Aero Commander 500-B N411FS accident near Charlotte Amali

Probable cause

The failure of maintenance personnel to identify inadequate clamping of the aluminum line during inspection, and the undetected fatigue cracking of the line which resulted in the loss of hydraulic fluid.

NTSB analysis

While inbound for landing, undetected fatigue cracks in a hard aluminum hydraulic line near a flared end cracked through the tube wall thickness resulting in the loss of hydraulic fluid and the inability of the pilot to fully extend all landing gears using either the normal or emergency landing gear extension systems. During the landing roll, the left main landing gear collapsed. Fatigue cracking of the tube was likely caused by vibratory loads due to in-service bends and improper clamping; the tube was only clamped in one location though two clamps were required. Additionally, wear on the tube in the area of the clamp was consistent with a loose clamp. The airplane was last inspected in accordance with an Annual/100-Hour inspection on April 30, 2008, or approximately 62 hours earlier. Inspection of the tube for condition is required during the 100 hour inspection.

Text from the NTSB. Open the NTSB docket for MIA08LA149 for the full record.