WPR16FA166

Foreign object debris in the engine's main fuel control unit, which restricted fuel flow and subsequently resulted in the loss of engine power. Contributing to the accident was the installation or addition of an extra seal during the main fuel control unit rebuild.

The pilot of the experimental turbojet airplane, the lead airplane of a flight of two, was returning to the airport after providing combat training support. He led the formation to the overhead pattern, and shortly after the break to downwind, the engine lost power. The engine did not respond to throttle movements. The pilot started a turn toward the airport; however, he realized that he was unable to make the runway, so he turned left away from the runway toward a field and then successfully ejected from the airplane. The airplane subsequently struck terrain and was consumed by fire. No anomalies were noted during the initial airframe and engine examination that would have precluded normal operation. However, examination of the main fuel control (MFC) revealed foreign object debris (FOD) from a nonmetallic material inside the MFC unit. The material was identified as a nylon 6/6 material that was consistent with other seal material in the unit. However, all similar seal material inside the MFC was at its expected location. Further, the flow path made it unlikely that any nylon 6/6 material within the MFC could have migrated from known sources during the postimpact fire to where the FOD was located. Additionally, it was unlikely the nylon material was deposited into the MFC after the accident because examination of fuel components downstream of the MFC revealed no anomalies, obstructions, or nylon material. The MFC was rebuilt about 17 years before the accident, and the airplane had flown about 425 hours since then. It is likely that the FOD was part of an extra seal that was inadvertently installed or fell into the unit at the last maintenance overhaul. Subsequently, the FOD in the MFC eventually became positioned in such a way that restricted fuel flow and caused the loss of engine power.

LSV is a United States Air Force (USAF) owned, towered airport, with a field elevation of 1,869 ft. The airport was equipped with two concrete runways, runway 3L/21R (10,120 ft long by 200 ft wide) and runway 3R/21L (10,051 ft long by 150 ft wide). Airport remarks for the runway 21R, listed a caution for a crane training site north of the departure end of runway 03L, maximum height was 100 ft. The canopy, both ejection seats, and parachutes were examined by the NTSB IIC with a life support specialist from Draken International Inc. The ejection sequence appeared to function normally, and no anomalies were observed with the equipment. The investigation was unable to determine the ejection altitude. However, the pilot stated he may have delayed his ejection decision. Further, witnesses reported the ejection occurred just a few seconds prior to the airplanes impact, and the surveillance video confirmed what the witnessed observed. A review of the ejection seat assembly revealed that all inspections and time change requirements were current, with the exception of the separation rocket motor inspection, which were due on both ejection seats in July 2015. However, an extension of the inspections, was approved by the FAA, with the manufacturer's assessment memorandum. Draken International Inc. operated the airplane and was a contract air support organization that provided aggressor support, red air, and close air support for the U.S military, Department of Defense, and allied militaries globally. The organization operated the world's largest commercial fleet of tactical ex-military jet airplanes consisting of about 150 tactical fighter jet airplanes. A review of data from LSV, automated weather observation station revealed that at 0756 conditions were wind calm, visibility 10 statute miles, scattered clouds at 11,000 ft, temperature 30°C, dew point 9°C, and an altimeter setting of 29.91 inches of mercury. Toxicology testing was not performed on the pilot by the FAA, and the decision to conduct testing was left to be determined by Draken International Inc. under their established guidelines. According to the Draken International Inc, the pilot's results were negative from the testing performed by the USAF. The pilot held an airline transport pilot certificate with ratings for airplane single-engine land, multi-engine land, and instrument. He also held ratings for a flight instructor certificate in airplane single-engine and instrument. Additionally, he was type rated in the Boeing 737, and held an experimental airplane authorization for the Douglas Corporation A-4 Skyhawk. The pilot was issued a first-class airman medical certificate on August 15, 2016, without limitations or waivers. The pilot reported that he had accumulated 8,076 total flight hours, 230 hours in the accident make and model airplane, and had flown 211 hours in the last 3 months. He also had previously flown the General Dynamics (now Lockheed Martin) F-16 Fighting Falcon airplane for the United States Air Force and logged about 5,200 hours in it. The TA-4K Skyhawk was a swept-wing, two-seat jet airplane powered by a single Pratt & Whitney J52 turbojet engine that was manufactured in 1970 by the Douglas Corporation and later upgraded by Draken International Inc. The airplane was developed for the U.S. Navy and Marine Corps during the Vietnam war era. Maintenance was accomplished by Draken International Inc. A review of the maintenance logbooks revealed that the last continuous airworthy inspection was accomplished on July 29, 2016, at an airframe time of 6,850.2 hours. The engine had a total time of 3,211.5 hours, 428.7 hours since inspection, and 1,826.3 hours since overhaul. The airplane utilized a single Pratt & Whitney J52 turbojet engine that produced about 9,200 lbs of thrust. The J52 is a continuous flow, gas turbine engine which incorporates a split 12 stage, axial-flow compressor and 2 turbine stages. A 5-stage low-pressure compressor (LPC) is driven by a single-stage low pressure turbine (LPT) front compressor drive turbine rotor and a 7-stage high compressor (HPC) is driven by a single-stage high pressure turbine (HPT) rear compressor drive turbine rotor. The accident airplane had an engine write-up on May 18, 2016, for a thrust deficiency while performing acrobatic maneuvers. The write-up stated that the engine seemed like it was not producing the correct amount of thrust. Military (MIL) power, also referred to as full-power or 100% power, would only indicate 98% power, with a noticeable humming noise, and the airplane became slow during acrobatics with the normal power settings. As a result, maintenance accomplished an engine run to 75% and all engine parameters checked good. The write-up also stated that maintenance would monitor the engine for any trends at 75% power or greater. Fuel servicing records indicated that the accident airplane was fully refueled with 916 gallons on the morning of the accident. The fuel truck that serviced the airplane had a fuel sample tested after the accident, and the sample was within established standards. The airplane forms indicated 8,200 pounds of fuel was onboard, prior to the flight. According to the pilot, he confirmed that about 8,000 pounds of fuel was onboard the airplane during preflight. The pilot further stated that during the flight, the formation accomplished about 3 fuel checks in the area. According to the accident pilot's wingman, during the flight, after their area work was complete, a final battle damage assessment check with the lead airplane was accomplished, prior to returning to the LSV. The lead airplane reported 2,300 pounds of fuel and his status as the wingman was 1,800 pounds of fuel. Draken International Inc.'s operations procedures stated that the minimum fuel for the airplane was 800 pounds and emergency fuel was 500 pounds. Additionally, the fuel at initial or the final approach fix was 1,000 pounds. The aircraft's flight manual lists the following procedures for a Low Altitude Loss of Thrust/Flameout: Throttle – Check full forward. Zoom climb. If below 1,500 above ground level (agl) and 250 knots indicated airspeed (KIAS) - Eject. Throttle – Retard. Fuel Control switch – Manual. - If thrust is not regained immediately, proceed as follows: RAT (Ram Air Turbine) – Deploy Throttle - Ignition, then idle. (Monitor EGT for signs of relight). External Stores – Jettison, if required. Throttle – Cautiously advance. Below 5,000 ft agl – Nil engine response, eject. Above 5,000 ft agl – Airstart. (if time and altitude permit, establish 250 kts glide and commence airstart). The TA-4K aircraft flight manual stated: ejection is mandatory "when an engine flameout occurs below 1,500 ft agl and 250 kias," except when unusual circumstances clearly dictate otherwise. Examination of the accident site by the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) revealed that the airplane impacted desert terrain at an elevation of about 1,926 ft. All major components of the airplane were contained within the main wreckage site. The airplane impacted the ground at a relatively shallow angle and on a magnetic heading of about 087°. After impact, the airplane continued to slide forward on the ground for about 30 ft and then struck and breached a concrete wall. The airplane continued to slide forward for about another 45 ft before coming to rest on its right side against a berm. A post-crash fire ensured, and the debris was mostly contained from the concrete wall to where the airplane came to rest. The fuselage sustained substantial damage to most of its right side, from the vertical stabilizer forward to the cockpit area. The left speed brake was extended. The right speed brake was separated but a