Incident Overview
During climb through 20,000 feet in visual meteorological conditions, the captain's windshield shattered. The captain did not declare an emergency; the flight returned to the departure airport and landed uneventfully.
Examination of Damaged Windshield
The damaged windshield (PPG part number NP 139321-5, serial number 99018H7134) was removed from the airplane. Initial examination revealed that the center ply had failed. The window was further examined in the presence of representatives of the NTSB, FAA, Bombardier, and PPG at one of PPG's facilities.
A report prepared by PPG indicated that the fracture originated 0.20 inch from the bottom edge and 3.8 inches from the center of the forward corner. The origin was a peel chip that developed on the outboard surface in the bottom forward corner area. The initiation point of the peel chip was located 0.115 inch from the inner edge of the Teflon tape and 0.325 inch from the glass edge. Microscopic examination of the peel chip did not reveal any surface damage at the initiation point, nor was there any indication of manufacturing defects.
System Checks
No discrepancies were noted with the anti-ice heating system and sensing elements. An optical distortion check of the damaged window was performed, which revealed no slope-line distortion in the critical vision area, but facilities were not available to perform a quantitative distortion evaluation. Residual visibility examination could not be performed due to the absence of a standard and prescribed method of evaluation.
History
Manufacturing of windshield S/N 99018H7134 was completed on January 18, 1999. The window was installed in the incident airplane by Comair maintenance personnel on March 27, 1999, to replace the previous window, which had shattered while sitting at the gate with power off. The incident window had accumulated a reported 4,422.8 hours and 4,526 cycles at the time of failure.