of the flak curtains prior to takeoff will depend
upon mission requirements.
The radiation protection system on the A-7
aircraft is similar to that of the A-6 except that
it may be opened or closed manually or closed
automatically using pneumatic system pressure.
The A-7 protective closure consists of one fixed
and three movable fiber glass segments, which
enclose the entire cockpit viewing area when
extended. The forward segment of the closure
presses against the instrument panel cowl so that
a windshield curtain is not necessary.
In the open position, the movable segments
are retracted within the contour of the fixed
segment so that they do not restrict the pilot’s
vision.
An overcenter spring on each side of the
closure holds the panels in either the open or
closed positions.
The automatic closing sequence is accom-
plished in 0.2 second. A lock on the left-hand
canopy frame locks the closure open and prevents
extension until it is manually released.
Interference tolerances between the ejection
seat and the closure panels require that the seat
be within 1/4-inch of the full down position prior
to closure operation.
Manual actuation of the system is initiated by
placing the thermal closure switch to the CLOSE
position. This will cause the ejection seat to be
automatically lowered to provide proper clear-
ance. As the seat lowers, it actuates a seat posi-
tion switch, which directs current to the closure
selector valve. The energized valve releases 1,000
psi pneumatic system pressure through a restrictor
to the two closure actuators, rapidly extending the
closure panels.
When the thermal closure switch is released,
it returns to the OFF position, de-energizing the
closure selector valve and blocking pneumatic
system pressure to the actuator extend lines. De-
energizing of the selector valve also vents the
extend lines so that the closure panels may be
manually opened or closed as necessary.
In the automatic mode of operation, the
thermal closure system operates in the same
manner except the solenoid of the closure selector
valve is grounded through a switching
demodulator unit rather than the thermal closure
switch. The switching unit energizes the closure
selector valve and turns on the white cockpit
floodlights when the system is initiated (triggered)
by a nuclear flash sensor.
The nuclear flash sensor is mounted on the
pilot’s flight helmet. When activated by high-
intensity light, such as that created by a nuclear
blast, the sensor energizes the closure selector
valve for approximately 3 seconds. The closures
extend, are held closed for the 3-second interval,
and then the valve is de-energized and the actuator
lines are vented to allow manual opening and
closing of the panels.
NOTE: When flying a special weapons
mission in the A-7, the pilot’s helmet is equipped
with a flash-blindness protective (ELF) lens. When
the nuclear flash sensor that closes the radiation
panels is activated, current is also directed to
detonate a very small explosive charge contained
in the lens. The exploding charge releases a light-
blocking graphite suspension to the inner core of
the lens to protect the pilot’s eyes from thermal
flash while the closure panels are extending. The
ELF lenses are normally stored in containers in
the cockpit when not in use.
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