Setyr worked example — AMM 27-51 — Trailing Edge Flap Actuator Replacement Not approved for use. Version 1 · 2026-09-04
Worked example only — your site must author, review and approve its own
procedure under 29 CFR 1910.147(c)(4). setyr.com/procedures
AMM 27-51 — Trailing Edge Flap Actuator Replacement
Aviation MRO
B737-800 flap actuator change. ALL THREE hydraulic sources must be isolated - the flight controls are redundantly driven.
This is a worked example, not a procedure you can adopt. It describes equipment that does not exist, with illustrative tag numbers.
29 CFR 1910.147(c)(4) requires the employer to develop, document and
utilise energy control procedures specific to their own machines, and (c)(6)
requires the employer to inspect those procedures periodically. Neither duty
can be delegated to a vendor or discharged by this document.
Other standards apply to this work.
- The operator’s approved maintenance programme and the AMM task govern. This example illustrates energy isolation only.
Isolation points
| # | Tag (illustrative) | Type | Disposition | What it does and why | Dwell |
|---|---|---|---|---|---|
| 10 | AC-GEAR-PINS | Block | Apply & verify | Landing gear ground lock pins, all three gear. Prevents retraction. Fitted before work, removed LAST. | — |
| 20 | AC-EXT-PWR | Disconnect | Isolate & lock | External power / GPU disconnect at the forward service panel. | — |
| 30 | AC-APU-MASTER | Switch | Isolate & lock | APU master switch and APU fire switch. APU can start remotely and pressurise the pneumatic system. | — |
| 40 | HYD-A-EDP-SOV | Valve | Isolate & lock | System A engine-driven pump shutoff valve, engine 1 fire switch position. | — |
| 50 | HYD-A-EMDP-CB | Breaker | Isolate & lock | System A electric motor-driven pump circuit breaker, P6-1. Pull and collar. | — |
| 60 | HYD-A-ACC-BLEED | Bleed | Isolate & lock | System A accumulator bleed. 3000 psi with nitrogen precharge - bleed to zero and confirm on the gauge. | — |
| 70 | HYD-B-EDP-SOV | Valve | Isolate & lock | System B engine-driven pump shutoff valve, engine 2 fire switch position. | — |
| 80 | HYD-B-EMDP-CB | Breaker | Isolate & lock | System B electric motor-driven pump circuit breaker, P6-2. Pull and collar. | — |
| 90 | HYD-B-ACC-BLEED | Bleed | Isolate & lock | System B accumulator bleed. Independent of system A - both must be bled before flight control work. | — |
| 100 | AC-STBY-HYD-CB | Breaker | Isolate & lock | Standby hydraulic pump circuit breaker. THIRD source on the same flight controls - often missed. | — |
| 110 | AC-FLAP-LOCK | Block | Apply & verify | Trailing edge flap surface secured against movement. Residual pressure can drive the surface. | — |
| 120 | AC-CKPT-PLACARD | Switch | Not an isolation device | DO NOT OPERATE placards on the flap lever and hydraulic panel. Warning only - NOT an isolating device. | — |
| 130 | AC-BATT-SW | Switch | KEEP ENERGISED | Battery switch and battery bus. Hot battery bus REMAINS LIVE for fire detection - cannot be fully isolated. | — |
What your site must supply
- Your own asset and isolation-point tag numbers. The tags shown are illustrative and refer to equipment that does not exist.
- The actual location of every disconnect, valve and vent on your equipment.
- Measured stored-energy magnitudes and the dwell time required to dissipate them.
- Your verification method for each point, and who is authorised to perform it.
- Any additional energy sources present on your equipment and absent here.
Authorship and validation
This example was authored by Setyr for domain validation. It is not derived from any customer's controlled documents. It illustrates the elements 29 CFR 1910.147(c)(4)(ii) requires a procedure to contain — it does not certify compliance, which is a property of an employer's programme rather than of any document.