Which of the following factors are taken into account for estimating the runway length required for aircraft landing? 1. Normal maximum temperature 2. Airport elevation 3. Maximum landing weight 4. Effective runway gradient Select the correct answer using the codes given below A. 1, 2, 3 and 4 B. 1, 3 and 4 C. 2 and 3 D. 1, 2 and 4

The correct answer is: A. 1, 2, 3 and 4.

The runway length required for aircraft landing is estimated based on the following factors:

1. Normal maximum temperature: The higher the temperature, the thinner the air, and the longer the runway will need to be.
2. Airport elevation: The higher the airport, the thinner the air, and the longer the runway will need to be.
3. Maximum landing weight: The heavier the aircraft, the longer the runway will need to be to come to a stop.
4. Effective runway gradient: The effective runway gradient is the slope of the runway from the beginning to the end. A positive gradient will require a longer runway than a negative gradient.

The other options are not relevant to estimating the runway length required for aircraft landing.