N1113B

On April 30, 2023, about 1450 central daylight time, a Luscombe 8F airplane, N1113B, was substantially damaged when it was involved in an accident near Palmer, Texas. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

During an approach to the runway at Dallas South Port Airport (T13), 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 choose to land in a nearby field. During the landing, the left main landing gear collapsed and the left wing struck terrain, which resulted in substantial damage to the left wing.

Postaccident examination revealed that the left rudder cable separated at the pulley under the cabin floor. The cable was retained and sent to the National Transportation Safety Board Materials Laboratory for analysis, which revealed signatures consistent with severe wear and fatigue. Additionally, the cable had a 1/8-inch 7x7 construction that was not consistent with the original 1/8-inch 7x19 design construction. A review of historical Luscombe manufacturer drawings and current FAA-approved part manufacturer authorization showed that the rudder control system design only incorporated a 1/8-inch 7x19 cable.

Examination also revealed a missing rudder 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 left rudder shaft assembly sits aft of the right rudder assembly, and as such, the left rudder return spring requires a spacer attached between the spring and the firewall.

The Civil Aeronautics Administration issued Airworthiness Directive (AD) 51-10-02 in 1951 to address reoccurring flight control cable failures in the Luscombe Model 8 fleet. The AD requires that the flight control cables be removed annually from the airplane to the extent necessary to perform the inspection. The AD also references Luscombe Service Bulletin (SB) 1-51, issued in January 1951, regarding fatigue failures of these cables.

The mechanic who conducted the last annual inspection stated that he does not remove the cables as required by the AD due to the time-consuming process and instead actuates the rudder pedals to move the cable and allow inspection around the pulleys and fairleads.

Review of the airplane maintenance logbooks did not reveal the origin or installation date of the unapproved cable. The airplane owner reported that there was a missing airplane maintenance logbook that recorded maintenance between August 2009 and April 2014.

Review of historical manufacturer data also revealed that the installed rudder cable 2-inch pulley under the cabin floor had a cable bending angle of between 27° and 31° from a straight line. The currently available replacement 2-inch pulley, MS24566-3B, has a cable bending angle limitation of 15° for frequently used aircraft control cables. Additionally, a manufacturer design change was put into production in March 1959 to later serial numbers that increased the size of the pulley to a 3-inch A-120. However, the engineering reasoning behind the design change could not be determined due to a lost engineering order. There was no retroactive SB or AD issued to incorporate the design change on earlier serial numbers.