A remote pilot needs to inspect the underside of a bridge deck, requiring flight below the roadway. What Part 107 consideration applies most directly?

Flying beneath a bridge deck raises an altitude question that turns out to be easy and a visibility question that turns out to be hard. The altitude is straightforward: operations within 400 feet of a structure may go up to 400 feet above its uppermost limit, so a bridge inspection is comfortably within the ceiling. The genuine constraint is visual line of sight, which must be maintained throughout, and a structure that puts steel and concrete between the pilot and the aircraft breaks it — going under a deck is one of the most common ways to lose sight of the aircraft without intending to. The practical answers are repositioning the crew, using a visual observer positioned to see beneath the span, or breaking the work into segments flown from different vantage points. Relying on the camera feed does not satisfy the requirement, since the rule calls for unaided visual contact with the aircraft itself.

Structural inspection does not relieve the visual line of sight requirement, and flying beneath a deck readily puts the structure between pilot and aircraft, so the crew must be positioned to maintain sight throughout.

Part 107 requires the remote pilot or a visual observer to maintain unaided visual line of sight with the aircraft throughout the operation. The 400-foot limit is measured above ground or, within 400 feet of a structure, above the structure's uppermost limit.

The Structure Blocks the View. The altitude was never the problem — seeing the aircraft is.

The camera feed does not satisfy visual line of sight. The rule requires unaided visual contact with the aircraft itself.

• •Treating flight below a structure as an altitude problem
• •Substituting the camera feed for visual line of sight
• •Assuming a low-altitude waiver is needed