EZJ Easyjet Plc

By Andy Pasztor 

British air-crash investigators looking into an incident last year involving an easyJet PLC flight have documented how a bug in an electronic flight-data calculator on many Airbus Group SE jetliners could lead to takeoff problems.

The potential hazard and steps to eliminate it were disclosed in a report released last week by Britain's Air Accidents Investigation Branch.

Pilots of an easyJet Airbus A319 unintentionally altered some touchscreen settings on a computerized takeoff calculator -- called an electronic flight bag -- but failed to recognize the changes until after takeoff from Belfast International Airport last June, according to the report. Investigators determined that as a result of the data confusion, the crew set engine thrust so that the jet carrying 161 people used up all but the last roughly 650 feet of the strip before becoming airborne, a significantly smaller safety margin than normal.

Airbus and easyJet participated in the investigation, agreed with its main conclusions and have taken steps to prevent a repeat of the incident.

There were no injuries and the jet wasn't damaged, but the event highlighted the broader danger of pilots mistakenly entering the wrong takeoff parameters into such computers. Data-integrity issues and potential pilot distractions resulting in programming slip-ups prior to takeoff have long been identified as major hazards for all types of commercial aircraft, including models made by Boeing Co. and other manufacturers.

The AAIB report, which indicated European air-safety regulators and Airbus are pursuing various initiatives to reduce those risks, further highlights the work remaining to be done. Pilots typically double-check parameters before takeoff, but in the easyJet incident company rules didn't require that specific safeguard. The AAIB previously investigated two other easyJet takeoff incidents in 2015 in which crews relied on incorrect computerized takeoff-performance data. Neither of those events resulted in damage or injuries.

Still, last week's report emphasized the importance of each pilot cross-checking data entered into such electronic flight bags prior to takeoff. The report notes that Airbus has made some adjustments and is studying software revisions and other changes intended to catch pilot errors that can introduce incorrect data into such computers. One of the major changes was available to airlines prior to the Belfast incident, but investigators determined that easyJet hadn't installed the updated software nor adopted Airbus's recommendations regarding pilot cross-checking.

EasyJet is evaluating a number of procedural changes, according to the British report. And prompted by the Belfast incident, Airbus last October urged operators to catch data-entry mistakes by requiring "an independent computation made by both pilots" prior to the takeoff roll.

Also according to the AAIB, the European Aviation Safety Agency recently determined that when it comes to pre-takeoff data hazards, the "risk level and its trend need to be monitored continuously."

Long before the June 2015 mix-up, numerous other airlines world-wide suffered a series of data-input problems prior to takeoff, some involving larger aircraft and more-hazardous incidents or accidents.

In March 2014, a US Airways Airbus A320 struck its tail on a Philadelphia runway after the crew rejected takeoff following a computer glitch caused by mistaken data input. The captain initially opted to try to become airborne despite the loss of critical speed measurements and an automated warning he didn't understand. During the next several seconds, the captain commanded the nose of the plane to move sharply up and down three times, according to a National Transportation Safety Board report. The jet bounced on the runway, climbed to an altitude of 15 feet and then slammed back down, collapsing the nose gear, according to investigators. There were no injuries.

One of the most harrowing events occurred five years earlier in Melbourne, Australia, when the co-pilot of an Emirates Airline Airbus A340 mistakenly entered a takeoff weight into the electronic flight bag, or cockpit computer, that was 100 tons less than the plane's actual weight. Calculations for engine thrust and takeoff distance were based on the erroneous weight data, which the captain also overlooked.

The jet initially failed to become airborne when the control stick was used to try to raise the nose and climb. The captain applied full power and then the four-engine jet, carrying 275 people and bound for Dubai, hit some lights and antennas at the end of the strip. It rolled past the paved runway for about four seconds before starting to noticeably climb, according to Australian investigators. It took the pilots five minutes to realize their computational error, and investigators also found significant damage to the underside of the fuselage. After dumping fuel, the plane landed back at the airport about an hour later without any injuries.

Write to Andy Pasztor at andy.pasztor@wsj.com

(END) Dow Jones Newswires

May 14, 2016 22:21 ET (02:21 GMT)

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