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How does APG use these distances in runway analysis?

Takeoff Analysis

  • Balanced Field Length Aircraft:
    • Accelerate-go and accelerate-stop distances are equal.
    • The shortest of TORA, TODA, or ASDA limits the takeoff performance.
  • Unbalanced Field Length Aircraft:
    • Accelerate-go and accelerate-stop distances are calculated separately.
    • Accelerate-go: Limited by TORA + clearway (up to the max allowed by 14 CFR 25.113).
    • Accelerate-stop: Must be ≤ ASDA.

On wet runways, clearways cannot be used. The aircraft must reach 15 ft by the end of the TORA.

Landing Analysis

  • The Landing Distance Required (LDR) must be ≤ LDA.
  • LDR is calculated from a point 50 ft above the threshold, using normal touchdown and maximum braking.
Why does ASDA sometimes differ from TORA?
  • At some airports, ASDA is shorter than TORA due to land-use restrictions in the Runway Protection Zone (RPZ). This affects rejected takeoff performance and must be accounted for in balanced field length calculations.