Runway length adjustments – cap on combined corrections In runway length design, the total combined correction applied for elevation, temperature, and longitudinal gradient should not exceed which percentage of the basic runway length?

Introduction / Context:
Basic runway length (sea-level, standard temperature, level grade) is increased by correction factors for elevation, temperature, and gradient. Practical design imposes a cap so that cumulative adjustments do not inflate lengths beyond reasonable limits without a performance basis.

Given Data / Assumptions:

• Basic runway length computed for the reference aircraft.
• Corrections: elevation (lower air density), temperature (hot-day performance), gradient (uphill/downhill effect).
• A design cap is applied to the combined correction.

Concept / Approach:
While each factor could be significant, their sum is typically limited to a maximum percentage to preserve practicality and ensure that more precise performance calculations are used if the cap would otherwise be exceeded. A widely used examination value for this cap is 35%.

Step-by-Step Solution:
Identify that the question asks for the maximum allowed combined correction.Recall the standard cap employed in many syllabi: 35%.Select 35% from the options.

Verification / Alternative check:
Worked examples in airport engineering textbooks commonly use a 35% limit on total corrections unless aircraft-specific performance methods are adopted.

Why Other Options Are Wrong:
15–30% are lower than the commonly taught upper bound and would prematurely limit justified corrections in hot-and-high sites.

Common Pitfalls:
Applying the cap before computing individual corrections; forgetting that aircraft manufacturer performance data can override simplified caps.

Final Answer:
35%