NTSB Factual Report

On December 26, 2000, about 1729 eastern standard time, a Bombardier CL-600-2B19, N729CA, registered to First Union National Bank, operated by Comair, Inc., as flight 5751, experienced cracking of the captain's windshield while climbing to cruise after takeoff from the Cincinnati/Northern Kentucky International Airport, Hebron, Kentucky. Visual meteorological conditions prevailed at the time and an instrument flight rules (IFR) flight plan was filed for the 14 CFR Part 121, scheduled, domestic, passenger flight. The airplane was not damaged and there were no injuries to the airline transport-rated captain, commercial-rated first officer, flight attendant, or 50 passengers. The flight originated at 1719.

According to the airline safety manager, while climbing 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.

The damaged windshield (PPG part number NP 139321-5, S/N 99018H7134) was removed from the airplane and initial examination revealed that the center ply was failed. The window was further examined in the presence of representatives of the NTSB, FAA, Bombardier, and PPG, at one PPG's facilities.

A report of the damaged windshield prepared by PPG indicates, "The fracture originated 0.20 inch from the bottom edge and 3.8 inches from the center of the forward corner. The origin of the fracture was a peel chip that developed on the outboard surface in the bottom forward corner area. The initiation point of the peel chip damage was located 0.115 inch from the inner edge of the Teflon tape and 0.325 inch from the glass edge." The report also indicates that examination of the peel chip using a microscope, "...did not reveal any surface damage at the peel chip initiation point, nor was there any indication of manufacturing defects." No discrepancies were noted with the anti-ice heating system and sensing elements. Optical distortion check of the damaged window was performed which revealed, "There was no slope-line distortion apparent in the critical vision area. However, 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 (a copy of the report is an attachment to this report).

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 "shattered while sitting at gate power off." The incident window had accumulated a reported 4,422.8 hours and 4,526 cycles at the time of failure.

The airplane minus the retained captains windshield was released to Michael L. Mizell, compliance analyst for Comair, on January 17, 2001. The retained windshield was authorized by Michael L. Mizell, compliance analyst for Comair, to be disposed of (a copy of his letter authorizing such is an attachment to this report).

NTSB Probable Cause

The inadequate design of the flight compartment windshield by the windshield manufacturer resulting in cracking of the center ply.