Position and restraint system for aircrewman

An aircraft ejection seat position and restraint system for protecting an rcrewman against back injuries during emergency escape. The ejection sequence is initiated by the aircrewman pulling a lower ejection handle or a face curtain handle with both hands to release or shatter the cockpit canopy. A torso harness suit is concommittantly tightened with inflation of a vest worn between the aircrewman and the suit, and catapult rockets are fired to propel the seat out of the cockpit. The harness suit draws the aircrewman's upper torso against the back of the seat while the inflated vest pushes his hips back and down into the seat pan for optimally positioning his spine before ejection thereby negating the effects of an aircrewman purposely or inadvertently flying with a loose harness. After ejection, the seat is separated from the aircrewman but the vest remains inflated inside the harness providing cushioning against the opening shock force of the parachute which is attached to the harness suit. The inflatable vest is formed as a separate, one-piece garment which may be removed between flights.

BACKGROUND OF THE INVENTION 
This invention relates generally to restraint systems for aircraft ejection 
seats, and more particularly to a restraint system which optimally and 
securely positions an aircrewman in an aircraft ejection seat prior to 
emergency escape from the cockpit. 
High performance military aircraft are usually equipped with a catapult 
ejection seat which utilizes rocket thrust to propel it from the aircraft 
for emergency in-flight escape of aircrewman. A torso harness suit worn by 
the aircrewman over his flight coveralls serves both as a restraint system 
and a parachute harness. Typically, the harness suit includes a lap belt 
releasably connected to the lower seat portion, and shoulder straps 
attachable to an inertia reel mechanism fixed to the seat which permits 
free body movement during normal flight but automatically locks between 2 
and 3 G's deceleration to prevent further forward movement. The inertial 
reel mechanism also includes a gas-actuated motor which forcibly draws the 
aircrewman's shoulders against the back of the seat prior to emergency 
ejection, the purpose being to insure that his spine is along the 
direction of acceleration of the seat. 
Documented evidence has shown that injuries ranging from minor to severe 
still occur during or after egress due to improper restraint. See for 
example Report No. AMRL-TR-77-60, October 1977, entitled "F/FB-111 Escape 
Injury Mechanism Assessment" by Leon E. Kazarian, Aerospace Medical 
Research Laboratory, Aerospace Medical Division, Air Force Systems 
Command, Wright Patterson Air Force Base. Many of these injuries are 
attributable to an improperly fitted or loosely worn torso harness suit. A 
loosely worn harness suit causes the aircrewman to slide forward and under 
the lap belt and tilt his head forward. Under a high ejection force, this 
posture is highly susceptible to acute hyperflexion in the lumbar and 
cervical regions of the spine. Improper fit of the harness suit also 
diminishes effectiveness of the inertia reel retraction during 
positioning, induces flailing of the arms and legs in the windstream, and 
imposes additional shock loads on the aircrewman during parachute opening. 
SUMMARY OF THE INVENTION 
It is therefor an object of the present invention to provide an improved 
position and restraint system which forcibly places the aircrewman in 
optimal body alignment prior to ejection to minimize injuries to the 
aircrewman, and which automatically compensates for a poorly fitted or 
improperly adjusted harness suit. Another object is to provide a novel 
system which reduces force amplification during ejection and parachute 
opening shock and the tendency to induce flailing of the aircrewman's 
limbs. Still another object is to provide a restraint system which 
increases the bearing surface over which the ejection forces and parachute 
loads are applied to the aircrewman, which is readily adaptable to present 
ejection seats and harnesses, which can be easily removed between flights, 
and which compensates for poorly fitted or loosely secured harnesses. A 
still further object of the invention is to provide an effective restraint 
system during adverse flight conditions such as buffetting and high 
turbulence. These and other objects of the invention are achieved as 
described herein. 
Briefly, an inflatable bladder formed in a vest configuration is worn 
during flight between the aircrewman's flight coveralls and a torso 
harness suit of the type including a lap belt releasably connected to the 
seat and shoulder straps releasably and retractably connected to the seat 
and parachute risers. The vest is concommittantly inflated with retraction 
of the shoulder straps before the seat and aircrewman are catapulted from 
the cockpit. The vest remains inflated after the seat is separated from 
the aircrewman to provide a cushioning effect against the opening shock 
forces imparted by the parachute. 
Other objects, advantages and novel features of the invention will become 
apparent from the following detailed description of the invention when 
considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, an aircrewman is shown in solid outline in a 
position and restraint system 10 according to the invention secured to an 
ejection seat 11 in a typical inflight posture. For reasons of comfort 
during long flight periods rather than for the contingency of emergency 
ejection, the aircrewman prefers slack restraint which allows his hips to 
be forward of the back rest. This causes his head to be tilted forward of 
his shoulders. Consequently, the aircrewman's spinal column particularly 
in the lumbar and cervical regions are angularly displaced forward of the 
direction of the ejection force. This is illustrated by the angle 
.theta..sub.L subtended by the line of ejection E and the line LS tangent 
to the curvature of the lumbar spine at the hips, and the angle 
.theta..sub.c subtended by the ejection line E and the line CS tangent to 
the curvature of the cervical spine at the shoulders. Vertical 
acceleration of the torso when in such a posture results in acute 
hyperflexion in the lumbar and cervical regions by movement of the upper 
torso down into the seat behind the pelvis and forward rotation of the 
head about the shoulders. Under these conditions, injuries of the spine 
such as anterior wedge compression fractures and torn or ruptured 
interspinous ligaments are not uncommon. To minimize hyperflexion during 
ejection, the aircrewman's optimal position should be as shown in broken 
outline in FIG. 1. That is, the line LS' tangent to the lumbar spine and 
ejection line E are substantially parallel, and the angular displacement 
of the cervical spine along the line CS' has been significantly reduced to 
the angle .theta.'.sub.c. As experimental tests have shown, placement of 
the aircrewman in the latter position prior to ejection reduces the 
G-force component transverse to the spine together with a significant 
reduction in hyperflexion. 
The ejection seat 11 is slidably mounted on catapult guide rails 12 fixed 
to the aircraft. A lower ejection handle 13 attached to the seat pan 
between the aircrewman's legs or face curtain ejection handles (not shown) 
fire ejection seat catapult cartridges 14 which provide the thrust 
required for ejection. Handle 13 or the face curtain handles remain 
attached to the seat during ejection allowing him to retain his grip and 
prevent arm flailing when exposed to the wind blast. The seat headrest 
houses a personnel parachute pack 16 having two parachute risers 17 
extending from the pack and respectively connected through quick-release 
fasteners 18 to shoulder straps 19 of a torso harness suit 21. 
Shoulder straps 19 are also connected through retractable restraint straps 
22 to a gas pressure operated inertia reel 23 fixed to seat 11 which 
permit the aircrewman to move freely fore and aft under normal flight but 
automatically lock under high-G conditions to prevent untoward forward 
motion. As described herein, pulling the ejection handle 13 or the face 
curtain handles, actuates a gas generator producing a pressure at conduit 
25 which overrides normal operation and causes the inertial reel 23 to 
retract restraint straps 22 and forcibly pull the aircrewman shoulders 
against the seat 11 in anticipation of ejection. A cartridge-activated 
guillotine 24 severs the restraint straps 22 automatically after ejection, 
or manually for manual separation or emergency ground egress. The 
aircrewman is also secured at the lower torso by seat lap belts 26 through 
two quick-release fasteners 27 to either end of a harness suit lap belt 
28. The seat lap belts 26 are automatically releasable during man-seat 
separation by means not shown. 
The restraint system 10 further includes a separate inflatable vest 31 
having a front bib portion 32 and shoulder portions 33 generally 
conforming to and worn beneath the front and shoulder portions of the 
harness suit 21. Shoulder straps 34 and waist belt 35 securing the vest on 
the aircrewman are connected by a manually releasable fastener 36. 
Flexible tube 37 conducts compressed gas to the vest. 
To the extent pertinent to the present invention, FIG. 5 schematically 
illustrates an ejection control system. The control system may include 
other components, not shown, relating to post ejection operation but they 
do not form a part of the present invention. The lower ejection handle 13, 
or the face curtain handles (not shown), provides a signal through direct 
circuit 41 to cockpit canopy explosive bolts 42, through a time delay 
circuit 43 to a reel gas generator 44 and an inflatable vest gas generator 
45, and through time delay circuit 46 to catapult rocket 14. The delay 
time in circuit 43 (approximately 40 milliseconds) is sufficient to allow 
the canopy to be completely removed from the cockpit prior to ejection. 
The reel and vest gas generators 44 and 45 operate concommittantly since 
the vest 21 will be operationally inflated before restraint straps 22 are 
fully retracted by inertia reel 23. 
The ejection sequence as applied to the position and restraint system of 
the present invention is summarized as follows. The sequence is initiated 
by pulling the lower ejection handle 13, or the face curtain, which 
immediately fires explosive bolts 43 jettisonning the cockpit canopy. 
Following a 40 millisecond delay by circuit 43, reel and vest gas 
generators 44 and 45 produce gas pressure to override inertia reel 23 and 
to inflate vest 21 thereby forcing the upper and lower torso of the 
aircrewman against the back of the ejection seat 11. His spinal column is 
thereby positioned as near as possible along the direction of seat 
ejection. Approximately 300 milliseconds after pulling handle 13, the 
catapult rocket 14 is fired exerting the required ejection force. 
Following ejection, controls, not shown, operate guillotine 24 and seat 
lap belts 26 to separate the aircrewman from the seat and to initiate 
additional operating modes such as emergency oxygen system, life raft 
deployment, etc. 
FIGS. 6 and 7 graphically demonstrate the significant improvements 
attributable to the present invention in aircrewman protection against 
back injury. FIG. 6 is indicative of angular displacement of the cervical 
region of spine during ejection with and without the vest 31. The average 
peak horizontal acceleration of the aircrewman's head under these 
displacements were 66.44 G's and 88.18 G's, or a 25% reduction. FIG. 7 is 
the horizontal component of acceleration of the torso with and without the 
vest 31 and is indicative of a 26% reduction in horizontal hyperflexion 
force imparted on the spinal column. 
Some of the many advantages and novel features of the invention should now 
be apparent. For example, a system is provided which positions and 
restrains the aircrewman in the optimal position during seat ejection for 
protection against back injuries. The system compensates for improperly 
fitted or poorly adjusted torso harness suits. During seat-man separation, 
the seat is disconnected and falls away while the vest still inflated 
within the torso harness suit provides a cushioning effect between the 
parachute and the aircrewman against excessive opening shock forces that a 
parachute exerts. The inflated vest may also serve as a flotation device 
either augmenting or replacing the life preserver usually worn by the 
aircrewman. As a separate garment, the vest may be easily removed between 
flights and simplifies manufacture because it obviates modification of 
existing flight suit coveralls and harness suits for inflatable protection 
devices. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. Therefore to be understood that 
within the scope of the appended claims, the invention may be practiced 
otherwise than as specifically described.