In airport planning and design, identify the correct statements about runway basic length corrections, standard temperature with elevation, and the definition of aerodrome reference temperature.
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AOnly statements 1 and 2 are correct.
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BOnly statements 2 and 3 are correct.
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COnly statements 1 and 3 are correct.
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DAll of the statements (1–3) are correct.
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ENone of the statements are fully correct.
Answer
Correct Answer: Only statements 1 and 2 are correct.
Explanation
Introduction / Context:This aviation-planning question checks three fundamentals used in runway length estimation and climatic normalization: (1) elevation correction to basic runway length, (2) the ISA-based way to compute standard temperature at a site, and (3) the precise definition of aerodrome reference temperature used in design charts and manuals.
Given Data / Assumptions:
- Basic runway length is adjusted for elevation, temperature, and gradient.
- Standard sea-level temperature is 15°C.
- Standard temperature lapse rate near the surface is 6.5°C per 1000 m rise (ISA approximation).
- The statement offered for aerodrome reference temperature uses “monthly mean of mean daily temperature.”
Concept / Approach:Elevation increases required runway length because lower air density reduces aircraft performance. Temperature also affects density; therefore the standard temperature at the aerodrome elevation must be computed from ISA to derive corrections. The “aerodrome reference temperature” has a specific definition (mean of the daily maximum temperatures of the hottest month, not the mean of the daily means).
Step-by-Step Solution:
1) Elevation correction: A common design rule increases basic runway length by 7% for each 300 m elevation above mean sea level. This matches Statement 1, so Statement 1 is correct.2) Standard temperature at site: T_site(std) = 15 − 6.5 * (h/1000), where h is elevation in metres. This is exactly what Statement 2 says (“reducing 15°C at 6.5°C per 1000 m rise”), so Statement 2 is correct.3) Aerodrome reference temperature: It is defined using the monthly mean of the daily maximum temperatures of the hottest month, not the monthly mean of the mean daily temperatures. Hence Statement 3 is incorrect.Verification / Alternative check:
Compute examples: if h = 900 m, T_site(std) = 15 − 6.5 * 0.9 = 9.15°C. Elevation correction = 7% * (900/300) = 21% addition to basic runway length.Why Other Options Are Wrong:
b/c: Include Statement 3, which misdefines aerodrome reference temperature.d: All-correct is invalid because Statement 3 is wrong.e: At least Statements 1 and 2 are correct; “none” is false.Common Pitfalls:
Confusing “mean of daily maximums” with “mean of daily means”; forgetting that elevation and temperature corrections are applied sequentially to basic runway length.Final Answer:
Only statements 1 and 2 are correct.