NTSB Factual Report

On June 7, 2007, at 1030 central daylight time, a single-engine Cessna 172K airplane, N7370G, sustained substantial damage when the left main landing gear spring failed during the landing roll on Runway 23 at Tradewind Airport (TDW), near Amarillo, Texas. The student pilot, sole occupant of the airplane, was not injured. The airplane was registered to and operated by a private individual. A visual flight rules (VFR) flight plan was filed for the solo cross-country flight that originated near Memphis, Texas, around 0945. Visual meteorological conditions prevailed for the training flight conducted under 14 Code of Federal Regulations Part 91.

According to the student pilot, while attempting a crosswind landing on Runway 23, the right main landing gear tire touched down first, followed by the left main landing gear tire; however, when the left hand tire made contact with the ground "something went wrong." The student pilot added that he thought the tire was flat so he held the left wing-up for as long as possible to minimize the amount of weight on the tire. He added that the airplane subsequently went-off the side of the runway and he "lost complete control” of the airplane. The airplane impacted the airport perimeter fence and spun around 180-degrees before it came to rest.

A Federal Aviation Administration (FAA) safety inspector performed an on-scene investigation. According to the inspector, the left main landing gear spring assembly had fractured into two sections. One section, which included the tire and brake assembly, was found on the runway. The other half remained attached to the fuselage. In addition, the left wing and the engine firewall sustained structural damage.

The fractured spring assembly, including the foot-step and bracket, were shipped to the Safety Board's Materials Laboratory, in Washington, DC, for further examination. According to the Materials Factual Report, the spring gear fractured at the point where the foot-step was installed to the spring. The step was welded to the spring gear by two transverse weld beads on the top and side of the spring. In addition, there were two longitudinal weld beads on the lower surface of the spring. According to the report, "...the weld beads were tall and rounded with weld spatter on the surrounding surfaces and not consistent with good quality workmanship." The spring gear fracture intersected the longitudinal weld on the lower surface of the spring. A magnified examination of the fracture surface revealed the fracture initiated at this weld bead.

The airplane's last annual inspection was completed in January 2007. A review of the maintenance logbooks did not revealed any entries relating to a welding repair on the spring gear. According to the owner, who had recently purchased the airplane, he reported that he did not authorize anyone to make any repairs and no maintenance had been performed on the airplane since it was purchased.

According to the Cessna Aircraft Company Model 172 Skyhawk Series Service Manual, the foot-step should be bonded to the steel landing gear spring with EA9303 or a similar adhesive. In addition, according to FAA Advisory Circular AC43.13-1B CHG 1, Acceptable Methods, Techniques, and Practices-Aircraft Inspection and Repair, section 4-89, titled Aircraft Parts Not To Be Welded, part (A), "Do not weld alloy steel parts such as aircraft bolts, turnbuckle ends, etc., which have been heat treated to improve their mechanical properties."

The student pilot had accumulated a total of approximately 45 hours, all of which were in the same make and model airplane. His last FAA third class medical certificate was issued on December 13, 2006.

Weather at the Rick Husband Amarillo International Airport (AMA), Amarillo, Texas, located about 7 miles northeast of the Tradewind Airport, at 1053 reported wind from 250 degrees at 15 knots, visibility 10 statute miles, a broken ceiling at 24,000 feet, temperature 73 degrees Fahrenheit, dewpoint 37 degrees Fahrenheit, and a barometric pressure setting of 29.71 inches of Mercury.

NTSB Probable Cause

The failure of the left main landing gear spring assembly as a result of an unapproved repair by an unknown person(s), which resulted in a loss of directional control during the landing roll.