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Transcript of HUMAN FACTOR
Why is the purge door not noticed?
Error Prevention Strategies
BA’s Cardiff-maintenance team knew about the manual error, and had notified Boeing
The QEAN system at the maintenance organisation is an important system that allows production staff and planning staff to raise technical queries with the Technical Services group.
Do not have proper tracking system to track long term issues.
The maintenance organisation had a system in place, called QDR, which lent itself to maintenance error reporting but maintenance errors identified before the aircraft left the facility were not routinely being reported.
. A reporter might fear being blamed or a colleague being blamed, or the reporter might believe that no effective action would be taken to prevent a recurrence.
Thursday, June 10, 2004
BOEING 777 SPEWED FUEL FROM UNCOVERED FUEL TANK
Type of Maintenance: Base Maintenance
AIR TURN BACK
BA’s Cardiff, Wales heavy maintenance site
Consistently state task clearly in jobs cards
A standard template could be produced to reduce ambiguity of writing by different personnel or raise a routine card
If information is unclear, always ask and not assume
Plan and prepare ahead of task. Stay alert and be aware of task given
Check with experienced superior if all the task given is true and sufficient
Be vigilant at all times, during completion of task, question the possible dangers. If doubts are against manufacturer, contact manufacturer to double confirm
Aircraft configuration variability
Purge door should be made more accessible. Have the purge door painted in a different colour to avoid it going unnoticed
Employers should highlight the difference between two aircraft bodies during type training so that the engineers could be aware of any changes in procedures and respond accordingly when maintaining different aircraft
All engineers and technicians should always read up frequently on their task to help them understand their situation more. This helps to raise awareness in their job.
All request and response should be recorded and monitored closely to prevent confusion and mistakes. Response interval should be inspected frequently to prevent any chain errors.
The QEAN system only provided feedback to the originator of the query and not to staff in general.
Flight crew at holding point reported a trail of smoke
London Heathrow Airport to Harare, Zimbabwe
Jettison fuel to reduce to maximum landing weight
AIR TURN BACK
Aircraft landed with Autobrake 1
the left engine was shut down and the aircraft taxied to
Stand 406 where the passengers were disembarked normally.
Fuel escaping from the CWT through the open purge door
subsidiary of operator
Reasons for purge door removal
purging of the tank
Pass a light through the purge door opening to assist with the
rear spar inspection
Carrying out the CWT special
float switch check
CWT DRAIN AND PURGE PROCEDURE
To reduce fuel vapour level to an acceptable level
No mention of the purge door in the purging procedure
REAR SPAR INSPECTION
scheduled maintenance task required to be performed at every 2C check and it required access to the centre section of the CWT
front spar incorrectly
labelled as the rear spar
open purge door would not have assisted with those checks except to provide some minimal additional
FUEL QUANTITY CHECK
The fuel leak check could have detect the leak from the purge door.
AMM: Fuel required to check seven doors 32,000kg
Maintenance: Highest recorded fuel load 26,800kg
Revised AMM: Fuel required to check purge door: 52,163kg
Job cards for purge and drain:
1. left center fuel tank drained and purged
2. right center fuel tank drained and purged
3. center tank drained and purged
*No purge door removal are stated
Job cards for leak check:
1. leak check carried out for left center tank
2. leak check carried out for center tank
3. leak check carried out for right center tank
*No purge door leak checks are done
TTL 1 :
No reference to any baffle doors
Responsibilities of the operator’s department
Responsibilities of the maintenance organisation's departments
Operations Quality Manager
Technical Information Service manager
Technical documentation and Drawings
issuing and approving design documents for Boeing 747 and 777 series aircraft
Responsibility of Job Card?
Maintenance organisation was generating the job cards with no oversight from the operator yet the job cards had to be generated in accordance with the operator’s Approved Maintenance Programme
All contracted maintenance was carried out in accordance with the contract
The frequency of monitoring (or auditing) was to be agreed between the operator and the National Aviation Authority
included checks of safety actions
taken by the maintenance organisation
1 october 2004
Request for engineering advice form
Technical Services Group
UNSOLVED AFTER 2 YEARS
Query for Engineering Advice Note
QUERY TO BAFFLE DOOR
‘we request some panel numbers not part numbers. Now that you
have a part number for said panel could it not now be furnished
with a panel number and added to the relevant part of the AMM.’
Request Panel Identification
"Baffle doors missing from
Maintenance Planning Document"
‘Boeing baffle ribs are located at Ribs 2,3,4,5,13, and 15 on the
wing… each of these ribs have openings for access, but no panels.
There are no access panels to these areas on the bottom of the
Mistook the request to relate to the ribs inside the wing
Technical services appeared to overlook this discrepancy and no further action was taken
"not yet seen any evidence of the baffle panels appearing in the MPD or AMM"
‘these changes will come but at this present time they are slow and
we, unfortunately, cannot pressurise Boeing to speed up.’
Closed the issue having responded in 2002
Open query had not been tracked
QEAN had been closed
but query was still unanswered and not tracked
Removal of baffle doors was a routine task because it was necessary to remove them to carry
out the rear spar inspection
NO PANEL NUMBER
NO ACTION TAKEN TO GENERATE ROUTINE CARDS
RAISE DEFECT CARDS EACH TIME THE BAFFLE DOORS HAD TO BE REMOVED
BAFFLE DOOR REMOVED BUT REMOVAL NOT RECORDED ON DEFECT CARDS
UNRECORDED REMOVAL OF THE PURGE DOOR
CWT PURGE PROCEDURE
"Remove the center wing tank purge door"
747 purge door opening is twice the diameter of the 777 purge door opening
*No purge door removal are stated
Same colour as background
Tethered to the aircraft
Refit Job Card
Ensure that all panels were refitted
verifying that the panel storage rack was empty at the end of a maintenance
All fuel tank access doors, except for the purge door, have to be placed somewhere once removed and this would normally be on the panel rack. As a result, the purge door was forgotten during a check of the panel rack at the end of a maintenance input which serves as a ‘safety net’ that all panels have been re-installed.
4MARCH2004 - 5MARCH2004
Query relating to rear spar inspection diagram
REAR SPAR INSPECTION
Rear spar need inspecting
Contact aircraft manufacturer to query the rear spar inspection diagram
rear spar inspection diagram
Confirmed rear spar was the area to be inspected'
Confirmed diagram incorrect and will be corrected
Baffle issue not mentioned
No action was taken to withdraw the confusing diagram or to highlight its errors to other maintenance staff.
AMM revision shipped on 22 April 2004 on a Compact Disc
AMM FREEZE PERIOD
5 SEPT 2003
24 JANUARY 2005
To facilitate the implementation of the EWS
Operator's fleet engineers
Review future revisions
changes deemed to affect aircraft safety or health safety
Included change to rear spar inspection diagram
Replace many different legacy database systems in use by both the maintenance organisation and the operator
illustrations from the AMM will be included in the job card database system.
Double workload to revision to jobcards
planning group would often only have time to copy and paste the tasks from the aircraft manufacturer’s MPD.
Worked on maintenance organisation for 9 years
Work primarily on 747
Undergo 777 training course for 18 months
Authorised to work on 747 and 777
did not know where the purge door was
99% worked on 747
Was not trained on 777 but worked on 777 on 2 occasions
Did not know where the purge door was
worked for 747 and 777 for 4 years
did not know where the purge door is on 777
carry out rear spar inspection. used a sniffer(a fuel vapour level detector) to check vapour level. Misinterpreted forward spar for rear spa
carried out the fuel leak-checks on the wing tanks and CWT of G-YMME
worked for the maintenance for 11 years
completed 777 training course but only work on 777 for 10 days
did not know where the purge door is
Companies should enforce strict policies and distribute the responsibility accordingly.
Quality of job card poorly written and cause misinterpretations.
The rear spar inspection job card was inadequate because it simply reiterated the words from the Boeing task card without offering clear directions on the area to be inspected or noting the access requirements for the inspection
Unavailable reference to the purge door
The maintenance team did not have a procedure in place for handling removable panels
which may be left tethered
fuel quantity required to leak-check the purge door was incorrect
the rear inspection diagram incorrectly depicted the area to be inspected
Aircraft configuration variability
Employees working on a Boeing 747 have routine to remove the purge door, however the Boeing 777 does not require the purge door to be removed
The purge door, which was tethered to the aircraft ,was forgotten during a check of the panel rack at the end of a maintenance input which serves as a ‘safety net’ that all panels have been re-installed.
The purge door is in a remote corner and have the same color as the background, thus it could easily go unnoticed
747 purge door opening has twice the diameter of the 777 purge door opening
The audit period was extended and safety checks on aircraft were missed
QEAN do not have proper tracking system to track long term issues.
Due to AMM freeze period, revision to change the rear spar inspection diagram were not sent to the organisation
EASA 145 required an Interface Agreement and it did not state responsibility for job cards content
QEAN system only provided feedback to the originator of the query and not to staff in general.
Implementation of the EWS led to increased workload of revising job cards and undermines the engineering of job card
Request for panel number was mistaken for part number for baffle doors. Without panel number, there was no records of removal of baffle door. This undesirable practice contributed to the unrecorded removal of purge door.
No action was taken to withdraw the rear spar diagram or to highlight its errors to other maintenance staff.
Planners and planning engineer should be adequately trained before they are allowed to write or authorised job cards; otherwise supervision should be provided
All manuals and procedures should be reviewed thoroughly to check for any critical information that is not included.
Once identified, Boeing should be notified so that changes could be made to the manual as well as to the job cards, to be more comprehensive.
Boeing Manufacturers should revise on their maintenance manual and ensure that errors like in this case be non-existent. After which , an external party , like AAIB should verify if the maintenance manual fulfill its requirement of credibility.
Do not follow procedures/manual blindly. With the relevant experience, one should be able to identify the mistakes,
Otherwise, if in doubt, verify it with more senior and experience engineer/ Error in procedures/manual should be made known to manufacturer
Maintenance manual of a particular aircraft could cross reference to another aircraft during a similar but different procedure that could be mixed up to prevent confusion
In addition, companies should ensure that they undergo training/workshop that refresh and update the employee on new systems and procedures so that they stay up to date to the fast growing aircraft technology.
Inexperienced employee should never be left to their job alone, instead, they should be constantly supervised.
Frequent meeting should be held to report on any loop holes within the system so that they can be correctly immediately.
Ensure that the implementation of new system does not undermine any existing system or have effects on the organisation functions.
Manufacturers should be responsible for notify these companies by means of an email or fax immediately following an update of maintenance manual . Hence these companies have sufficient time to update their staff and provide immediate correction
If there is a change of technical service engineer before the queries are answer, make sure that information is passed down for continuity of work
Technical service engineers should always ensure that all queries are tracked and answered before the QEAN is closed
The CAA should closely monitor the frequency of audit carried out by the operators. It should be emphasized that any changes in the audit period should be consulted
Adequate resources must be available before a new system is introduced