N329AX

HISTORY OF FLIGHT

On May 18, 2012, at 1212 Pacific standard time, a Hawker Hunter Mk 58, single-seat turbojet fighter aircraft, N329AX, operated by ATAC (Airborne Tactical Advantage Company) under contract to Naval Air Systems Command (NAVAIR) crashed while on approach to Naval Air Station Point Mugu, California (NTD). The sole pilot aboard was killed, and the airplane was destroyed by impact forces. The flight was conducted under the provisions of a contract between ATAC and the U.S. Navy to provide ATAC owned and operated aircraft to support adversary and electronic warfare training with VMFAT-101 (Marine Fighter Attack Training Squadron 101). The airplane was operating as a non-military public aircraft under the provisions of Title 49 of the United States Code Sections 40102 and 40125.

The airplane departed NTD at 1113 as the wingman in a flight of two Hunters, intending to participate in a fleet training exercise in off shore warning area W291. The flight's radio call sign was "COUGR21."

As the accident airplane was not equipped with any recording devices, and all radio communications with the accident pilot were via air-to-air with the flight lead, the sequence of events is based upon the flight lead's interview with investigators and information he separately provided to ATAC personnel following the accident.

According to the flight lead, shortly after takeoff, the accident pilot advised him, on an air-to-air frequency, that his lateral stick trim was almost all the way to the right in order to maintain wings level flight. The pilots discussed a maintenance issue involving a fuel transfer valve two days before the accident flight and concluded that an under-fueled right outboard tank was the likely cause.. The flight lead asked the accident pilot if he had checked the tank during preflight and if there was fuel in it and the accident pilot replied "I don't know." The flight lead said he recommended that the accident pilot return to the airport, "because we knew we had an issue right off the bat." The accident pilot elected to continue the flight and shortly afterward reported that the right outboard tank was indicating empty, much earlier than normally expected.

As the pilots continued to discuss the problem, the accident pilot also related that he believed that the airplane was also not drawing fuel from the left wing and external tanks. The accident pilot reported that he turned off the right boost pump, in an attempt to balance fuel, by configuring the fuel system so that the engine would draw fuel only from the left side.

After arrival in the training area, the flight lead indicated that he repeated his suggestion to return, but the accident pilot said he would give it more time to see if he could get fuel to transfer from the left side. Fuel transfer from the left outboard tank could only be confirmed once it empties (the magnetic indicator would change from black to white indicating empty). The accident pilot also reported that he saw the fuel quantity indicator on the left inboard tank began to show a reducing quantity in that tank, indicating 1300 pounds, and he thought he was getting a slow transfer from that tank.

Additionally, the low fuel light for the left feed tank illuminated, indicating that the tank was not full although there was still fuel in other tanks that should have transferred into the feed tank to keep it full. When this light illuminated, the accident pilot, at the flight lead's suggestion, cycled the left fuel transfer switch multiple times to read the front tank contents, as the gauge would indicate only the front tank quantity while the valve was in transit. At this point, after further discussions with the flight lead, the accident pilot decided to return to base because there were indications that fuel was not correctly transferring.

The flight lead elected to accompany him, and the pilots switched positions, with the accident pilot taking lead and flight lead flying echelon left (slightly above and behind to the left). During the return flight, the pilots continued to discuss the airplane systems and what indications the accident pilot should look for. The flight lead noted that the information relayed did not make sense regarding the fuel system compared to the cockpit indications. The accident pilot repeated that he thought he was getting a slow transfer from the left side fuel system, but could not determine the actual quantity of fuel in the left outboard tank (which would be the first to be depleted if fuel was transferring). He did not indicate the stick position or asymmetry. The pilots estimated how long it would normally take for the left outboard tank to reach empty, however, it was still indicating it contained fuel. About 10 to 15 minutes from the airport, the accident pilot related that he saw 1000 pounds remaining in the left inboard tank.

ATC restricted the flight to 15,000 feet until nearing the airport, and then cleared the flight for descent. Neither the pilots nor ATC declared an emergency or urgency situation. The flight lead stated that the accident pilot did not appear to have conducted a controllability check. The aircraft crossed the shoreline at about 6,000 to 7,000 feet on a left downwind leg for runway 21. They planned to extend the downwind leg to lose altitude and turn in for a long straight-in final approach. The flight lead reported that at a point approximately abeam the approach end of the runway at about 5,000 feet and an indicated airspeed of about 270 to 280 knots, the accident airplane began "a nice gentle left hand turn" which he said "didn't make sense." The flight lead said he was about 100 feet above and behind the accident airplane when it began to turn across his path, and it continued to turn and roll until it "turned into a barrel roll" on a course of about 030 degrees. He stated that it was a slow roll but it "was evident it was out of control." When the loss of control occurred, the flight had been airborne about 60 minutes.

The flight lead said that the accident airplane did not appear to slow down but he reactively maneuvered as needed to stay in position, although he noted that the airplane generally does not slow down noticeably in a descent if the throttle was already set at 6,000 rpm or less. They had not yet begun configuring for landing. The flight lead leveled off but banked left to observe the accident airplane pass below, which he said seemed to be briefly in level flight, and then "saw it snap over" and enter a steep nose down, left rolling maneuver. The flight lead reported he saw "lots of fuel coming out of the [external] tanks." He saw two objects come out as he was yelling "eject" on the radio, and initially thought they may have been the canopy and the ejection seat. He later concluded the objects were the left side external tanks separating from the wing. The airplane impacted less than three seconds later. He saw the two objects impact about 100 yards from the airplane (consistent with the ground position of the left external tanks). The airplane impacted at a steep angle and a small fireball was visible. The flight lead did not see a chute, and then he called the tower to launch the search and rescue effort.

Previous Flight of N329AX

On May 16, 2012, the airplane was flown by a different pilot on a similar mission, and experienced a fuel transfer incident. The accident pilot was the wingman on this flight. The aircraft fuel tanks had been filled and he also had an electronic warfare pod on the right wing station.

The preflight, start-up, and taxi out were uneventful. On initial climb-out, he started noticing an asymmetry developing so he checked the fuel system. He said the left transfer system indicator was showing no fuel was coming from the left internal or external tanks to the feeder tank. He cycled the selector switch between Auto, Rear, and Wing, six to eight times without any changes. During this time he kept adding right stick and right trim as no fuel was burning from the left wing tanks. At this point he was about 4 to 5 minutes into the flight when the left low fuel light came on indicating fuel was being drawn from the feeder tank. He elected to turn off the left fuel boost pump to preserve fuel in the left feeder tank.

The incident pilot said his wingman (the accident pilot) stated that nothing appeared unusual from the exterior and no fuel appeared to be venting. He applied a positive and negative G which did not have any affect. He then decided to return to land and his wingman continued the mission. During the return to the airport, he conducted a controllability check where he found that the left wing was heavier than the right wing. About that time he saw that the right wing outboard tank magnetic indicator turned white, indicating that tank was empty. He landed on runway 3 with no difficulty, and estimated the total flight time as about 17 to 18 minutes.

Troubleshooting and Maintenance

After landing, and before the incident pilot shut down the engine, maintenance personnel checked the fuel transfer valve and motor while he cycled the left wing switch to rear but the transfer valve was not working. The attempt to troubleshoot took about 15 minutes. (Tests at Lortie Aviation indicated the engine ground idle fuel burn was about 145 pounds per hour.) He believed that after shutdown, the left side exterior tanks were still full, the right outboard was empty, and the right inboard had burned some fuel but was not yet empty. Investigators estimated that the fuel burn during the incident flight would have left the airplane with a shutdown fuel load of approximately 6000 pounds. The incident pilot conducted a post-flight debrief with the wingman (accident pilot) after his return.

The ATAC Point Mugu Maintenance Manager (MM) took part in the troubleshooting. He said the procedure they followed was to first...