Journal of Accident Investigation

MATTHEW R. FOX, CARL R. SCHULTHEISZ, JAMES R. REEDER, AND BRIAN J. JENSEN
Analysis of the flight data recorder revealed that the airplane
had performed a series of yawing maneuvers in the seconds before
separation of the vertical stabilizer, and that the separation of
the vertical stabilizer occurred while the airplane was pointed to
the left of its flight path. This orientation would have produced
a bending moment on the vertical stabilizer, leading to tension
on the right-side attachments and compression on the left.
Most of the separated pieces of the vertical stabilizer and
rudder were recovered from the water of Jamaica Bay, some
distance from the main crash site. The vertical stabilizer was
largely intact, and had separated from the fuselage by fractures
at the lower end where it had been connected to the fuselage.
Although a detailed examination of the rudder was completed
during the accident investigation, early indications from the
performance analysis of the flight recorder data indicated
that the rudder performed as designed through the accident
sequence until the vertical stabilizer separated from the fuselage,
and loads analysis indicated that the vertical stabilizer would
fail before the rudder. Thus, investigators determined that
the rudder failure was secondary to the failure of the vertical
stabilizer. As part of the overall investigation into the accident,
investigators examined and tested the composite materials of
the vertical stabilizer and conducted a detailed examination of
the fractures in the vertical stabilizer to determine the failure
mechanism and direction of fracture propagation, where
possible. The possibilities of pre-existing damage, fatigue
cracking, or inadequacies in the manufacturing process were
also addressed.
Using accident loads derived from analysis of recorded flight
data, three lug tests were conducted on vertical stabilizer aft lugs
from an unused skin panel and from another airplane. Fracture
patterns for these three test specimens were compared to the
corresponding structure on the accident airplane.
This paper describes the structure of the vertical stabilizer, the
results of the materials testing and microstructural examination,
fractography of the vertical stabilizer, and how the results led
investigators to understand the failure. The paper also presents
fractographic examination results for the three lug tests and
significance of the fracture features.
DESCRIPTION OF THE STRUCTURE
Development of the Airbus A300-600 model began in 1980,
and certification occurred in 1984. The accident airplane was
delivered new to American Airlines in 1988.
Vertical Stabilizer Structure
An internal view of the vertical stabilizer is shown in figure 1.
The vertical stabilizer for the Airbus A300-600 series airplane
is a stiffened box with removable leading edge fairings and
trailing edge panels. The stiffened box consists of two integrally
stiffened skin panels for the left and right sides, spars for the
forward and aft sides, and closure ribs at the upper and lower
ends. The integral stiffeners in the skin panels consist of
Figure 1. Airbus A300-600 vertical stabilizer construction. The vertical stabilizer and rudder for this model airplane, which has a symmetric airfoil shape,
are 27 feet 3 inches tall and from leading edge to trailing edge, 25 feet wide at the base, and 10 feet 2 inches wide at the tip. The vertical stabilizer and
rudder were made almost entirely of composite materials, including the composite lugs at the six main attachment locations for connecting the vertical
stabilizer to the fuselage.
10 NTSB JOURNAL OF ACCIDENT INVESTIGATION, SPRING 2006; VOLUME 2, ISSUE 1