United States of America

During an aerial fire suppression mission for the California Department of Forestry (CDF), two Grumman TS-2A airplanes, operating as Tanker 92 (N442DF) and Tanker 87 (N450DF), collided in flight while in a holding pattern awaiting a retardant drop assignment on the fire. All of the airplanes fighting the fire were TS-2A's, painted in identical paint schemes. The Air Tactical Group Supervisor (AirTac) was orbiting clockwise 1,000 feet above the tankers, who were in a counterclockwise orbit at 3,000 feet mean sea level (msl). The pilots of both aircraft involved in the collision had previously made several drops on the fire. Records from the Air Tac show that Tankers 86, 91, and 92 were in orbit, and investigation found that Tanker 87 was inbound to enter the orbit after reloading at a nearby airport base. AirTac would write down the tanker numbers as they made their 3-minutes-out call, and usually ordered their drops in the same order as their check-in. The AirTac's log recorded the sequence 86, 91, 21, and 92. The log did not contain an entry for Tanker 87. Other pilots on frequency did not recall hearing Tanker 87 check in. Based on clock codes with 12-o'clock being north, the tankers were in the following approximate positions of the orbit when the collision occurred. Tanker 92 was at the 2-o'clock position; Tanker 86 was turning in at the 5-o'clock position; and Tanker 91 was in the 7-o'clock position. The AirTac's log indicated that Tanker 92 was going to move up in sequence and follow Tanker 86 in order to drop immediately after him. Post accident examination determined that Tanker 92's flaps were down, indicating that the pilot had configured the airplane for a drop. Tanker 92 swung out of the orbit wide (in an area where ground witnesses had not seen tankers all day) to move behind Tanker 86, and the pilot would likely have been focusing on Tanker 86 out of his left side window. Tanker 87 was on line direct to the center of the fire on a path that witnesses had not observed tankers use that day. Reconstruction of the positions of the airplanes disclosed that Tankers 86 and 91 would have been directly in front of Tanker 87, and Tanker 92 would have been wide to his left. Ground witnesses said that Tanker 87 had cleared a ridgeline just prior to the collision, and this ridgeline could have masked both collision aircraft from the visual perspective of the respective pilots. The right propeller, engine, and cockpit of Tanker 92 contacted and separated the empennage of Tanker 87. The propeller chop was about 47 degrees counterclockwise to the longitudinal axis of Tanker 87 as viewed from the top. The collision appeared to have occurred about 2,500 feet, which was below orbit altitude. CDF had no standard operating manual, no established reporting or entry point for the holding orbits, and a tanker could enter any point of the orbit from any direction. While no standardized procedures were encoded in an operating manual, a CDF training syllabus noted that a tanker was not to enter an orbit until establishing positive radio contact with the AirTac. The entering tanker would approach 1,000 feet below AirTac's altitude and stay in a left orbit that was similar to a salad bowl, high and wide enough to see and clear all other tankers until locating the tanker that it was to follow, then adjust speed and altitude to fall in behind the preceding airplane.

The airline transport rated pilot was attempting to land under visual flight rules for a scheduled passenger pick-up and subsequent charter flight. The pilot was communicating with a pilot at the airport, who was utilizing a hand held radio. The accident pilot reported he was not able to see the runway lights due to ground fog and continued to circle the airport for about 20 minutes. The pilot on the ground stated the airplane appeared to be about 1,500 feet above the ground when it circled, and then entered a downwind for runway 26. He was not able to hear or see the airplane as it flew away from the airport. He then began to hear the airplane during its final approach. The airplane's engines sounded normal. He then heard a "terrible sound of impact," followed by silence. When he arrived at the accident site, the airplane was fully engulfed in flames. The airplane impacted trees about 80-feet tall, located about 2,000 feet from, and on a 240 degree course to the approach end of runway 26. Several freshly broken tree limbs and trunks, up to 15-inches in diameter, were observed strewn along a debris path, which measured 370 feet. Examination of the wreckage did not reveal any pre-impact malfunctions. The weather reported at an airport about 19 miles south-southeast of the accident site, included a visibility of 1 3/4 miles, in mist, with clear skies and a temperature and dew point of 17 degrees Celsius. Witnesses in the area of the accident site generally described conditions of "thick fog" and a resident who lived across from the accident site stated visibility was "near zero" and he could barely see across the road.

While departing from the airport, with the second-in-command (SIC) at the controls, the airplane impacted a fence, and subsequently the ground about 1,000 feet beyond the departure end of the runway. A witness on the ramp area south of the runway, stated that he heard the engines spool up; however, due to the fog, he could only see the strobe lights on the airplane. He then observed the airplane rotate about 3,500 feet from the departure end of the runway and begin to climb at a steep angle, before losing sight of it when it was about 150 feet above ground level. The weather reported, at 0550 was, calm winds; 1/2 statute miles of visibility, fog; overcast cloud layer at 100 feet; temperature and dew point of 17 degrees Celsius. Excerpts of the cockpit voice recorder (CVR) transcript revealed that the flightcrew discussed the prevailing visibility at the airport on numerous occasions, and indicated that it appeared to be less than one mile. Examination of the wreckage revealed no anomalies with the airframe or engines. According to the FAA Instrument Flying Handbook, "Flying in instrument meteorological conditions (IMC) can result in sensations that are misleading to the body's sensory system...A rapid acceleration, such as experienced during takeoff, stimulates the otolith organs in the same way as tilting the head backwards. This action creates the somatogravic illusion of being in a nose-up attitude, especially in situations without good visual references. The disoriented pilot may push the aircraft into a nose-low or dive attitude."

The airplane's fuel tanks were fueled from a self serve fuel pump with 63 gallons of fuel prior to departure. The pilot initiated the takeoff roll from runway 30 with a 10 knot tailwind. The airplane was reported to have used the entire length of the runway during the takeoff roll. The airplane became airborne, attained a height approximately 100 feet agl, entered a descent, and subsequently, impacted the ground. A post accident fire consumed the airplane. Immediately following the accident, the pilot reported to local authorities that "he was leaving the airstrip and the plane stalled due to lack of airspeed." The 3,000-foot runway rises rapidly at its north end, such that the departure end of runway 30 was 50 feet higher than the approach end. At the time of the accident, the wind was from 130 degrees at 10 knots and the density altitude was 4,136 feet. Examination of the engine did not reveal any anomalies that would have precluded its operation prior to the accident.