CA2086890A1 - Inflatable bolster for head strike protection in bulkhead seating - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention relates to an inflatable bolster apparatus attached to an aircraft bulkhead which inflates if a crash sensor detects a crash. The inflated bolster provides head strike protection for occupants seated in rows directly aft of bulkhead structures. The uninflated bolster is folded and stowed within a frame that is attached to the bulkhead structure. When a crash is detected, the crash sensor transmits an electrical signal which ignites the gas generator(s) and inflates the bolster. In a preferred embodiment, the bolster comprises one of more cells that can be customized for the number of occupants it protects. Each bolster cell contains an internal web structure with a series of holes that regulates gas circulation within the bolster, thus stabilizing the bolster apparatus.

Description

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BACRGROUND
Field of Inve~tion The present invention relates to safety apparatus for protecting the head of an occupant seated directly aft of bulkhead structures in normal, utility, commuter and transport category aircraft. More specifically, it relates to an inflat-able bolster system that reduces the extent and severity of injuries sustained during a crash by cushioning the head from direct impact with the bulkhead structure.
~aak~roun~ of the Invention Conventional lap belts are used to restrain occupant~
of aircraft during crashes and periods of abrupt acceleration or deceleration. However, the protection provided by lap belts for occupants seated directly aft of bulkheads is inadequate. For the purpose of this discussion, bulkheads are wall-like struc-tures aboard aircraft, such as structural bulkheads, compartment partitions, and the walls of lavatories or galleys. The Federal Aviation Administration (FAA) and its International counterparts have recognized that occupants seated at these positions are most vulnerable during a crash with respect to head injury. The larger distance between the seat and the bulkhead allows the occupant's head to impact the bulkhead with a larger velocity than the heads of those sitting directly behind other seats. The larger velocity results in a greater impact that inflicts more serious injuries. Occupants seated in bulkhead rows are more likely to suffer serious or fatal head injuries than other occu-pants~
The FAA has addressed this particular head strike problem by establishing new seating requirements under Federal ,,-.......... ~ , ;, .............. . . .
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Aviation Regulations (FAR's) 25.562 and 23.562. These regulations set new head injury standards for normal, utility and commuter category airplanes certificated after Sleptember 14, 198 and for transport airplanes certificated after June 16, 1988.
Additionally, a retrofit of in-service airplanes is anticipated to meet these requirements.
Specifically, FAR's 25.562 and 23.562 require that occupants be protected against serious head injuries caused by impact against broad interior surfaces during a crash. These and other regulations also address protection from low impact, cos-metic head injuries that may involve irreversible nerve damage or permanent disfigurement. In the event of a crash, the regula-tions generally allow a three-inch, permanent, forward displace-ment of the seating structure. It follows that during a crash, the dynamic seat deflection can exceed three inches. This deflection thus creates an even larger head strike envelope in which the heads of occupants sitting in bulkhead rows can suffer an even greater risk of impact.
Thus far, no newly certificated airplanes have met either FAR 25.562 or 23.562 head injury criterion for bulkhead seating. However, the Canadair Regional Jet and British Aero-space J-41 type certificates were recently issued, each with a one-year waiver for the head injury criterion.
Several countermeasures have been suggested by seat and airframe manufacturers to solve the bulkhead problem including:
bulkhead air bags, additional bulkhead padding, shoulder restraints for these positions, bulkheads with partially ; . . .
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frangible panels, the removal or relocation of a row of seats aft of each bulkhead, and special seats that rotate the occupant's legs upward in the event of a crash. All of these potential solutions suffer serious drawbacks.
The first countermeasure, bulkhead air bags, depending on configuration, may have a number of disadvantages. First, they are a potential cause of injury, rebounding the occupant back into the seat with excessive force. Second, they are particularly dangerous to occupants assuming a typical crash--braced position, in which the head is above or on the knees.
~hird, bulkhead air bags are designed such that they will strLke an occupant whether or not the head would come in contact with the bulkhead. For example, a small child is not in danger of impacting with the bulkhead structure, yet he or she would be needlessly struck by the inflating air bag. Fourth, when the air bag deploys, it may produce excessive noise and smoke. This is likely to alarm occupants. Finally, large, post-deployed air bags potentially impede emergency egress.
The second countermeasure, padding the bulkhead, also has severe drawbacks. First, a great deal of energy absorbing material would be needed to effectively pad the bulkhead. Thus, a great deal of occupiable space (i.e., six inches) would be eliminated. Additionally, energy absorbing padding may increase the frequency or severity of neck injuries.
The third option proposes the addition of shoulder har-nesses for the occupants of bulkhead rows. The major drawback of this countermeasure is the negative impact on passenger percep-~8~9~

tion. Occupants will perceive a safety difference according toseating location.
The fourth option proposes bulkheads designed with frangible panels that allow occupants' heads to partially pene-trate or punch through the structure. Although this solution may reduce impact head injury, the frangible panels have the poten-~ial to inflict cosmetic injuries involving irreversible nerve damage or permanent disfigurement. This type of injury is more likely to occur during the rebound phase of the crash.
The fifth solution proposes to increase seat setbac]c from the bulkhead to a distance that would preclude head impact.
Moving the bulkhead seats would require the repositioning of all the aircraft seats, as well as the removal of some seats entirely. This solution would result in lost passenger revenues for the airlines.
Finally, designing a special seat for these bulkhead positions offers an unproven solution. Seat manufacturers have suggested a seating structure with a seat pan that rotates the occupant's legs upward during the crash. Although some initial test results have been positive, the design has not been proven effective in a crash environment.
In view of the potential problems with the proposed countermeasures, effective head strike protection for seating directly aft of bulkheads must provide adequate energy absorption for the head region, while not creating a more hazardous environ-ment for occupants regardless of body position or occupant size.
In addition, the system should neither alarm nor create negative , . , ~,,, , , :. , ... .
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passenger perceptions, inflict serious cosmetic injuries, impede emergency egress, or require excessive space or cost.
8~ARY OF TlI13 }NVENTION
The present invention comprises an inflatable bolster system whose bladder member(s) are stowed within a lightweight frame that is mounted to the bulkhead of an aircraft.
The bolster is a continuous cushion that can be partitioned into a number of separate bladders or cells. There is no gas exchange between cells. The number of cells is determined by the number of seats in the row directly aft of a particular bulkhead. Generally, there is one cell for each seat.
This multi-celled configuration increases the stability and effectiveness of the bolster and allows the system to be con-veniently customized for a particular aircraft seating con-figuration.
The bolster apparatus is connected to a crash sensor.
When a collision occurs, the sensor sends an electrical signal to gas generators in the bolster, igniting the generators and thus inflating the cell or cells. The gas generators are located directly behind the bolster cell(s) and are integrated into the bolster structure. Each cell may have more than one gas generator.
Each bolster cell contains a number of internal webs.
The internal webs run both horizontally and vertically and con-tain a number of openings or holes that allow gas to circulate within each cell. The webs thus define a number of smaller compartments within each cell. When the bolster is impacted by a " ' :,' . ~ ~: : ' ~86~

body part, the holes in the internal web structure restrict the speed of gas circulation within the cell, thereby improving the performance of the bolster. The number of internal webs and internal web openings can be varied in order to customize the impact absorbing profile of the bolster. The internal web structure also results in the inflated bolster having an "air mattress-like" appearance.
The generated gas inflates the individual cells simul-taneously. As gas flows into the cells, the bolster deploys from its stowed position. In the fully deployed state, the bolster forms an "air" cushion that extends approximately 12 inches out from the bulkhead surface. The inflated bolster protects the occupant's head from direct and excessive impact with the bulk-head surface.
When used in conjunction with conventional lap belts, the inflated bolster provides an effective strike protection system that meets the head impact criterion of FAR's 25.562 and 23.562. It functions by distributing load over the entire contact area of the occupant's head. The bolster is positioned at an average seated head-level that provides head strike pro-tection for a wide range of occupant sizes (i.e., a 95~ male down to a small child). Additionally, the bolster provides strike protection for the upper torso and upper extremities of some laryer occupants.
The bolster has a number of advantages over conven-tional air bag devices. First, it is much smaller and can deploy at a much slower velocity. This means that the violent "punch"

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or abrupt acceleration that is often imparted by air bags (on the occupant) can be avoided. Second, unlike conventional air bags, the bolster is designed to deploy without striking the occupant.
This avoids unnece sary air bag inflicted injuries. It is also less hazardous for occupants that have assumed a crash-braced position. Third, the inflating bolster is a smaller device that preferably uses an energetic, smokeless propellant. Therefore, it produces significantly less noise and smoke than air bags, which is critical for occupant composure and orderly post-crash egress. Finally, the inflated bolster will not significantly impede emergency egress because it does not hang to the floor, as would large air bags.
An additional advantage of this system over other devices is that it will not likely cause cosmetic injuries involving irreversible nerve damage or permanent disfigurement.
It is also an economically feasible solution that requires minimal space when stowed. Finally, it will have little or no effect on passenger safety perception because its system com-ponents are relatively concealed.
The undeployed bolster assembly is unobtrusive, extending approximately one inch out from the surface of the bulkhead. Pref0rably, it will protrude less than one inch. ln the undeployed state, the bolster is concealed by a protective cover that provides a durable and aesthetically pleasing package.
The fabric chosen for the cover can be coordinated to match the interior of the airplane. In the event of a crash, the outer ,., , :

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layer of the protective cover separates from the bulkhead under the force of the inflating bolster.
The bolster system is a totally self-contained system that can be installed during manufacture or be retrofitted into in-service airplanes. The system is complete with its own battery unit, requiring no integration with the aircraft's exist-ing electrical system.
The durable housing that contains the crash sensor also contains the battery unit. Generally, the crash sensor/diagnos-tictbattery unit is mounted at the seat track-level in order to accurately detect crash impacts to which the occupant is expo~ed.
The sensor/diagnostic/battery unit ~an be mounted at the base of the bulkhead on either side of the structure or at some other proximate location. The sensor/diagnostic/battery unit also includes a diagnostic means for checking the integrity of the electronic circuitry and the battery charge.
Accordingly, it is an object of the present invention to provide a protective apparatus, used in conjunction with conventional lap belts, that inflates to protect the head and face of a restrained, seated occupant of a transport vehîcle such as an aircraft from excessive impact with the bulkhead structure during a crash.
It is another object of the present invention that provides an inflatable bolster that is not potentially dangerous to occupants assuming a typical crash position.
It is another object of the present invention to pro-vide an inflatable bolster that in the deployed and undeployed :
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states does not obstruct emergency exits or impede passenger emergency egress.
It is another object of the present invention to pro-vide an inflatable bolster system that attaches to the bulkhead and provides convenient access to the seat.
It is another object of the present invention to pro vide an inflatable bolster system that is self-contained, re~uir-ing no integration with the vehicle's electrical system.
It is another object of the present invention to pro-vide an inflatable bolster system that does not exert excessive force on the occupant's head upon inflation.
It is another object of the present invention to pro-vide an inflatable bolster system that provides a head strike protection system that protects the occupant from cosmetic head injuries involving irreversible nerve damage or permanent dis-figurement.
It is another object of the present invention to pro-vide an inflatable bolster system that provides a head strike protection system that can be customized for a particular bulk-head seating configuration.
It is another object of this invention to provide an inflatable bolster system with a sensor/diagnosticjbattery unit located to provide convenient access to the seat.
It is a further object of the present invention to provide an inflatable bolster system that does not have a sig-nificant negative impact on passenger safety perception.

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::.. ~ : . . : . . -~086~0 It is another object of the present invention to pro-vide an inflatable bolster system that provides a head strike protection system that does not unduly alarm the occupants by producing excessive smoke or noise upon deployment.
It is another object of the present in~ention to pro-vide an inflatable bolster system that provides a head strike protection system that is cost effective.
These and other objects are described in greater detail in the detailed description, the appended drawings, and the attached claims.
DB8~RIPTION OF THE DRAWINGB
Figure 1 shows the present invention installed in a typical transport aircraft bulkhead with portions being broken away to show underlying features.
Figure 2a shows the present invention in the uninflated state with respect to seated occupants.
Figure 2b shows the present invention in the inflated s~ate with respect to seated occupants.
Figure 3 is a cross-sectional view of the inflated bolster.
Figure 4 is a detailed view of a web internal to the bolster.
DETAILED DE~C~IPTION OF T~E INVENTIO~
The preferred embodiment of the present invention is shown in Figures 1-3. The inflatable bolster system 8 of the present invention is shown in the uninflated state. It comprises inflatable bolster 1, gas generators 2, frame structure 3, crash : , . .
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sensor/diagnostic/battery unit 6, as well as cover 4, electrical cable 7, and mounting devices 5. The present invention is shown as being attached to a typical aircraft bulkhead. The invention is designed to be used in normal, utility, commuter and transport category aircraft in which passengers are seated directly aft of the bulkhead structures. The present invention can also be used in other types of vehicles such as trains, buses, ships or boats.
Bolster 1 can be made up of several distinct cells.
Figures 1, 2a, 2b and 3 illustrate a bolster system having two cells to accommodate a row containing two seats. Other bolsters can have multiple cells or as few as one cell in order to customize the system for a particular seating configuration.
Generally, the bolster contains as many cells as there are seats in a particular row. Each bolster cell has at least one gas generator 2 integrated into its rear wall for in~lation purposes.
Inflatable bolster 1 can be formed from an impregnated fabric, such as nylon coated on both sides with neoprene, that is relatively impervious to gas. The selected material must meet FAA flammability requirements. As shown in Figure 1, undeployed bolster 1 is contained within a frame structure 3. The preferred method for stowing the bolster within frame 3 is by aligning the front wall of the bolster directly over the rear wall and folding the side walls between them in an accordion manner. As stowed, bolster 1 is concealed under a protective cover 4. Frame struc-ture 3 is made of a lightweight, durable material such as aluminum. Frame structure 3 is basically a rectangular frame with vertical cross members (not shown) onto which gas generators ~86~9~

2 are suitably attached. The cross members are flush with the outer frame members. Mounting brackets 5 attach frame structure 3 to bulkhead 9. The bolster/frame assembly is positioned on the bulkhead at seated head-level. The undeployed bolster assembly extends out from the bulkhead approximately one inch or less. It extends up the bulkhead approximately 24-30 inches. Its width is determined by the number of cells in a particular bolster and the anticipated range of occupant motion.
When inflation is initiated, the internal gas pressure of bolster 1 forcibly separates cover 4 from frame 3, and the bolster inflates. In a first embodiment, cover 4 is bonded to the front surface of bolster 1, allowing cover 4 to deploy along with the bolster. In this case, the cover material may enhance the energy-absorbing function of bolster 1.
In a second embodiment, cover 4 includes a network of weak seams along which cover 4 ruptures, thus allowing bolster 1 to inflate. The preferred rupture pattern minimizes the trajec-tory of the cover material in the direction of the occupant. It also minimizes the amount of cover fabric that remains in the vicinity of the emergency exits following deployment, thus minimizing egress problems. For example, four flaps can be formed from Gover 4; two large flaps and two small flaps. Of the larger flaps, one would deploy downward and the other outward, away from the nearest aisle. Of the smaller two flaps, one would deploy upward and the other outward, toward the nearest aisle.
This last flap could also be designed to soften the corner of the bulkhead structure.

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Smokeless propellants are preferred. Preferably, highly energetic propellants such as nitrocellulose or hybrid inflators using pyrotechnic hezters and argon gas would be used.
Propellants using sodium azide, such as those used by U.S. auto-motive air bag systems, would preferably not be used.
Figure 2b shows bolster 1 fully deployed. Fully deployed bolster 1 bulges out approximately 6 to 18 inches from bulkhead 9 to provide an effective energy-absorbing cushion for the occupants' heads. Inflatable bolster system 8 takes approxi-mately 30 to 40 milliseconds to inflate, while bulkhead head impacts generally occur in 70-90 milliseconds. The internal pressure of bolster 1 is comparable to the internal pressure in conventional air bags. The internal pressure is generally less than 2 psi. The preferred internal pressure is 1 psi or slightly lower. ;
Figure 3 is a cross-sectional view of inflated bolster 1. Figure 3 shows that each bolster cell has outer walls 10 that prohibit gas ~rom passing between cells. Internal webs 11 are positioned both horizontally and vertically, further dividing each bolster cell into smaller compartments. These internal webs give bolster 1 an air mattress-like appearance, as shown in Figure 2b. More importantly, internal webs 11 provide bolster 1 with improved stability.
Figure 4 shows a detailed view of internal web 11.
Each internal web includes openings or holes 12 that permit gas to circulate within a particular cell. Upon impact, gas is forced to disperse from the impacted cell compartment. However, :
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holes 12 limit the speed of gas circulation, thereby providing more efficient impact protection. The number and size of holes in internal web 11 can be varied to optimize system performance for a specific aircraft configuration. Smaller holes are pre-ferable because they allow the use of a bolster having a smaller internal pressure. This is possible because the smaller holes further restrict gases from dispersing away from the area of impact, thus causing a local area of higher pressure that is needed for impact protection. This can also reduce the amount of propellant that is required because the bolster requires less gas. Generally, the larger the distance between the seating structure and the bulkhead, the more gas pressure is needed to provide adequate impact protection, therefore less holes or smaller holes are preferred. However, when the distance between the seating structure and the bulkhead reaches a certain point, head impact with the bulkhead structure will no longer occur.
~ olster 1 is able to distribute the force of the impact over the entire contact area of the occupant's head. After inflation, bolster 1 will remain sufficiently inflated to proYide additional protection in the event of multiple impact crashes.
Figures 1, 2a, 2b and 3 illustrate a bolster having an internal web system that includes three horizontal webs and one vertical web per cell. Figure 2b shows that this specific internal web configuration produces a bolster having eight tufted surfaces per cell. The number of internal webs can be varied in order to optimize the impact absorbing characteristics of bolster 1. There are a number of facts that can influence the number of . , .
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webs or holes in the internal web structure, such as the inflated gas pressure of the bolster and the seat setback from the bulk-head.
As shown in Figure l, gas generators 2 are connected by electrical cable 7 to crash sensor/diagnostic/ba1:tery unit 6.
When the crash sensor detects an impact, it sends a signal through electrical cable 7 to the initiators in gas generators 2.
The initiators then ignite, causing the propellant to burn, thus producing gas.
Following inflation, the gas in bolster l is retained by venting means 13 (shown in Figure 3) that is initially closed.
When the occupant strikes the inflated bolster, the deformation of bolster l causes the vent to open. This provides an energy absorbing means that prevents the occupant's head from rehounding off bolster l with excessive velocity. Venting means 13 opens when it senses bolster deformation and/or when the internal pressure of bolster l increases by a given increment ~e.a., by l or 2 psi). After contact, the vent may reclose to provide resi-dual protection from subsequent impacts. Each bolster has at least one vent located in the bottom portion of the bolster.
Crash sensor/diagnostic/battery unit 6 contains a crash sensing device and a long-life, replaceable battery pack. It is best attached to a relatively stiff structure at seat track-level by solid connections. A solid connection is required in order for the crash sensor to accurately detect impacts. The crash sensor determines a crash environment when certain acceleration and velocity change criteria are met. These criteria can be .: ~ , , .. - ,:, , -~86~

fined tuned for different bulkhead locations aboard the airplane and for different airplanes. Inflatable bolster system 8 is preferably powered by long-life batteries, such as lithium batteries that have a life expectancy of five to ten years. The bolster system requires no integration with the aircraft's elec-trical system, although it could be adapted to use the existing electrical system, if desired. Crash sensor/diagnostic/battery unit 6 also includes a means for checking the integrity of the electronic circuitry and ~he battery charge.
Although mounting brackets 5 and electrical cable 7 are shown clearly in Figure 1, these components would normally be concealed by the fabric or material that covers bulkhead struc-ture 9. Electrical cable 7 could also be located on the opposite side of the bulkhead. Crash sensor/diagnostic/battery unit 6 can also be mounted on the opposite side of the bulkhead structure to minimize passenger interference. Figures 2a and 2b illustrate a preferred inflatable bolster system 8 whose electrical cable, mounting brackets, and crash sensor/diagnostic/battery unit are concealed accordingly.
The foregoing disclosure o a preferred embodiment of a preferred invention has been presented for the purposes of illus-tration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. In par-ticular, the present invention may be used in vehicles other than aircraft, such as in trains, buses, ships and boats. Many varia-tions and modifications of the embodiment described herein will be obvious to one of ordinary skill in the art in light of the : ~ . . : :
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above disclosure. The scope of the invention is to be de~ined only by the claims appended hereto.
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Claims (30)

1. A protection system for occupants seated at seating positions directly aft of bulkheads comprising:
(a) a normally uninflated bolster, said bolster comprising at least one cell, each such cell having at least one internal web, each web having a plurality of holes;
(b) at least one gas generator means in each cell of the bolster for inflating said cell;
(c) venting means in each cell; and (d) a crash sensor, said crash sensor being electrically connected to each gas generator.

2. The protection system of claim 1, wherein the bolster and the cell are fabricated from impermeable, impregnated fabric.

3. The protection system of claim 2, wherein the web is fabricated from permeable fabric.

4. The protection system of claim 2, wherein the web is fabricated from impermeable fabric.

5. The protection system of claim 4, wherein each cell comprises at least two webs, and wherein the webs intersect at the interior of the cell, the webs thus defining at least four compartments within each cell.

6. The protection system of claim 4, wherein each cell comprises at least one horizontal web and at least one vertical web, the webs thus defining at least four compartments within each cell.

7. The protection system of claim 1, wherein the crash sensor comprises electronic circuits and a replaceable battery pack, further comprising diagnostic means for determining the integrity of the electronic circuits and the charge of the replaceable battery pack.

8. The protection system of claim 1, further com-prising a cover that conceals the bolster in its uninflated state.

9. The protection system of claim 8, wherein the cover comprises a plurality of weak seams, such seams being designed to rupture upon inflation of the bolster.

10. The protection system of claim 1, wherein the venting means opens if the internal pressure within the cell increases by a predetermined increment.

11. The protection system of claim 1, further com-prising means for detecting deformation of the bolster, and means for opening the venting means when deformation of the bolster is detected.

12. The protection system of claim 1, further com-prising a lightweight frame within which the cells of the bolster are stowed, said frame being mounted on the bulkhead.

13. The protection system of claim 1, wherein the bolster comprises one cell for each occupant seating position directly aft of the bulkhead.

14. The protection system of claim 1, wherein the uninflated bolster extends less than approximately 1 inch from the bulkhead.

15. The protection system of claim 1, wherein the bolster is designed such that, upon inflation, it extends less than approximately 12 inches from the bulkhead.

16. A protection system for occupants seated at seating positions directly aft of bulkheads comprising:
(a) a frame attached to the bulkhead;
(b) an inflatable bolster comprising at least one cell stowed within the frame and attached to the frame, each such cell having at least one internal web, each web having a plurality of holes;
(c) at least one gas generator means integrated into the rear wall of each cell of the bolster for inflating said cell; and (d) a crash sensor, said crash sensor being electri-cally connected to each gas generator.

17. The protection system of claim 16, wherein the gas generator uses a smokeless propellant.

18. The protection system of claim 16, wherein when fully inflated, the bolster extends 8 to 12 inches from the bulkhead.

19. The protection system of claim 16, further com-prises venting means for each cell.

20. The protection system of claim 19, further com-prising means for detecting deformation of the inflated bolster, and means for opening the venting means when deformation of the inflated bolster is detected.

21. The protection system of claim 20, further com-prising means for closing the venting means after a predetermined time period.

22. The protection system of claim 20, further com-prising means for closing the venting means when deformation of the inflated bolster is no longer detected.

23. The protection system of claim 19, further com-prising means for opening the venting means if the internal pressure within the cell increases by a first predetermined increment.

24. The protection system of claim 23, further com-prising means for closing the venting means when the internal pressure within the cell decreases by a second predetermined increment.

25. A method for protecting occupants seated directly aft of a bulkhead comprising:
(a) providing an inflatable bolster, said bolster comprising at least one cell, each such cell having at least one internal web, each web having a plurality of holes, at least one gas generator in each cell of the bolster, venting means in each cell, and a crash sensor, said crash sensor being electrically connected to each gas generator, wherein each gas generator comprises an initiator and a propellant;
(b) detecting a crash with the crash sensor;
(c) initiating the gas generators by igniting initiators in the gas generators;
(d) igniting the propellant;

(e) inflating the bolster;
(f) detecting an impact of the occupant upon the at least one cell;
(g) opening the venting means in the at least one cell in the bolster; and (h) closing the venting means after the impact.

26. The method of claim 25, wherein before inflation, the bolster extends less than approximately one inch from the bulkhead.

27. The method of claim 25, wherein after inflation, the bolster extends approximately 6 to 18 inches from the bulk-head.

28. The method of claim 25, wherein the inflatable bolster is covered by a cover, said cover having weak seams, further comprising the step of opening the cover by rupturing the weak seams and allowing the bolster to inflate.

29. The method of claim 25, wherein the impact of the occupant upon the cell is detected by detecting a deformation of the bolster.

30. The method of claim 25, wherein the impact of the occupant upon the cell is detected by detecting an increase in the internal pressure within the cell by a predetermined incre-ment.