Narrative:A Boeing 707-321B aerial tanker plane, registered N707AR, was destroyed when it suffered a runway excursion accident on takeoff from Port Hueneme-Point Mugu NAS, CA (NTD). There were three crew members on board and all escaped unhurt.
The flight crew indicated that they delayed their takeoff due to high wind conditions. Once the winds were within limits, they reported that startup was normal. Prior to takeoff, they decided to add 5 knots to their rotation speed, and power up slowly and as smoothly as possible.
The captain was the flying pilot. The first officer called critical engine failure recognition speed (V1) reference speed at 141 knots, and rotation speed (Vr) at 150 knots. The captain rotated the airplane, and it then lifted off about 7,000 feet down the 11,000-foot runway. About 20 feet above ground level (agl), the number two engine (left inboard) throttle lever slammed back to the idle position. The No. 2 engine pylon had separated from the left wing. The No. 2 engine nacelle and pylon assembly struck the No. 1 engine nacelle, causing the No. 1 engine inlet cowl to separate, which degraded the engine’s ability to produce thrust and resulted in a significant loss of thrust on the left side of the airplane.
The flight crew reported that the airplane began to drift to the left and descend. The captain lowered the pitch slightly and leveled the wings just prior to the airplane contacting the runway. He informed the other crew members that they were going to put it back down. He placed the throttle levers in the idle position, and activated the speed brakes. The airplane departed the left side of the runway surface; the crew reported a couple of impacts and then one final violent impact prior to the airplane coming to rest in a wetland marsh.
The flight crew had to force the cockpit door open due to debris that had piled up against it. They noted significant damage from the forward galley aft, and a large fire in the vicinity of the left wing. They opened the left main cabin door, and deployed the slide. They exited into the mud, and made it to dry land and away from the burning wreckage.
Investigators examined the wreckage at the accident site. The observed debris field extended 4,120 feet on a heading of 218 degrees. The first pieces of wreckage found along the debris path were fragments of the number two (left inboard) engine pylon; they were just past taxiway Alpha 2, about 7,500 feet from the beginning of runway 21. The number one engine (left outboard) nose cowl was about 450 feet further into the debris field and left of the runway surface in the grass infield.
The number two engine nose cowl was near the runway arresting gear on the left side of the runway at the 8,500 foot point. The number two engine was about 230 feet further, and on the left side of the runway surface.
The airplane departed the asphalt surface near taxiway Alpha 1, which was 9,500 feet from the departure end of the runway. Ground scars continued through the grass infield to taxiway Alpha at the end of the runway. The number one engine was in the grass infield near taxiway Alpha.
The main wreckage came to rest in a wetland marsh left of the runway overrun, and caught fire. Fire consumed the top of the cabin and the cockpit. The main wreckage consisted of the cockpit, cabin, right wing with the number three (right inboard) engine partially attached, empennage, and the inboard half of the left wing, which sustained thermal damage and was under water. Scattered debris aft of the main wreckage included the nose gear, remnants of the burned outboard left wing, right main landing gear truck, and number four (right outboard) engine.
A visual examination of a fracture surface on the number two engine pylon inboard mid-spar support fitting determined that it was flat and discolored with an arcing terminus.
The aircraft was registered and operated by Omega Air Inc., an air refueling contractor that uses specially-equipped and converted civilian airplanes to serve as air refueling platforms for the military. The flight was conducted under the provisions of a contract between Omega and the US Naval Air Systems Command (NAVAIR) to provide aerial refueling of Navy F/A-18s in offshore warning area airspace.
PROBABLE CAUSE: "The NTSB determines that the probable cause of this accident was the failure of a midspar fitting, which was susceptible to fatigue cracking and should have been replaced with a newer, more fatigue-resistant version of the fitting as required by an airworthiness directive. Also causal was an erroneous maintenance entry made by a previous aircraft owner, which incorrectly reflected that the newer fitting had been installed."
No. 2 engine on the runway with MLG tire marks
No. 2 engine and pylon
No. 1 engine
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