From The Canadian Transport Safety Board...
On 06 March 2005, Air Transat Flight 961, an Airbus 310-308,
Canadian registration C-GPAT, serial number 597, lost the major
part of its rudder while in flight from Varadero, Cuba, to Quebec
City, Canada. The flight returned to Varadero where an uneventful
landing was carried out.
The Transportation Safety Board of Canada (TSB) was notified of
the accident at 11001 and responded by deploying two investigators
from the Dorval, Canada, regional office and one investigator from
the TSB Engineering Laboratory in Ottawa, Canada. Because the event
occurred over international waters, Canada, as the State of
Registry, is conducting the investigation.
The investigation team
is composed of the following five main groups: operational, air
traffic control (ATC), human factor, technical, performance, and
recorders group. Four subgroups under the technical group have been
established; a system group, a structure and maintenance group, a
maintenance records group, and a manufacturing group. The Bureau
d'Enqu�tes et d'Analyses pour la Securite de l'Aviation
Civile (BEA) of France, the German Federal Bureau of Aircraft
Accidents Investigation (BFU), and the National Transportation
Safety Board (NTSB) of the United States assigned accredited
representatives to participate in the investigation. Technical
advisors from Airbus, Transport Canada, the Direction Generale de
l'Aviation Civile (DGAC), the Federal Aviation Administration
(FAA), the German Aerospace Center (DLR), and Air Transat are also
participating and assisting in the investigation.
Factual Information The A310-308, operated by Air Transat, was on a
charter flight from Varadero, Cuba, to Qu�bec City, Canada,
with a crew of 9 and 261 passengers on board. While at an altitude
of 35 000 feet, the flight crew heard a loud bang with simultaneous
vibrations that lasted a few seconds. The aircraft entered a
periodic rolling and yawing motion known as dutch roll that
decreased as the aircraft descended to a lower altitude. Once the
aircraft reached about 19 000 feet, the flight crew had no
indication of any abnormalities from systems monitoring. The flight
crew considered landing at Fort Lauderdale, Florida, but elected to
return to Varadero where an uneventful landing was carried out. It
is only once on the ground that the flight crew noted during a
visual inspection that a major part of the rudder was missing.
There were no fatalities. One flight attendant sustained minor
injuries.
The investigation team observed that only the lower rudder spar
and the base rib of the rudder were remaining. Less than five per
cent of the total rudder surface actually remained attached to the
spar. The rudder is attached to the vertical fin through seven
A-frame hinges, numbered one to seven, starting from the bottom.
The remaining parts of the rudder were attached to the vertical
fin's rear spar by the actuators and the four lower rudder hinges.
Hinges five and six were were still in place on the fin spar, but
only the attachment fittings of the rudder were attached to them.
The rudder position sensor was still attached to the remaining
piece of the rudder. Rudder hinge number seven was torn off from
the fin spar.
The panels that cover the rudder are made of carbon fibre
reinforced plastic (CFRP). The panels were manufactured in 1991 by
Soko in Mostar, former Yugoslavia. The rudder panels (serial number
1331) were assembled at Airbus facilities in Stade, Germany, and
then installed on the aircraft in 1992. The aircraft had
accumulated 49 224 flight hours since manufactured in 1992.
The flight data recorder (FDR), the cockpit voice recorder
(CVR), and the digital AIDS (aircraft integrated data system)
recorder (DAR) were sent to the TSB Engineering Laboratory for
downloads of all data recorded to determine the sequence of events
and the contributing factors of this event. The work is still in
progress.
On 19 March 2005, the vertical tailplane (VTP) and the rudder
were transported from Cuba to Bremen, Germany, for further
examination. The VTP, to which the rudder is attached, is bolted to
the top of the fuselage by six attachment lugs. The VTP was subject
to ultrasonic inspection, which revealed delamination damage to the
two rear attachment lugs. Loads and aeroelastic models are being
formulated to evaluate the noted damage. An elasticity laminate
checker (ELCH) test on sample in-service rudders is also in
progress to check rudder panels in depth, from the outer skin to
the inner skin. This test will provide information on rudder skin
and core damage over a sampling, ranging from 13-year-old rudders
to more recent rudders. At this time, one test has been carried out
on one of the selected rudders, and no discrepancies have been
found.
The rudder control systems were checked and tested in Varadero
with no anomalies found. The three servo-controls that control
rudder movement were inspected and tested at Goodrich facilities in
Paris, France, during the second week of April. Rudder
servo-control spring rods were also investigated in Airbus
facilities in Hamburg, Germany, and no deficiencies were found.
Maintenance and technical records of the aircraft are being
reviewed by the maintenance and records group to determine if any
past maintenance activities on the aircraft, or if any past
reported operational events may have played a role in the
detachment of the rudder.
Safety Action Taken Following the event, a number of actions have
been taken. On 17 March 2005, Airbus produced an All Operator Telex
(AOT) to verify the structural integrity of the rudder and its
attachment by means of a one-time detailed visual inspection and
tap test inspection as a precautionary measure. On 18 March 2005,
the Direction Generale de l'Aviation Civile (DGAC) of France issued
an Emergency Airworthiness Directive (EAD) that includes mandatory
actions and compliance times to perform inspection and apply
corrective measures if necessary in accordance with the
instructions specified in the Airbus AOT. On 28 March 2005, the FAA
issued a similar Airworthiness Directive (AD). All results and
feedback from these mandatory inspections are being compiled by
Airbus.
Once validated safety deficiencies are identified during the
course of an investigation, the Board can, at any time during the
investigation, recommend action designed to reduce or eliminate
such deficiencies from the transportation system.
Investigation Plan There is still a considerable amount of work to
be done to bring this investigation to a conclusion by the Board.
In the following months, further ELCH tests will continue on other
rudders of the defined samples to check rudder panels in depth,
from outer to inner skin, and to measure rudder structural
rigidity. The preparation of the draft report will take months to
be completed with emphasis on the analysis of collected factual
information gathered by the detailed examination of the failed
rudder, the fin box lugs, the AOT and ELCH test results and any
appropriate investigation work.
When the investigation team's draft report is complete, it will
be reviewed by the Investigation Branch Standards and Performance
section, and approved by the Director, Air Investigations. The
draft report will then be submitted to the Board for its approval
and released as a confidential draft report to designated
reviewers. The Board will consider the representations of the
designated reviewers, amend the report if required, and issue the
final investigation report.
From The NTSB...
The National
Transportation Safety Board continues to assist the Transportation
Safety Board of Canada as it investigates an accident that occurred
March 6, 2005, when an Air Transat Airbus A310-308 (C-GPAT) lost
most of its rudder in-flight while en-route from Cuba to Quebec
City, Canada.
The NTSB has dispatched a team of investigators to participate
in the readout of the aircraft's flight recorders and the
development of aircraft performance studies; to participate in the
examination of the aircraft's vertical stabilizer, remnants of the
rudder, and rudder actuators; and to work with the TSB's chief
investigator in developing the issues to be addressed in the
investigation.
Based on information released by the TSB, NTSB investigators
have noted significant differences between the circumstances of the
Air Transat accident and two previous accidents investigated by the
NTSB that also involved structural damage to composite components
on Airbus aircraft.
On November 12, 2001, American Airlines flight 587, an A300-605R
(N14053), crashed shortly after takeoff from John F. Kennedy
International Airport in New York City, killing all 260 persons
aboard and 5 persons on the ground. The NTSB found that the
vertical stabilizer separated from the aircraft in flight after
experiencing aerodynamic loads beyond the plane's design strength
following the first officer's unnecessary and excessive rudder
pedal inputs. On May 12, 1997, American Airlines flight 903,
an A300-600 (N90070), experienced an in-flight loss of control near
West Palm Beach, Florida. The aircraft landed safely.
During the recovery of the aircraft, the significant rudder pedal
inputs led to aerodynamic loads that caused damage to the vertical
stabilizer. The damage was not discovered until an ultrasonic
examination of the stabilizer following the crash of flight
587.
In both of those cases,
significant rudder inputs by pilots played a major role in
producing the aerodynamic loads on the vertical stabilizer.
Preliminary indications from the Air Transat event data show that
the pilots were not manipulating the rudder before the events
leading up to the loss of the rudder.
Furthermore, NTSB investigators note that in the flight 903
accident the rudder remained attached to the vertical fin and no
significant damage was found on the rudder after the event.
In the case of the flight 587 accident, the data indicate that the
rudder remained intact and attached to the vertical fin until the
fin separated from the airplane.
The NTSB will continue to participate and assist the TSB of
Canada's investigation into the reason for the loss of the Air
Transat rudder, and will continue to compare data from the earlier
accidents to determine whether there are any similarities between
all three events (beyond the fact that all three aircraft
experienced damage to rear lugs of the vertical stabilizer).