Corrections are applied to the basic length of the runway strip considering:

(i) The elevation H (in m) of the airport above Mean Sea Level (MSL)
(ii) Corrected air temperature T (in ◦ C) with respect to the standard temperature at elevation H
(iii) The effective gradient G (in %) along the length of the runway Respective correction applied to the basic length of the runway is:

The correct answer is: 0.07 × H/300;0.01 × T;0.10 × G

To determine the corrections applied to the basic runway length of an airport, standard specifications recommended by the International Civil Aviation Organization (ICAO) are followed. These corrections are applied sequentially in the following order:

1. Correction for Elevation (H)
As the elevation of the airport increases, the atmospheric pressure and air density decrease. This reduction in air density decreases both the aerodynamic lift on the aircraft wings and the engine thrust. To compensate for this loss of performance, the runway length must be increased.
According to standard ICAO recommendations, the basic runway length is increased at the rate of 7% for every 300 meters rise in elevation above the Mean Sea Level (MSL).

$$\text{Correction for Elevation}=\frac{7}{100}\times \frac{H}{300}=0.07\times \frac{H}{300}$$

2. Correction for Temperature (T)
Higher ambient air temperatures further reduce air density, which negatively affects aircraft performance. This temperature correction is applied to the runway length after it has already been corrected for elevation.
The runway length is increased at the rate of 1% for every 1°C rise of the airport reference temperature (T) above the standard temperature at that elevation H.

$$\text{Correction for Temperature}=\frac{1}{100}\times T=0.01\times T$$

3. Correction for Effective Gradient (G)
An uphill gradient reduces the acceleration rate of the aircraft, thereby increasing the takeoff distance. This correction is applied to the runway length after both the elevation and temperature corrections have been made.
The runway length is increased at the rate of 10% for every 1% of the effective gradient (G).

$$\text{Correction for Gradient}=\frac{10}{100}\times G=0.10\times G$$

Combining the three sequential corrections, we get the respective correction values as:
0.07 × H/300; 0.01 × T; 0.10 × G