According to ICAO standards, what is the slope (rise:run) of the transitional surface measured at right angles to the runway center line?
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A1 in 4
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B1 in 5
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C1 in 6
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D1 in 7
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E1 in 10
Answer
Correct Answer: 1 in 7
Explanation
Introduction:The question examines knowledge of obstacle limitation surfaces (OLS) around aerodromes. The transitional surface, rising outward from the runway strip and approach surfaces, protects airspace for safe operations.
Given Data / Assumptions:
- Standard ICAO OLS definitions apply.
- Transitional surface slope is expressed as vertical rise to horizontal run.
Concept / Approach:
For typical non-precision and precision runway environments, ICAO prescribes a transitional surface slope commonly taken as 1:7 (one unit vertical for seven units horizontal), unless special categories dictate otherwise.
Step-by-Step Solution:
Identify the relevant OLS (transitional surface) adjoining runway strip/approach.Recall standard slope values: transitional ≈ 1:7 in many ICAO layouts.Match with the given options → 1 in 7.Verification / Alternative check:
Cross-checking with common OLS tables confirms 1:7 is the canonical slope for transitional surfaces in standard cases.
Why Other Options Are Wrong:
- 1 in 4, 1 in 5, 1 in 6: Steeper than typical ICAO prescription for transitional surface.
- 1 in 10: Flatter than standard and not the typical ICAO value for this surface.
Common Pitfalls:
- Mixing up transitional surface slope with conical surface slope values.
- Forgetting slopes are run-to-rise ratios and selecting reversed values.
Final Answer:
1 in 7