Abstract:
A method for mitigating toe strike in a cockpit of an aircraft includes providing an airbag module attached to an instrument console located in the cockpit of the aircraft; releasing an airbag from the airbag module after an ejection sequence begins; using the airbag to protect a pilot&#39;s lower limbs from striking the instrument console as the pilot begins ejecting.

Description:
STATEMENT OF GOVERNMENT INTEREST 
   The invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties therefor. 

   BACKGROUND OF THE INVENTION 
   The invention relates in general to aircraft pilot ejection safety devices and in particular to a safety device for mitigating toe strike during pilot ejection from an aircraft. 
   Both small and large aircraft pilots place their legs within the narrow foot well (or foot wells) of an aircraft cockpit to reach the rudder pedals. The foot well is generally defined by the instrument panel and the floor of the aircraft. During the ejection process, as the legs are withdrawn upward through the foot wells, it is possible for the feet and toes to strike the top of the foot well and instrument console. This condition is commonly known as “toe strike” and can lead to serious injury. 
   Although the acceleration forces of ejection do help pull the legs down, the rapid rise of the seat, an occupant&#39;s leg size and the confines of the cockpit, particularly the foot well, can work against clearing the feet from the instrument console. The Air Force and Navy have developed a set of anthropometrical cases to describe the range of the aircrew population, see Table 1 below. 
   
     
       
             
           
             
             
             
             
             
             
             
             
             
           
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Joint DOD Anthropometric Cases (partial listing of attributes) 
             
           
        
         
             
                 
                 
                 
                 
               Case 4 
                 
                 
                 
                 
             
             
                 
                 
               Case 2 
               Case 3 
               Tall 
             
             
                 
                 
               Medium 
               Medium 
               Sitting 
             
             
                 
                 
               Build 
               Build 
               Height 
               Case 5 
               Case 6 
               Case 7 
               Case 8 
             
             
                 
               Case 1 
               Short 
               Long 
               Short 
               Overall 
               Longest 
               Overall 
               Largest 
             
             
               Feature 
               Small 
               Limbs 
               Limbs 
               Limbs 
               Large 
               Limbs 
               Small 
               Torso 
             
             
                 
             
             
               Buttock-knee 
               21.3 
               21.3 
               26.5 
               22.7 
               27.4 
               27.9 
               20.8 
               25.4 
             
             
               length 
             
             
               Knee-height 
               18.7 
               19.1 
               23.3 
               20.6 
               24.7 
               24.8 
               18.1 
               23.2 
             
             
               sitting 
             
             
               Thigh 
               18.5-25.0 
               17.1-25.0 
               20.2-27.6 
               17.6-26.3 
               18.6-29.2 
               19.1-29.7 
               17.8-25.2 
               18.6-29.1 
             
             
               circumference 
             
             
               range 
             
           
        
         
             
               Boot Size 
               5-13 
             
             
                 
             
           
        
       
     
   
   In Case 6 of Table 1, the geometry of combining a long buttock-knee and tibia (knee-height sitting) results in the knee being farther forward than in any other case. The larger thigh circumference can create a large thigh tangent angle, a space between the ejection seat and the bottom of the thigh that must be made up during the ejection process. As a result, the ejection seat can be in a slightly higher position after it fully supports the thigh. Therefore, the larger tibia is confined, takes longer to clear the same area compared to other cases, thereby resulting in the foot injury. 
   This type of foot injury may also occur with combinations of Table 1 Features and other human factors not defined in Table 1, in combination with ejection seat height adjustment prior to ejection. Other factors relating to the construction of the aircraft, including but not limited to the cockpit and placement of the ejection seat within the cockpit, can also affect the likelihood of injury. 
   In such a case an airbag system in accordance with the present invention can mitigate the toe strike damage by 1) receiving its initiation signal from the initiation sequencing system; 2) initiating its gas generator; 3) deploying from its frangible container; 4) deflecting the occupant&#39;s limb, particularly the lower leg, and particularly the foot and toes, as the ejection seat (which has also been previously been initiated) rises from the cockpit; and 5) collapsing harmlessly out of the escape path for the remainder of the ejection sequence. 
   The invention will be better understood, and further objects, features, and advantages thereof will become more apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, which are not necessarily to scale, like or corresponding parts are denoted by like or corresponding reference numerals. 
       FIG. 1  is a schematic side view of a normally situated pilot in an aircraft cockpit. 
       FIG. 2  is a schematic side view of the pilot during ejection. 
       FIG. 3  is a schematic side view of one embodiment of the invention. 
       FIG. 4A  is a schematic side view of a second embodiment of the invention. 
       FIG. 4B  is a schematic front view of the embodiment of FIG.  4 A. 
       FIG. 5A  is a schematic side view of a third embodiment of the invention. 
       FIG. 5B  is a schematic front view of the embodiment of FIG.  5 A. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The invention is an airbag system, implemented in a number of embodiments, to mitigate foot and toe strike hazards arising during aircrew ejection.  FIG. 1  is a side view of a normally situated pilot  10  in an aircraft cockpit  20 . Cockpit  20  includes a floor  22 , an ejection seat  12 , instrument console  14  and rudder pedals  16 . Pilot  10  has feet  18 .  FIG. 2  is a side view of the pilot  10  during ejection. In  FIG. 2 , the feet  18  of pilot  10  strike the console  14 , thereby causing possibly serious injury to the pilot&#39;s feet and toes. 
     FIG. 3  is a side view of one embodiment of the invention. In  FIG. 3 , an airbag module  24  is flush mounted below the instrument console  14  on a bottom surface  15  thereof. Dashed lines indicate the deployed state of the airbag  26 . Airbag  26  is a balloon type airbag, such as the driver and passenger side balloon airbags used in the automotive industry. The airbag module  24  is flush mounted to minimize the risk of creating a new strike hazard in the event the airbag fails to deploy. The airbag  26  deploys after receiving a signal (typically electric, but may be laser, ballistic gas, radio frequency or other forms) from the escape system sequencing system. The airbag  26  is integrated into the escape system sequencing system in a known manner, such as is disclosed in U.S. patent application Ser. No. 10/681,499 filed on Oct. 9, 2003, which is hereby incorporated by reference. 
   Airbag  26  helps deflect the feet  18  and legs of pilot  10  down and away from the instrument console  14 , and also cushions any impact with the console  14 . The placement of the flush mounted airbag module  24  is preferably near the front of the console  14 , because the size of the inflated airbag  26  must increase as its location moves farther from the front of the instrument console  14 . 
     FIG. 4A  is a schematic side view of a second embodiment of the invention.  FIG. 4B  is a schematic front view of the embodiment of FIG.  4 A. In  FIGS. 4A and 4B , an airbag module  30  is surface mounted below the instrument console  14  on a bottom surface  15  thereof. In  FIG. 4B , walls  36 , console  14  and floor  22  define a foot well  38 . Dashed lines indicate the deployed state of the airbag  32 . Airbag  32  is a balloon type airbag, such as the driver and passenger side balloon airbags used in the automotive industry. Airbag module  30  may also include one or more side curtain airbags  34 , shown in deployed state by dotted lines. As in the first embodiment, the airbags  32 ,  34  deploy after receiving a signal from the escape system sequencing system. 
   The airbags  32 ,  34  help deflect the feet  18  and legs down and away from the instrument console  14 , as well as to cushion any impact. The surface mounted airbags provide greater surface area coverage than the flush mounted airbags. The placement of the surface mounted airbag module  30  could be at any position along the length of the foot well  38 . The surface area of the inflated airbags  32 ,  34  must be sufficient to mitigate any hazard created by the surface mounted airbag module  30 . 
     FIG. 5A  is a schematic side view of a third embodiment of the invention.  FIG. 5B  is a schematic front view of the embodiment of FIG.  5 A. In  FIGS. 5A and 5B , an airbag module  40  is mounted behind the instrument console  14 . Airbag module  40  is mounted on a rear surface  17  of the instrument console  14  and flush with a bottom surface  15  of the console  14 . In  FIG. 5B , walls  36 , console  14  and floor  22  define a foot well  38 . Dashed lines indicate the deployed state of the airbag  42 . Airbag  42  is a balloon type airbag, such as the driver and passenger side balloon airbags used in the automotive industry. Airbag module  40  may also include one or more side curtain airbags  44 , shown in deployed state by dotted lines. As in the first and second embodiments, the airbags  42 ,  44  deploy after receiving a signal from the escape system sequencing system. The airbags  42 ,  44  help deflect the feet  18  and legs down and away from the instrument console  14 , as well as to cushion any impact. 
   In the invention, different types of airbag construction technologies can be employed, such as driver steering balloon, passenger balloon and side curtain, all typically used in the automotive industry. The specific size and shape of the airbag is primarily a function of the need to conform to the foot well(s) of the aircraft and the placement of the airbag. The invention may be retrofitted to certain aircraft escape systems. Airbags require no periodic maintenance, other than service life change out. 
   While the invention has been described with reference to certain preferred embodiments, numerous changes, alterations and modifications to the described embodiments are possible without departing from the spirit and scope of the invention as defined in the appended claims, and equivalents thereof.