DADE Aircraft Performance & Limitations 3 — Questions and Answers
Question 1: An aircraft dispatcher must ensure that the en route terrain clearance with one engine inoperative allows the aircraft to clear all terrain by at least:
- 500 feet within 5 miles of the intended track
- 1,000 feet within 5 miles of the intended track (Correct answer)
- 2,000 feet within 10 miles of the intended track
- 1,000 feet within 10 miles of the intended track
Correct answer: 1,000 feet within 5 miles of the intended track
Under 14 CFR Part 121.191, the aircraft must be able to clear all terrain and obstructions by at least 1,000 feet within 5 statute miles on either side of the intended route with one engine inoperative.
Question 2: What is 'VMCA' and how does it affect dispatch decisions?
- Maximum crosswind for takeoff; limits usable runways
- Minimum control speed in the air; the aircraft cannot be dispatched to operate slower than this speed on approach
- Minimum control speed in the air with critical engine inoperative; must remain below V2 speed (Correct answer)
- Maximum certified altitude; limits cruise levels
Correct answer: Minimum control speed in the air with critical engine inoperative; must remain below V2 speed
VMCA is the minimum control speed in the air with the critical engine inoperative, and V2 must be equal to or greater than 1.1 × VMCA to ensure controllability after engine failure during takeoff.
Question 3: When dispatching an aircraft to a high-altitude airport (above 8,000 feet MSL), which performance limitation typically becomes most critical?
- Maximum landing weight due to faster groundspeed at touchdown
- Runway length due to reduced air density lowering engine thrust and aerodynamic lift (Correct answer)
- Maximum fuel load due to thin air carburetor icing
- Structural limits due to lower atmospheric pressure
Correct answer: Runway length due to reduced air density lowering engine thrust and aerodynamic lift
At high-altitude airports, reduced air density decreases both engine thrust output and aerodynamic lift, requiring higher ground speeds for liftoff and significantly increasing runway length requirements.
Question 4: Under 14 CFR 121.197, what runway length requirement applies for dispatching to an alternate airport for landing?
- 60% of the available runway length
- 70% of the available runway length
- 80% of the available runway length (Correct answer)
- The same as the destination landing distance requirement
Correct answer: 80% of the available runway length
For alternate airports, 14 CFR 121.197 requires that the landing distance not exceed 80% of the effective runway length, providing a greater margin than the 60% typically applied at the destination.
Question 5: The 'drift down' procedure for ETOPS or extended over-water operations refers to:
- Controlled descent during turbulence penetration
- The one-engine-inoperative cruise altitude capability after an engine failure at optimum altitude (Correct answer)
- The procedure for dumping fuel to reach maximum landing weight
- The descent path used during an emergency depressurization
Correct answer: The one-engine-inoperative cruise altitude capability after an engine failure at optimum altitude
Drift down is the OEI performance profile showing the aircraft's ability to maintain altitude or descend gradually after an engine failure at cruise altitude while remaining above minimum enroute altitudes.
Question 6: Which of the following best describes 'obstacle clearance limit' (OCL) takeoff weight?
- The maximum weight allowing a 35-foot obstacle clearance during initial climb
- The maximum weight permitting the net takeoff flight path to clear all obstacles in the departure area by required margins (Correct answer)
- The weight limit imposed by airport noise abatement procedures
- The weight at which the aircraft can maintain a positive climb gradient
Correct answer: The maximum weight permitting the net takeoff flight path to clear all obstacles in the departure area by required margins
The obstacle clearance limit takeoff weight is the maximum weight at which the net takeoff flight path clears all relevant obstacles by the required lateral and vertical margins in the departure corridor.
Question 7: How does anti-ice system usage typically affect aircraft takeoff performance?
- It improves performance by reducing ice accumulation during the takeoff roll
- It decreases available thrust and reduces maximum allowable takeoff weight (Correct answer)
- It has no effect if OAT is above 0°C
- It increases V speeds but does not affect weight limits
Correct answer: It decreases available thrust and reduces maximum allowable takeoff weight
Engine anti-ice systems bleed pressurized air from the compressor, reducing net thrust available and therefore decreasing the maximum allowable takeoff weight when the system must be activated.
DADE Aircraft Performance & Limitations 3
An aircraft dispatcher must ensure that the en route terrain clearance with one engine inoperative allows the aircraft to clear all terrain by at least: