ATL99FA072

The simulated combat flight made a course change maneuver associated with a climb or a descent. The accident airplane preformed the maneuver with a descending left turn. While descending and turning, the safety pilot instructed the client to turn harder and to bury the nose. While following the safety pilot's instructions the right wing assembly separated from the airframe. The main airplane wreckage collided with the ground along the edge of a wooded area of a subdivision. The right wing assembly was located approximately 1/2 mile north of the main wreckage. Examination of the airplane disclosed fatigue cracking in the spar material in the vicinity of wing spar fracture face. The T-34A design 'G' load limits are +6.0 and -3.0.

This report was modified on November 2, 2005.

History of flight

On April 19, 1999, at 1246 eastern daylight time, a Beech T-34A, N140SW, collided with the ground following the in-flight separation of the right wing near Rydal, Georgia. The laser combat simulation flight, "dogfight", was operated by Sky Warriors Aerial Laser Combat under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The air transport pilot/safety pilot (pilot-in-command) and the pilot/client were fatally injured. The flight departed Fulton County Airport in Atlanta, Georgia, at 1200.

The operator reported that, N140SW and another T-34, N141SW, entered the training area near Rydal to complete the pre-briefed simulation mission as outlined in phase two of the four-phase combat simulation program. Approximately 45 minutes into the mission, both airplanes set up a "beyond visual range engagement". Both airplanes initiated the engagement at a predetermined altitude and direction. After the initial turn toward each other, N140SW started a descending left turn, and an increase roll rate (see attached Operator's Aircraft Accident Report).

The operator reported that the airplane was equipped with an on-board video recorder with three cameras installed to capture the events of the flight. A review of the on-board videotape, the safety pilot provided maneuvering instructions to the client with intercept instructions. Seconds before the accident, as they were in pursuit of the other airplane, the safety pilot of the accident airplane instructed the client to "roll all the way through harder, harder- all the way through. That's it. That's right. Bury your nose, bring it down. That's it, good". The client respond by saying "Okay". As the pursuit continued the safety pilot told the client, "now don't chase him into the ground".

According to the safety pilot of the second T-34, while maneuvering in the left descending turn, the right wing separated from the airplane. The airplane entered a spiral, and impacted the ground on the edge of a nearby tree line, north of a new sub-division.

Personnel information

The safety pilot of the accident airplane held an airline transport pilot certificate with single engine land, single engine sea, multi-engine land, and instrument airplane ratings. On November 1998, the safety pilot was issued a first class medical certificate with no limitations. A review the safety pilot's flight experience disclosed that he completed the requirements for the biennial flight review in November 1998; the flight review was taken in a Boeing 767 airplane. The safety pilot had accumulated approximately 15,500 hours of total flight time. The review of the pilot's records showed that he had accumulated a total of 450 hours in the Beech T-34A airplane; within 90 days of the accident, the pilot had flown 20 hours in the Beech T-34A. According to the operator, the safety pilot had worked for approximately 2 years as a safety pilot for Sky Warriors. The operator also reported that the safety pilot on the accident airplane, as well as all of the safety pilot s with Sky Warriors are ex-military fighter pilot.

Additional review of the client information disclosed that he was also a certificated pilot. Reportedly, the client was a 25,000-hour retired airline pilot (see attached Supplement "E").

Aircraft information

N140SW was owned and operated by Sky Warriors, Inc. Additional information about the airplane is located in the factual report on page 2, under the "Aircraft Information" data field. The T34A/B airplane is a two-place, single-engine, tandem-seat trainer, manufactured by Beech Aircraft Corporation. The airplane was designed to meet the requirements of a primary trainer, and at the same time prepare the student pilot for the transition to heavier, higher-performance aircraft.

The over-all dimensions of the airplane are wingspan 32.8 feet, length 25.9 feet, height at rest 9.6 feet. The normal gross weight of the airplane is 2,950 pounds. The entire T34A and B production was sold to U.S. military customers, or was exported to foreign military customers.

N140SW was also equipped with three video cameras and a VHS video recorder; the accident VHS tape for the accident flight was recovered. Other unspecified mission equipment was also installed on the airplane.

Maintenance records showed that N140SW was routinely inspected under a wing spar X-ray program since 1996; no significant findings were discovered under this inspection program initiated by the operator. According to the operator, records of cumulative "G" loading for each flight were not maintained. The operator also reported that no simulated combat flight ever exceeded the designed "G" loading limits. The design "G" load limits are +6.0 and -3.0.

Meteorological information

Visual meteorological conditions prevailed at the time of the accident. Additional information about the weather is located on pages 3 and 4, under the section titled "Weather Information."

Wreckage and impact information

The main wreckage was located near the intersection of Lauren Lane and Landers Road, near Rydal, Georgia. No evidence of in-flight or postimpact fire was noted. The right wing forward spar had separated at a point just outboard of the forward wing attach fittings. The rear spar had separated in generally two locations. One area involved separation of the upper and lower spar cap assemblies at a point just outboard of the right main landing gear aft trunnion fitting. The other area involved the area of the aft wing attach fittings. The rear spar upper cap assembly separated at a point just outboard of the aft upper wing attach fitting. The aft lower wing attach fitting separated 3.8 inches outboard of the face of the fitting, which is just outboard of the "bathtub" portion of the fitting.

Examination of the accident site disclosed that the main wreckage, with the left wing attached, rested in a 6 foot deep crater adjacent to the tree line. The right wing assembly, minus the inboard over the wing walk surface and the inboard section of the right rear wing spar, was located approximately one mile north of the main wreckage. The remainder of the right wing structure was located 1/4 mile northeast of the wing assembly. Examination of the main wreckage site also disclosed that the tail section of the airframe extended vertically about five feet above ground level. The left wing sustained perpendicular crushing damage along the entire leading edge; the postimpact chord of the left wing was approximately 8 inches long.

Postaccident examinations of the right wing forward and aft spar structures and the left wing forward and aft spar structures were conducted by the National transportation Safety Board (NTSB) Materials Laboratory. The examination revealed that the upper elements of the forward spar assembly from the right wing were separated perpendicular to the length of the wing. This separation occurred 5.8 inches outboard of the wing joint along the upper surface. The lower portions of the forward spar assembly were separated 11.5 inches outboard of the wing joint, at the last rivet hole on the outboard end of the wing fitting tang. The aft spar assembly was separated through the wing fitting area 8.2 inches outboard of the wing joint along the top of the spar assembly and 3.8 inches outboard of the wing joint on the bottom of the assembly.

The aft spar structure was also separated farther outboard on the wing, at the outboard end of the landing trunnion fitting. The fractures in the upper spar structure were matte, textured, and oriented along a shear plane. Examination of the fracture surfaces in the lower spar structure revealed 11 flat, shiny fatigue regions. Use of a scanning electron microscope (SEM) revealed striations, ductile dimples, crack arrest markings, and ratchet marks throughout the fatigue regions. Although the