A dispatcher calculates that a turbojet's accelerate-stop distance required (ASDR) is 8,200 feet and its accelerate-go distance required (all-engine takeoff distance continuing after an engine failure) is 7,600 feet. The runway available is 8,000 feet with no stopway or clearway. Which statement correctly describes the required action?
- AA clearway may be used to satisfy the shortfall without reducing takeoff weight
- BThe takeoff may proceed as planned because accelerate-stop distance is not a limiting factor for turbojets
- CThe takeoff weight must be reduced because accelerate-stop distance required exceeds the runway length available
- DThe takeoff may proceed at the planned weight since accelerate-go distance is less than runway available
Show answer & explanationAnswer & explanation
Correct answer: C. The takeoff weight must be reduced because accelerate-stop distance required exceeds the runway length available
Both accelerate-stop and accelerate-go distances must fit within the available runway (plus any stopway/clearway as applicable). Since ASDR (8,200 ft) exceeds the runway available (8,000 ft) and there is no stopway, weight must be reduced until ASDR does not exceed available distance; a clearway would not help because it cannot be used for stopping distance.
Why the other options are wrong
- A. A clearway only extends the usable distance for accelerate-go (takeoff distance), not accelerate-stop.
- B. Incorrect; ASDR is always a required limiting check for turbojet dispatch.
- D. Ignores that ASDR, not just accelerate-go, must also fit within runway available.
Balanced Field Length Concept
Takeoff weight must satisfy both accelerate-stop distance required (ASDR) and accelerate-go/takeoff distance required (TODR); the runway (plus stopway/clearway as applicable) must accommodate the greater of the two.
- ASDR uses runway + stopway (not clearway)
- TODR (accelerate-go) may use runway + clearway
- Balanced field length: ASDR = TODR at chosen V1
- Weight is reduced until both distances fit available surfaces
Memory trick: Stopway helps you STOP, clearway helps you GO — don't mix them up