Sparta, TN, USA
N9792E
BELLANCA 17-30A
During a normal landing, the weld that joins the right side nose landing gear to the engine mount failed, resulting in a partial collapse of the nose landing gear. The pilot was unable to maintain directional control of the airplane. The airplane travelled off the runway and collided with a fence resulting in substantial damage. The engine mount was modified about 18 years prior to the accident. The modification included the addition of vertically oriented tubes welded on both sides of the engine mount near the nose landing gear attach points, inadequate weld repair on the right side resulted in voids or gaps, and no fusion in some areas. Although the engine mount had been removed and inspected in 2003, and extensive maintenance was completed the month before the accident, visual inspection of the suspect area would not have been able to detect the inadequate weld repair.
On September 6, 2008, about 1600 central daylight time, a Bellanca 17-30A, N9792E, registered to a private individual, experienced partial collapse of the nose landing gear during the landing roll at Upper Cumberland Regional Airport (SRB), Sparta, Tennessee. Visual meteorological conditions prevailed at the time and an instrument flight rules (IFR) flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 91 personal flight from York Airport (THV), York, Pennsylvania to SRB. The airplane was substantially damaged and the private certificated pilot, the sole occupant, was not injured. The flight originated from THV about 1230 eastern daylight time. The pilot stated that on approach to runway 4 for a full-stop landing, the wind was from 010 degrees at less than 5 knots. He did not have any crosswind correction on final, nor was any needed, and he landed first on the main landing gears. The airplane bounced a few feet then settled back on the main landing gears. The landing roll continued and as soon as the nose landing gear contacted the runway, the airplane instantly jerked to the left. He attempted to correct with full right rudder input but was unsuccessful. The airplane traveled off the runway and continued turning to the left. He applied aft elevator input and cleared a ditch ahead but then collided with a fence. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed the nose landing gear was partially collapsed. Further inspection of the engine mount assembly, part number (P/N) 191898, revealed it was fractured in two locations near the right side of the nose landing gear attach point. Sections of the engine mount were removed and sent to the National Transportation Safety Board Materials Laboratory (Safety Boards’ Materials Laboratory) located in Washington, D.C. Examination of the engine mount sections by the Safety Boards’ Materials Laboratory revealed one tube P/N 191902-8 exhibited overstress fracture near its juncture with the right hand bed rail and the front bed rail. The fracture was through the tube wall approximately ½ inch from the assembly welds; no evidence of preexisting cracking or corrosion were visible on the fracture surface. The second tube (vertically oriented) was separated at the upper weld bead near the right bed rail. Overstress fracture features of only a thin band of the weld bead around the entire periphery was noted. Approximately 80 percent of the weld bead remained attached to the vertical tube while a small portion of weld bead remained attached to the right bed rail. Magnified inspection of the upper weld bead revealed gaps or void spaces, lack of weld penetration to the root of the joint, and regions without fusion of the weld to the bed rail and tube. Additionally, energy dispersive x-ray spectra (EDS) of the weld fusion zone revealed no chromium was present, indicating an inappropriate filler rod was used during the welding process. The airplane was manufactured in 1976, and on September 21, 1977, FAA Approved Bellanca Service Letter B-96 was disseminated by the Type Certificate Data Sheet holder, and was applicable to the accident airplane. The service letter informed owner/operators of having received reports of cracks developing in the nose landing gear mount, and specified that if cracks or damage to a tube is found, the mount should be repaired in accordance with (IAW) Service Kit (SK1267-4019), which installed vertical oriented tubes on either side of the engine mount. Installation of the service kit eliminated repetitive inspections of specific areas of the engine mount tubes identified in FAA Airworthiness Directive (AD) 77-22-02, dated November 2, 1977. Safety Board review of the maintenance records revealed the engine mount was modified IAW SK1267-4019 on February 1, 1990. The service kit installation was signed off by an airframe and powerplant mechanic with inspection authorization. The maintenance records further indicate that the engine mount was removed and inspected in December 2003, due to propeller contact. Additionally, extensive work to the entire airframe was signed off as being completed on August 21, 2008; the airplane had been operated for 7 hours since the work was completed.
Failure of the nose landing gear mount during a normal landing due to an improper weld.
Source: NTSB Aviation Accident Database
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