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

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.

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 take-off 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 load sheet, 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 load sheet 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 load sheet.

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 load sheet 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 take-off.

The manufacturer stated that the CG for the take-off 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 take-off, 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 take-off and landing, and the loading requirements for the flight.

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 take-off.

7. Using the aircraft's Performance Supplement Manual.

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 load sheet
the Flight Crew Operating Manual has been amended to place shared responsibility for the final check of an aircraft’s load sheet 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.