Abstract:
An emergency exit system for use primarily in a helicopter or other aircraft includes a panel closing an opening in the fuselage of the aircraft, a plurality of latches for releasably securing the panel in the opening; a release mechanism including slides on each side of the opening for retracting the latches to release the panel; a drive for operating the slides, a drive latch for releasably locking the drive in a cocked condition; and a plurality of principal grab bars strategically located in recesses adjacent to the opening and connected to the drive by cables, whereby actuation of any one of the grab bars causes simultaneous release of all of the latches so that the panel can be jettisoned.

Description:
This application claims benefit of provisional application Ser. No. 60/131,670 Apr. 29, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an emergency exit system, and in particular to an emergency exit system for use in a helicopter or other aircraft. 
     While the system of the present invention was designed specifically for use in an aircraft, it will be appreciated that the system could be used in other vehicles such as trains or buses. 
     2. Discussion of the Prior Art 
     Applicants&#39; international patent application PCT/CA98/00739 filed on Jul. 31, 1998 discloses an emergency exit system of generally the same type as disclosed herein. As mentioned in the PCT application, vehicle accidents occurring in water have a lower survival rate than accidents occurring on land. In water accidents, the aircraft usually sink very rapidly, either in an upright or inverted position. Underwater conditions are drastically different from land based conditions. Visibility is reduced—the majority of people can see only 1.5 meters underwater and 3.1 meters in the best lit conditions. Survivors of a crash or forced landing must depend on their breath-holding ability to make a successful escape. Generally, a person&#39;s breath-holding ability is reduced 25-50% in water under 15° C . Maximum breath-holding time can be as short as 10 seconds. Survivors are often disoriented due to the sudden immersion in water, loss of gravitational references, poor depth perception, nasal inhalation of water and darkness. Disorientation is magnified when the vehicle is inverted. Under the latter condition, finding a handle to jettison an escape door or window, which is a simple procedure to execute in an upright position on dry land, can be a most challenging task even if the handle is only a few centimeters away from the survivor&#39;s hand. 
     Usually handles for opening escape doors or windows are small, and are positioned between knee and chest level. The various positions, i.e. locked or secured and released, would not be obvious to the survivor unless he or she is familiar with the particular escape system. Existing escape hatches for aircraft are difficult to replace or reinstall once jettisoned. Consequently, even persons being trained as aircrew do not receive practice in emergency escape procedures. Most existing mechanisms are adapted to remove an entire door or window, including the frame, requiring a complicated jettison mechanism, which is not always dependable. Most escape hatches are operated by movement of a single handle in one direction only. Thus, valuable time and effort can be wasted in attempting to operate the hatch release mechanism. Moreover, existing systems do not provide feedback, i.e. there is no visual or other indication that the door, window or hatch as been successfully jettisoned. 
     GB-A-761 627 and U.S. Pat. No. 3,851,845 disclose systems for the jettisoning of aircraft canopies or doors which are inappropriate for use in a door or window release. The U.S. patent teaches the use of lever or a lever and a handle combination for releasing a door. When submerged in water such a system could be difficult to operate, particularly when it is necessary to operate a handle and a separate lever to effect release of the door. 
     GENERAL DESCRIPTION OF THE INVENTION 
     An object of the present invention is to provide an emergency exit system of the type which includes at least one easily accessible actuator adapted to operate in more than one direction to affect release of a Window or door panel to provide an escape exit. 
     In applicant&#39;s earlier invention, cables were mainly relied upon to release a panel. When repeatedly subjected to longitudinal forces, cables tend to stretch. Accordingly, while cable are still used in the present case they play a smaller roll in operation of the exit system, namely to release a spring operated drive which effects panel release. 
     Accordingly, the present invention relates to an emergency exit system including a panel for closing in an opening in a vehicle wall comprising a plurality of spaced apart panel latch means for releasably latching said panel in said opening; release means for simultaneously releasing all said panel latch means, drive means for operating said release means; drive latch means for releasably retaining said drive means in an inoperative condition; and principal actuating means rotatable in said vehicle wall proximate said opening for releasing said drive means, whereby rotation of said principal actuating means causes said drive means operate said release means to simultaneously release all said panel latch means. 
     The use of an opposed auxiliary release handles on the inside and outside of the vehicle provides an alternate means for operating the panel latch means, and permits the operation of the panel latch means by a rescuer from the exterior of the vehicle. 
     The invention described herein also includes light means in said actuating means which provide a visual aid for locating the escape panel, and for positively indicating that the panel has been jettisoned. The light means is adapted to operate in a steady (always on) or a strobe mode. In one mode, the light means acts as a locating aid, and in the other mode, the light means provides a positive indication that the panel has been jettisoned. 
     The provision of a simple mechanism for replacing the panel in the opening encourages practice of escape procedures before an emergency situation arises. Whereas it is difficult and time consuming to replace existing escape hatches, once released, using the system of the present invention, the panel can be re-mounted in the opening typically in 5 to 10 seconds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described below in greater detail with reference to the accompanying drawings, which illustrate a preferred embodiment of the invention, and wherein: 
     FIG. 1 is a schematic front view of a section of the interior of a helicopter fuselage incorporating an emergency exit system in accordance with the invention; 
     FIG. 2 is a partly sectioned front view of the interior of a window used in the system of FIG. 1; 
     FIG. 3 is a partly sectioned view of the interior of the system of FIG. 1; 
     FIG. 4 is a partly sectioned front view of a portion of a release assembly used in the system of FIGS. 1 and 2; 
     FIGS. 5 and 6 are cross-sectional views of a jettison pin assembly used in the system of FIGS. 1 and 2; 
     FIG. 7 is a front view of a drive mechanism used in the system of FIGS. 1 and 2; 
     FIG. 8 is a longitudinal sectional view of a drive actuation assembly used in the system of FIGS. 1 and 2; 
     FIG. 9 is a front view of one end of a grab bar and cable connector used in the system of FIGS. 1 and 2; 
     FIG. 10 is a cross section taken generally along line  10 — 10  of FIG. 9; 
     FIG. 11 is a partly sectioned front view of a lock assembly on a second end of a grab bar used in the system of FIGS. 1 and 2; 
     FIG. 12 is an end view of the latch assembly as seen from the right in FIG. 11; 
     FIG. 13 is a cross section of handles for an auxiliary release assembly used in the system of FIGS. 1 and 2; 
     FIGS. 14 and 15 are partly sectioned front and rear views of the auxiliary release assembly used in the system of FIGS. 1 and 2; 
     FIG. 16 is a front view of a light assembly used in the system of FIGS.  1  and  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, the basic elements of the exit system visible from the interior of a helicopter include a window generally indicated at  1 , which is mounted in an opening in a helicopter fuselage, four grab bar assemblies  2  generally indicated at  2  on all four sides of the opening, and an auxiliary release handle  3 . The window is releasably mounted in a frame  4  (FIG. 3) between the inner skin  6  and the outer skin  7  (FIG. 13) of the fuselage. The grab bar assemblies  2  and the auxiliary release handle  3  are located in recesses  8  and  9 , respectively in the inner skin  6  of the fuselage. 
     The window  1  is defined by a metal panel  11  normally closing the opening in the fuselage, and a transparent plastic pane  12  which is retained in an opening in the panel  11  by a flexible rubber molding  13 . As a last resort, e.g. in the event of a mechanical failure of the escape system described below, the pane  12  can be physically knocked out of the panel  11  to permit escape from the aircraft. A square cross section reinforcing bar  15  connected to the panel  11  extends around the periphery of the rubber molding  13 . In such circumstances, the window panel  11  remains in place in the frame  4  which reduces the size of the egress opening. 
     The window  1  is normally retained in the opening by two pairs of pins  16  extending out of the frame  4  into sockets  17  (FIG. 2) in the sides  18  of the bar  15 . Referring to FIGS. 3 and 4, each pair of pins  16  is slidably mounted in tracks  19  for lateral movement into and out of the sockets  17 . As best shown in FIG. 4, one track  19  is mounted on each side of the window opening, the tracks  19  forming the sides of the frame  4 , The pins  16  are slidably mounted in the sides  21  and  22  of the track  19  for lateral movement into and out of the sockets  17  in the bar  15  of the window  1 . A cam slide  23  is slidably mounted in the track  19  for causing movement of the pins  16 . For such purpose, the cam slide  23  includes inclined ribs  25  bordered by a pair of rollers  26  in recesses  27  in the pins  16 . Vertical movement of the slide  23  thus causes simultaneous lateral movement of the pins  16 . 
     Movement of the pins  16  from the window engaging to the release position, not only releases the window, but results in mechanical jettisoning of the window. With reference to FIGS. 4 to  6 , a generally drop-shaped groove  29  is provided in each pin  16  near the outer free end thereof. When the window  1  is in the closed position (FIG. 5) a jettison pin  30  (FIGS. 2,  5  and  6 ) extends inwardly from an L-shaped bracket  31  mounted on the reinforcing bar  15  of the window into the groove  29 . During movement of the pin  16  towards the release position (FIG. 6) the pin  30  rides up a ramp  33  at the tapering outer end of the groove  29  to push the window  1  out of the opening. 
     Vertical movement of the slides  23  is effected by a drive mechanism generally indicated at  35  (FIG.  3 ). As best shown in FIG. 7, the drive mechanism  35  includes a block  36  mounted beneath the window  1  between the inner and outer skins  6  and  7 , respectively of the fuselage. A pair of racks  37  and  38  are slidably mounted in slots  39  and  40 , respectively in the block  36 . A pinion  41  with a hexagonal recess  42  in the outer surface thereof is rotatably mounted in the block  36  in constant engagement with both racks  37  and  38 , whereby movement of one rack  37  in one direction causes a corresponding movement of the other rack  38  in the opposite direction. The recess  42  in the outer surface thereof is accessed via an opening (not shown) in the outer skin  7  of the fuselage when replacing the window  1  in the opening as described hereinafter in greater detail. The outer ends of the racks  37  and  38  are pivotally connected to bottom arms  43  of bell crank levers  44  by linkage rods  45  and  46 , respectively and clevises  47 . The bodies  48  of the levers  44  are securely connected to shafts  49 , the ends of which are rotatably mounted in bearings  50 . The bearings  50  are mounted in small frames (not shown) between the inner and outer skins  6  and  7  proximate the bottom corners of the window  1 . The top arms  52  of the levers  44  are pivotally connected to the bottom ends of the slides  23  by a linkage bars  53 . Thus, lateral reciprocating movement of the racks  37  and  38 , and consequently of rods  45  and  46  results in a corresponding rotation of the levers  44  and vertical movement of the slides  23 . As mentioned above, such vertical movement of the slides  23  causes retraction or extension of the pins  16 . 
     In the extended or locked position of the pins  16 , the inner free ends  56  of the racks  37  and  38  oppose each other. The racks  37  and  38  are biased to the window release positions by a helical spring  57  mounted on the rod  45 . The spring  57  extends between one end of the slot  40  in the block  36  and abuts a small sleeve  59 , which forms part of a release assembly. The rod  45  is slidable through the sleeve  59 , which is slidable in to a wide end of the slot  40 . Movement of the sleeve  59  toward the narrow end of the slot  40  (to the right in FIG. 7) is limited by a shoulder  60  between the wide and narrow ends of the slot  40 . The sleeve  59  is retained in the window locking position by a pin  62 , which forms part of a drive latch assembly. 
     Referring to FIG. 8, the drive latch assembly includes a housing  63  which is mounted on the bottom end of the block  36  (FIG.  7 ). The pin  62  is slidably mounted in a vertical hole  64  in the housing  63 . The pin  62  is biased to the extended sleeve engaging position by a helical spring  66  sandwiched between the bottom end of the pin  62  and a plate  67  connected to the housing  63  by bolts  68 . The pin  62  is moved to the release position by a pair of opposed slides  70 , which are slidably mounted in a passage  71  in the housing. Each slide  70  includes a narrow neck portion  72  (one shown) with a ramp  73  at one end thereof for engaging a roller  75  mounted in a notch  76  in the outer side of the pin  62 . The slides  70  extend through the notch  76 , intersecting the path of travel of the roller  75  during longitudinal movement of the pin  62 . Movement of the slides  70  into the housing  63  is limited by shoulders  78  on the slides which engage shoulders  79  in the passage  71 . When either slide  70  is moved longitudinally in the housing  63 , i.e. outwardly, the ramp  73  pushes the roller  75  and consequently the pin  62  downwardly to release the sleeve  59 . Once the sleeve  59  is released, the spring  57  forces the bottom rack  37  to the left (in FIG. 7) and the pinion  42  moves the rack  38  to the right. Such movement causes rotation of the levers  44  and downward movement of the slides  23  to force the pins  16  to the release position. 
     The slides  70  are retained in the inner positions (FIG. 8) by helical springs  81  retained in the outer ends of the passage  71  by end plates  82  connected to the ends of the housing  63  by bolts  83 . Movement of either of the slides  70  against the bias of the springs  81  is effected by cables  85  the ends of which are slidably retained in passages  87  in the outer ends of the slides  70  by swaged lugs  88 . When one cable  85  is pulled to move a slide  70 , the other cable  85  in the same slide  70  remains stationary, in effect, the lug  88  thereon sliding in a passage  87  while the other lug  88  pulls the slide  70  outwardly compressing the spring  81 . The cables  85  (one complete one shown in FIG. 3) extend from the housing  63  to the four grab bar assemblies  2  (FIG.  1 ). 
     As mentioned above, each grab bar assembly  2  is pivotably mounted in a recess  8  in the inner skin  6  of the fuselage. Each grab bar assembly  2  includes a cylindrical grab bar  90  which can be pushed or pulled to release the win row  1 . The ends of each grab bar  90  are connected at each end to a shaft  91  by generally chevron-shaped pivot arms  92  (FIG.  9 ). Pushing or pulling of a grab bar  90  results in rotation of the shaft  91  in bearings  94  and  95  mounted in L-shaped brackets  96  and  97 , respectively (FIGS.  9  and  11 ). The shaft  91  extends through the bearing  94  and  95 , and the brackets  96  and  97 . 
     Referring to FIGS. 9 and 10, a nut  99  retains a generally triangular lever  100  on one outer end  102  of the shaft  91 . The shaft  91  is connected to one corner of the lever  100 , and one end  104  of one cable  85  is connected to an opposite corner of the lever by a pivoting cable clamp  107 . Thus, rotation of the shaft  91  and consequently of the lever  100  in either direction results in pulling of the cable  85  to move the pin  62  (FIG. 8) of the drive latch assembly to the release position. The spring  57  in the drive mechanism  35  (FIG. 7) pushes the sleeve  59  and the rack  37  in one direction, and the pinion  42  causes movement of the rack  38  in the opposite direction to move the pins  16  to the window releasing position. The end  104  of the cable  85  passes between guide rollers  110 , defined by ball bearings mounted on the brackets  96 . The cable  85  passes around a third, guide pulley  111 . A threaded coupler  112  on the end of the cable  85  is mounted in an L-shaped bracket  114  mounted on the bracket  96  beneath the lever  100 . 
     Release of the window  1  by accidental rotation of one of the grab bars  90  is prevented by a solenoid  115  mounted on the lever  100 . The solenoid  115  is connected by a wire  116  to a switch  118  (FIG. 16) in the cockpit of the aircraft for actuation by an operator of the aircraft. One end  119  of the solenoid plunger  120  extends through the lever  100  into a recess  121  in the bracket  96  preventing rotation of the lever  100  and consequently of the shaft  91  until the plunger  120  is retracted by de-energizing the solenoid  115 . The other end  122  of the plunger  120  extends beyond the free end of the solenoid body. A helical spring  124  retained on the plunger  120  by a C-clip  125  and a washer  126  retracts the plunger  120  from the latching position when the solenoid  115  is de-energized. Thus, when the electrical system of the aircraft is turned on, the grab bars  90  are automatically disabled, i.e. the solenoid  115  is energized. The solenoids  115  (one for each grab bar  90 ) are automatically disabled by a plurality of sensors, i.e. impact, rollover or immersion (not shown) in a lighting control unit  127  (FIG. 16) which triggers in an emergency situation. Loss of aircraft power will also de-energize the solenoids  115  and enable the grab bars  90 . When the solenoids  115  are de-energized, the springs  124  retract the plungers  120  from the recesses  121  in brackets  96  permitting rotation of the shafts  91  and the grab bars  90 . 
     Once the window I is released, the grab bar  90  which has been pushed or pulled to the release position remains in such release position. With reference to FIGS. 11 and 12, the grab bars  90  and the shafts  91  are releasably held in neutral positions and positively retained in the panel release position by a detent mechanism at the other end of each grab bar assembly  2 . For such purpose, the other end  128  of each shaft  91  extends through and is rotatable in the bearings  95  in the L-shaped brackets  97 . A nut  129  retains a detent arm  130  on such other end  128  of the shaft  91 . A plunger  132  with a rounded bottom end is slidably mounted in the arm  130  for releasably engaging a conical recess  133  in an arcuate detent housing  134  mounted on the bracket  97 . The plunger  132  is biased into the recess  133  by a helical spring  135  mounted on the plunger  132  between one end  137  of a notch  138  in the arm  130  and an annular flange  139  on the plunger  132 . When the shaft  91  is rotated in either direction (clockwise or counterclockwise), the plunger  132  escapes from the recess  133  and slides along an arcuate side  141  of the detent housing  134  where it enters one of a pair of holes  142  near the ends of the housing  134 . At the same time, the one side of the arm  130  encounters one of a pair of stop pins  143  mounted on the bracket  97  proximate the ends of the detent housing  134 . When the plunger  132  enters either of the holes  142 , the grab bar  90  and the shaft  91  are locked in the release position. 
     In order to return the grab bar  90  to the neutral position, the plunger  132  must be forcibly pushed out of the hole  142 . This is effected by a release plunger  145  mounted in each of the holes  142 . The plungers  145  are moved to the release position by an arcuate cam slide  146  slidably mounted in a channel  147  of generally C-shaped cross section in the outside of the housing  134 . In their neutral position, the hemispherical outer ends of the plungers  145  rest in tapering recesses  148  in the inner side of the cam slide  146 . Pins  149  extend outwardly from the slide  146  through arcuate slots  150  in the housing  134  for guiding the slide  146  along an arcuate path of travel parallel to the side  141  of the housing  134 . 
     The slide  146  is normally retained in a rest position (FIG.  11 ), in which the plungers  145  are retracted, by a helical spring  151  extending between one of the pins  149  and a post  152  on the housing  134 . The slide  146  is moved to the plunger release position by pushing on a detent release button  154  in one end of a housing  155  mounted on the bracket  97 . When the button  154  is pressed, a plunger  156  extending out of the other end of the housing pushes against the body  157  of one of the pins  149  which moves the cam slide  146  against the bias of the spring  151 . Pushing the cam slide  146  causes the plungers  145  to ride out of the recesses  148 , pushing the plunger  132  out of the hole  142 . With the plunger  132  released, it is possible to rotate the grab bar  90  manually to the rest position, i.e. to reset the grab bar assembly  2 . When the button  154  is released, the spring  151  returns the slide  146  to the rest position. 
     Referring to FIGS. 13 to  15 , the auxiliary release handle  3  (FIGS. 1 and 3) forms part of an auxiliary release assembly generally indicated at  160  (FIG.  14 ). As mentioned above, the handle  3  is mounted in a recess  9  in the inner skin  6  of the fuselage. The handle  3  is mounted on one end of a hollow spindle  161  by means of a nut  162 . A similar handle  164  is retained on the other end of the spindle  161  by a nut  165  in a recess  166  in the outer skin  7  of the fuselage. The recess  166  similar to and opposed to the recess  9 . Both of the handles  3  and  164  and consequently the spindle  161  can be rotated in a clockwise or counterclockwise direction. The spindle  161  is mounted. in housings  168  and  169  connected to the inner and outer skins  6  and  7 , respectively of the fuselage. A toothed pulley  170  is securely mounted on the centre of the spindle  161  between the housing  168  and  169  for rotating an endless drive belt  171 . A limit pin  172  extends inwardly from one end of the handle  3  into a semicircular slot  173  in the housing for limiting rotation of either handle  3  or  164  in either direction. A detent plunger  174  in the housing  168  releasably retains the spindle  161  and consequently the handles  3  and  164  in the vertical rest or non-use positions (FIGS.  1  and  3 ). 
     As best shown in FIGS. 3 and 14, the drive belt  171  extends around a second toothed pulley  175  rotatably mounted on a shaft  176  in a small frame (not shown) between the inner and outer skins  6  and  7 . The shaft  176  carries a pair of opposed, generally chevron-shaped arms  178  and  179 , which are rotatable on the shaft  176 . A pair of lugs  180  and  181  extend outwardly from the shaft  176  for engaging pins  182  and  183  on the arms  178  and  179 , respectively. When the handle  3  or  164  and consequently the shaft  176  are rotated in one direction, the lug  180  engages pin  182  to cause rotation of the arm  178  while the arm  179  continues to rotate on the shaft  176 . By the same token, when the handle  3  or  164  is rotated in the opposite direction, the lug  181  engages the pin  183  to cause rotation of the arm  179  while the arm  178  is free to rotate relative to the shaft  176 . 
     The free ends of the arms  178  and  179  are pivotally connected by linkage rods  185  and  186  to the outer ends of generally triangular levers  190  and  191 , respectively. The levers  190  and  191  are securely mounted on the shaft  49  carrying the bell crank lever  44 , so that rotation of either lever  190  or  191  causes corresponding rotation of the shaft  49 . When the shaft  49  rotates the bell crank lever  44  also rotates pushing the rod  45  and consequently the rack  37 . During this action, the rod  45  slides through the spring  57  and the sleeve  59 . Movement of the rack  37  results in simultaneous movement of the rack  38 , rotation of the other lever  44 , and consequently movement of the pins  16  to the release position. 
     In order to re-latch the window  1 , the first step is to depress the push button  154  (FIG. 11) to release the shaft  91  in the manner described above. The grab handle  90  can then be manually returned to the rest or neutral position. If one of the handles  3  or  164  was rotated to release the window  1 , the handle is re-positioned by rotating it in the opposite direction to the vertical position. The window is pushed into the opening. An Allen key (not shown) is inserted into the recess  42  in the pinion  41 . When the pinion  41  is rotated (counterclockwise in FIG. 7) the racks  37  and  38  are caused to move back to the cocked position shown in FIG.  7 . In the event that one of the grab handles  90  was used to release the window, movement of the rack  37  in this manner pushes the sleeve  59  against the spring  57  to compress the latter. When the sleeve  59  reaches the center of the block  36 , the spring  66  of the drive release assembly (FIG. 8) pushes the pin  62  into the sleeve  59 , i.e. the drive mechanism is re-cocked. In either case, rotation of the pinion  41  causes movement of the racks  37  and  38  in the opposite direction to that used for release, whereby the bell crank levers  44  are rotated and the slides  23  are moved upwardly to return the pins  16  to the extended, window engaging positions re-latching the window  1  in the fuselage. 
     An emergency lighting system (FIG. 16) facilitates location of the grab bars  90  and the handles  3  and  164 , and provides a positive indication that the window has been jettisoned. The lighting system includes high intensity light emitting diodes (LEDs)  195  located in transparent, plastic sections of each grab bar  90  and in the auxiliary release handles  3  and  164 , and a strobing switch  196  which signals the jettisoning of the window  1  to the lighting control unit  127 . 
     The lighting control unit  127  is mounted on the inner skin  6  of the aircraft at a separate location from the emergency escape window  1 , and is connected to the wiring for the window lighting system by a power cable  199 . The lighting control unit  127  contains a microprocessor, a rechargeable battery pack, an immersion sensor, a rollover sensor, an impact sensor, a watertight, fully submersible casing and an external system test switch  201 . Wires  202 ,  203  and  204  connect the power cable  199  to the grab bars  90 , the handles  3  and  164 , the solenoids  115  and the strobing switch  196 . The lighting system can also be activated by the manually operated switch  118  mounted in the aircraft (typically in the cockpit) which is connected to the control unit  127  by a wire  207 . 
     The emergency lighting system serves three functions during an emergency, namely it provides illumination to the grab bars  90  and the auxiliary handles  3  and  164  for easy location thereof, it identifies the location of the exit by illumination of all four sides thereof using the lighted grab bars  90 , and it indicates the lighting window has been jettisoned by changing the status of the lighted grab bars  90  and the handles  3  and  164  from continuously lit to strobing illumination. The lighting system is activated manually by the on/off switch  118 , or automatically by immersion of the aircraft in water to submerge the control unit  127 , impact of the aircraft with water or land with a force exceeding a preset value, or inversion of the aircraft by more than  90 ° from its normal vertical upright position. Upon initial activation, the four grab bars  90  and the handles  3  and  164  will be illuminated in a continuous mode. The lighted handle  164  on the exterior of the aircraft is intended to assist rescuers in finding the emergency exit release. Jettisoning of the window  1  closes the switch  196  to change the lighting system status from continuous to intermittent strobing, indicating that the exit opening is clear for egress from the aircraft. 
     Thus, there has been described a unique, relatively simple emergency exit system in which the window  1  is released by a spring assisted release mechanism. In existing systems, the operator must provide the energy required to release and jettison the escape hatch. In contradistinction, with the system of the present invention, pushing or pulling on any of the grab bars  90  releases a spring drive which provides the energy for releasing the window  1 . Moreover, because the window  1  is quickly and easily re-installed in the fuselage, there is a greater incentive to practice emergency escape procedures during flight training.