Spectrum Aeronautical 33 N322LA

Summary

On 25 July 2006 at about 22:06 local time, a Spectrum Aeronautical 33 registered N322LA was involved in an accident near Spanish Fork, Utah, United States. 2 people were on board and 2 died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

25 July 2006 at 22:06

Classification

Accident

Location

Spanish Fork, Utah, United States

Nearest airport

Spanish Fork - Springville (U77)

Coordinates

40.1417, -111.6614

Aircraft

Spectrum Aeronautical 33

Registration

N322LA

Category

Airplane

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Flight Test

Phase of flight

Not recorded

Route

Spanish Fork → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

SEA06FA146

2 people died.

Incorrect installation by company maintenance personnel of the aft upper torque tube bell crank resulting in roll control that was opposite to that commanded in the cockpit. Contributing factors were the lack of maintenance documentation detailing the installation of the bell crank, the installing mechanic's incorrect assumption that the bell crank could only be installed in one position, and the failure of maintenance personnel and the flight crew to check the position of the control stick relative to the ailerons after the maintenance and during the preflight checks.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The proto-type experimental light jet airplane was departing on a local maintenance test flight. Witnesses reported that the airplane entered a right roll almost immediately after liftoff. The roll continued to about 90 degrees right wing down at which point the right wingtip impacted the ground. During examination of the wreckage, the aileron control system was found connected such that the airplane rolled in the opposite direction to that commanded in the cockpit. The maintenance performed on the airplane before the accident flight included removal of the main landing gear (MLG) in order to stiffen the MLG struts. Interviews with the mechanics who performed the maintenance revealed that during re-installation and system testing of the MLG, it was discovered that the changes to the MLG struts impacted the V-bracket holding the aileron control system's upper torque tube. The V-bracket was removed and a redesigned V-bracket was installed in its place. This work required the disconnection of a portion of the aileron control system, including the removal of the aft upper torque tube bell crank from the torque tube. The mechanic who reinstalled the aft upper torque tube bell crank was under the incorrect assumption that there was only one way to install the bell crank on the torque tube. However, there are actually two positions in which the bell crank could be installed. The incorrect installation is accomplished by rotating the bell crank 180° about the axis of the torque tube and flipping it front to back, and this is the way the bell crank was found installed. With the bell crank installed incorrectly and the rest of the system installed as designed, there is binding in the system. This binding was noticed on the accident airplane during the inspection after initial installation. However, the mechanic did not recognize that the bell crank was improperly installed on the torque tube. Instead of fixing the problem by removing and correctly reinstalling the bell crank, he fixed the problem by disconnecting the necessary tie rods and rotating the upper torque tube so that the arm of the bell crank pointed up and to the left. This action reversed the movement of the ailerons. According to all of the personnel interviewed, there was no maintenance documentation to instruct mechanics how to perform the work since this was a proof-of-concept airplane. None of the mechanics who performed the work could recall if the position of the ailerons in relation to the position of the control stick was checked. Such a position check, if it had been performed by either the mechanics after the maintenance or by the flight crew during the preflight checks, would assuredly have indicated that the system was installed incorrectly.

Quoted verbatim from the NTSB record.