According to ICAO standards, what is the slope (rise:run) of the transitional surface measured at right angles to the runway center line?

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:

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