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Quad City Challenger, Aircraft Wing Bracket Failure, Wing Failure Advisory
Transport Canada, Aviation Safety Advisory!
Effecting Quad City Aircraft Challenger's. Ultralight, Experimental, and Amateurbuilt Aircraft!
Wing Bracket Failure. Incident Report.
The right wing of a privately owned Quad City Challenger II aircraft registration C-IGKT, separated from the aircraft when it was at an altitude of approximately 1000 feet. The aircraft entered an uncontrolled descent and collided with terrain in a wooded area.
A post-impact fire ensued. The pilot was fatally injured and the aircraft was destroyed.
As part of the investigation into this accident the TSB retrieved and examined both right wing lift struts (front and rear) and the respective attachment brackets. It was determined that the bracket securing the right front lift strut to the fuselage failed while in flight as a result of fatigue. Following this failure, the lift strut detached from the fuselage and the right wing separated from the aircraft.
Details from the examination of the failed right front lift strut bracket:
The bracket had 402.2 hours since installation (including the accident flight).
A fatigue crack was found across the bottom end of the bracket, through the bolt hole and parallel to the bracket sides
The initiation point of the crack was determined to be on the edge of the bolt hole.
The fatigue region (Figure 2) accounts for more than 60% of the cross-section area of the bracket. It shows striations along the fracture surface, which are an indication of the fatigue cycles.
The scanning electron microscope observation of the fracture surface found a significant number of secondary and parallel cracks underneath the surface of the bracket (Figure 3). These cracks resemble material delamination, a material defect introduced likely due to, or consistent with, the fabrication process used.
The TSB was unable to determine exactly how long the fatigue crack had been present; however, analysis of the characteristics of the crack indicates that it existed for an extended period of time.
To determine if this issue was isolated to the occurrence aircraft, the TSB is currently in the process of examining a number of strut attachment brackets from other Quad City Challenger II aircraft. So far, 22 brackets have been examined, and within that group, 8 brackets were found to have cracks.
Time in service for the 8 failed brackets is as follows:
1 at 4.1 hrs. 1 at 90 hrs,. 2 at 430 hrs. 2 at 511 hrs, and 2 at 830 hrs.
The cracks identified vary in size and origin; some resulted from fatigue, whereas others were caused by material delamination.
A review of the National Transportation Safety Board aviation accident database revealed four other Quad City Challenger II accidents involving in-flight wing attachment bracket failures that led to in-flight wing separations .
Three of these accidents were fatal. In the nonfatal accident, the pilot successfully deployed a ballistic parachute and was not injured.
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