Factual Report: Loss of Control leads to Conquest breakup

 - October 8, 2007, 10:53 AM

CESSNA 425 CONQUEST I, SAN JOSE, CALIF., MARCH 6, 2002–At 10:35 a.m., Conquest I N444JV experienced a loss of control and broke up in flight in IMC. The aircraft was destroyed and the instrument-rated private pilot and two passengers were killed. The aircraft had departed Reid-Hillview Airport (RHV) in San Jose six minutes earlier and was en route to La Paz, Mexico, on an IFR flight plan.
The aircraft was climbing at about 2,000 fpm through 6,700 feet when it began a series of heading and altitude changes that were not consistent with its ATC clearance. The airplane turned right and climbed to 8,600 feet, then turned left and descended to 8,000 feet. It turned right and climbed to 8,500 feet and then began a rapidly descending right turn. At 10:34:33, as the aircraft was descending through 7,000 feet, the pilot advised ATC, “Four Juliet Victor, I just lost my needle give me…”

No further transmissions were received and the last radar return showed the airplane descending through 3,200 feet at about 11,000 fpm.

The normal rate of climb for this type of airplane under similar conditions is about 2,000 fpm. During the climb to 13,000 feet, one minute 50 seconds before the crash, N444JV’s maximum climb rate reached approximately 6,000 fpm. Over a 60-second period, the vertical speed fluctuated between 1,500 and 3,000 fpm up, decreased to zero, went back to 1,500 fpm up, followed by a rapid decrease to 500 fpm up. It then spiked to 5,500 fpm up, with a rapid reversal to 2,100 fpm down, then back to 1,500 fpm up before it rapidly built to 16,500 fpm down in the terminal descent.

The computed true airspeed showed a rapid increase to 220 knots at the time of the last mode-C altitude report. Maximum operating speed (VMO) is 230 knots. At 10:34:30, in the terminal descent, the airplane was in a 78-degree bank angle at a roll rate of six degrees per second. The computed vertical load factor after 10:33:30 oscillates rapidly between 0.75 and 2.3 g.

A ground witness heard a loud “screaming” jet sound and saw the aircraft descend out of the clouds “in a corkscrew pattern.” As the airplane neared the ground, it started to climb while still in the corkscrew turn. The airplane seemed to level off before it began an arcing and spiraling turn and disappeared behind a hill. Other witnesses heard a loud sound like an explosion or gunshot. The airplane then rolled level and continued in an arcing horizontal spin until it disappeared. These two witnesses reported that they saw parts falling from the airplane and that it was “smoking.”

The NWS radar summary chart for 10:15 a.m. depicted an area of echoes over California, ranging from light to moderate intensity (level 1 to 2) to strong to very strong intensity (level 3 to 4) activity in the immediate vicinity and southeast of the accident site.

Current airmets advised of occasional overcast ceilings below 1,000 feet and visibilities below three miles in clouds, precipitation, mist, mountain obscuration and turbulence over portions of the area.

The Conquest’s right wing with the engine was separated at about the center-section-to-wing-panel attach point; however, the wing remained attached to the fuselage via control cables, fuel lines and electrical wires. The forward and aft spars of the right wing revealed evidence of compressive and tensile overstress on the upper and lower spar caps, respectively, consistent with a primary failure of the wing in a positive direction. A metallurgical analysis report concluded that the spars failed due to overload fractures.

The right pitot heat switch was found in the on position, while the left switch was off. The left heat switch toggle lever was noticeably displaced to the left. The right switch was intact, while the toggle lever mechanism of the left switch was broken loose from the housing. Microscopic examination of the left switch housing fracture surface revealed embedded debris and wear marks indicative of an old fracture, which allowed an internal buildup of large coarse fibrous lint-like debris. The combined effects of the broken housing, the resulting misalignment of the toggle mechanism, the dirty contacts and the debris prevented reliable electrical switching of the device and allowed intermittently open electrical contacts.