NTSB Factual Report

On July 7, 2003, at 1256 mountain standard time, a Piper PA-28-181, N288PA, collided with a tree during an emergency landing 18 miles northeast of Phoenix Deer Valley Airport (DVT), Phoenix, Arizona. The emergency landing was precipitated by a loss of aileron and elevator control while maneuvering. Pan Am International Flight Academy, Phoenix, operated the airplane under the provisions of 14 CFR Part 91 as an instructional flight. The private pilot, the sole occupant, was not injured; the airplane sustained substantial damage. The local flight departed DVT about 1215. Visual meteorological conditions prevailed, and a flight plan had not been filed.

During an interview with the National Transportation Safety Board investigator-in-charge (IIC), the pilot, who was working toward his commercial certificate, stated that he departed DVT about 1215 to practice maneuvers. He attempted to make a clearing turn at 5,000 feet above ground level (agl) by moving the control wheel to the right, but the airplane did not respond. He looked at the wing as he continued moving the control wheel and realized that the ailerons were not operating. The pilot immediately contacted Deer Valley tower and declared an emergency. He landed the airplane on a dirt road using rudder and throttle to control movement. During the landing, the right wing impacted a tree. The wing was displaced upwards, blocking the cabin door and baggage door from opening. The door assembly was removed at the hinges by a pedestrian in order to evacuate the pilot.

The design of the control wheel to control column interface utilizes a nut plate installed inside the column. A screw and collar are then inserted through the bottom of the control wheel and into the nut plate inside the column to secure it to the column. Various Federal Aviation Administration (FAA) and Society of Automotive Engineers (SAE) publications note that for proper clamping action at least three threads should show above the nut. FAA publication AC 43.12 notes that screws and bolts should ideally be put in from the top down when at all possible to prevent the effects of gravity and vibration from loosening the fasteners.

During an on scene examination of the airplane, the FAA inspector found the attaching screw and nut plate from the left control wheel on the floor. The screw and nut plate attaches the control wheel to the control column. The head of the screw was painted and did not appear to have been removed by a screwdriver. The inspector moved the left control wheel and found that the column would not move. He moved the column and verified aileron continuity. He also noted excess oil on the control column.

The left screw was installed and then removed with a screwdriver. The marking on the head of the left screw was "X and F." The right control wheel assembly was checked for tightness using a screwdriver. The screw turned in the direction of tightening about 1/4 turn before it became fully torqued. The marking on the head of the right screw was "X and F."

A post accident investigation was performed at Pan Am International Flight Academy in Phoenix under the supervision of an FAA inspector. According to the manufacturer's representative, the left control wheel was reassembled and the screw was tightened with a screwdriver. About one thread was exposed above the nut plate. The screw was tightened, and only minor resistance was felt as it entered the nut plate. The screw was measured using a ruler and a micrometer. The ruler indicated that the screw was about 1 1/16 inches in length. The micrometer indicated that the screw was 1.0875 inches in length.

The right screw was removed and measured using a ruler and micrometer. The ruler indicated that the screw was about 1 1/16 inches long. The micrometer indicated that the screw was 1.088 inches in length. It was then installed into the nut plate and tightened using hand force. A portion of the thread of the screw was exposed beyond the top of the nut plate. The control wheel was reassembled and the screw was tightened with a screwdriver. About one thread was exposed beyond the top of the nut plate.

Using a new screw and nut plate, the screw was threaded into the nut plate and tightened by hand. The screw did not protrude through the nut plate before the locking force exceeded the hand torque.

For comparison, both control wheel covers were removed from another PA-28-181, Serial Number (S/N) 28-43307, and the thread engagement was visually checked. About 1 1/2 threads were exposed beyond the top of the nut plate. The screw from the left control wheel assembly was removed and measured using a micrometer. The ruler indicated that the screw was about 1 3/32 inches in length. The micrometer indicated that the screw was 1.104 inches in length. The markings on the head of the screws were "X and MAC."

The left control wheel covers were removed from three other PA-28-181's; S/N's 28-43500, S/N 28-43499, and S/N 28-43306. All three exhibited about one thread exposed beyond the nut plate, and the screws required additional turns to fully tighten. The markings on the head of all three screws were "F and X."

According to the Director of Maintenance for Pan Am International Flight Academy, the torque of the fastenings was checked on all 35 Pipers in their fleet. Their fleet consists of 19 PA-28-181's and 11 PA-44-180's. Ten control wheel screws were found to be loose. The screws turned 1/8 to 1/4 revolution before coming up to torque. The director contacted four other flight schools and was told that they also had found loose screws that required 1/8 to 1/4 revolution turns before coming up to torque.

NTSB Probable Cause

The disengagement of the left control wheel from the control column, which was due to the attaching screw backing out of the nut plate. Also causal was the manufacturer's inadequate design of the installation and the improper length of the screw.