N143CC

On March 1, 2024, at 1243 eastern standard time, a Cub Crafters PA18-150 airplane, N143CC, was substantially damaged when it was involved in an accident near Edgewater, Florida. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 banner tow flight.

After dropping his banner, the pilot stated that while on short final approach to land, and about 20 to 30 feet above the runway, he heard a loud snap, the control stick went slack in his hand, and he lost aileron control of the airplane. The airplane rolled to the right, and the pilot used the rudder and elevator to attempt to control the airplane. The airplane traveled between two airplanes that were on a taxiway and impacted the side of a hangar, resulting in substantial damage to the fuselage and both wings.

Postaccident examination of the airplane revealed that the left aileron direct cable was separated where the cable went through a pulley on the lower left side of the fuselage. The damage on the separated cable was consistent with having occurred before the impact (see figure 1). The separated ends of the cable displayed significant wear of the cable strands, consistent with the cable rubbing against the pulley. The control cable also displayed significant corrosion in multiple locations and the area around the separation was coated with dirt, grime, and a greasy substance. The aileron pulley at the location of the cable separation was checked for operation and the pulley would bind while attempting to rotate. The pulley was removed from the airframe, the pulley bushing and bolt displayed significant corrosion and a small portion of the outer part of the pulley had broken free. The fracture area was coated with the same dirt, grime, and greasy substances as found on the control cable, consistent with the fracture occurring before the accident.

Figure 1 - Broken left aileron direct cable after cleaning.

Control continuity was established for the remaining flight control cables. Inspection of the right aileron direct cable revealed corrosion on the portions of the cable that were outside of the airframe structure. The corrosion resulted in the cable being stiff and when bent with large flakes of corroded metal breaking free from the cable (see figure 2). The inspection revealed about 10 broken cable strands in the right aileron direct cable. The right aileron direct cable also displayed wear damage where it went through the right lower fuselage cable pulley. Further examination of the airframe revealed corrosion of several of the structural tubes and the landing gear.

Figure 2 - Right aileron direct cable corrosion and broken strands.

Postaccident examination of the engine revealed severe corrosion concentrated around the cylinder bases. The valve springs on several of the cylinders also displayed corrosion; however, none of the valve springs had fractured. Visible indications of exhaust leaks were found on the Nos. 2 and No. 3 cylinders around the exhaust riser flanges. There were no anomalies observed that would have precluded normal operation of the engine. The pilot reported the engine operated normally during the flight and was running at the time of impact with the hangar.

A review of the maintenance records showed that the airplane had 3 100-hour inspections in the past 6 months, and the last 100-hour inspection was performed 67.7 hours before the accident, on February 2, 2024. Further review of the maintenance records revealed that both the left and right aileron direct cables were changed on June 11, 2015, at a tachometer time of 4,377.6. The tachometer time at the time of the accident was 7,045.6, indicating the left aileron control cable had been in service for 2,668 hours. The right aileron direct cable had been replaced on September 23, 2021, and had been in service for 1,419.4 hours. The logbooks indicated that before changing the aileron direct cables in 2015, the cables were made of stainless steel and maintenance personnel had switched to a part that was composed of galvanized steel. When asked why the maintenance personnel switched to galvanized steel, the mechanic responded that they had found broken strands on multiple occasions with the stainless-steel cables and were trying to improve cable longevity. When asked if maintenance personnel applied anti-corrosion products to the galvanized steel, the mechanic replied that they did not routinely use anti-corrosion products on the galvanized steel cables on the accident airplane.

The following is an excerpt from the Piper Aircraft Corporation Inspection Report for the PA-18:

Inspect aileron and flap cables, turnbuckles, guides, and pulleys for safety, damage, corrosion, and operation. (See Notes 9 and 24.)

Note 24 of the Inspection Report for the PA-18 states the following:

Examine cables for broken strands by wiping them with a cloth for their entire length. Visually inspect the cable thoroughly for damage not detected by the cloth. Replace any damaged or frayed cables.