California

On May 18, 2011, about 1727 Pacific daylight time, a modified Boeing 707, registration N707AR, operating as Omega Aerial Refueling Services (Omega) flight 70 crashed on takeoff from runway 21 at Point Mugu Naval Air Station, California (KNTD). The airplane collided with a marsh area to the left side beyond the departure end of the runway and was substantially damaged by postimpact fire. The three flight crewmembers sustained minor injuries. 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. According to the Federal Aviation Administration (FAA), Omega, and the US Navy, the airplane was operating as a nonmilitary public aircraft under the provisions of 49 United States Code Sections 40102 and 40125. The accident flight crew consisted of a captain, first officer, and flight engineer who had flown with each other many times previously. The crewmembers reported conducting a normal preflight inspection. As the airplane taxied toward the runway, the reported wind was from 280º magnetic at 24 knots, gusting to 34 knots; the flight crew reported that the windsock showed very little change in the wind direction and a slight amount of gust. The crew had calculated a takeoff decision speed (V1) of 141 knots and a rotation speed (Vr) of 147 knots. The crew elected to add 5 knots to the rotation speed to compensate for the wind gusts and briefed a maximum power takeoff. The first officer, who was the pilot monitoring, stated that he advised the captain, who was the pilot flying, about advancing the power relatively smoothly to avoid a compressor stall with the crosswind, and the captain agreed. About 1723, air traffic control cleared the flight for takeoff from runway 21 and instructed the crew to turn left to a heading of 160º after departure. The captain applied takeoff thrust, and the first officer told investigators that, as the pilot in the right seat, he applied forward pressure on the yoke and right aileron input to compensate for the right crosswind. According to the crew, the takeoff roll was normal. At rotation speed, the captain rotated the airplane to an initial target pitch attitude of 11º airplane nose up. Shortly after liftoff, when the airplane was about 20 feet above the runway and about 7,000 feet down the runway, all three crewmembers heard a loud noise and observed the thrust lever for the No. 2 (left inboard) engine rapidly retard to the aft limit of the throttle quadrant. The captain stated that he applied full right rudder and near full right aileron to maintain directional control and level the wings, but the airplane continued to drift to the left. The captain reported that he perceived the airplane would not continue to climb and decided to “put it back on the ground.” Witnesses and a cell phone video from another Omega 707 crewmember observing the takeoff indicated that the No. 2 (left inboard) engine separated and traveled up above the left wing as the airplane was passing abeam taxiway A2. The inlet cowling for the No. 1 (left outboard) engine separated immediately thereafter, consistent with being struck by the No. 2 engine nacelle. The airplane began to descend with the remaining three engine power levers at maximum power, and the left wing dipped slightly (Pratt & Whitney indicated that loss of the inlet cowling on the No. 1 engine would increase drag, effectively resulting in less than zero thrust output). The captain said he lowered the nose and leveled the wings just as the airplane touched down on the runway between taxiway A2 and A1. The airplane made multiple contacts with the runway before drifting left and departing the runway surface before the airplane reached taxiway A1. The airplane crossed taxiway A and came to rest in the marsh area. According to the flight crewmembers, they observed flames in the cabin area and did not have time to perform an engine shutdown or evacuation checklist. The crew reported difficulty exiting the cockpit due to mud and debris blocking the cockpit door. All three crewmembers successfully evacuated through the left forward entrance via the escape slide.

Witnesses reported that the airplane’s takeoff ground roll appeared to be normal. Shortly after the airplane lifted off, it stopped climbing and yawed to the left. Several witnesses heard abnormal sounds, which they attributed to propeller blade angle changes. The airplane’s flight path deteriorated to a left skid and its airspeed began to slow. The airplane’s left bank angle increased to between 45 and 90 degrees, and its nose dropped to a nearly vertical attitude. Just before impact, the airplane’s bank angle and pitch began to flatten out. The airplane had turned left about 100 degrees when it impacted the ground about 1,500 feet from the midpoint of the 10,000-foot runway. A fire then erupted, which consumed the fuselage. Review of a security camera video of the takeoff revealed that the airplane was near the midpoint of the runway, about 140 feet above the ground, and at a ground speed of about 130 knots when it began to yaw left. The left yaw coincided with the appearance, behind the airplane, of a dark grayish area that appeared to be smoke. A witness, who was an aviation mechanic with extensive experience working on airplanes of the same make and model as the accident airplane, reported hearing two loud “pops” about the time the smoke appeared, which he believed were generated by one of the engines intermittently relighting and extinguishing. Post accident examination of the airframe, the engines, and the propellers did not identify any anomalies that would have precluded normal operation. Both engines and propellers sustained nearly symmetrical damage, indicating that the two engines were operating at similar low- to mid-range power settings at impact. The airplane’s fuel system was comprised of two separate fuel systems (one for each engine) that consisted of multiple wing fuel tanks feeding into a nacelle tank and then to the engine. The left and right nacelle tanks were breached during the impact sequence and no fuel was found in either tank. Samples taken from the fuel truck, which supplied the airplane's fuel, tested negative for contamination. However, a fuels research engineer with the United States Air Force Fuels Engineering Research Laboratory stated that water contamination can result from condensation in the air cavity above a partially full fuel tank. Both diurnal temperature variations and the atmospheric pressure variations experienced with normal flight cycles can contribute to this type of condensation. He stated that the simplest preventive action is to drain the airplane’s fuel tank sumps before every flight. There were six fuel drains on each wing that the Pilot’s Operating Handbook (POH) for the airplane dictated should be drained before every flight. The investigation revealed that the pilot’s previous employer, where he had acquired most of his King Air 200 flight experience, did not have its pilots drain the fuel tank sumps before every flight. Instead, maintenance personnel drained the sumps at some unknown interval. No witnesses were identified who observed the pilot conduct the preflight inspection of the airplane before the accident flight, and it could not be determined whether the pilot had drained the airplane’s fuel tank sumps. He had been the only pilot of the airplane for its previous 40 flights. Because the airplane was not on a Part 135 certificate or a continuous maintenance program, it is unlikely that a mechanic was routinely draining the airplane's fuel sumps. The witness observations, video evidence, and the postaccident examination indicated that the left engine experienced a momentary power interruption during the takeoff initial climb, which was consistent with a power interruption resulting from water contamination of the left engine's fuel supply. It is likely that, during the takeoff rotation and initial climb, water present in the bottom of the left nacelle tank was drawn into the left engine. When the water flowed through the engine's fuel nozzles into the burner can, it momentarily extinguished the engine’s fire. The engine then stopped producing power, and its propeller changed pitch, resulting in the propeller noises heard by witnesses. Subsequently, a mixture of water and fuel reached the nozzles and the engine intermittently relighted and extinguished, which produced the grayish smoke observed in the video and the “pop” noises heard by the mechanic witness. Finally, uncontaminated fuel flow was reestablished, and the engine resumed normal operation. About 5 months before the accident, the pilot successfully completed a 14 Code of Federal Regulations Part 135 pilot-in-command check flight in a King Air 90. However, no documentation was found indicating that he had ever received training in a full-motion King Air simulator. Although simulator training was not required, if the pilot had received this type of training, it is likely that he would have been better prepared to maintain directional control in response to the left yaw from asymmetrical power. Given that the airplane’s airspeed was more than 40 knots above the minimum control speed of 86 knots when the left yaw began, the pilot should have been able to maintain directional control during the momentary power interruption. Although the airplane’s estimated weight at the time of the accident was about 650 pounds over the maximum allowable gross takeoff weight of 12,500 pounds, the investigation determined that the additional weight would not have precluded the pilot from maintaining directional control of the airplane.

The pilot departed the airport mid-morning to fly to his home airport, 63 miles to the northwest. Weather conditions at the departureb airport were visual flight rules (VFR), the weather at the destination airport was not reported, and the weather conditions en-route were marginal VFR. The global positioning system (GPS) track for the flight indicated that the airplane departed from the airport and headed west along a highway corridor flying approximately 1,000 feet above ground level (agl) through a mountain pass. For the majority of the flight, the airplane maintained altitudes between 900 feet and 1,200 feet agl. Twenty-nine minutes after takeoff, the airplane’s GPS track turned southwest away from an area of concentrated precipitation and directly towards an isolated mountain peak that rose approximately 1,000 feet above the surrounding terrain. The pilot contacted the local air traffic control facility, reported his position and requested traffic advisories through the local airspace to his destination airport. About 6 minutes later, the pilot stated that he was having difficulty maintaining VFR and asked for an instrument flight rules (IFR)clearance. At the same time, the GPS track showed that the airplane came within 50 feet of the mountainous terrain. No further transmissions from the pilot were received. The final GPS position was recorded 1 minute later, at 500 feet agl and approximately half a mile from the crash site. The terrain rapidly ascended in this area and intersected the airplane's flight path over the remaining 1/2 mile. An airport located about 4 miles from the accident site and in an area of flat terrain 1,000 feet below the isolated mountain top, recorded weather at the time of the accident as few clouds at 900 feet agl, overcast clouds at 1,500 feet agl, and a variable ceiling between 1,200 and 1,800 feet agl, in drizzle. Weather radar images at the time of the accident depicted precipitation at the elevation and location of the accident site, indicating probable mountain obscuration.

Shortly after takeoff for a repositioning flight for the airplane’s upcoming annual inspection, numerous witnesses, including the two air traffic controllers, reported observing the airplane climbing out normally until it was about 1/2 mile beyond the runway. The witnesses stated that the airplane then underwent a short series of attitude excursions, rolled right, and descended steeply into a lagoon. All radio communications between the airplane and the air traffic controllers were normal. Ground-based radar tracking data indicated that the airplane's climb to about 500 feet was normal and that it was airborne for about 40 seconds. Postaccident examination of the airframe, systems, and engines did not reveal any mechanical failures that would have precluded continued normal operation. Damage to both engines’ propeller blades suggested low or moderate power at the time of impact; however, the right propeller blades exhibited less damage than the left. The propeller damage, witness-observed airplane dynamics, and the airplane’s trajectory were consistent with a loss of power in the right engine and a subsequent loss of control due to airspeed decay below the minimum control speed (referred to as VMC). Although required by the Federal Aviation Administration (FAA)-approved Airplane Flight Manual, no evidence of a cockpit placard to designate the single engine operating speeds, including VMC, was found in the wreckage. The underlying reason for the loss of power in the right engine could not be determined. The airplane's certification basis (Civil Air Regulation [CAR] 3) did not require either a red radial line denoting VMC or a blue radial line denoting the single engine climb speed (VYSE) on the airspeed indicators; no such markings were observed on the airspeed indicators in the wreckage. Those markings were only mandated for airplanes certificated under Federal Aviation Regulation Part 23, which became effective about 3 years after the accident airplane was manufactured. Neither the Federal Aviation Administration (FAA) nor the airplane manufacturer mandated or recommended such VMC or VYSE markings on the airspeed indicators of the accident airplane make and model. In addition, a cursory search did not reveal any such retroactive guidance for any twin-engine airplane models certificated under CAR 3. Follow-up communication from the FAA Small Airplane Directorate stated that the FAA has "not discussed this as a possible retroactive action... Our take from the accident studies is that because of the accident record with light/reciprocating engine twins, the insurance industry has restricted them to a select group of pilot/owners…" Toxicology testing revealed evidence consistent with previous use of marijuana by the pilot; however, it was not possible to determine when that usage occurred or whether the pilot might have been impaired by its use during the accident flight.

The pilot was conducting a cross-country flight with a certified flight instructor (CFI). During the climb-to-cruise phase of the flight, as the airplane was ascending through 16,000 feet mean sea level (msl), the pilot noticed a reduction in manifold pressure. He advanced the throttle and observed an increase of one or two inches of manifold pressure. Shortly thereafter, the pilot heard a loud bang originate from the engine followed by an immediate loss of engine power. The pilot and CFI attempted to troubleshoot the engine anomalies and noted that it seemed to respond with the low boost "on", however it began to run rough whenever the throttle was advanced more than half way. They diverted to a nearby airport and conducted an emergency descent. As the airplane approached the airport, the pilot descended through an overcast cloud layer and attempted to enter the airport traffic pattern. While on final approach to the airport, the pilot thought the airplane was high and extended the landing gear and applied flaps. Shortly thereafter, the airspeed and altitude decreased drastically and the pilot realized he was too low. The pilot applied throttle and noticed no change in engine performance. The airplane subsequently struck a fence and landed hard in an open field just short of the airport, which resulted in structural damage to the fuselage and wings. A postaccident examination of the engine revealed that the induction elbow for cylinders 1-3-5 (right side) was displaced from the throttle and metering assembly where the elbow couples with the throttle and metering assembly by an induction hose and clamp. The clamp was secure to the induction hose, however, the portion of the clamp that should have been installed
beyond the retention bead on the throttle and control assembly was observed on the inboard side of the bead on the induction elbow. Review of the aircraft maintenance logbooks revealed that cylinders 4 and 5 were recently replaced prior to the accident flight due to low compression. The replacement of these cylinders required removal of the induction system to allow for cylinder removal and installation. In addition, a manufacturer service bulletin stated that during the reinstallation of the induction system, one must slide the induction hose and clamp(s) onto one of the tubes to be joined and that the connection joint and both tube beads are to be positioned in the center of the induction hose. The clamps should be installed in a position centered between the tubing bead and end of the induction hose.

The pilot was on a cross-country flight near mountainous terrain when he encountered clouds along the flight path. A comparison of recorded radar data and weather reports in the local area indicated that the pilot was maneuvering near the cloud bases in an area with low visibility and ceilings. Based on the erratic and circling flight path, it is likely that the pilot was having difficulty determining his location and desired flight track when the airplane collided with terrain. Post accident examination of the airframe and engine revealed no mechanical failures or malfunctions that would have precluded normal operation.