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(BB, note TORA is mentioned. I told you I didn't made that up)
"On 21 July 2017 at 1539 hrs, C-FWGH took off from Belfast International Airport with a thrust setting which was significantly below that required for the conditions of the day. Preliminary evidence indicated that, after the aircraft lifted off from the runway, one of the aircraft tyres struck a runway approach light, which was 35 cm high and 29 m beyond the end of the runway."
The AAIB reported that neither UK's Civil Aviation Authority not the AAIB had been informed about the occurrence by captain, operator or tour operator although the Canadian TSB had been informed about the occurrence. ATC filed a Mandatory Occurrence Report which was not read by the AAIB until Jul 24th, as result the data off the flight fata and cockpit voice recorders were not available to the investigation as the aircraft had flown 16 sectors in the meantime and the data of the occurrence flight on both flight data and cockpit voice recorders were overwritten.
The AAIB reported: "The crew were cleared for takeoff on Runway 07 from Taxiway D (Figure 1), which gave a Takeoff Run Available (TORA) of 2,654 m. During the takeoff, at around 120 to 130 kt, the crew realised that the aircraft was not accelerating normally. They estimated, during post-flight interviews, that they reached V1 1 with around 900 m of the runway remaining and rotated shortly afterwards. The aircraft was seen, by multiple witnesses, during rotation and took a significant time to lift off before climbing at a very shallow angle. ... After takeoff, the crew checked the aircraft’s FMC which showed that an N1 of 81.5% had been used for the takeoff. This figure was significantly below the required N1 setting of 93.3% calculated by the operator and shown on the pre-flight paperwork."
With respect to N1 settings the AAIB reported:
Passing the upwind end of the runway the aircraft’s ACARS sent a takeoff report, which confirmed that the engines were at an N1 of approximately 81.5%. Other ACARS messages confirmed that the correct weights for the aircraft had been entered into the FMC.
The aircraft’s auto-throttle BITE8 history showed two messages generated during the climbout. Both messages were consistent with the crew having manually advanced each throttle to a power setting above an N1 of 81.5% when the aircraft was approximately 800 ft aal.
The Electronic Flight Bags (EFB) used by the crew to calculate the performance figures for entry into the FMC were provided to the AAIB. Initial examination of these devices indicated that the correct figures were calculated by the EFB performance software prior to the aircraft’s departure.
The AAIB conducted simulator tests to find out whether the aircraft would be able to climb out or stop in case of an engine failure and how such a performance of N1=81.5% could occur in the FMS. The AAIB wrote:
The AAIB and operator carried out independent assessments of how the incorrect thrust setting might have been programmed into the FMC. Both assessments concluded that the only credible way to achieve a grossly low N1 setting was to enter an extremely low value into the outside air temperature (OAT) field on the n1 limit page. It was found that the takeoff N1 setting used on the flight (81.5%) would be calculated by the FMC if:
a. The expected top-of-climb outside air temperature (OAT) was entered into the OAT field on the n1 limit page instead of the OAT at the airport (a figure of - 52°C as opposed to +16°C);
and b. The correct assumed temperature9 of 48°C was entered into the FMC. No other combination of data entries was found which would achieve the same result.
During the simulation carried out by the AAIB, the aircraft’s performance was assessed following an engine failure immediately prior to V1, with the pilot making a decision by V1 to either abandon or continue the takeoff. In the simulator, the aircraft was able to stop in the runway remaining following a decision to abandon the takeoff, but was unable to climb away safely following a decision to continue the takeoff.
The AAIB analysed:
The aircraft took off from Runway 07 with a thrust setting significantly below that required to achieve the correct takeoff performance, and struck a Runway 25 approach light shortly after lifting off.
The N1 required to achieve the required takeoff performance was 93.3% but 81.5% was used instead. Independent assessments by the AAIB and operator showed that the only credible way for this to have happened was for an error to have been made whilst entering the OAT into the FMC. If the top-of-climb OAT was mistakenly inserted into the OAT field on the n1 limit page (a figure of -52°C as opposed to +16°C), and the correct assumed temperature of 48°C was entered, the FMC would have calculated a target takeoff N1 of 81.5%. The investigation will consider how such a data entry error could have been made, and whether actual aircraft performance matched that which would be expected given the N1 power setting used.
The AAIB reported that neither UK's Civil Aviation Authority not the AAIB had been informed about the occurrence by captain, operator or tour operator although the Canadian TSB had been informed about the occurrence. ATC filed a Mandatory Occurrence Report which was not read by the AAIB until Jul 24th, as result the data off the flight fata and cockpit voice recorders were not available to the investigation as the aircraft had flown 16 sectors in the meantime and the data of the occurrence flight on both flight data and cockpit voice recorders were overwritten.
The AAIB reported: "The crew were cleared for takeoff on Runway 07 from Taxiway D (Figure 1), which gave a Takeoff Run Available (TORA) of 2,654 m. During the takeoff, at around 120 to 130 kt, the crew realised that the aircraft was not accelerating normally. They estimated, during post-flight interviews, that they reached V1 1 with around 900 m of the runway remaining and rotated shortly afterwards. The aircraft was seen, by multiple witnesses, during rotation and took a significant time to lift off before climbing at a very shallow angle. ... After takeoff, the crew checked the aircraft’s FMC which showed that an N1 of 81.5% had been used for the takeoff. This figure was significantly below the required N1 setting of 93.3% calculated by the operator and shown on the pre-flight paperwork."
With respect to N1 settings the AAIB reported:
Passing the upwind end of the runway the aircraft’s ACARS sent a takeoff report, which confirmed that the engines were at an N1 of approximately 81.5%. Other ACARS messages confirmed that the correct weights for the aircraft had been entered into the FMC.
The aircraft’s auto-throttle BITE8 history showed two messages generated during the climbout. Both messages were consistent with the crew having manually advanced each throttle to a power setting above an N1 of 81.5% when the aircraft was approximately 800 ft aal.
The Electronic Flight Bags (EFB) used by the crew to calculate the performance figures for entry into the FMC were provided to the AAIB. Initial examination of these devices indicated that the correct figures were calculated by the EFB performance software prior to the aircraft’s departure.
The AAIB conducted simulator tests to find out whether the aircraft would be able to climb out or stop in case of an engine failure and how such a performance of N1=81.5% could occur in the FMS. The AAIB wrote:
The AAIB and operator carried out independent assessments of how the incorrect thrust setting might have been programmed into the FMC. Both assessments concluded that the only credible way to achieve a grossly low N1 setting was to enter an extremely low value into the outside air temperature (OAT) field on the n1 limit page. It was found that the takeoff N1 setting used on the flight (81.5%) would be calculated by the FMC if:
a. The expected top-of-climb outside air temperature (OAT) was entered into the OAT field on the n1 limit page instead of the OAT at the airport (a figure of - 52°C as opposed to +16°C);
and b. The correct assumed temperature9 of 48°C was entered into the FMC. No other combination of data entries was found which would achieve the same result.
During the simulation carried out by the AAIB, the aircraft’s performance was assessed following an engine failure immediately prior to V1, with the pilot making a decision by V1 to either abandon or continue the takeoff. In the simulator, the aircraft was able to stop in the runway remaining following a decision to abandon the takeoff, but was unable to climb away safely following a decision to continue the takeoff.
The AAIB analysed:
The aircraft took off from Runway 07 with a thrust setting significantly below that required to achieve the correct takeoff performance, and struck a Runway 25 approach light shortly after lifting off.
The N1 required to achieve the required takeoff performance was 93.3% but 81.5% was used instead. Independent assessments by the AAIB and operator showed that the only credible way for this to have happened was for an error to have been made whilst entering the OAT into the FMC. If the top-of-climb OAT was mistakenly inserted into the OAT field on the n1 limit page (a figure of -52°C as opposed to +16°C), and the correct assumed temperature of 48°C was entered, the FMC would have calculated a target takeoff N1 of 81.5%. The investigation will consider how such a data entry error could have been made, and whether actual aircraft performance matched that which would be expected given the N1 power setting used.
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