The longitudinal sections of a runway have gradients as shown in the table. Consider the reduced level (RL) at the starting point of the runway as 100 m.End to end for sections of runway (m) Gradient (%) 0 to 200 +1.0 200 to 600 -1.0 600 to 1200 +0.8 1200 to 1600 +0.2 1600 to 2000 -0.5
The effective gradient of the runway is
Runway Effective Gradient Calculation
The effective gradient represents the overall slope of the runway. It is calculated by dividing the total vertical rise or fall by the total horizontal length of the runway.
Runway Sections and Gradients
| Section Range (m) | Length (m) | Gradient (%) | Vertical Change (m) |
| 0 to 200 | 200 | +1.0 | $200 \times 0.01 = +2.0$ |
| 200 to 600 | 400 | -1.0 | $400 \times (-0.01) = -4.0$ |
| 600 to 1200 | 600 | +0.8 | $600 \times 0.008 = +4.8$ |
| 1200 to 1600 | 400 | +0.2 | $400 \times 0.002 = +0.8$ |
| 1600 to 2000 | 400 | +0.5 | $400 \times 0.005 = +2.0$ |
| Total | 2000 | +5.6 |
Total Runway Length
The total horizontal length is the sum of the individual section lengths:
Total Length $= 200 \text{ m} + 400 \text{ m} + 600 \text{ m} + 400 \text{ m} + 400 \text{ m} = 2000$ m.
Total Vertical Change
The total vertical change is the sum of the vertical changes for each section:
Total Vertical Change $= (+2.0) + (-4.0) + (+4.8) + (+0.8) + (+2.0) = +5.6$ m.
Effective Gradient Calculation
Use the formula for effective gradient:
Effective Gradient $= \left( \frac{\text{Total Vertical Change}}{\text{Total Length}} \right) \times 100\% $
Calculate the effective gradient:
Effective Gradient $= \left( \frac{5.6 \text{ m}}{2000 \text{ m}} \right) \times 100\% = 0.0028 \times 100\% = 0.28\% $
The effective gradient of the runway is 0.28%.
Important Questions from Design of Airports
The point of intersection of the obstruction clearance line and the extended plane of the runway surface and the other end of the runway is called as:
For the hottest month of the year at the proposed airport site, the monthly mean of the average daily temperature is 390C. The monthly of the maximum daily temperature is 480C for the same month of the year. From the given information, the calculated Airport Reference Temperature (in 0C), is
Calculate the turning radius of the taxiway for an airport serving large subsonic jet planes. The design speed of turning is 60 kmph and assume friction coefficient between tyre and pavement surface as 0.15.
A runway is being constructed in a new airport as per the International Civil Aviation Organization (ICAO) recommendations. The elevation and the airport reference temperature of the airport are 535 m above the mean sea level and 22.65°C, respectively. Consider the effective gradient of runway as 1%. The length of runway required for a design-aircraft under the standard condition is 2000 m. Within the framework of applying sequential corrections as per the ICAO recommendations, the length of runway corrected for the temperature is
What is the airport reference temperature, if the monthly mean of average daily temperature for the hottest month of a study year = 24°C and the monthly mean of the maximum daily temperature for the same month of the same year = 30°C
