Abstract:
An inflatable evacuation slide system ( 10 ) is selectively deployable in either a foreshortened or lengthened configuration. The foot end ( 50 ) of the escape slide ( 12 ) includes a compartment ( 92 ) containing an extensible slide portion ( 70 ) stored in an undeployed condition. The compartment is sealed by means of conventional speed lacing ( 92 ) held together by a single master loop ( 96 ). A pyrotechnic cable cutter ( 98 ) is attached to the master loop ( 96 ) to severe it at the appropriate time thereby releasing the extensible portion of the slide. A control circuit ( 100 ) determines whether to deploy the extensible portion based on input from a non-contacting electronic sensor ( 110 ) such as an inclinometer.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to emergency evacuation equipment for aircraft, in particular, to inflatable aircraft evacuation slides.  
           [0002]    The requirement for reliably evacuating airline passengers in the event of an emergency is well known. Emergencies at take-off and landing often demands swift removal of the passengers from the aircraft because of the potential of injuries from fire, explosion, or sinking in water. A conventional method of quickly evacuating a large number of passengers from an aircraft is to provide multiple emergency exits, each of which is equipped with an inflatable evacuation slide. These inflatable slides are normally stored in an uninflated condition in a container or packboard requiring a minimum of space in the interior of the aircraft and are typically either mounted on the interior of the aircraft door or immediately adjacent thereto. Opening of the aircraft emergency evacuation exit initiates the inflation of the emergency evacuation slide. The slide is rapidly inflated and ready for evacuation of passengers who in a very short period of time following opening of the exit. The descent of evacuees on an inflatable evacuation slide is primarily governed by the angle formed between the slide surface and the ground. The optimum rate is usually achieved when the angle they are between is from about 30° at a minimum to about 50° at a maximum. The lower the angle, the slower the rate of descent and the evacuation may not proceed with sufficient dispatch. If the angle is much greater than 50°, the slide surface may be too precipitous and evacuees may balk at descending the slide and/or may be injured upon impact with the ground.  
           [0003]    Controlling the proper angle between the slide and ground is made more complex since the evacuation slides are normally utilized only in emergency situations. In such situations it may be that one or more of the landing gear of the aircraft have been damaged or collapsed such that the aircraft itself may be canted at a number of different possible angles. For example, if the nose landing gear collapses, the nose of the aircraft will drop and the fuselage will pivot about the main landing gear so that an escape exit located at the tail of the plane may be elevated substantially. An escape slide that is disposed at the proper angle for rapid but safe evacuation at a normal height would become too steep for safe evacuation from the elevated exits. Similarly, an escape slide that is disposed near the nose of the aircraft may be deployed at too shallow an angle for rapid evacuation.  
           [0004]    Use of variable length evacuation slides has been suggested as a means to accommodate evacuation of passengers from an evacuation exit that may be elevated or depressed relative to the ground. U.S. Pat. No. 2,936,056 to Heyniger discloses an inflatable evacuation slide having an extensible portion held within a compartment closed by a zipper. If the evacuation slide is to be deployed in the long configuration, prior to inflation the zipper must be manually removed. Accordingly, whether to deploy the evacuation slide in the long configuration requires a manual act predicated on human judgement at a time of possible emotional stress.  
           [0005]    U.S. Pat. No. 3,463,266 to Day discloses an extensible escape slide having inflatable side beams that are normally foreshortened in length but which may be extended when additional length is required. The determination as to whether to deploy the slide in the foreshortened or lengthened condition is made by dropping a weight attached to a predetermined length of cord. If the weight touches the ground, an electrical connection remains open and the extensible side beams are restrained in their foreshortened condition. If, however, the weight does not touch the ground, the weight closes a switch that releases a restraint allowing the side beams to deploy to their fullest extent.  
           [0006]    Similarly, U.S. Pat. No. 3,544,344 to Summer, et al. discloses a variable length inflatable slide comprising a height sensing means consisting of a weight attached to a predetermined length of cable. Upon initiation of the evacuation slide, the weight is dropped. If the weight contacts the ground the cable is not activated to release the extensible portion and the slide deploys in its foreshortened condition. If, however, the mass does not contact the ground the weight draws a cone through a sleeve which locks the cable in a fixed position. As the slide deploys, the cable in its locked position releases the extensible portion under the force of the inflating slide.  
           [0007]    As noted hereinbefore, evacuation slides having a manually deployed extension require human judgement at a time of possible emotional stress and therefore may be improperly deployed. Consequently these slides may be unreliable in service. Similarly, extensible escape slides that rely on the dropping of a plumb line to measure the distance from the slide to the ground are cumbersome and, because the weight and line may become fouled upon deployment, these designs also suffer from potential reliability problems. Accordingly, what is needed is an extensible emergency evacuation slide that does not rely on manual actuation or physical measurement of the distance to the ground to determine whether the slide is to be deployed in the foreshortened or extended configuration.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention comprises an inflatable evacuation slide system including an evacuation slide that is selectively deployable in either a foreshortened or lengthened configuration based on the input from an electronic sensor. In an illustrative embodiment, the slide comprises a pair of main support tubes supporting a flexible slide surface. The foot end of the escape slide includes a compartment containing an extensible slide portion stored in an undeployed condition. The compartment is sealed by means of conventional speed lacing held together by a single master loop. A pyrotechnic cable cutter is attached to the master loop to sever it at the appropriate time, thereby releasing the extensible portion of the slide.  
           [0009]    A control circuit determines whether to deploy the extensible portion based on input from a non-contacting electronic sensor such as an inclinometer. As noted hereinbefore, the principal reason for an egress opening to be elevated or depressed from its normal height during an emergency evacuation is that one or more of the aircraft landing gear has collapsed. The detection of a collapsed landing gear is translated to a deviation of the aircraft fuselage from its normal horizontal attitude into a nose down, tail down, port or starboard wing down attitude. Since the nose down, tail down, port or starboard wing down attitude can be detected electronically as a pitch and/or roll angle, a simple logic circuit can deploy each of the nose, over-wing and/or tail evacuation slides in the appropriate configuration reliably and without the use of cumbersome direct measurement techniques such as the dropping of a weight attached to a cable. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0010]    The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which like references designate like elements and, in which:  
         [0011]    [0011]FIG. 1 is a side elevational view of an aircraft equipped with prior art evacuation slides having landed in a nose-down attitude;  
         [0012]    [0012]FIG. 2 is a perspective view of an inflatable escape slide system incorporating features of the present invention deployed in a foreshortened condition;  
         [0013]    [0013]FIG. 3 is a perspective view of an inflatable escape slide system incorporating features of the present invention deployed in an extended configuration;  
         [0014]    [0014]FIG. 4 is a partial perspective cutaway view of the toe portion of the escape slide of FIG. 2 showing details of the extensible portion;  
         [0015]    [0015]FIG. 5 is a is a partial perspective cutaway view of the toe portion of the escape slide of FIG. 2 showing details of the extensible portion; and  
         [0016]    [0016]FIG. 6 is a schematic diagram of an electronic control circuit for deploying the inflatable escape slide. 
     
    
     DETAILED DESCRIPTION  
       [0017]    The drawing figures are intended to illustrate the general matter of construction and are not necessarily to scale. In the detailed description and the drawing figures, specific illustrative examples are shown and herein described in detail. It should be understood, however, that the drawing figures and detailed description are not intended to limit the invention to the particular form disclosed but are merely illustrative and intended to teach one of ordinary skill how to make and/or use the invention claimed herein and for setting forth the best mode for carrying out the invention.  
         [0018]    As noted hereinbefore, the descent of evacuees on an inflatable evacuation slide is primarily governed by the angle formed between the slide surface and the ground. For optimum egress, the evacuation slide must be deployed within a certain range of angles. If the angle is too low, the evacuees will not descend the slide with sufficient speed. If the angle is too steep, the slide surface may be too precipitous and evacuees may balk at descending the slide and/or may be injured upon impact with the ground. Controlling the proper angle between the slide and ground is made more complex since the evacuation slides are normally utilized only in an emergency situation in which the aircraft may not be in its normal horizontal attitude. For example, as shown in FIG. 1 if the nose landing gear collapses after an emergency landing, the nose of the aircraft will drop and the fuselage will pivot about the main landing gear so that an escape slide located at the nose of the plane will be at a distance L1. This distance is substantially less than L0, the distance from the threshold of the emergency exit door to the ground when the plane is in a normal horizontal attitude. Similarly, the tail of the plane is elevated to a level L2 that is substantially greater than L0. As such, a prior art evacuation slide of fixed dimensions will be deployed at too shallow an angle at the nose of the aircraft and too precipitous an angle at the tail of the aircraft.  
         [0019]    With reference to FIGS. 2 and 3, an extensible evacuation slide system  10  incorporating features of the present invention includes an inflatable evacuation slide  12  and an inflator  14 , which may be a conventional pyrotechnic, compressed gas, or hybrid inflator well-known in the art. Extensible evacuation slide system  10  is stored in an undeployed condition in a packboard housing inside the fuselage of aircraft  16 . In a deployed condition, inflatable evacuation slide  12  extends outward from a location proximal the egress opening  18  of aircraft  16  and extends downward to ground level  20  or other lower supporting surface.  
         [0020]    Inflatable evacuation slide  12  comprises upper main support tubes  22  and  26  and lower main support tubes  24  and  28  supporting a flexible slide surface  30 . Flexible sliding surface  30  is composed of a left main panel  32 , a right main panel  34 , a foot end panel  36  and a head end panel  42 . The head end  44  of extensible evacuation slide  12  is secured to aircraft  16  by a conventional girt  46 . Upper main support tubes  22  and  26  are maintained in a spaced-apart configuration by an upper toe end transverse tube  48  located at the foot end  50  of extensible evacuation slide  12  and an upper head end transverse tube (not shown) located at head end  44  of extensible evacuation slide  12 . Lower main support tubes  24  and  28  are similarly maintained in a spaced-apart configuration by transverse tubes (also not shown). A center support tube  58  bisects flexible sliding surface  30  to create two substantially parallel sides. A lateral support tube  60  provides additional support for head end  44  of extensible evacuation slide  12 .  
         [0021]    Additional support to prevent extensible evacuation slide  12  from buckling under heavy load is provided by a lower truss tube  62  and an upper truss tube  64  each of which comprises a U-shaped tube extending from lower main support tube  24  to lower main support tube  28 . Optionally, lower truss tube  62  and upper truss tube  64  comprise E-shaped tubes interconnecting lower main support tube  24 , lower main support tube  28  and center support tube  58 . A plurality of truss straps  66  act as tension members to support extensible evacuation slide  12  against buckling under heavy load.  
         [0022]    With particular reference to FIG. 3, extensible evacuation slide  12  includes an extensible portion  70  comprising main support tube extensions  72  and  74 , center support tube extension  76 , and slide surface extension  78 . Main support tube extensions  72  and  74  are maintained in a spaced-apart configuration by extension transverse tube  80  and additional resistance to buckling is provided by extension truss tube  82 .  
         [0023]    With reference to FIGS. 4 and 5, the inflatable tubular members of extensible portion  70  are pneumatically interconnected with upper main support tubes  22  and  26  so that they are pressurized when the remainder of extensible evacuation slide  12  is inflated. Extensible portion  70  is prevented from deploying, however, because it is retained in a pouch  90  adjacent upper toe end transverse tube  48  at the foot end  50  of evacuation slide  12 . As shown in FIGS. 4 and 5, pouch  90  is maintained in a closed configuration by means of a series of loops  92   a - j , fed through a series of grommets  94   a - j  with each loop passed through the preceding loop to form what is conventionally referred to as “speed lacing.” The speed lacing is held together at the center by means of a master loop  96 . Attached to master loop  96  is a cord cutter  98  comprising a pyrotechnically driven knife edge discussed more fully hereinafter. As can be determined from inspection of FIG. 5, once master loop  96  is severed by cord cutter  98  each of loops  92   a - j  are released permitting extensible portion  70  to deploy.  
         [0024]    With reference to FIG. 6, control circuit  100  comprises a logic circuit together with a conventional firing circuit for initiating the inflation of an inflatable evacuation slide. Interconnected with logic circuit  100  are a power source  102 , switch  104  and an electronic sensor  110 . The electronic sensor  110  comprises a conventional solid state inclinometer, mercury switch or other sensor that may be positioned within an aircraft to sense pitch and/or roll of the aircraft. In operation, if emergency exit door  112  is opened in the armed position, switch  104  closes and sends a signal to electronic control circuit  100 . In response to the signal from switch  104 , electronic control circuit  100  initiates inflator  14  which begins the inflation of extensible evacuation slide  12 . Contemporaneously, electronic control circuit  100  interrogates electronic sensor  110  to determine whether the aircraft is in a horizontal attitude, a nose down attitude or some other attitude. In response to the signal from electronic sensor  110 , electronic control circuit  100  deploys extensible evacuation slide  12  in either the foreshortened or lengthened configuration. If extensible evacuation slide  12  is to be deployed in the extended configuration, a firing circuit within electronic control circuit  100  initiates squib  112  of cord cutter  98  which, in turn, initiates a pyrotechnic composition  114 . Pyrotechnic composition  114  burns rapidly and the expanding gas drives knife edge  116  through master loop  96  severing it. This permits the speed lacing formed of loops  92   a - j  to unravel thereby releasing extensible portion  70  to deploy. If extensible evacuation slide  12  is to be deployed in the foreshortened configuration, cord cutter  98  is not initiated and therefore master loop  96  remains intact preventing deployment of extensible portion  70 .  
         [0025]    As can be determined from the foregoing, use of an electronic sensor, such as an inclinometer as the environmental sensor to determine whether to deploy extensible evacuation slide in the foreshortened or lengthened configuration provides for an extremely reliable and compact system as compared with prior art systems which rely on mechanical measurements such as the dropping of a weight attached to a fixed length of cord. Although certain illustrative embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the spirit and scope of the invention. For example, the inclinometer may be replaced with other non-contacting electronic sensors such as an infrared or ultrasonic rangefinder. Accordingly, it is intended that the invention shall be limited only the extent required by the appended claims and the rules and principals of applicable law.