Critical Clamp Marker

A visual indicator applied to an EWIS harness — typically a 50/50 marker split on each side of a clamp — that tells maintenance technicians where a clamp belongs, so a harness that shifts during access work can be returned to its designed location.

Technical detail

Critical clamp markers are not required by FAA 25.1707(i) but are widely recommended for EWIS harnesses routed near flight or other mechanical control cables, where maintenance drift can place the harness in a hazardous position.

Markers reduce inspection time and improve installation consistency. Clamp condition inspection items belong in the Instructions for Continued Airworthiness and in the Enhanced Zonal Analysis Program.

When it matters

EWIS routing through flight-control runs, control surface bays, and any maintenance-access zone where a harness can be unclamped and re-clamped.

Related terms

FAA 25.1707 — System Separation Requirements
The Federal Aviation Regulation that requires EWIS to be physically separated and electrically isolated from other EWIS, aircraft systems, fluid lines, control cables, and heated equipment such that no credible failure can produce a hazardous condition.
Instructions for Continued Airworthiness
The set of documents an aircraft manufacturer or STC holder provides to the operator that defines the inspections, maintenance actions, and intervals needed to keep the aircraft airworthy through its service life. EWIS items belong in the ICA.
Enhanced Zonal Analysis Program
A maintenance-program structure that drives zone-by-zone inspection of EWIS, used to ensure that age-related EWIS issues are surfaced before they create hazardous conditions.