft returns to a bank angle of 33° . The bank angle protection is not an "auto-wings-level" — it simply stops the bank from increasing beyond the limits. See Section 8 . — This is a key FBW distinction: stick neutral = maintain 33° bank, not wings level. "Normal law" FBW is load factor demand, not attitude demand.
Q3. High speed protection on a fly-by-wire aircraft prevents exceeding Vd/Md by:
- A.Automatically retarding the thrust levers
- B.Deploying the speed brakes automatically
- C.Adding a nose-up g demand proportional to overshoot beyond VMO/MMO✓
- D.Limiting elevator deflection to nose-down only
Why: High speed protection adds a positive nose-up g demand proportional to the amount of speed overshoot beyond VMO/MMO. Input = airspeed/Mach from ADC; output to elevators. See Section 6 . — The g demand is proportional — the further beyond VMO/MMO, the stronger the nose-up pitch input. This allows steep dives knowing the system will auto-recover.
Q4. Autopilot pitch and roll authority is significantly reduced as the aircraft nears the ground during autoland. This is an example of:
- A.Fail-passive operation
- B.Flight envelope protection
- C.Gain adaption / gain scheduling✓
- D.Minimum speed reversion
Why: Gain adaption / gain scheduling reduces the autopilot's pitch and roll authority during the final phase of automatic approach and autoland. The bank angle limit progressively reduces from ~45° in manual mode, to 30° for LOC/VOR tracking, to 15° for autoland finals. See Section 10 . — Gain scheduling was introduced in Chapter 25 for FDS and applies equally to the autopilot — reducing authority near the ground and at high Q to prevent dangerous manoeuvres.
Q5. On a fly-by-wire aircraft with pitch attitude protection, what are the maximum pitch attitude limits?
- A.25° nose-up and 10° nose-down
- B.30° nose-up and 15° nose-down✓
- C.20° nose-up and 20° nose-down
- D.45° nose-up and 30° nose-down
Why: Pitch attitude protection limits are 30° nose-up and 15° nose-down . See Section 7 . — Asymmetric limits — nose-up is more than nose-down — reflect that overpitch in the dive (nose-down) is corrected more aggressively (hits speed limits faster) than nose-up, which has AoA protection as a further back-stop.
Q6. During a 737-400 AFS minimum speed reversion while in V/S (Vertical Speed) mode, the AFDS will automatically revert to:
- A.ALT HOLD
- B.LVL CHG✓
- C.Speed (SPD) mode
- D.ARM mode
Why: If operating in V/S mode and actual speed becomes equal to or slightly less than the minimum speed, the under-speed limiting symbol appears in the MCP IAS/Mach display and the AFDS reverts to LVL CHG . The AFDS then commands nose-down pitch to increase airspeed if thrust levers are not advanced. See Section 3 . — No minimum speed reversion is available when A/T is OFF and AFDS is in ALT HOLD, ALT ACQ, or after G/S capture — this is an important limitation to note.