ROCKWELL COMMANDER 690A, BISHOP, CALIF., AUG. 11, 2002–The pilot of Aero Commander N690TB, which crashed near Bishop Airport (BIH), “failed to maintain an appropriate terrain clearance altitude while maneuvering in the traffic pattern due to the sensory and visual illusions created by a lack of ground reference lights and/or terrain conspicuity [sic], and the dark nighttime conditions,” said the NTSB in determining the probable cause of this accident. The accident occurred at 1:23 a.m. local during a descending turn from base to final approach. The impact destroyed the airplane and killed the pilot and three passengers. VMC prevailed during the nighttime flight, and no flight plan had been filed. The pilot had reported no difficulty with the airplane. With Bishop in sight, he started a VFR descent from 17,500 feet and radar service was terminated at 16,000 feet.
Two witnesses on the ground saw the airplane enter the pattern, turn left onto base for Runway 30 and plummet. During the turn, the airplane’s bank angle suddenly increased, reaching between 70 and 90 degrees. Then the airplane descended rapidly. The airplane hit level desert terrain about 1.6 miles southeast of the threshold, descending in a left wing- and nose-low attitude. There were no ground reference lights in the accident-site area. An examination of the airplane structure, control systems, engines and propellers revealed no evidence of pre-impact malfunctions or failures. The pilot was familiar with the area, but he had made only two nighttime landings within the preceding 90 days.
About two weeks earlier, pressurization leaks were found on the airplane, most along fuselage seams, windows and the main entry door seal. The aircraft was serviced, but no log entry was made approving the airplane for return to service. Later, another pilot reported cabin pressure to be 3.2 psi, well below the normal 5.2 psi, and a passenger noticed an air leak in the floor air duct. The owner-pilot said a part had been ordered and repair was plann