Flight History
On 16 November 2017, a Boeing B737-700 operated by MyJet Asia was preparing for a flight from Seletar Airport, Singapore to Beijing, China. The flight crew consisted of two captains, with the pilot-in-command serving as pilot flying and the other as pilot monitoring. The aircraft's take-off weight was 67,106 kg, and it carried 24,050 kg of fuel, which was 5,856 kg more than required for the trip.
During pre-flight calculations, the pilots used their Electronic Flight Bags with Onboard Performance Tool (OPT) software to compute V-speeds and N1 thrust setting. Initial inputs included an outside air temperature (OAT) of 26°C, Runway 03, take-off thrust, and flap setting 5. The OPTs produced V1 129 knots, VR 134 knots, V2 142 knots, and N1 102.1%. The pilots then entered data into the Flight Management Computer (FMC), including a zero fuel weight of 43,186 kg and take-off weight of 67,106 kg. They accepted the FMC output, but could not recall the figures; flight data recorder later showed V1 138 knots, VR 139 knots, V2 142 knots, and N1 90.4%.
After pushback at 0854 LT, air traffic control provided updated OAT of 29°C. The pilots recalculated using OPTs, obtaining V1 129 knots, VR 134 knots, V2 142 knots, and N1 102.5%, and noted V-speeds unchanged. The pilot monitoring updated the FMC with the new OAT, which caused the V-speeds to be de-selected and a "VERIFY TAKE-OFF SPEEDS" message to appear. While backtracking on Runway 21, the pilots saw the message and the pilot monitoring re-selected the V-speeds.
Take-off began at 0908 LT on Runway 03. The tower controller observed the aircraft lift off close to the runway end and climb slowly at a shallow angle. The flight crew reported nothing unusual, attributing a longer roll to the extra fuel. A subsequent runway inspection revealed damage to 10 approach lights at the end of Runway 03. Air traffic control informed the flight crew, who checked aircraft systems and found no anomalies. They decided to continue to Beijing. After arrival, two tyres on the left main landing gear were found damaged with cuts and gouges. There were no injuries.
Findings
The investigation determined that the aircraft took off with a thrust setting significantly below that required for the conditions. The flight crew had not ensured that the take-off N1 setting and V-speeds were correctly set in the FMC. The FMC output showed a lower N1 (90.4%) than the OPT calculations (102.5%), but the crew did not verify or use the correct values. The discrepancy arose because the FMC used a different zero fuel weight and possibly other parameters, and the crew's updates did not properly coordinate with the FMC logic.
Conclusion
The Transport Safety Investigation Bureau classified the occurrence as a serious incident. The probable cause was the flight crew's failure to ensure that the take-off N1 setting and V-speeds were set correctly before the take-off.