On the occasion of Farnborough Air Show, in lieu of the initial 189-seater, Boeing announced the launch of a greater capacity 200-seater version of its 737 MAX-8. In order to do be able to do this, strangely perhaps, they will not have to enlarge the fuselage, but simply add a pair of additional doors. How come ?
Simply because the regulations for any commercial aircraft in this domain are very strict. The number of doors on an airplane not only depends on the number of seats on board, but also allow all passengers to evacuate in less than 90 seconds.
On a slightly more technical note, Aircraft manufacturers actually have seven certified types of doors to choose from. Each type of door, normally supplied in pairs, varies in height and width, and corresponds to the number of passengers that can evacuate through it.
For example : A pair of Type A doors corresponds to 110 passengers, requiring therefore, a total of eight pairs for an A-380, because all passengers must be able to exit the super-jumbo within the regulatory maximum time limit.
Certain aircraft, however, can be equipped with two different types of door, as is generally the case with short-hauls.
When manufacturers define the passenger carrying capacity of an aircraft, systematically, they have to take out their slide rules to determine the type and number of pairs of doors required. Its civil certification depends on it.