Amateur-built VELOCITY SUV N399DG accident near Puyallup, Washington

Probable cause

The airplane builder's failure to install safety wires on the brake disc attachment bolts, and the mechanic’s failure to identify the omission during the condition inspection. The subsequent brake disc separation resulted in a loss of directional control during the landing roll.

NTSB analysis

The private pilot stated that, during the landing roll, the right brake of the experimental amateur-built airplane failed. The airplane subsequently departed the runway and impacted an airport fence, resulting in substantial damage. The airplane was equipped with a castering nosewheel and steering was accomplished through differential brake pressure; therefore, the pilot did not have any other means to either stop the airplane or maintain directional control once it had slowed to a speed below which rudder authority was available.

Postaccident examination revealed that the right brake disc had detached from the wheel hub. None of its attachment bolts were found, and the attachment bolts on the left brake disc were loose. The bolts and discs had holes to accommodate safety wires, but no safety wires were found on either assembly.

The pilot had recently purchased the airplane following the completion of a condition inspection. Before the inspection, the airplane's builder had adjusted the landing gear, which necessitated removal of the brake discs. The builder could not recall using safety wires to secure the brake discs during the reinstallation, and the mechanic who performed the subsequent inspection also could not recall if safety wires were used.

Text from the NTSB. Open the NTSB docket for WPR17LA114 for the full record.