Easyjet A21N at Edinburgh and Bristol on Jan 3rd 2021, operated outside of permitted CG envelope

Last Update: October 14, 2021 / 14:10:50 GMT/Zulu time

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Incident Facts

Date of incident
Jan 3, 2021

Classification
Incident

Airline
Easyjet

Flight number
U2-426

Aircraft Registration
G-UZMI

Aircraft Type
Airbus A321-Neo

ICAO Type Designator
A21N

An Easyjet Airbus A321-200N, registration G-UZMI performing flight U2-426 from Edinburgh,SC to Bristol,EN (UK), departed Edinburgh's runway 06, climbed to FL330 enroute and landed on Bristol's runway 09 about 50 minutes after departure.

The UK AAIB reported they have opened an investigation because the flight "operated outside the flight CG envelope". The occurrence was rated a serious incident.

On Oct 14th 2021 the AAIB released their bulletin stating, that during boarding of flight U2-426 from Edinburgh to Bristol it was discovered that the previous flight U2-425 from Bristol to Edinburgh may have been operated outside limits for CG. The AAIB released following discussion:

This serious incident was caused by a combination of operating factors in a complex system interacting in a manner which had neither been designed nor predicted. If passenger and cargo distribution on an aircraft leads to an undetected out of trim condition, the potential outcome could be unexpected handling qualities or control limitations.

The final weight and balance calculation is completed by the operating crew based on the loading data presented to them by ground personnel. If that information is incorrect, unless further evidence is available to indicate an anomaly, this final safety barrier is compromised as was the case at Bristol Airport.

Prior to the Covid-19 pandemic, the turn around coordinator (TCO) would hand the Loading Form and Certificate (LFC) to the flight crew, providing an opportunity for them to query any Last Minute Changes (LMCs) directly. However, the operator’s biosecurity measures required interactions with the flight deck to be minimised, so the LFC was delivered to the cabin manager (CM) in the cabin. As the TCO was not on the flight deck, the crew were more likely to accept changes presented to them without discussion and complete their tasks as defined in their SOPs. However, as the CM checked the LFC before handing it to the commander at Edinburgh, the error was identified and trapped. This resulted in the commander filing the safety report which triggered the operator’s investigation, which ultimately led to the cause of the error being detected.

The AAIB reported that the scheduled aircraft, an A320, to perform the rotation from Bristol to Edinburgh and back, had to be replaced with an A21N aircraft in Bristol. The crew originally scheduled was not qualified to operate the A321 Neo, a standby crew was called in, accepted the LFC handed by the TCO to the CM, who in turn handed the LFC to the flight crew. The flight to Edinburgh went on as normal and was completed with a safe landing.

During boarding in Edinburgh the TCO in Edinburgh handed the LFC to the CM, who in turn handed the LFC to the flight crew commenting, that it did not appear the passengers were distributed as shown on the LFC. The commander therefore ordered a manual count of the passengers in the zones, which confirmed the passenger distribution was incorrect. The flight crew used their electronic flight bag (EFB) to compute the mass and balance from the manual count and found the CG was forward of the permitted operatiing limit. The captain instructed the CM to reseat the passengers to their proper seats and annotated the LFC with the correct seating. The captain left the cockpit to discuss the issue with the TCO, they agreed that there was an IT system issue following the aircraft change, the LFC did not reflect the correct zones of the A21N. The aircraft departed and continued this and the subsequent two sectors without incidents. The commander, after return to Bristol following another rotation from Bristol to Barcelona and back, filed an air safety report, which triggered an internal investigation by the operator and Airbus.

Initial checks found, that the flight U2-425 to Edinburgh had indeed been operated out of the permitted CG limits. The AAIB stated:

It was concluded that following the change of aircraft type on the day of operation, the aircraft type and registration had been updated on the aircraft management system, but that change had not been identified by the departure control system responsible for generating the information recorded on the LFCs. When the TCO arrived for duty, he was advised by the operations centre that the flight had been changed from an A320 to an A321-NEO.

He prepared the LFC with the correct type and registration details. On arrival at the gate, he extracted the load details from the departure control system to complete the LFC but, unknown to him, the type change had not registered. Consequently, the flight was closed with the passenger distribution reflecting the seating configuration for an A320 and not an A321-NEO.

For the sector from Edinburgh, it was found that the ground handling agent had noted that an aircraft type change had been recorded in the aircraft management system. However, the TCO was directed to deal with an aircraft returning to another stand with a technical issue so did not review the departure control system. Rather, at the point of close-out of the flight, the load details were passed over the radio by the gate staff to the TCO to complete the LFC. While this was in accordance with procedures, the opportunity to detect the information in the system being in error was reduced. The investigation commented that:

‘This clearly contributed to why the issue was not already noticed. Trust was put in the fact that there was no reason to think the departure control system would not update the bays in line with the type change’.

The aircraft manufacturer concluded, that even on the sector U2-425 from Bristol to Edinburgh no certified aircraft limitations had been exceeded, there was no impact on the controllability of the aircraft, stating: "Following their analysis of the Flight Data Recorder, Post-Flight Report and load sheets, the manufacturer concluded that the flight was conducted within certified limits and that the aircraft could be returned to service. "

The operator further determined that a computing process running in the background every five minutes would detect such changes like aircraft type changes and update any changes. However, due to Covid a high number of schedule changes by the operator caused the validation process to take longer than normal. "Therefore, changes made outside the five-minute
window were not detected automatically by the system."

Metars Edinburgh:
EGPH 031850Z 03004KT 350V060 9999 -RA SCT007 BKN016 BKN033 02/02 Q1028=
EGPH 031820Z 02003KT 9000 SCT012 BKN021 02/02 Q1028 RESHGS=
EGPH 031750Z 15004KT 2700 SHGS BKN012 OVC031 02/01 Q1028=
EGPH 031720Z 02001KT 9999 BKN016 02/01 Q1027=
EGPH 031650Z 11007KT 020V150 9999 SCT008 BKN036 02/02 Q1027 RERA=
EGPH 031620Z VRB02KT 9999 SCT049 02/01 Q1027=
EGPH 031550Z 36003KT 9999 SCT045 02/01 Q1027=
EGPH 031520Z 01004KT 330V060 9999 6000N -RA BKN012 BKN023 OVC038 03/02 Q1027=
EGPH 031450Z 08004KT 9999 -RA BKN018 03/02 Q1026=

Metars Bristol:
EGGD 031950Z AUTO 04012KT 9999 OVC006 02/02 Q1019=
EGGD 031920Z AUTO 04012KT 9999 OVC005 02/02 Q1018=
EGGD 031850Z AUTO 03010KT 340V060 9000 -RA OVC006 03/02 Q1018=
EGGD 031820Z AUTO 03011KT 9999 BKN007 OVC035 02/02 Q1018=
EGGD 031750Z AUTO 03011KT 9999 BKN007 OVC033 03/02 Q1018=
EGGD 031720Z AUTO 04013KT 9999 BKN006 OVC031 02/02 Q1018=
EGGD 031650Z AUTO 03012KT 9999 BKN005 OVC029 02/02 Q1018=
EGGD 031620Z AUTO 03012KT 9999 OVC004 02/02 Q1018=
EGGD 031550Z AUTO 02008KT 9999 BKN006 OVC019 03/02 Q1018=
Incident Facts

Date of incident
Jan 3, 2021

Classification
Incident

Airline
Easyjet

Flight number
U2-426

Aircraft Registration
G-UZMI

Aircraft Type
Airbus A321-Neo

ICAO Type Designator
A21N

This article is published under license from Avherald.com. © of text by Avherald.com.
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