MIL --- PRF --- 51191G(EA)
4.4 Verification methods and procedures.
4.4.1 Interface requirements verification.
4.4.1.1 Maximum critical dimensions. Verify that critical dimensions do not exceed
maximum values specified in 3.2.1 by examintion with measurement.
4.4.1.2 Compatibility with interfacing parts. Verify orientation and number of ports con-
forms to Drawing 5 --- 19 --- 1782. Verify that the screw threads in the inlet and outlet ports and
those in the heater for the attachment of the controller conform to 3.2.2 (Drawing
5 --- 19 --- 1782) by use of appropriate gages which conform to ASME B1.2 and B1.3. Verify no
galvanic corrosion between the plugs and housing by materials study or analysis. Verify that
all pairs of male and female electrical connectors external to the controller and heater may be
pulled loose using ordinary hand force and reattached. Verify hole size and pattern of mount-
ing bracket are as specified in 3.2.2.
4.4.1.3 Controller features. Remove the controller from the heater and reattach it.
Move the controller 45 degrees in either direction to the vertical plane that is perpendicular
to the mounting bracket. Verify that mounting holes in controller are located consistent with
the requirements of 3.2.3.
4.4.2 Operating requirements verification.
4.4.2.1 Compatability with vehicle electrical system. The heater shall be tested with test
equipment capable of measuring surge and spike voltages described herein. Operate the
heater with the input voltage set to a nominal steady state voltage of 27.5 Vdc. Apply a con-
tinuous 39 Vdc surge voltage for 10 seconds to the power input terminals and determine
whether the recovery time is less or equal to 0.015 sec. The recovery time is the interval be-
tween the time a voltage deviates from the steady state voltage limits (25 to 30 Vdc) and the
time it returns and remains within that same range. Then apply a 250 Vdc spike voltage for
0.015 milliseconds.
4.4.2.2 Operability during movement. Rotate inlet and outlet ports 180 degrees to each
side of the vertical position while the heater is energized by a 27.5 Vdc source and operating.
4.4.2.3 Heating capability and power consumption. Two calibrated thermocouples shall
be installed in the system, one at the inlet and one at the outlet port, to measure the inlet and
outlet air temperature. The thermocouples shall be installed approximately one inch from
their respective ports. The heater shall be connected to a suitable power source capable of
producing 27.5 Vdc. A voltmeter and ammeter shall be connected to the electrical circuit.
The heater shall be conditioned for 24 hours at 0±4_F prior to testing. Air, at 0±4_F and
flowing at 4.5 cfm, shall pass through a calibrated gas metering device and then through the
heater. Two of the 4 heater samples shall be tested with air flowing through the end inlet and
outlet ports and the remaining two shall be tested with air flowing through the side inlet and
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