TASK 47-31-02-740-804
5. BDU Ground Test Menu
(Figure 208)
A. General
(1) This task gives the instructions to operate the BDU control panel for the BDU Ground Test
Menu.
(2) To help you scroll through the BDU ground test structure, refer to Figure 208.
(3) The BDU ground test menu supplies the controls to do three types of BDU manually initiated
built-in-tests (IBIT). The IBIT tests include these ground tests:
(a) System IBIT
(b) Electrical IBIT
(c) NGS performance IBIT
(4) BDU System IBIT (System Test?)
(a) The BDU system test is manually initiated test done by the NGS controller when the NGS
system is pressurized. To do the system test, it is necessary to pressurize the NGS with
bleed air pressure and operate the left air conditioning pack. The system test is a timed
sequence test that does a check of the open and closed position of all of the electrically
controlled valves. This includes the NGS shutoff valve, ram air valve, overtemperature
shutoff valve and the ASM high-flow valve. The system test also does a test of the filter
pressure switch and a test for sensor drift for the NGS bleed pressure sensor.
(b) The NGS controller will not start the test (test inhibited) or once started, stop the test (test
aborted), if the airplane configuration is incorrect. This includes: NGS inlet pressure less
than 15 psig (103 kPa), the airplane in air mode, the packs are off, the center wing tank
refuel valves open, or an invalid aircraft ID.
(c) The NGS controller will also not start the test if an NGS sensor that is used to control the
open/closed position of a valve is out of limits. The test will not start if there are existing
fault messages. The NGS controller will also inhibit the test if a controller valve driver, or
valve solenoid/torque motor is inoperative.
(d) When the system test is started, the NGS controller monitors the NGS system
performance. The NGS controller will stop the test if there is a change in the airplane
configuration as noted in the previous step. Other events that will cause the test to stop
include an overtemperature condition or an NGS fault is detected by the controller. The
test can also be stopped manually if the MENU or ON/OFF push button controls are
pushed during the test. If the system test is stopped before the test is fully done, all
latched system faults that were present prior to the start of the system test will continue to
be recorded as latched faults.
(5) BDU Electrical IBIT (Electrical Test?)
(a) The BDU electrical test is manually initiated test done by the NGS controller to test the
controller valve drivers (on and off conditions), sensor interfaces, sensor open/short
conditions, solenoid or torque motor open/short conditions and airplane discrete inputs.
The electrical test can be done with the NGS system in a pressurized or non-pressurized
condition. The electrical test opens and closes the NGS shutoff and overtemperature
shutoff valves in a timed sequence to stop the pressurization of the NGS system.
(b) The NGS controller will not start the test (test inhibited) or when started, stop the test
(test aborted), if the airplane configuration is incorrect. This includes: the airplane in air
mode, a different BDU ground test in progress, or an invalid aircraft ID.
737-600/700/800/900
AIRCRAFT MAINTENANCE MANUAL
47-31-02
Page 233
D633A101-ILF Oct 15/2019
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
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