BAE Systems MK-67 HAWK N506XX

The swept-wing advanced trainer/light attack airplane was privately owned and contracted to provide support to the US Air Force (USAF) under public aircraft provisions. It was equipped with wing-mounted external fuel tanks and bomb rack/dispensers loaded with practice ordinance. During takeoff, the airline transport pilot was unable to maintain airplane control following rotation. The airplane did not climb, departed the left side of the runway, and struck a pickup truck, which was involved in construction activities and parked about 150 ft from the runway edge. The occupant of the truck was killed, the pilot and his passenger (who was flying as a "ride along") were not injured, and the airplane sustained substantial damage. The entire accident sequence was captured by an onboard video camera, which was positioned inside the canopy at the rear of the cockpit. The camera recorded some engine instruments, the primary flight instruments, the back of the pilot's head, and the runway and horizon. Analysis of the recording revealed that the pilot initiated rotation about 8 knots before reaching the correct indicated airspeed and that the airplane lifted off the ground about 10 knots early, about the same time as it reached its target pitch attitude. The video image, which up until this point had been smooth, then began to shudder in a manner consistent with the airplane experiencing the buffet of an aerodynamic stall. The airplane immediately rolled aggressively left, and the main landing gear struck the ground hard. The airplane then pitched up aggressively and began a series of roll-and-pitch oscillations, bouncing from left to right with the outboard bomb dispensers and landing gear alternately striking the ground as the pilot attempted to establish control. The airplane passed beyond the runway edge and reached its target takeoff speed just before striking the truck, but by this time, it had departed controlled flight, was in a steep right bank at almost twice its target pitch attitude, indicating that it had likely aerodynamically stalled. The pilot reported that he felt the airplane's nose become light as the airplane approached rotation speed, and the video revealed that the nose was oscillating lightly up and down a few seconds before rotation, consistent with his statement. The pilot stated that, before takeoff, he set the pitch trim to 3 degrees nose up, which was consistent with the operator's policy for takeoff with external stores. The policy was in place to relieve stick pressure on rotation; however, the airplane's flight manual specified that 0 degrees pitch trim should be used for takeoff in all configurations. During the postaccident examination, the airplane's pitch trim was found at almost full nose up for reasons that could not be determined. It is likely that the pilot initiated an early rotation instinctively as the airplane's nose became light due to the excessive nose-up pitch trim. The operator stated that the company policy for nose-up trim on takeoff was intended to give the airplane control stick pressures on rotation comparable to other U.S. fighter aircraft, such as the FA-18 and F-16. Although the operator had used this technique without incident on many prior missions, it was in direct contrast with the manufacturer's takeoff recommendations and likely increased the risk of early rotation. Postaccident examination of the airframe and flight control systems did not reveal any anomalies that would have precluded normal operation. The primary engine components were undamaged, and the video revealed that the engine appeared to operate uninterrupted and at high power levels throughout the accident sequence. The external fuel tanks were partially filled with fuel, which was allowed per the airplane's flight manual, (assuming the airplane was flown at the correct airspeeds). The bomb dispensers were not on the airplane manufacturer's list of approved weapons; therefore, the operator had commissioned an Federal Aviation Administration (FAA)-designated engineering representative to prepare a structural comparison report to assess the viability of installing the alternate dispensers. Although the report concluded that the use of the alternate dispensers was structurally satisfactory, it did not take into account the aerodynamic effects of using the alternate dispensers. It is possible that the airplane's stall margin was eroded further by the use of the alternate dispensers, along with a shift in the center of gravity due to the partially filled fuel tanks. The majority of the airport was operated and governed by the Department of Defense (DoD), specifically the US Marine Corps (USMC). It was operated as a "shared use" airport concurrently supporting both military and civilian operations, although the accident runway was used almost exclusively for military flights. A USMC construction crew was preparing the area immediately adjacent to the runway for the installation of an arresting gear system. The operation was composed of about 20 people, along with support vehicles and construction equipment, and the group occupied the space from the runway edge outward about 150 ft. The truck that was struck was located on the outer edge of the space, farthest from the runway, and was occupied by a Marine Lance Corporal who was providing operational escort and safety support for the construction crew. USMC airport-specific station orders did not prohibit construction activities in this area, and no notice to airmen relating to construction was issued at the time of the accident nor was one required. If the airport had been under operating under Part 139 regulations and full FAA oversight, no such construction activities would have been permitted while the runway was active, and the ground fatality would have been avoided. About 21 months before the accident, the DoD issued a directive that all aircraft owned, leased, operated, used, designed, or modified by DoD must have undergone an airworthiness assessment in accordance with the applicable military department policy and that management authorities within the military departments should be established to provide ongoing oversight. The directive allowed the use of DoD or FAA airworthiness certification standards. Under the auspices of this directive, the operator had undergone a series of oversight inspections from the Naval Air Systems Command and interim flight clearance was granted to perform missions for the USMC. Although the accident flight departed from a USMC base, it was operating in support of the USAF, and the USAF chose to place the responsibility of certification and ongoing oversight with the FAA. However, because the airplane's missions were flown under the umbrella of "public aircraft," the FAA was not providing, nor was it required to provide, any oversight beyond issuance of the airplane's initial airworthiness certificate. As such, the operator was effectively operating without oversight at the time of the accident. This lack of oversight likely enabled the continued operating philosophy, which resulted in the difference in takeoff procedure between the operator and the manufacturer and the use of inadequately evaluated weapons system components.

Quoted verbatim from the NTSB record.