Human error is the leading cause of aviation accidents and incidents, contributing to 60-80% of cases. Maintenance errors can have serious consequences, from hydraulic leaks that cause warning lights to engine damage from forgotten tools. Proper training programs in human factors and maintenance resource management can help address underlying causes like fatigue, distraction, and organizational pressures to reduce human errors and improve aviation safety.
Future Integrated Systems Concept for Preventing Aircraft Loss-of-Control (L...
Consequences of Errors in Aviation
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2. CONSEQUENCES OF ERRORS IN AVIATION MAINTENANCE PREPARED BY: SQN LDR OMAR HAYAT KHAN PAF BASE MIANWALI
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4. MAINTENANCE ERROR “ A maintenance error is considered to have occurred when the maintenance system , which includes the human element, fails to perform in the manner expected in order to achieve its safety objectives .”
10. A technician over torqued the outlet union nut damaging internal threads of the hydraulic filter cover and de-shaping the sealing ring of the assembly (F-7P) Error – 1 UNION AND SEAL OF THE HYDRAULIC FILTER COVER ASSEMBLY
11. After 10 minutes of Flight (F-7P), once gears were lowered for a touch and go landing, main hydraulic warning light came steady on with pressure dropping to below normal limit due to hydraulic leak ! Error – 1 (Consequence)
12. A technician adopted incorrect posture for locking fasteners of the electronic nose compartment (F-7P) using a T-handle. Error – 2
13. While applying force upon the T-handle to tighten the fasteners, the tool slipped and impacted the front wind shield of the aircraft inducing a crack ! Error – 2 (Consequence)
14. Maintenance team worked inside the gas path to rectify an engine anomaly (F-7P). A tool was left behind which went undetected through all supervisory checks and the aircraft was given a full power ground run! Error – 3
15. The undetected tool inside the gas path was ingested during Funco run and induced damage to compressor blades (all six stages)! Error – 3 (Consequence)
16. BA maintenance technician on night shift installed the incorrect bolts during windscreen replacement and did not consult the applicable IPB/Tech Manual . Error – 4
17. The incorrect bolts could not hold the left windscreen in flight due to cabin pressure resulting in the wind screen blowing off in air . The pilot was jerked out of his seat by the rushing air and was forced out of the cockpit with his knees snagging onto the flight controls! Error – 4 (Consequence)
18. To save on engine change time, AA maintenance bypassed TO procedure (DC-10 Aircraft) of step-wise removal of engine + pylon and started removing them as a set for the plea of saving 200 man-hours and reducing the number of disconnects (i.e., hydraulic and fuel lines, electrical cables, and wiring) from 72 to 27. Error – 5
19. The self evolved maintenance procedure for engine change resulted in damage to the left wing engine pylon during engine change on aircraft DC-10 (Tail No. N110AA) at AA aircraft maintenance facility on March 29, 1979. Eight Weeks later, the aircraft when scheduled as Flight 191, crashed just after take-off due to No.1 engine/pylon separation from the left wing . Error – 5
20. HUMAN FACTORS ACCIDENT SCENARIO Defenses Gaps Teamwork Reliable Maintenance Good Management Ambiguous instruction (goes unchallenged) Pilot lets it go / fails to check Mis-judgment by Supervisor Error by Worker Operational pressure High work load. Reason’s Swiss Cheese Model
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22. ORGANIZATIONAL & LOCAL FACTORS CRITICAL TO DEVELOPING A SAFETY CULTURE Organizational Local Training and selection of personnel. Knowledge and skill of personnel. Quality of resources as distributed. Quality of resources at Flight Lines / Shops / COE. Organizational Structure Hangar environment. Opportunities for career development. Morale & personalities of Aircraft Technicians.
SIR, THE TOPIC I SHALL SHED LIGHT UPON TODAY IS “CONSEQUENCES OF ERRORS IN AVIATION MAINTENANCE”. THIS PRESENTATION IS PART OF A PROGRAM WHICH DTE OF FIELD TRAINING HAS UNDERTAKEN TO ENHANCE AWARENESS OF AIRMEN ON CERTAIN SALIENT TOPICS WHICH ARE CENTRAL TO FORMULATION OF AN EFFICIENT AND EFFECTIVE SAFETY CULTURE IN PAKISTAN AIR FORCE.
FOREMOST WE MUST UNDERSTAND WHAT DO WE MEAN BY ERRORS? AN ERROR IS A FAILURE ARISING FROM AN ACTION THAT WAS NOT COMPLETED AS INTENDED OR A PLAN FOR ACTION THAT WAS INADEQUATE TO BEGIN WITH ERRORS ARE EITHER SKILL BASED OR KNOWLEDGE BASED. THE SKILL BASED ERROR OCCURS AT EXECUTION STAGE AND IS LINKED TO MEMORY LAPSES THE KNOWLEDGE BASED ERROR OCCURS AT THE PLANNING OR INFERENCE STAGE ONE IMPORTANT THING TO KEEP IN MIND IS THAT ERROR BY DEFINITION HAS NOTHING TO DO WITH THE ASOCIATED OUTCOME WHETHER IT BE CATASTROPHIC OR INCONSEQUENTIAL!
IN THE AVIATION BUISINESS LETS REVIEW THE DEFINITION OF A MAINTENANCE ERROR. A MAINTENANCE ERROR IS CONSIDERED TO HAVE OCCURRED WHEN THE MAINTENANCE SYSTEM, WHICH INCLUDES THE HUMAN ELEMENT, FAILS TO PERFORM IN THE MANNER EXPECTED IN ORDER TO ACHIEVE ITS SAFETY OBJECTIVES.
GENTLEMEN, WE ALL ARE QUITE AWARE OF THE PROVERB “TO ERR IS HUMAN”. SO WE AS HUMAN BEINGS ARE HIGHLY VULNERABLE TO COMMIT ERRORS. HOWEVER, HAVING SAID THAT RESEARCHERS HAVE COME A LONG WAY IN DEVISING METHODS AND TECHNIQUES WHICH MAY HELP US (HUMAN BEINGS) IN REDUCING OR AVOIDING ERRORS WHICH ARE AVOIDABLE.
AT THE ONSET, WE MUST UNDERSTAND THAT ACCIDENTS WHICH CONCERN US THE MOST ARE THE RESULT OF ERRORS WHICH ENDED UP IN CATASTROPHIC CONSEQUENCES BUT SIMPLY THEY ARE JUST THE TIP OF THE ICE BERG. THE ERRORS WHICH REALLY OUGHT TO CATCH OUR ATTENTION ARE THE ONES WHICH NEVER GET REPORTED OR DO NOT END UP INTO ACCIDENTS. HOWEVER IF THEY PERSIST IN BECOMING A TREND OR A CULTURAL NORM THEY ARE BOUND TO BOIL UP INTO ACCIDENTS SOONER OR LATER.
THE WAY AVIATION SAFETY HAS VIEWED HUMAN ERRORS HISTORICALLY HAS EVOLVED WITH PASSING TIME. IN THE PAST, HUMAN ERROR WAS CONSIDERED THE MAIN CAUSE OF ACCIDENTS AND AS TECHNOLOGY MADE RAPID ADVANCES HUMAN ACTION WAS RESTRICTED TO AS MINIMUM AS POSSIBLE TO ELIMINATE THE PROBABILITY OF HUMAN ERROR. HOWEVER, DESPITE STATE OF THE ART FLYING MACHINES AVIATION STILL WITNESSES ACCIDENTS WHICH HAVE PROVOKED AVIATION SAFETY TO VIEW HUMAN ERROR AS AN EFFECT OF DEEPER ISSUES. MOREOVER THE HUMAN ELEMENT HAS TO BE AN INTEGRAL ELEMENT INTO CREATING SAFETY. AVIATION SAFETY HAS GRADUALLY MOVED AWAY FROM BLAMING A PERSON AND FOCUSES ON UNDERTSTANDING THE UNDERLYING REASONS WHICH LED TO A CERTAIN PERSON COMMITING AN ERROR. WE HAVE REALIZED THAT SAFETY CAN ONLY BE IMPROVED THROUGH UNDERSTANDING HUMAN AND ORGANIZATIONAL PERFORMANCE.
IN THE PAST DECADE PAF HAS ALSO RECOGNIZED THE IMPORTANCE OF HUMAN FACTORS IN SAFETY. TO THIS EFFECT, A DIRECTORATE OF HUMAN FACTORS WAS ESTABLISHED IN 2002. THE DTE INITIALLY FOCUSEDINITIALLY FOCUSED UPON ADDRESSING HF ISSUES AMONGST AIRCREW BY LAUNCHING A CRM (CREW RESOURCE MANAGEMENT) WORKSHOP. LATER ON IT WAS MADE MANDATORY FOR ALL AIRCREW. SUBSEQUENTLY, TO ADDRESS HF ISSUES AMONGST GROUND CREW, AN MRM (MAINTENANCE RESOURCE MANAGEMENT) PROGRAM WAS FORMALIZED AND OFFICERS INVOLVED IN AIRCRAFT MAINTENANCE HAVE BEEN GRANTED TRAINING TO FURTHER PROMOTE ITS UNDERSTANDING AMONGST PAF AIRMEN.
GENTLEMEN, MRM IS A VAST FIELD AND DUE TO PAUCITY OF TIME I SHALL COVER ONLY THE CRUCKS OF THE MATER. MRM REVOLVES AROUND MANAGING A SET OF NEGATIVE HABITS FOUND AMONGST MAINTENNACE PERSONNEL WHICH LEAD THEM TO COMMITING ERRORS. THESES ILL HABITS ARE COMMONLY REFERED TO AS “THE DIRTY DOZEN”. THEY ARE :-
WE WILL NOW REVIEW SOME ERRORS AND THEIR CONSEQUENCES. I SHALL START WITH PAF AND BEGIN BY CITING AN EXAMPLE WHERE A TECHNICIAN OVER TORQUED THE OUTLET UNION NUT AND DAMAGED THE INTERNAL THREADS OF THE HYDRAULIC FILTER COVER WHICH RESULTED IN DE-SHAPING OF THE SEALING RING OF THE ASSEMBLY. THE AIRCRAFT TYPE WAS AN F-7P.
WHILE THE AIRCRAFT WAS COMING BACK FOR A TOUCH AND GO LANDING AFTER 10 MINUTES OF FLIGHT MAIN HYDRAULIC WARNING LIGHT CAME STEADY ON WITH PRESSURE DROPPING TO BELOW NORMAL LIMIT DUE TO HYDRAULIC LEAK !
LETS REVIEW ANOTHER INSTANCE WHERE A TECHNICIAN HAD ADOPTED AN INCORRECT POSTURE FOR LOCKING FASTENERS OF THE ELECTRONIC COMPARTMENT OF F-7 AIRCRAFT USING A T-HANDLE.
THE RESULT WAS THAT WHILE APPLYING FORCE ON THE T-HANDLE, THE TOOL SLIPPED AND IMPACTED THE FRONT WIND SHIELD OF THE AIRCRAFT THUS INDUCING A CRACK.
IN A THIRD INCIDENT, WHILE THE MAINTENANCE TEAM WORKED INSIDE THE GAS PATH TO RECTIFY AN ENGINE ANOMALY IN AN F-7P AIRCRAFT AT COE. A TOOL WAS LEFT BEHIND WHICH WENT UNDETECTED THROUGH ALL SUPERVISORY CHECKS AND THE AIRCRAFT WAS GIVEN A FULL POWER GROUND RUN!
THE UNDETECTED TOOL INSIDE THE GAS PATH WAS INGESTED DURING FUNCO RUN AND INDUCED DAMAGE TO COMPRESSOR BLADES (ALL SIX STAGES) A SIMPLE TOOL WORTH A FEW DOLARS ENDED UP CAUSING DAMAGE WORTH MILLIONS
LETS REVIEW SOME EXAMPLES AROUND THE WORLD. A BRITISH AIRWAYS MAINTENANCE TECHNICIAN ON A NIGHT SHIFT INSTALLLED INCORRECT BOLTS DURING WINDSCREEN REPLACEMENT AND DID NOT CONSULT THE APPLICABLE IPB/TECH MANUAL .
GENTLEMEN THE RESULT WAS HORRIFIC!!! THE INCORRECT BOLTS COULD NOT HOLD THE LEFT WINDSCREEN IN FLIGHT DUE TO CABIN PRESSURE RESULTING IN THE WIND SCREEN BLOWING OFF IN AIR. THE PILOT WAS JERKED OUT OF HIS SEAT BY THE RUSHING AIR AND WAS FORCED OUT OF THE COCKPIT WITH HIS KNEES SNAGGING ONTO THE FLIGHT CONTROLS!
TO SAVE ON ENGINE CHANGE TIME, AMERICAN AIRLINES MAINTENANCE BYPASSED TO PROCEDURE APPLICABLE ON A DC-10 AIRCRAFT OF STEP-WISE REMOVAL OF ENGINE + PYLON. HOWEVER THE AIRLINE TECHNICAL STAFF IGNORED TE INSTRUCTIONS AND STARTED REMOVING THEM AS A SET FOR THE PLEA OF SAVING 200 MAN-HOURS AND REDUCING THE NUMBER OF DISCONNECTS (I.E., HYDRAULIC AND FUEL LINES, ELECTRICAL CABLES, AND WIRING) FROM 72 TO 27.
THE RESULT WAS CATASTROPHIC! THE SELF EVOLVED MAINTENANCE PROCEDURE FOR ENGINE CHANGE RESULTED IN DAMAGE TO THE LEFT WING ENGINE PYLON DURING ENGINE CHANGE ON AIRCRAFT DC-10 (TAIL NO. N110AA) AT AA AIRCRAFT MAINTENANCE FACILITY ON MARCH 29, 1979. EIGHT WEEKS LATER, THE AIRCRAFT WHEN SCHEDULED AS FLIGHT 191, CRASHED JUST AFTER TAKE-OFF DUE TO NO.1 ENGINE/PYLON SEPARATION FROM THE LEFT WING. ALL ABOARD THE AIRCRAFT LOST THEIR LIVES.
GENTLEMEN IN AVIATION A SINGLE ERROR ALONE USUALLY DOES NOT END UP IN A CATASTROPHIC ACCIDENT. ITS ONLY WHEN MULTIPLE ERRORS OR LAPSES DAISY CHAIN TO CREATE THE CONDITIONS IN WHICH AN ACCIDENT BECOMES UNAVIODABLE. THIS CONCEPT HAS BEEN EXPLAINED IN REASON’S SWISS CHEESE MODEL. IN THIS MODEL AS YOU CAN SEE HAZARDS ONLY TRANSFORM INTO LOSSES WHEN THEY FIND A STRAIGHT PATH THROUGH HOLES IN MULTIPLE SWISS CHEESE BLOCKS. TEAMWORK, RELIABLE MAINTENANCE AND GOOD MANAGEMENT AVOID HOLES BECOMING ALIGNED TO GIVE WAY TO HAZARDS BECOMING LOSSES. ON THE OTHER HAND OPERATIONAL PRESSURE, HIGH WORK LOAD, ERROR BY WORKER, MISJUDGEMENT BY SUPERVISOR, PILOT FAILING TO CHECK THE ANOMALY OR BECOMES COMPLACENT ARE ALL ERRORS WHICH WHEN DAISY CHAINED ALLOW SWISS CHEESE HOLES TO PERFECTLY ALIGN AND THUS BECOME THE PERFECT RECIPE FOR A DISASTER TO TAKE PLACE.
IT MAYBE WORTHWHILE TO REVIEW THE TOP SIXC MAINTENANCE ERRORS WHICH TIME AND AGAIN HAVE LEAD TO ACCIDENTS. AS THE FAMOUS SAYING GOES – “THERE ARE NEVER NEW ACCIDENTS – ONLY NEW VICTIMS” THE TO SIX ERRORS ARE :- 1- INCORRECT INSTALLATION OF COMPONENTS. 2 - THE FITTING OF WRONG PARTS. 3 - ELECTRICAL WIRING DISCREPANCIES (INCLUDING CROSS-CONNECTION). 4 - LOOSE OBJECTS (TOOLS, ETC.) LEFT IN AIRCRAFT. 5 - INADEQUATE LUBRICATION. 6 - COWLINGS, ACCESS PANELS AND FAIRINGS NOT SECURED.
I WILL NOW COVER SOME FACTORS WHICH ARE CRITICAL TO DEVELOPING A SAFETY CULTURE BOTH AT THE ORGANIZATIONAL LEVEL AND AT A LOCAL LEVEL. THESE ARE:-
GENTLEMEN, PAKISTAN AIR FORCE HAS LOST 73 AIRCRAFT AND MANY PRECIOUS LIVES SINCE THE YEAR 2000. HOWEVER 2010 WAS THE FIRST YEAR IN THE HISTORY OF PAF WHICH WENT BY AS AN ACCIDENT FREE YEAR! LETS ALL MAKE A RESOLVE TO GIVE OUR BEST OF ABILITIES TO OUR PROFESSION AND BY AVOIDING THE DIRTY DOZEN AND FURNISH OUR CONTRIBUTION TO PAF BY MAKING MANY MORE YEARS ACCIDENT FREE BECAUSE THAT IS THE LEAST WE OWE TO PAKISTAN…….