1. Field of the Invention
This invention relates generally to inflatable structures, and more particularly to evacuation slides with means for adjusting the rate of descent of an evacuee.
2. Description of the Related Art
The inflatable evacuation slides and/or slide rafts provide a rapid means for evacuating passengers from commercial aircraft in the event of an emergency. These inflatable structures are normally stored uninflated within an aircraft. In use it is only necessary to open the door to automatically deploy the slide in the event of an emergency evacuation. When the door is opened, the gravity can take effect to unfold or unroll the slide outside of the doorway. Once outside the doorway, the slide is rapidly inflated through the application of air pressure and is ready for receiving evacuating passengers within a very short period of time following door opening.
Although the rate of evacuee descent is dependent on many factors, it is primarily governed by the angle formed between the slide surface and the ground. The optimum rate of descent for evacuees is usually achieved when the angle between the slide surface and ground is between about 30.degree. and 50.degree.. If the angle is much greater than 50.degree., the slide surface may be too steep and may result in evacuee injury upon impact with the ground.
In many instances, the ideal range of angles cannot be controlled since the slide surface has a fixed length and since the exit door may be at different heights. In emergency situations where one or more of the aircraft landing gears are damaged or collapsed, the aircraft itself may be tilted or canted at a number of different possible angles. Consequently, the aircraft door may be considerably higher with respect to the ground than in a normal landing position. With the increase in height between the door and ground, the angle between the slide and ground also increases, leading to an undesirable rate of descent for evacuees. This phenomena can also occur for normal landing positions when the evacuation slide encounters terrain which varies in slope.
In recognition of this problem, a number of proposals have been advanced in order to control the speed at which an evacuee travels down the slide. By way of example, U.S. Pat. No. 4,246,980 proposes an evacuation slide with a deceleration panel at a lower end thereof. The deceleration panel includes a fixed number of transversely extending grooves and ridges that, during sliding are contacted by an evacuee, so as to slow the evacuee's rate of descent. Although the grooves and ridges located at only the lower end of the inflatable may be effective in slowing the evacuee's rate of descent before exiting the slide, no provision has been made for controlling the rate of descent along its entire length. Thus, where the angle of the slide with respect to horizontal is great, the evacuee may experience undesirable acceleration along a substantial portion of the length of the slide before contacting the deceleration panel. Moreover, since the ridges in this slide are of a fixed number and of a predetermined height, they cannot substantially vary the rate of descent based on the particular landing conditions of the aircraft.