Weight and balance event, Airbus A330-301, Changi Singapore, VH-QPC

FACTUAL INFORMATION¹

History of the flight

At 1503 Coordinated Universal Time (UTC) on 9 December 2004, the
pilot in command of an Airbus Industrie A330-301 aircraft (A330),
registered VH-QPC, commenced the takeoff from Singapore on a
scheduled regular public transport service to Darwin, NT. The pilot
in command reported that the aircraft felt nose heavy during
rotation², but that after the aircraft was trimmed, a
more normal feel was restored. Following the flight it was found
that the aircraft's take-off centre of gravity³ (CG) was
forward of the manufacturer's forward limit.

The decision by the operator to operate the
domestically-configured aircraft on an international service was
not communicated to the company department that had responsibility
for updating the aircraft's flight document library. As a result,
the take-off performance charts for the departure from Singapore
were unavailable for use by the flight crew. The flight crew
reverted to calculating the aircraft's take-off performance using
the aircraft's Performance Supplement Manual.

The operator maintained two distinct weight and balance profiles
for application in its A330 operations. The profiles were:

an international profile, employing a basic index⁴
(BI) of about 292, and used in conjunction with an international
weight and balance template
a domestic profile, with a BI of about 192, and used in
conjunction with a domestic weight and balance template.

The aircraft's international weight and balance profile was
created a number of months before the occurrence flight. During
that process a corrupted international profile was created. The
system and the operator did not recognise that there was an error
in the data in the new profile. There was no requirement for the
audit of that profile as it was created from existing certified
data. Subsequently, the aircraft's corrupted international profile
remained undetected during the intervening months of domestic
operations leading up to the occurrence flight.

A number of company defences were promulgated to ensure that the
operator's aircraft were correctly loaded:

the Flight Administration Manual placed responsibility with all
flight crew members to ensure that company aircraft were operated
within their CG limits
the Route Manual Supplement required that, before accepting a
provisional loadsheet, the crew 'should' confirm their aircraft's
critical load data against other aircraft documentation
the Flight Crew Operating Manual specified that the pilot in
command was responsible for the final check of an aircraft's
loadsheet data.

The copilot reported extracting the aircraft's basic
weight⁵ (BW) and BI parameters from a fleet weight and
balance folder that was located in the operator's Singapore flight
dispatch office. The parameters were then provided to the local
load control staff in order for them to produce the
loadsheet⁶ for the flight.

The flight crew reported that, in this instance, neither the
copilot nor the second officer could recall having checked the
aircraft's critical load data, and that the pilot in command did
not check the aircraft's loadsheet.

There was no evidence that the load control staff completed the
required independent check of the BW and BI parameters for the
aircraft and, as a result, an international BI was unwittingly
applied to what remained, effectively, the aircraft's domestic
weight and balance template.

Aircraft information

No evidence was found of a defect in the aircraft or its systems
that may have influenced the circumstances of the occurrence.

The loadsheet indicated to the flight crew and load control
staff that the aircraft had been correctly loaded in order for the
aircraft's CG to remain within limits for all phases of the flight.
The investigation determined that the aircraft's CG was located
forward of the manufacturer's forward limit for the takeoff.

The manufacturer stated that the CG for the takeoff did not
exceed the aircraft's structural and landing gear limitations, and
that the aircraft was 'sufficiently manoeuvrable' at all times.
However, an out of limits forward CG increases the risk of there
being insufficient elevator authority for a pilot to rotate an
aircraft during takeoff, or to flare an aircraft for landing. The
result would be that take-off and landing distances would be
greater than planned by the pilot.

There was no capability for the aircraft's systems to warn the
flight crew of an out of limits CG while on the ground. Airborne
warning of an out of limits aft CG was possible.

Only those investigation areas
identified by the headings and subheadings were considered to be
relevant to the circumstances of the occurrence.
Positive, nose-up pitch of the
aeroplane about the lateral axis immediately prior to becoming
airborne.
The point at which an aircraft would
balance if suspended. It must be located within specific limits for
safe flight.
In simplified terms, the position of
the aircraft's centre of gravity before fuel and payload are
added.
Mass of the aircraft, including of
the aircraft's fixed equipment and residual fluids.
A performance planning document that
annotated the aircraft's weight, centre of gravity for takeoff and
landing, and the loading requirements for the flight.

SAFETY ACTIONS

Operator

The operator has implemented the following safety actions in order to enhance
the existing organisational and individual risk controls affecting A330 aircraft
loading:

planning is underway for a single load control system commencing March
2007 for the company’s domestic and international operations
inter-departmental communication lists have been amended to ensure the
timely promulgation and availability of relevant aircraft documentation for
use by flight crews
the Route Manual Supplement has been amended to clearly mandate the requirement
for flight crews to check an aircraft’s critical load data against
other company documentation before accepting a provisional loadsheet
the Flight Crew Operating Manual has been amended to place shared responsibility
for the final check of an aircraft’s loadsheet data with the pilot
in command, and copilot
the load control officer training syllabus has been revised to include
aspects of this occurrence, and additional load control checklists have been
introduced for use by load controllers
the audit process when updating the company’s load control system has
been amended to include an independent cross-check of any changes to an aircraft’s
basic record, or of any ‘copied’ details
a log has been created to record all out of hours changes to the company’s
load control system.

ANALYSIS

The risk for the operator of employing two weight and balance
profiles was that it increased the possibility of errors during
operations.

The lack of an audit requirement affecting the newly created
weight and balance profile, and the lack of a capability for an
on-ground warning to the crew of an incorrectly loaded aircraft,
meant that the operator's load control system relied on the
recognition by the crew of any error in the aircraft's load
profile. The investigation could not quantify the impact on
workload caused by the requirement for the crew to calculate the
aircraft's take-off performance⁷, but it may have
precluded their critical analysis of the aircraft's weight and
balance profile. In any case, in this instance, the company's
reliance on crew intervention to prevent the application of the
incorrect load profile proved unreliable.

The omission of an independent check of the aircraft's basic
weight and index parameters by the company's Singapore load
controllers negated another potential defence in the operator's
load control system. In addition, the implied discretionary
requirement in the Route Manual Supplement for flight crews to
check flight critical data could have contributed to the apparent
breakdown in the crew's loading preparations for the flight. Had
either of the Singapore load controllers, or the flight crew more
comprehensively followed company procedures, the error in the
aircraft's weight and balance profile may have been detected prior
to commencing the takeoff.

7. Using the aircraft's Performance Supplement Manual.

At 1503 Coordinated Universal Time (UTC) on 9 December 2004, the pilot in
command of an Airbus Industrie A330-301 aircraft, registered VH-QPC, commenced
the takeoff from Changi Airport, Singapore on a scheduled regular public transport
service to Darwin, NT. The pilot in command reported that the aircraft felt
nose heavy during rotation, but that after the aircraft was trimmed, a more
normal feel was restored. Following the flight it was found that the aircraft’s
take-off centre of gravity (CG) was forward of the manufacturer’s forward
limit.

The investigation found that:

there had been a corruption of the aircraft’s
weight and balance data within the international load control system
the error
did not manifest itself until the aircraft was used on an international service
and the aircraft’s weight and balance was calculated using the
corrupted data in the international load control system
the Singapore load controllers
did not carry out a check of the basic aircraft’s
data as they were required to do by the operator
the flight crew did not carry
out a check of the basic aircraft data as they were required to do by the
operator.

The
operator made a number of changes to procedures that will enhance the existing
organisational and individual risk controls affecting A330 aircraft loading.
The operator will also introduce a single load control system from March 2007,
which will minimize the likelihood of a recurrence of the data corruption event
leading to this incident.