The left-hand flight deck
overhead window provides the flight crew with a secondary emergency
egress route. The left overhead window consists of three panes
of glass, an inner pane attached to the crew compartment and a
center and outer pane attached to the upper forward fuselage.
When the secondary emergency egress path is utilized, pulling
the T handle located forward of the flight deck center console
(between the commander and pilot) activates the overhead window
jettison system. When initiated, the center and outer panes are
jettisoned as a unit, upward and aft. A time delay in the pyrotechnic
firing circuit delays the initiation of the jettisoning of the
inner pane 0.3 of a second after the center and outer panes are
jettisoned. Upon the initiation of the jettisoning of the inner
window pane, it rotates downward and aft into the crew compartment
aft flight deck on hinges located at the aft portion of the window
frame. A capture device attenuates the opening rate and holds
the window in position.
The overhead window jettison system consists primarily of expanding
tube assemblies, mild detonating fuses, frangible bolts and associated
The left overhead window jettison system can be initiated from
the outside of the orbiter on the right side of the forward fuselage
by ground personnel.
Egress steps are mounted at the aft flight deck station (left
side) to assist the flight crew up through the window.
Emergency ground descent devices are stowed on the overhead aft
flight deck adjacent to the left overhead window. One device is
provided for each flight crew member. The emergency ground descent
device enables flight crew members to lower themselves to the
ground over the side of the orbiter.