FTW99FA123

The twin-engine airplane impacted the ground in an uncontrolled descent following the in-flight separation of the right wing during a normal descent. The airplane had accumulated a total time of 20,457 hours and had been flown 52 hours since the most recent annual inspection, which was performed by the current operator 3 weeks prior to the accident. Available maintenance records indicated that since 1988, maintenance personnel had made numerous repairs to the right wing, including repairing skin cracks, working rivets, wing stub spar straps, and the right main landing gear. Metallurgical examination revealed that the right wing's front spar failed due to fatigue that started at an area of mechanical damage and rough machining marks. The presence of primer covering the mechanical damage strongly suggests that the damage was produced during the manufacturing process. It could not be determined whether the mechanical damage or the machining, acting alone, could have caused the fatigue cracking to initiate. Fatigue cracking found on the rear spar and the forward auxiliary spar is most likely secondary fatigue due to load shedding as the crack grew in the front spar.

History of flight

On April 27, 1999, at 0916 central daylight time, a Cessna 402C, twin-engine airplane, N819BW, was destroyed by terrain impact following an in-flight separation of the right wing during descent, near Goldsby, Oklahoma. The commercial pilot, sole occupant, received fatal injuries. The airplane was operated as Flight 818 by Texas Air Charters, Inc., of Denton, Texas, under 14 Code of Regulations (CFR) Part 135 as an on-demand cargo flight from Dallas, Texas, to Oklahoma City, Oklahoma. The flight departed Dallas Love Field Airport about 0816 on an instrument flight rules (IFR) flight plan.

During interviews, conducted by the NTSB investigator-in-charge (IIC), witnesses, located approximately 1/2 mile from the accident site, reported observing the airplane level at approximately 1,000 feet agl, when the wing departed the aircraft. The aircraft then turned right, entered a spiral, and nose dived to the ground. Upon ground impact, the airplane bounced into the air approximately 10 to 12 feet before coming to rest in the wheat field. The wing descended rapidly at first and then slowed and "drifted" to the ground. Some witnesses reported hearing high rpm engine sounds. Witnesses reported that they did not see any other airplanes in the area at the time of the wing separation.

Personnel information

A review of FAA records revealed that the pilot was issued a first class medical certificate on March 24, 1999, with a limitation for corrective lenses. The commercial pilot held airplane single-engine land, multiengine land, and instrument ratings. He was a certificated flight instructor for the airplane single-engine land and instrument ratings.

The pilot was employed by Texas Air Charter, Inc., in September 1998, and he completed their training program for all Cessna 400 series aircraft operated by the company. He satisfactorily completed the CFR Part 135 airman competency/proficiency check in a Cessna 401B aircraft on September 22, 1998, given by the company chief pilot/check airman.

In the pilot's logbook, the accumulated flight time logged as of April 15, 1999, was 1,754.2 hours. According to company flight/duty records for 1999, the pilot had flown 478.3 hours of charter flights in the Cessna 400 series multiengine aircraft from January through March 1999.

Aircraft information

The FAA records and available maintenance records were reviewed by the NTSB IIC. The Cessna 402C aircraft Type Certification Data (A7CE) was issued under Part 3 of the Civil Air Regulations (CAR) dated May 15, 1956. The original delivery documents for the Cessna 402C aircraft, serial number 402C0423, showed a December 1980, FAA airworthiness certification. Records included the following registration history for the aircraft: N67827, 1981, Casper Air Service, Inc., Casper, Wyoming; N67827, 1984, Stowers Aircraft, Pond Creek, Oklahoma; N104GP, 1986, Wrangler Air, Inc., Ft. Lauderdale, Florida; N104GP 1989, GP Express Airlines., Grand Island, Nebraska; N819AN, 1993, Abbeymere, Inc., Las Vegas, Nevada; N819AN [N819BW], 1998, Balter Worldwide, Corp., Van Nuys, California; N819BW, 1998, Hyannis Air Service, Inc., Hyannis, Massachusetts; N819BW, 1998, Balter Worldwide Corporation, Van Nuys, California; N819BW, 1999, Sunshine Air, Inc., Van Nuys, California. On April 6, 1999, N819BW was purchased by Texas Air Charters, Inc., of Denton, Texas.

There were no maintenance records showing the complete history on the accident aircraft. Available records indicated that the aircraft sustained substantial damage and the right main landing gear separated from the aircraft during an accident in Dickerson, North Dakota, in 1981. Maintenance repair records following the North Dakota accident were not located by the NTSB IIC. Records did indicate that the aircraft was repainted in 1990 (N104GP) and in 1998 (N819BW).

There were maintenance flight logs dating from 1991 to 1999 and aircraft discrepancy logs that revealed the following maintenance history for the right wing area. On July 9, 1988, GP-Express Airlines, at 7781.8 hours, found both left and right wing main spar webs cracked and complied with Cessna Service Bulletin ME84-12. On October 23, 1992, Air Nevada Airlines, at 13,863.0 hours, found the right lower landing gear well skin cracked at W.S. 86.19, stop drilled the crack and fabricated a doubler and surface patch. On July 28, 1996, Air Nevada Airlines, at 18,589.9 hours. found the left and right wing stub lower spar straps loose and replaced and re-torqued the screws. On August 20, 1996, Air Nevada Airlines found and repaired a loose patch on the inboard side of the right main landing gear door. On October 9, 1996, Air Nevada Airlines, at 18,901.3 hours, replaced rivets for the right engine cowl. On January 8, 1997, at 19,157.0 hours, under Air Nevada Airlines FAA Approved Aircraft Inspection Program (AAIP), the left and right wing special inspections (Type A and Type B according to Cessna Maintenance Manual Chapter 57) were performed for the wings. An FAA Major Repair and Alteration Form 337 signed by Aeroshear Aviation, Van Nuys, California, and dated May 27, 1998, showed a repair of a crack on the right wing lower skin panel. An Air Nevada Airlines aircraft discrepancy log for January 2, 1998, at 20,144.4 hours, indicated the right main landing gear up-locks were replaced. On August 26, 1998, working rivets were repaired on both wings, and a crack was repaired on the right wing.

A pre-purchase report was issued by Pacific Continental Engines, Inc., of Van Nuys, California, on March 31, 1999, at an accumulated aircraft time of 20,399.3 hours. The president of Texas Air Charters, Inc., stated to the NTSB IIC that he reviewed the report prior to purchasing the aircraft. He further stated that he had personally flown the aircraft from California to Texas.

The airplane was maintained under CFR Part 135.411 (a)(1) by Texas Air Charters, Inc., at the time of the accident. The last annual inspection was performed on April 6, 1999, by Texas Air Charters, Inc., at a total aircraft time of 20,404.7 hours. The maintenance release stated that the annual inspection was completed using maintenance manual P/N D2527-5-13. The Texas Air Charters, Inc., Director of Maintenance certified that this "airframe has been inspected in accordance with a[n] annual inspection and was determined to be in an airworthy condition" and returned the aircraft to service. The accumulated time on the aircraft at the time of the accident was 20,457.2 hours (52.3 hours since the last annual inspection).

The left engine, a Continental TSIO-520-VB (2), serial number 278478-R, was a factory remanufactured engine sold to Sierra Nevada Airways, Las, Vegas, Nevada, in June 1992. This engine, at occurrence, had accumulated 287.7 hours since major overhaul (SMOH). The left propeller had accumulated 618.8 hours SMOH.

The right engine, a Continental TSIO-520-VB (1), serial number 278310-R, was a factory remanufactured engine sold to Lynns Aircraft, El Monte, California, in December 1990. This engine had accumulated 1,197.7 hours SMOH. The right propeller had accumulated 1,912 hours SMOH.

Meteorological information

At 0856, the surface weather observation for Oklahoma City (located about 14 nautical miles north-northwest of the accident site), indicated clear skies; visibility 10 statute miles; temperature 59 degrees Fahrenheit; dew point 54 degrees Fahrenheit; winds from 320 degrees at 7 knots; altimeter setting 29.87 inches of mercury.

Upper air data from Norman, Oklahoma (located about 4 nautical miles north-northeast of the accident site), at 0700, showed northwest winds at 25 to 30 knots from 3,000 to 6,000 feet msl. Satellite visibility data for 0902 and 0915 showed generally clear skies in the accident area. A review of pilot weather reports (PIREPS) showed no turbulence within about a 50 nautical mile radius of