(h)
The interlock signal from the adjacent SCM on the same shelf.
(i)
The SCM itself.
E.
Power Supply Module (PSM)
(1)
The PSM supplies the CSEU with the necessary dc regulated and ac unregulated power. A total of four PSMs (two for the left CSEU and two for the right CSEU) are installed.
(2)
The two PSMs in each CSEU use power combining (dc) and power changeover (ac) networks to make sure there is continuity to the CSEU loads if one PSM fails. Either PSM can carry the entire CSEU load. However, there is no power combining between the left CSEU PSMs (M536, M537) and the right CSEU PSMs (M538, M539).
(3)
The PSMs (M536, M537) for the left CSEU receive the 28-volt dc and 115-volt ac power sources from the dc and ac standby buses. The PSMs (M538, M539) for the right CSEU receive the 28-volt dc and 115-volt ac power sources from the main left and right dc and ac buses.
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(4) Power generated by the PSMs also supplies the linear variable differential transformers (LVDT), and the rotary variable differential transformers (RVDT), for the position monitor and feedback function of the applicable flight controls and control surfaces. The LVDTs and the RVDTs are frequently referred to as the transducers.
3. Operation
_________
A. Functional Description
(1)
CSEU power supply module distribution (Fig. 3).
(2)
CSEU air/ground and hydraulic discrete inputs (Fig. 6).
(a)
Each of the control modules within the left and right CSEUs receives air/ground mode signals and hydraulic pressure sense signals. The module uses these signals to enable or inhibit its own CSEU functions.
(b)
Four air/ground relays supply air/ground discrete signals to the CSEU when a proximity switch electronics unit (PSEU) signal is received (Ref 32-09-02).
(c)
The air/ground relays energize when the PSEU output signal to the CSEU is a ground, which indicates the main gear truck is not tilted (the airplane is in the ground mode).
(d)
Examples of the air/ground discrete effects in the ground mode on the CSEU function include the enable of the rudder ratio changer ground tests, and the enable of the speedbrake commands by the SCM.
(e)
Hydraulic pressure sense switches operate from the left, right and center hydraulic systems. These switches provide a high and low pair of logic discrete signals (pressure is valid/pressure is not valid) to the CSEU (Ref 29-11-00).
(f)
Examples of a valid hydraulic pressure discrete (the system pressure is good) affecting the CSEU function include the enable of the engage relays for the rudder ratio changer in the air, and the enable of the monitor of SCM failures.
(g)
An invalid air/ground discrete or a hydraulic pressure discrete to the CSEU will cause an AIR/GRD, a HYD PRESS, or other applicable faultball (or fault message on modules with BITE displays) to show a failure.
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CSEU LEFT SHELF POWER DISTRIBUTION
115V AC PSM 1 FAIL
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