Aircraft maintenance isolates hydraulic systems that can move a flap with enough force to kill, electrical buses that power those systems, and pneumatic bleeds — on an airframe where the "equipment" has a maintenance manual that is the authority.
The AMM chapter and the shop's energy-control procedure have to agree. When they do not, the technician follows the AMM and the lockout record is fiction.
Multiple trades on one aircraft, each with their own task card, each needing the same hydraulic system down.
Aircraft on external power for another trade's task; the flap actuator circuit is live.
The hydraulic reservoir reads zero; the brake accumulator holds enough to move a surface.
Avionics restores a bus that structures had relied on being dead.
Real isolation-point structure, illustrative tags, equipment that does not exist. Free to read and download. An example to learn from — not a document to adopt.
B737-800 flap actuator change. ALL THREE hydraulic sources must be isolated - the flight controls are redundantly driven.
- 13 isolation points
- 1 must stay energised
Also applies: The operator’s approved maintenance programme and the AMM task govern. This example illustrates energy isolation only.
Read the exampleThe worked example follows the AMM chapter structure so the lockout and the manual agree on what is isolated.
Each trade's lock on the shared hydraulic isolation is recorded; restoration is gated on all of them.
Safety-critical steps can require a second attestation from a different person.
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