According to Torenbeek (1996), the T/W – thrust-to-weight ratio and the W/S – wing loading (W/S) are very important parameters that influence performance and they have to be optimised largely. As an example, if the initial wing loading is low, then it would give a larger area for the fuel tanks and landing gear. However, this can result in heavier drag and wing. For short takeoff, a large wing having low values of W/S and low values for T/W are required. With a 10% variation in the stalling speed, recommendations for wing loading is: 4942 < p < 5328 N/m2. Where p is the wing loading and the calculations have to follow the recommended values. Following figure gives allowable range of W/S.
Recommended values for T/W is taken as 0.3 and so a thrust requirement is 0.3 x Wg or 174.2 kN. These are however threshold requirements and they would vary depending on the wind conditions and weather conditions in which the aircraft would fly. The maximum take off weight Wto is fixed with a recommendation of 120 kilograms per passenger.
Time limit for flying:
According to the regulations of FAR 135.265(a), pilots have certain restrictions on the duration of their flights. The pilot can fly a maximum of 8 hours continuously in any consecutive 24 hour flight. This is true when the flight crew is made of one pilot. In addition, there should be a minimum of 8 hours rest between flights. There are some more rules that are applied and these are: a pilot is not allowed to fly for more than 34 hours in any 7 days consecutively and for not more than 120 hours in a month. In addition, the maximum hours a pilot can fly is 1200 hours in a year (Air Line Pilots Association, June 2002).