Critical Decision Method

Case Study: B747

Disclaimer: Knowledge, Skills & Ability must known to the SME correct as at 17 Jul 08

• Sweep 1: Identifying and selecting incidents• Sweep 2: Timeline verification and decision point identification

Location: Korea Weather: Winter Time: Dec 2007 morning Event: During push-back, B-747 flight back to Singapore, engine unable to start. Cause of Defects: Starter unable to rotate Decision Point 1: 30 mins to departure -

Option 1: Technical Flight delay (involving 400 pax, 3-hr down-time, spares may not be available) Option 2: Use 1xair-blower to melt the ice (adopted)

Decision Point 2: 20 mins to departure – Realized ice was melting slowing:

Option 3: Revert to Option 1 - Technical Flight delay (involving 400 pax, 3-hr down-time, spares may not be available)

Option 4: Use hammer to break the ice (adopted) Decision Point 3: 15 mins to departure –

Observation: Bits of ice were “dropping off” : Hopeful… Option 5: Blew ground air unit to maximum speed to drive the rotor

Observation: Starter unit came to live Outcomes: Able to start the engine & departure as per schedule

Option 6: Call for immediate Technical Flight delay

Critical Decision Method:B747

• Sweep 3: Progressive Deepening (the story behind the story)

Perceptions: If delay: SME “kena” – passengers complained, supervisors demanded explanation/report, admin loading to the ground crew, … No logistic spares Nature Instinct: Make good/rectify faults as the engine just need to start

Expectations: Must NOT cause any damage to the rotor To start the engine without causing flight delays

Judgements: Safety NOT an issue - Usage of Air Blower – SME observed that the ice was catching the rotor and there was no point to change the rotor Usage of Hammer – SME opined that hammer will create the vibrations with calibrated knocks to loosen the ice. Knocking must

be near to the rotor (approximately 2” from the rotor blade)

Goals: Start the engine by all means: no flight delays

Uncertainties: Usage of Air Blower & Hammer – Not proven methodology & Not in the Manuals

Concerns: Answerable to Stakeholders (Branding: Top Airlines in the World)

Critical Decision Method: B747

• Sweep 4: “What if?”:– Case 1: Ice not breaking up

• Continued blowing hot air to increase temperature to melt the ice

– Case 2: Hammer calibrated wrongly & broke rotor• Activated Technical Flight Delay

– Case 3: If novice was in charge, how?• Refer to Manual & delay flight

– Case 4: If the time has been different, how?• Longer Time

– Monitor & wait for the ice to melt– Use Air Blower to blow longer– Will NOT use hammer

• Shorter Time– If Ice is melting, will increase temperature and delay the flight slightly– If Ice is NOT melting, will declare Technical Flight Delay

– Case 5: What training will have to offer an advantage?• Basic principles of working components

– Case 6: What knowledge, information or tools could have helped?• Availability of spares• Know where to pull items from other operators

Critical Decision Method: B747