Easyjet Europe A319 at London on Sep 30th 2018, error in takeoff calculation

Last Update: June 13, 2019 / 14:09:10 GMT/Zulu time

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Photo of Easyjet Europe OE-LQE, Airbus A319 — Easyjet Europe OE-LQE, Airbus A319 (Photo credit: FlugZüge / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Sep 30, 2018

Classification
Incident

Airline
Easyjet Europe

Flight number
U2-8175

Departure
London Gatwick, United Kingdom

Destination
Sevilla, Spain

Aircraft Registration
OE-LQE

Aircraft Type
Airbus A319

ICAO Type Designator
A319

An Easyjet Europe Airbus A319-100, registration OE-LQE performing flight U2-8175 from London Gatwick,EN (UK) to Sevilla,SP (Spain) with 144 passengers and 6 crew, departed Gatwick's runway 26L at 07:04L (06:04Z) and completed the flight with a safe landing on Sevilla's runway 27 about 2:15 hours after departure.

On Oct 11th 2018 the British AAIB reported however, that there had been an error in the takeoff calculations. The occurrence was rated a serious incident and is being investigated by the AAIB.

On Jun 13th 2019 the AAIB released their bulletin concluding the probable cause of the serious incident was:

A data entry error led to an aircraft taking off using incorrect takeoff parameters. The crew noted an anomaly but could not detect an associated error. They continued with a reduced thrust takeoff, agreeing to use TOGA thrust if they had concerns about aircraft performance during the takeoff. Experience has shown, however, that pilots often do not notice the low acceleration associated with insufficient takeoff thrust.

The AAIB reported:

As part of the cockpit preparation process, Pilot Monitoring (PM) was responsible for generating the aircraft loadsheet using his Electronic Flight Bag (EFB). He used the application’s ‘Detailed’ mode to input passenger and cargo data from the Loading Form Certificate (LFC) (Figure 1) compiled by the Handling Agent. Pilot Flying (PF) later reviewed PM’s data entries. A cross-check of the loadsheet output revealed approximately two tonnes discrepancy between the calculated Zero Fuel Weight (ZFW) and the flight plan’s estimated ZFW. With such a significant difference, the crew re-checked their working but could not find any obvious errors and so used the existing loadsheet for their takeoff calculations.

Prior to departure, the Handling Agent notified the crew of a Last-Minute Change (LMC) to passenger and cargo numbers. The crew used the application’s ‘Reduced’ mode to update the loadsheet to reflect the change, which reduced the calculated AUW by 384 kg. The new loadsheet did not invalidate the crew’s previous takeoff calculations, which were already loaded into the aircraft’s flight management system. Having not fully resolved the ZFW discrepancy, the crew discussed the anomaly while at the runway Holding Point. The takeoff calculations had specified a reduced-thrust departure.

The crew resolved that if they had any concerns regarding aircraft performance during the takeoff they would select TOGA thrust (see Aircraft Information paragraph below). The crew based their decision on the fact that the LMC reduced the AUW, and there was a ‘central [CG] position and excess performance at [Gatwick]’. The subsequent departure was uneventful.

Once established in the cruise, the crew re-checked their loading calculations. They discovered that the Males, Females and Children data fields in the loadsheet application had been incorrectly populated. They contained the passenger cabin zone distribution figures (Figure 2) rather than the correct gender/age data (Figure 3). The resulting incorrect gender/age profile meant that the total passenger weight was underestimated by 1,962 kg. The flight continued to destination without further incident, whereupon the commander reported the loadsheet error to the Company Duty Pilot.

The AAIB analysed:

This serious incident resulted from the error of inputting incorrect data into three fields on the loadsheet application. Once the mistake had been made, human performance limitations reduced the likelihood that the slip would be detected. The crew noticed a ZFW anomaly, but despite looking for an error they could not find one. The lack of commonality between LFC and EFB formats was considered by the operator to be an exacerbating factor, as was the lack of gender/age profile information in the loadsheet application’s Reduced mode.

The undetected error led to the departure being flown with incorrect takeoff performance parameters. The crew’s decision to use TOGA thrust if they had any performance concerns during takeoff might not have been a reliable risk control because the C-FWGH incident showed that pilots are unlikely to perceive when extra thrust is required.

The C-FWGH report highlighted the challenges of finding data entry errors and the limited ability of pilots to detect abnormally low aircraft acceleration. Procedural barriers, such as parallel EFB calculations, attempt to reduce the likelihood that these types of error occur. Technical barriers to capture the errors once made are still in their infancy.