How One Incomplete Task Became Four, and the System Fix That Stoped It.

Executive snapshot (60 seconds)

• Aircraft / task: BK117 C2; replace main rotor blade (MRB) upper/lower fittings.

• What went wrong: One blade left incomplete on Day 1 (bushings chilled, no pass‑down). Day 2 team finished the other three, installed all four blades, and released the aircraft for flight. Recurrent vibration squawks followed; returning the aircraft revealed no bushings installed on the Day‑1 blade.

• Why it happened: Time pressure, “tribal” shortcuts (skipping chill), missing pass‑down/Incomplete‑Work tag, and no independent inspection (QA hold‑point) before install.

• What we recommended: Incomplete‑Work tags + pass‑down log, QA hold‑points at MRB fitting completion and pre‑install, and a cooler log for chilled parts, tool/FOD controls.

• What to track next: FFP rate (missed steps ÷ total steps), hold‑point compliance, repeat vibration squawks, days without FOD/FFP.

• Why it matters: Fewer reworks, cleaner audits, and more in‑service hours without adding headcount.

Situation

A BK117 C2 entered scheduled maintenance to replace main rotor blade (MRB) upper/lower fittings. On Day 1, Mechanic A completed the disassembly and partial reassembly of one blade, placed new bushings in the cooler per the Maintenance Manual (MM), then left for two days—no pass‑down, no tag on the blade.

On Day 2, Mechanics B/C (maintenance facility) and Mechanic D (visiting from the aircraft’s base) finished the remaining three fittings and installed all four blades. The aircraft returned to service and was flown to the base.

Symptoms

Pilots reported an unusual vibration. Field balancing showed values within limits; aircraft remained in service. After several flights and continued squawks, the aircraft returned to the facility.

Finding

During removal, one blade had no bushings installed. Mechanic A later located the original chilled bushings still in the cooler—now ten days old.

What failed (facts, not blame)

• Handover: No pass‑down; the partially completed blade wasn’t tagged as Incomplete/Unserviceable.

• Procedure: The follow‑on team didn’t chill bushings as required by the MM, and no one verified prior work on the first blade.

• Inspection: No independent inspection / QA hold‑point was requested during reassembly or at blade installation.

Contributing factors (MEDA/Dirty Dozen)

• Time pressure to complete scheduled work.

• Norms / “tribal know‑how” (belief that chilling was optional).

• Communication gaps across shifts.

• Tool/parts control gaps (no cooler log).

Corrective action (our recommendations)

• Institute Incomplete Work tags for any open task; required named pass‑down before leaving a job.

• Add QA hold‑points: (1) MRB fitting completion, (2) pre‑install verification.

• Implement a Cooler Log (part number, in/out time, work order), and tool shadow boards with torque‑wrench check‑in/out.

Key takeaway: Misses didn’t come from one person, they came from a system without handover discipline, parts/tool controls, or independent inspection at the right points. Fix the system, and the misses stop.

Why OAS (and how we help)

Optimal Aviation Solutions can show you how to turn downtime into revenue by hard‑wiring compliance and operational excellence with small controls that crews accept and auditors respect. Our Regulatory Compliance Review pinpoints procedure drift, installs the right hold‑points, and leaves you with a solid control plan.

👉Book a 60‑minute Compliance Snapshot