TEST CHAMBER ASSEMBLY, MODEL 452
OPERATION UNDER USUAL CONDITIONS - CONT
INITIAL ADJUSTMENT BEFORE USE CONT
2. Verify that ON/OFF switch (5) of the test chamber is in OFF position and CLIMB/FALL/COCK
switch (8) in FALL position (centered).
3. Plug power cord (16) into 110 VAC outlet.
Record test data on maintenance log (WP 0042 00).
To avoid damaging the test chamber do not switch the test chamber on/off switch
to on while the air compressor or vacuum pump is under load (while the altitude
chamber is under vacuum or the air cylinder is pressurized). If it has recently
been used, wait one to two minutes for pressure trapped in the system to bleed
4. Position ON/OFF switch (5) on test chamber to ON. The indicator light (6) will illuminate, and
the air compressor and vacuum pump will start. When switching the test chamber ON,
immediately look under the transparent altitude chamber at the ends of both air compressor
and vacuum pump to ensure that the cooling fans are spinning on both units. If either fan is
not spinning, immediately cycle the CLIMB/FALL/COCK switch (8) between FALL and COCK
until the fans spin. Move the CLIMB/FALL/COCK switch (8) on test chamber to CLIMB
position and adjust the altitude control regulator (14) to an altitude of 6,500 feet.
Pressure vs. rate of fall varies greatly with altitude; as altitude increases, the rate
of fall will also increase for a given pressure reading on the gauge. To be sure of
the exact rate of fall, always check it with a stop watch over the 1,000-foot
interval from 500 feet above to 500 feet below the dial setting of the AR2.
Check pressure vs. rate of fall values shown on FUNCTIONS decal once each
hour with a stop watch to verify accuracy. These checks should be conducted
between 6,000 and 5,000 feet simulated altitude with a barometric pressure
adjustment of 29.92 on the altimeter. Values shown on the FUNCTIONS decal
correspond approximately to rate of fall indicated thereon. The AR2 rate-of-fall
mechanism senses rate of pressure change (PSI/sec), which corresponds to its
rate of fall. To obtain correct rate-of-fall data, always install an AR2 in the
altitude chamber before testing.
It is not necessary to wait for the AR2 to stabilize since these checks do not
result in actuation.