Incorrect takeoff speeds lead to tail scrape during Boeing 747 departure

Casualties unknown • Johannesburg International Airport S26° 08’ 01” E 028° 14’ 32” at an elevation of 5558’ AMSL, ZA

A Boeing 747-300 experienced a tail scrape during takeoff from Johannesburg International Airport after incorrect weight data led to inaccurate airspeed settings.

What happened

On 11 March 2003, a Boeing B747-300, registered ZS-SAJ, was preparing for an international scheduled flight from Johannesburg International Airport to Sao Paulo. The departure was initially hampered by technical issues when the Auxiliary Power Unit (APU) failed to provide adequate airflow to the cabin and failed to start the engines. To compensate, the crew planned to use a ground air cart for engine starts.

During the departure sequence, the aircraft was subject to several distractions on the flight deck, including a sudden change in the expected ATC delay. During the takeoff roll on Runway 03L, the pilot-in-command initiated rotation based on the speeds set on the airspeed indicators. However, the pilot noted the aircraft felt unusually nose-heavy and subsequently delayed rotation by 15 knots. As the aircraft became airborne, the pilot requested additional thrust due to a sluggish sensation, while the flight engineer reported the aircraft was sinking. Following the takeoff, air traffic control informed the crew that a tail scrape had occurred. The aircraft returned to Johannesburg International Airport, where fuel was dumped before landing. There were no fatalities and no injuries among the passengers or crew.

The investigation

The investigation focused on the calculation of takeoff performance and the accuracy of the airspeed indicators. Investigators examined the data entry process used to determine takeoff speeds and the role of flight deck distractions during the pre-flight phase. The inquiry also looked into the sequence of events involving the flight engineer's use of the handheld performance computer and the subsequent verification of the takeoff cards by the flight crew.

Findings

  • The flight engineer entered the aircraft's Zero Fuel Weight of 203,580 kg into the handheld performance computer instead of the actual Take Off Weight of 324,456 kg.
  • This error resulted in the calculation of incorrect takeoff speeds being transferred to the takeoff cards.
  • The pilot-in-command failed to identify the incorrect speeds during the verification process, as the first officer was occupied with other tasks.
  • Both pilots subsequently set the incorrect speed bugs on their airspeed indicators.
  • Several distractions on the flight deck, including the sudden reduction in the expected ATC delay, contributed to the lack of oversight during the performance calculation phase.

Probable cause

The primary cause was the unintentional entry of the incorrect zero fuel weight into the performance computer, which led to incorrect takeoff speeds being programmed into the aircraft's airspeed indicators. This error was compounded by flight deck distractions and a lack of effective cross-checking by the crew.

Frequently asked questions

What happened in the 2003-03-11 Boeing B747-300 accident near Johannesburg International Airport S26° 08’ 01” E 028° 14’ 32” at an elevation of 5558’ AMSL, ZA?

A Boeing 747-300 experienced a tail scrape during takeoff from Johannesburg International Airport after incorrect weight data led to inaccurate airspeed settings.

What aircraft was involved and where did it happen?

The accident on 2003-03-11 involved a Boeing B747-300, registration ZS-SAJ, at Johannesburg International Airport S26° 08’ 01” E 028° 14’ 32” at an elevation of 5558’ AMSL, ZA.

What was the probable cause of the accident?

The primary cause was the unintentional entry of the incorrect zero fuel weight into the performance computer, which led to incorrect takeoff speeds being programmed into the aircraft's airspeed indicators. This error was compounded by flight deck distractions and a lack of effective cross-checking by the crew.

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