Canadian Transportation Board Says Plane Was Overloaded, Other Factors Involved

The Canadian Transportation Safety Board has released its final report in an accident that occurred in March, 2008 that claimed the lives of the pilot and four passengers on the plane.

The pilot, Regan Williams, was the president of A.D. Williams Engineering, which owned the plane. He held an instrument rating and had about 2,200 hours in his logbook, of which 987 hours were in the PA-46-310P model and 166 hours were in the aircraft he was flying at the time of the accident.

The investigation centered on a mechanical gyro, which Williams had had examined prior to the flight. According to the TSB report, 'He had the KI256 and the associated KC192 autopilot computer removed and bench tested before the occurrence flight. The KI256 signal outputs to the autopilot computer were found to be too unstable (jittery) to adjust, and the rotor bearings were noisy when operating. An overhaul was recommended but could not be performed until the following week, and a replacement or exchange instrument was not available. Because the KI256 display appeared to be within bench test parameters, the pilot requested that the units be reinstalled to complete the occurrence flight before further repairs were completed, with the knowledge that the autopilot problems had not been rectified. Section 1.1.1 of Appendix A of the COM stated “Autopilot must be serviceable for planned single pilot operations.”

TSB examination of the KI256 gyro/horizon revealed significant internal wear and damage that pre-dated the occurrence:

• The rotor bearings and shaft had excessive wear and fretting damage.
• The gimbal roll shaft had considerable fretting damage.

PA46 File Photo

Paint transfer from the rotor to the housing at impact did not exhibit smearing, indicating that the rotor was stationary at the time of impact.

While the gyro seemed to be a principal factor in the accident, TSB listed several causes and contributing factors. Among them:

• The gyro/horizon failed due to excessive wear on bearings and other components, resulting from a lack of maintenance and due to a vacuum system that was possibly not at minimum operating requirements for the instrument.
• The gyro/horizon was reinstalled into the aircraft to complete the occurrence flight without the benefit of the recommended overhaul.
• The autopilot became unusable when the attitude information from the gyro/horizon was disrupted.
• The pilot had not practised partial panel instrument flying for a number of years, was not able to transition to a partial panel situation, and lost control of the aircraft while flying in instrument meteorological conditions.
• The aircraft was loaded in excess of its certified gross weight and had a center of gravity (C of G) that exceeded its aft limit. These two factors made the aircraft more difficult to handle due to an increase of the aircraft’s pitch control sensitivity and a reduction of longitudinal stability.
• The structural limitations of the aircraft were exceeded during the uncontrolled descent; this resulted in the in-flight breakup.
• There were a number of deficiencies with the company’s safety management system (SMS), in which the hazards should have been identified and the  associated risks mitigated.

The Edmundton Journal reports that the accident happened five months to the day after another crash that killed the founder of the company, Arlen Williams.

FMI: www.tsb.gc.ca/eng/