Question

According to I.C.A.O, the slope of transitional surface at right angles to the centre line of runway, is

• A. 1 in 4
• B. 1 in 5
• C. 1 in 6
• D. 1 in 7

Hint:

ICAO’s transitional surface slope of 1 in 7 ensures safe aircraft operations by providing a gradual clearance zone around runways. This slope helps protect aircraft from obstacles during takeoff and landing, balancing safety with practical airport design.

Answer 1

The Correct Option is D

Step 1: Identify the given data.
The question asks for the slope of the transitional surface at right angles to the centre line of a runway, as per the International Civil Aviation Organization (ICAO) standards. The options are:
(1) 1 in 4
(2) 1 in 5
(3) 1 in 6
(4) 1 in 7
We need to determine the correct slope based on ICAO specifications.
Step 2: Recall the ICAO standards for runway transitional surfaces.
The ICAO (International Civil Aviation Organization) defines standards for airport design in Annex 14, which includes specifications for obstacle limitation surfaces to ensure safe aircraft operations. The transitional surface is a sloping surface that extends outward and upward from the edges of the runway strip and approach surfaces, at right angles to the runway centre line. Its purpose is to protect aircraft during takeoff and landing by limiting obstacles in the vicinity of the runway.
According to ICAO Annex 14, the slope of the transitional surface at right angles to the runway centre line is typically 1 in 7 (or 1:7), meaning for every 7 units of horizontal distance, the surface rises by 1 unit vertically. This slope applies to most runway categories unless specified otherwise (e.g., for precision approach runways).
Step 3: Interpret the slope notation.
A slope of "1 in 7" means a gradient of 1 vertical unit for every 7 horizontal units, or a slope of \( \frac{1}{7} \), which is approximately 14.3% or an angle of about 8.13 degrees. This is a relatively gentle slope, allowing for safe aircraft operations while providing clearance over obstacles.
Step 4: Compare with the options.
1 in 4 (Option 1): This is a steeper slope (25% gradient), not typically used for transitional surfaces.
1 in 5 (Option 2): Also steeper (20% gradient), not the ICAO standard.
1 in 6 (Option 3): Still steeper (16.67% gradient), not correct.
1 in 7 (Option 4): Matches the ICAO standard slope for the transitional surface.
Step 5: Select the correct option.
The slope of the transitional surface at right angles to the runway centre line, as per ICAO, is 1 in 7, matching option (4).
\[ \boxed{1 \, \text{in} \, 7} \]