Yuma, AZ, USA
N506XX
BAE SYSTEMS MK-67 HAWK
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.
HISTORY OF FLIGHTOn March 11, 2015, at 1149 mountain standard time, a BAe Systems Hawk MK-67, N506XX, call sign BADGER1, collided with a truck during takeoff from the Yuma Marine Corps Air Station (MCAS)/Yuma International Airport (KNYL), Yuma, Arizona. The airplane was owned by Air USA, Inc., and operated as a public aircraft flight in support of the United States Air Force (USAF). The airline transport pilot and pilot-rated passenger were not injured. The driver of the truck sustained fatal injuries. The airplane sustained substantial damage during the accident sequence. The local area flight departed Yuma at 1148. Visual meteorological conditions prevailed, and a Military visual flight rules flight plan had been filed. The airplane was being utilized along with a second similarly equipped Hawk (callsign BADGER2) by Air USA in support of the USAF as part of the Special Operation Terminal Attack Controller Course (SOTACC). They were performing a 15-second staggered takeoff, and their mission was to provide close air support (CAS) for the training of Joint Terminal Attack Controllers (JTAC's). The airplane was equipped with external fuel tanks on the inboard pylon of each wing, and bomb rack/dispensers loaded with practice ordinance attached to the outboard wing pylons. At the time of the accident, a construction crew from the United States Marine Corps (USMC) was preparing a concrete pad at the left edge of runway 03L in preparation for the installation of an expeditionary arresting gear system. The pad was located 10 feet from the runway edge, about 6,500 feet from the runway 03L landing threshold. The construction operation, which included support vehicles, crew, and construction equipment, occupied the space from the runway pad outwards about 150 feet. The truck that was struck was located 140 feet beyond the runway edge, and was occupied by a Marine Lance Corporal who was providing operational escort and safety support for the construction crew. The pilot reported that the preflight, engine start, taxi, and line-up on runway 03L were uneventful. The airplane was positioned on the right side of the runway, with BADGER2 positioned as the wingman to the left and aft. The pilot stated that once cleared for takeoff, he applied engine thrust and the engine spool-up, takeoff roll, and acceleration check speeds were as expected. He stated that he felt the airplane's nose wheel become light about the time they reached rotation speed. The nose of the airplane then lifted, and a short time later the main wheels became airborne. The left wing then dropped, and the nose yawed about 10 degrees to the left. He attempted to maintain a low angle of attack, applying slight rudder and aileron corrections. He considered aborting the takeoff, but due to the airplane's angle relative to the runway he was concerned the airplane might tumble if they entered the undulating adjacent terrain. He continued to apply corrective control inputs, but the airplane did not respond in a positive manner as he expected, and the left drift progressed. The airplane continued to bank left and then right, with the main landing gear and bomb dispensers striking the adjoining shoulder multiple times. The airplane was now flying directly over the gravel shoulder, about 100 feet left of the runway edge, when the construction crew came into view. The right wing struck the truck, and the airplane yawed to the right, coming to rest on the shoulder, about 650 feet beyond the point of impact. The truck came to rest about 160 feet beyond the point of impact. PERSONNEL INFORMATIONThe pilot held an airline transport pilot certificate with ratings for airplane single-engine and multiengine land along with type ratings, authorized experimental aircraft: AV-L39, Hawk. He held a first-class medical certificate issued on August 7, 2014; it had no limitations or waivers. At the time of the accident, the pilot was a current and active A-10 pilot for the Air National Guard. The A-10 is a twin-engine, straight-wing, close air support airplane utilized by the USAF. His aviation career began in 2000, initially as crew chief for the A-10; in 2008 he was commissioned to fly the A-10, having received training in both the T-37 and T-38. In March 2014 he began working as a contractor for Air USA, flying the L39. The pilot reported a total flight experience of 2,116 hours, the majority of which (about 1,500 hours) took place in Tactical Jet aircraft, and primarily in the A-10. His total flight experience in the 12 months prior to the accident was 328 hours, and his total experience in the Hawk was 67 hours, with 55 as pilot-in-command. His last Federal Aviation Administration (FAA) checkride took place on January 19, 2015, and was for his airline transport pilot certificate. The pilot's experience with the Hawk was gained exclusively while at Air USA, where he began his Hawk training in August 2014. The training was composed of flight manual study, followed by 2 days of ground school, cockpit familiarization, and ejection seat training. He then flew three graded instructional flights including five cross-country flights to establish basic and advanced aircraft handling along with instrument procedures, after which he was cleared to take the checkride for type rating with an FAA designated pilot examiner (DPE). Having gained his type rating, he went on to receive further instruction gaining initial qualification, mission qualification, air-to-ground qualification, and flight lead upgrade training, and after about 12 hours of total flight time, he was approved by Air USA to fly solo missions. Documentation provided by Air USA revealed that he scored 100 percent on all written examinations, and during air-to-ground training received the following comments, "Had some A-10 pilot tendencies during tight turns," "Has adjusted to the increased speed of the Hawk very well." Air USA was the only private operator of the Hawk in the United States, and as such, the FAA DPE who performed the pilot type rating checkride did not have direct experience flying the Hawk. (The United States Navy operates the T-45 Goshawk, which is a Hawk variant). The pilot-rated passenger was not an employee or contractor for Air USA. He had flown on the two previous missions with the pilot in the accident airplane, and was flying as a potential future pilot for Air USA in a "ride along" capacity. AIRCRAFT INFORMATIONThe Hawk MK-67 was a swept-wing, two-seat, advanced trainer/light attack airplane, powered by a single Rolls-Royce Adour turbofan engine. The accident airplane was manufactured in 1992 by BAe Systems in the UK as part of a group of 20 Hawks configured specifically for export to the Republic of Korea Air Force (ROKAF). The airplane was then utilized by the ROKAF for training until it was sold to Air USA, along with 11 other Hawk MK-67's in September 2013. The sale included documentation for the fleet, along with a series of spare parts. The airplane was subsequently exported to, and registered in, the United States, where it was issued a special airworthiness certificate by the FAA in the experimental/exhibition category in March 2014. The later variants of the Hawk remain in production, with over 900 built since 1974. Maintenance Maintenance was performed in-house by Air USA mechanics on a continuous airworthiness basis, utilizing an OEM (original equipment manufacturer) inspection program. At the time of the accident, the airplane had accrued a total flight time of 5,625.3 hours. The engine total time was 3,782.7 hours, with the last overhaul occurring 155.7 flight hours prior. Fuel System The airplane's fuel system was comprised of an internal fuselage bag tank connected to integral wing tanks, with a total system capacity of 3,006 pounds. Two wing-mounted external "drop" tanks, mounted to the inboard wing pylons, increased fuel capacity by an additional 1,078 pounds per side. Fuel flowed from each external tank to the fuselage tank, and during transfer the integral tank system was automatically kept above 2,400 pounds until the external tanks were empty. The external tanks structural integrity was maintained through a series of internal ribs and stringers; the tanks did not contain baffles, and the fuel was free to move within the tanks during flight. The external tank fuel quantities were the subject of handling and maneuvering limitations in-flight, but no limitation existed regarding the fuel quantity held in the tanks during takeoff. The airplane's flight manual, "External Wing Fuel Tank - Limits" section noted the following, "10 seconds of straight-and-level flight is recommended before jettison to permit the fuel contents to stabilize." The accident pilot reported that the Hawk was the only airplane he had flown that does not place limitations on partially filled external tanks during takeoff, and that in his experience, takeoff with partially filled tanks is not recommended due to the increased sensitivity of pitch control, decrease in lateral directional control at low speeds, and the potential for tank damage. A BAe test pilot was interviewed during the investigation. He stated that although there are no external tank quantity limitations for takeoff, his personal practice is to always takeoff with the external tanks either full or empty, so that should they need to be jettisoned during departure, they will fall from the airframe in a predictable manner. The Air USA Chief Pilot reported that 75 percent of all Air USA missions were conducted with the external tanks partially filled at takeoff, and that they had no previous issues. The airplane had been experiencing intermittent external tank fuel transfer problems in early February 2015, when it was performing live fire exercise for the USMC in North Carolina. The external tanks were not consistently transferring fuel automatically to the internal tanks, and the airplane was flown to Air USA's primary maintenance facility in Quincy, Illinois, on February 13 for further diagnosis. Maintenance personnel replaced the internal tank high level float switch and refuel valve, and the airplane was placed back into service on February 20. During the repositioning flight from Quincy to MCAS Yuma, the external tanks again failed to transfer, so the pilot diverted to Salinas, Kansas. During the descent, the tanks started to transfer, and upon landing the transfer to the internal tank was complete. The pilot refueled the external tanks with 500 pounds of fuel per side, and flew to MCAS Yuma uneventfully. The airplane was not flown again until the day prior to the accident. On that morning (March 10), mechanics performed a pre-flight inspection, and serviced the airplane with fuel. The airplane flew two uneventful missions that day with fuel transferring normally from the partially filled external tanks. The third flight was a night mission, and was flown by the accident pilot. The airplane departed with full fuel; however, the external tanks again would not transfer, so he ended the mission early, returning with about 1,000 pounds of fuel in the internal tanks, and about 1,000 pounds in each external tank. On the morning of the accident, the Chief of Maintenance performed a ground run with the airplane in order to duplicate the transfer problem. The system operated normally, and after additional troubleshooting steps he concluded that the problem was still most likely an intermittent high level float switch in the internal tank. He instructed the ground crew to disconnect and secure the external tank transfer valves (commanding the valves to the normally open position, thereby allowing fuel to transfer directly to the internal tank). He briefed the pilot of the findings, advising him that the tanks may still not transfer, and he fueled the internal tanks to 3,000 pounds, and left the external tanks with about 600 pounds in each. METEOROLOGICAL INFORMATIONAn automated surface weather observation for MCAS Yuma was issued 8 minutes after the accident. It indicated variable wind at 3 knots, 10 miles or greater visibility, with scattered clouds at 12,000 ft, broken clouds at 18,000 ft and 25,000 ft, temperature 27 degrees C, dew point 01 degrees C, and an altimeter setting at 30.06 inches of mercury. AIRPORT INFORMATIONThe Hawk MK-67 was a swept-wing, two-seat, advanced trainer/light attack airplane, powered by a single Rolls-Royce Adour turbofan engine. The accident airplane was manufactured in 1992 by BAe Systems in the UK as part of a group of 20 Hawks configured specifically for export to the Republic of Korea Air Force (ROKAF). The airplane was then utilized by the ROKAF for training until it was sold to Air USA, along with 11 other Hawk MK-67's in September 2013. The sale included documentation for the fleet, along with a series of spare parts. The airplane was subsequently exported to, and registered in, the United States, where it was issued a special airworthiness certificate by the FAA in the experimental/exhibition category in March 2014. The later variants of the Hawk remain in production, with over 900 built since 1974. Maintenance Maintenance was performed in-house by Air USA mechanics on a continuous airworthiness basis, utilizing an OEM (original equipment manufacturer) inspection program. At the time of the accident, the airplane had accrued a total flight time of 5,625.3 hours. The engine total time was 3,782.7 hours, with the last overhaul occurring 155.7 flight hours prior. Fuel System The airplane's fuel system was comprised of an internal fuselage bag tank connected to integral wing tanks, with a total system capacity of 3,006 pounds. Two wing-mounted external "drop" tanks, mounted to the inboard wing pylons, increased fuel capacity by an additional 1,078 pounds per side. Fuel flowed from each external tank to the fuselage tank, and during transfer the integral tank system was automatically kept above 2,400 pounds until the external tanks were empty. The external tanks structural integrity was maintained through a series of internal ribs and stringers; the tanks did not contain baffles, and the fuel was free to move within the tanks during flight. The external tank fuel quantities were the subject of handling and maneuvering limitations in-flight, but no limitation existed regarding the fuel quantity held in the tanks during takeoff. The airplane's flight manual, "External Wing Fuel Tank - Limits" section noted the following, "10 seconds of straight-and-level flight is recommended before jettison to permit the fuel contents to stabilize." The accident pilot reported that the Hawk was the only airplane he had flown that does not place limitations on partially filled external tanks during takeoff, and that in his experience, takeoff with partially filled tanks is not recommended due to the increased sensitivity of pitch control, decrease in lateral directional control at low speeds, and the potential for tank damage. A BAe test pilot was interviewed during the investigation. He stated that although there are no external tank quantity limitations for takeoff, his personal practice is to always takeoff with the external tanks either full or empty, so that should they need to be jettisoned during departure, they will fall from the airframe in a predictable manner. The Air USA Chief Pilot reported that 75 percent of all Air USA missions were conducted with the external tanks partially filled at takeoff, and that they had no previous issues. The airplane had been experiencing intermittent external tank fuel transfer problems in early February 2015, when it was performing live fire exercise for the USMC in North Carolina. The external tanks were not consistently transferring fuel automatically to the internal tanks, and the airplane was flown to Air USA's primary maintenance facility in Quincy, Illinois, on February 13 for further diagnosis. Maintenance personnel replaced the internal tank high level float switch and refuel valve, and the airplane was placed back into service on February 20. During the repositioning flight from Quincy to MCAS Yuma, the external tanks again failed to transfer, so the pilot diverted to Salinas, Kansas. During the descent, the tanks started to transfer, and upon landing the transfer to th
The pilot’s initiation of an early rotation during takeoff, which led to an aerodynamic stall and loss of airplane control. Contributing to the accident were the pilot's use of nose up pitch trim and the operator's policy to use nose-up pitch trim during takeoff and the lack of oversight of the operator by the US Air Force. Contributing to the severity of the accident were US Marine Corps airport policies that allowed construction activities immediately adjacent to an active runway, which resulted in the airplane's collision with a truck.
Source: NTSB Aviation Accident Database
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