NTSB Factual Report

On October 27, 2001, about 1545 Pacific standard time an amateur built, experimental Thomson Harmon Rocket II airplane, N325L, nosed over during an off-airport emergency landing near Perris, California. Neither the commercial pilot nor the commercial copilot were injured; the airplane was substantially damaged. Visual meteorological conditions prevailed for the personal flight operating under the provisions of 14 CFR Part 91, and no flight plan had been filed. The local area flight originated at Chino, California, about 1500.

The tandem-seat, low-wing airplane had recently been built and was undergoing its Phase 1 flight testing, as required by FAR Part 91.319. The purpose of the accident flight was to conduct a "brief proving run [and] systems check pertaining to average engine oil temperature indications." According to the written statement provided by the pilots, the pilot in the front seat was documenting the systems check, while the pilot in the back seat was flying and maintaining a visual lookout for other traffic.

The pilot flew the airplane to 7,500 feet msl, and conducted the systems checks. Upon completion of the checks, the rear-seat pilot initiated a left turn and descent to return to Chino. The front seat pilot noticed that the airplane was "gradually diverging from the desired heading" and asked the rear-seat pilot to turn the airplane back toward the right. It was at this time that both pilots "became aware that something was seriously wrong with the airplane's controls." The front-seat pilot applied aileron control input and got no reaction. He then applied a pitch input and "got a strange reaction." The pilots determined that the only reliable control inputs were through the rudder and electric pitch trim (though only "intermittent" pitch trim control). They were able to obtain "severely limited aileron control" from the rear-seat controls.

After assessing the situation, the pilots elected to land in a large clear area as soon as practical and decided on the March Air Reserve Base (ARB). The front-seat pilot made a mayday call on 121.5, squawked 7700 on the transponder, and informed air traffic control (ATC) they had "little to no control of the aircraft" and were landing at March ARB.

While making their way to March ARB, the pilots noticed the left wing "drop abruptly" on several occasions, which the pilots would control with rudder input. The pilots then elected to land straight ahead and make no additional turns. They observed a large plowed field south of March ARB and informed ATC they were going to land in the field. The front-seat pilot maintained directional control with the rudders and pitch control with power and electric trim. The rear-seat pilot attempted to maintain a wings level attitude with the control stick.

According to the pilots, the approach was "relatively flat and the touchdown was smooth." As the airplane slowed, the landing gear wheels began digging into the soft soil. The airplane eventually nosed over, coming to rest inverted. The pilots were pushed down into their seats and the canopy was partially broken, "collapsing around their heads." Witnesses assisted the pilots by lifting the right wing, allowing the pilots to "drop/slide/crawl out from the aircraft cockpit."

A review of the airplane's building plans revealed that the recommended flight control system utilizes both an outside and inside control tube. The front and rear control sticks are attached to the outer control tube, which attaches to the aileron control pushrods. The control sticks are also attached to the inner control tube, which moves fore and aft within the outer control tube, to control elevator movement. The outer control tube is then supported by hangar bearings (modified rod ends); one located aft of the front-seat control stick, and the other located forward of the rear-seat control stick. The fuselage frame supported the hangar bearings. This hangar bearing area is then covered and protected with a piece of sheet metal.

According to the Federal Aviation Administration inspector who conducted a post-accident examination of the airplane, the nut and bolt (AN 365-1032 and AN 3-7A, respectively) that attaches the outer control tube to the front hangar bearing were not in place. The AN 365-1032 nut is known as a Nylock self locking nut and incorporates the use of a nylon insert to prevent its rotation around the bolt once installed.

The airplane accumulated a total of 6.9 hours of flight time since its completion and issuance of its special airworthiness certificate, which was issued on March 8, 2001. The rear-seat pilot was the builder of the airplane.

NTSB Probable Cause

the airplane builder's failure to properly install a bolt and nut into the aileron and elevator flight control system. A contributing factor was the soft terrain conditions for the ensuing forced landing.