Proximity Switch Electronic Unit (PSEU)

The PSEU monitors the following systems:

  • Takeoff configuration warnings.
  • Landing configurations warnings.
  • Landing gear.
  • Air/ground sensing.

If a flight lock on any of the overwing exits has failed locked, the PSEU light, the
OVERHEAD annunciator, and the MASTER CAUTION lights illuminate.

The PSEU, its sensors, and its input signals are monitored for internal faults.
When designated faults are detected, a PSEU light on the aft overhead panel
illuminates, and the OVERHEAD system annunciator light and MASTER
CAUTION lights illuminate. The PSEU light can be reset following a
maintenance BITE check or repair of the cause of the fault.

The PSEU light and OVERHEAD system annunciator do not illuminate for
simple faults unless a system annunciator panel is pushed for recall. In this
case, a simple fault, resetting the MASTER CAUTION system extinguishes the
PSEU light.

The PSEU light is inhibited:

  • In flight.
  • When the thrust levers are advanced toward takeoff power.
  • For 30 seconds after landing.