ELECTRONIC TEST CHAMBER ASSEMBLY, MODEL 453
OPERATION UNDER UNUSUAL CONDITIONS (HIGH ALTITUDE FACILITES)
TESTING AT HIGH ALTITUDE
1. If the test facility is located at high altitude, it may be necessary to conduct tests of the AR2
with dial settings lower than the elevation of the test site. Under such conditions, the
pressure inside the altitude chamber will be greater than that outside, and the lid will not stay
closed since it has no locks or latches. Nevertheless, testing may be conducted by clamping
the lid shut using two standard C-clamps with a 6-inch opening capacity and a throat depth of
approximately 3.5 inches. Care must be taken, however, to avoid clamping the lid too tightly.
2. Use the following procedure to obtain the proper clamping force;
a. Install the AR2 to be tested in the altitude chamber (refer to WP 0010 00); close the
altitude chamber lid.
b. Select an altitude approximately 15,000 feet higher than the test site elevation and cause
the chamber to climb to that altitude. This will fully compress the altitude chamber
Be sure to clamp only the main body of the chamber.
c. Position the C-clamps as shown, using small pads of cardboard, cloth, or rubber to
prevent marring the surfaces of the altitude chamber. Do not clamp fittings, tubing, or
any other parts of the chamber which may be damaged.
d. Tighten the clamps using only enough force to keep them from slipping or moving around
on the altitude chamber lid.
3. Any test altitude may now be selected and testing conducted (refer to WP 0010 00). The
clamps will prevent the lid from lifting, regardless of the internal pressure.
4. Since the chamber must be opened to change the AR2 dial setting, installing and removing
the clamps will slow the testing process. Employ them only when low altitudes cannot be
reached using normal test procedures.