Aviation & Marine Engineering Case Study 2

Background:

The pilot of the aircraft reported that there had been a Failure at 27,000 ft. of the
interior lamination of the left hand windshield of a commercial aircraft. Trident was asked to determine the cause of the crack damage.

The obvious damage to the windshield is a densely cracked (diced) failure of the interior
glass lamination originating near the top centerline corner of the wind-shield. Photograph 1, below, provides an overall view of the left hand wind-shield.

PHOTOGRAPH 1Field Overall exterior view of the left hand (pilot’s) windshield. The red arrow indicates the area of the origin of the crack failure.
PHOTOGRAPH 2A closeup exterior view of the top centerline corner of the left hand windshield. As above, the red arrow indicates the area of the origin. Note how the crack pattern expanded outward from the area of the origin. A segment of the black plastic hump (edge) seal has been removed to facilitate the microscopic search for the origin.

PHOTOGRAPH 3Closeup interior view of the top centerline corner
of the left hand windshield.The red arrow indicates the origin of the crack failure. This photograph also shows how the crack pattern expanded outward from the origin. The centerline edge of the left hand (pilot’s) windshield is to the right in the photograph.
PHOTOGRAPH 4Microscopic (15X) interior view of the origin of the
overall crack failure of the interior lamination of the windshield. This image has been back-lighted
to show the details of the peel chip. The orientation of the photograph is the same as shown in Photograph 3, above left; the top edge of the windshield is above and the centerline edge is to the right of the photograph.

Conclusion:

Trident Engineering Associates, Inc. concludes to a reasonable degree of engineering
certainty that:.

a. The cause of failure of the interior (innermost) glass lamination of the left hand (pilot’s) windshield was internal stresses which were concentrated at the top centerline corner of the windshield. The internal stresses caused a peel chip to form in the interior lamination of the windshield.

b. The overall crack failure of the windshield originated at the peel chip at the top
centerline corner. Subsequent stress-relieving resulted in the densely cracked failure of the tempered glass interior lamination.

c. There is no indication of foreign object damage to the outer surface of the windshield
as a cause of the failure, particularly since it is the interior lamination that has failed.

Trident’s analysis will allow Trident’s client to submit a claim against the manufacturer
(or installer) of this windshield, which has a value of around $40,000.