Doors: Emergency Egress

Emergency situations (e. g., fire hazard and ditching on water or land) require a fast exit from the aircraft cabin to safety. The FAA initially imposed a 120-s egress time but, in 1967, changed it to a maximum of 90 s. This was feasible through advances made in slide and chute technology. To obtain an airworthiness certi­fication, an aircraft manufacturer must demonstrate that complete egress is pos­sible within 90 s by conducting simulated tests. The EASA has similar require­ments.

FAR Part 25, Sections 25.783 and 25.807, give requirements for the main cabin doors and emergency exit doors, respectively. Several types of emergency exit doors are listed in Table 15.7 (in inches); all are rectangular in shape with a corner radius. The sizes are a minimum size and designers can make them larger. Oversized doors need not be rectangular as long as the minimum rectangular size is inscribed.

All doors except Type III (i. e., an inside step up of 20 inches and an outside step down of 27 inches) and Type IV (i. e., an inside step up of 29 inches and an outside step down of 36 inches) are from the floor level. If a Type II door is located over the wing, it can have an inside step up of 10 inches and an outside step down

of 17 inches. Emergency doors are placed at both sides of the aircraft and do not need to be diametrically opposite; however, they should be uniformly distributed (i. e., no more than 60 ft apart) and easily accessible for evenly distributing loading passengers when required. The safety drill by the cabin crew is an important aspect in saving lives, and all passengers should listen to the demonstration regardless of how frequently one flies. There are differences among door types.

An aircraft should have at least one easily accessible external main door. The combination of main and emergency doors is at the discretion of the manufac­turer, which must demonstrate a simulated evacuation within the stipulated time. The fuselage length also determines the number of emergency doors because they should not be spaced more than 60 ft apart. Table 15.8 lists the minimum number of emergency doors; it is recommended that more than the minimum be provided. Types A, B, and C also can be used and they are deployed in larger aircraft.

There may be other types of doors such as a door at the tail cone and ventral doors, the dimensions of which are listed in Table 15.9. Flight-crew emergency-exit doors are provided separately in the flight deck.

When the door level is high above the ground, inflatable escape slides and chutes are provided, as shown in Figure 15.14. In an emergency situation in which stairs may not be available (or there may not be time to wait for them to arrive), inflatable chutes are used for passenger evacuation within the specified time. The slides and chutes also serve as rafts with floating attachments.

As aircraft size increases, the technological demand to facilitate quick egress becomes a more challenging task. In March 2006, the Airbus 380 demonstrated that 850 passengers could be evacuated in 80 sec (although with minor injuries). How­ever, a typical Airbus 380 passenger load is fewer than 650 passengers with a mixed – class arrangement. The Airbus has sixteen exits but was successful in the evacuation using only eight doors (i. e., half remained closed).

Figure 15.14. Inflatable escape chute and slide

Coursework Exercise

There is a coursework exercise in this chapter. The configuration developed in Chapter 6 is to be reverified. The Bizjet must have the following features:

It is best for all doors to have Type III standards for component commonality, which reduces production costs.