Luscombe 8F N1113B accident near Palmer, Texas

Probable cause

The installation of an unapproved rudder control cable, which resulted in a fatigue failure and subsequent loss of rudder control during cruise flight. Contributing to the accident was the mechanic’s inadequate inspection of the rudder control system.

NTSB analysis

During the landing approach, the pilot felt the left rudder cable break and subsequently lost rudder control. The pilot placed the airplane into a left-wing-low crab attitude and chose to land in a nearby field. During the landing, the left main landing gear collapsed and the left wing impacted terrain, which resulted in substantial damage.

Postaccident examination revealed that the left rudder cable had separated at the pulley under the cabin floor. Examination of the cable revealed that it did not meet the airplane manufacturer’s specifications for the rudder control system, and that the cable displayed evidence of fatigue due to an excessive bending angle at the pulley.

Additionally, the rudder assembly was missing an attach link on the left rudder cable return spring between the spring and firewall. The link is used to balance the tension forces on the rudder cables due to the design of the rudder system. The tension forces on the left cable were likely greater than design due to the missing part, which could have increased the risk of fatigue.

The mechanic who conducted the most recent annual inspection did not remove the rudder control cables for inspection as required by an airworthiness directive. The mechanic stated that he did not remove the cables due to the time-consuming process and instead actuated the rudder pedals to move the cable and allow inspection around the pulleys and fairleads. It is likely that the degraded condition of the cable would have been discovered during the annual inspection if the mechanic had complied with the AD requirement to remove the cables. Additionally, the mechanic should have identified that the rudder control cable itself did not meet manufacturer specifications, and that the rudder assembly was missing a rudder attach link.

Review of the airplane maintenance logbooks did not reveal the origin or installation date of the unapproved cable.

Text from the NTSB. Open the NTSB docket for CEN23LA170 for the full record.