Singapore Airlines Flight 368 Engine Fire Airlines Flight 368 Engine Fire Ng Junsheng Head...
Transcript of Singapore Airlines Flight 368 Engine Fire Airlines Flight 368 Engine Fire Ng Junsheng Head...
Singapore Airlines Flight 368 Engine Fire
Ng JunshengHead (Technical)/Senior Air Safety Investigation
Transport Safety Investigation Bureau
3rd Annual Singapore Aviation Safety Seminar29 March 2017
What Happened?
• 27 June 2016, Boeing 777-300ER departed Singapore
• 2 hrs into flight, low oil quantity indication for right
engine
• Subsequently, vibration felt in control column and
cockpit floor
• Decision to return on Singapore with right engine at idle
power
• After landing, fire observed in vicinity of right engine
• Fire extinguished, disembarkation via mobile stairs
Scope
• Investigation Process
• Key Findings
• Areas of Safety Concern
• Safety Improvements
• Safety Recommendations
Investigation Process
• Investigation conducted in accordance with ICAO
Annex 13
• Aim to improve safety, not to apportion blame or liability
• Investigation team included:
o TSIB Singapore
o NTSB
o Advisors from engine, aircraft manufacturer & FAA
• Field investigation in Singapore
• Engine and component teardown in US
Investigation Process
• Scope of investigation included:
o Identifying ignition sequence and fire development
o Reviewing regulatory and design issues
o Human factors in relation to flight operation and decision
making
Key Findings
• Fuel found in areas usually filled with oil
• A cracked tube found within the Main Fuel Oil Heat
Exchanger (MFOHE) of right engine
Key Findings
• Fuel leak into:
o Right engine oil system
o Various areas within right engine
o Fan air flow path
• High velocity of airflow around engine in-flight
o Unsuitable for ignition and sustained combustion
• On landing, thrust reversers deployed
o Airflow over core exhaust nozzle reduced
o Most significant reduction – area aft of turkey feather
seal
o Hot surface ignition occurred
o Accumulated fuel in fan duct distributed over lower
surface of wing
Key Findings
Turkey feather seal
Area discoloured due
to high temperature
exposure
Key Findings• Fire development:
o Into engine core:
1. Fire progressed forward in fan duct
2. Through reverser blocker doors
3. Into booster
4. Progressed to high pressure compressor &
variable bleed valve system
o Fire on runway
- Engine was shut down
- During spool down, excess fuel in booster cavity discharged
through fan duct
- Collected on runway and caught fire
o Fuel distributed over lower surface of right
wing caught fire
Areas of Safety Concern
Design of MFOHE
• Event MFOHE design revised based on original MFOHE
designed for basic GE90 engine
• Met all regulatory requirements through combination of
o Similarity in design
o Actual testing
• No tube cracking in original MFOHE design
• Tube cracking only in high service hour MFOHE units
based on revised design
Areas of Safety Concern
Design of MFOHE
• Root cause of cracked tubes:
o Diffusion bonding – adhesion of tubes to baffle walls
o Stress concentration in crimped areas – contributing factor
• Potential for all tubes to crack, regardless if crimped
• MFOHE designed for unlimited service lifespan
• No periodic inspection requirement on MFOHE internal
portion
Areas of Safety Concern
Resolution for cracked tube problem
• Service Bulletin (SB) in place after event of lesser
consequence in Aug 14
o Corrective actions required by next engine shop visit
• Event MFOHE not incorporated with SB
o Last shop maintenance before SB issuance
• Urgency for SB compliance based on FAA’s Continuous
Airworthiness Assessment Methodologies (CAAM)
• Despite adherence to CAAM, cracked tube recurred
with a more severe consequence
Areas of Safety Concern
Execution of checklist
• Flight crew encountered “FUEL DISAGREE” message
on return journey
• TOTALIZER fuel quantity less than CALCULATED fuel
quantity
o Should have proceeded on to FUEL LEAK checklist
• Crew believed CALCULATED fuel quantity was not valid
due to:
o Input changes to flight management system
o No longer on planned flight route
o At last routine fuel check, 600 kg more fuel than
expected
Areas of Safety Concern
Execution of checklist
• Crew performed own calculation which tallied well with
TOTALIZER value
• Crew concluded “FUEL DISAGREE” was spurious
• FUEL DISAGREE checklist was not performed as
intended
• Additional observations:
o FUEL LEAK checklist cannot be performed at unequal
thrust setting
o Infrequently used checklist may not be reviewed/
refreshed after initial training
Areas of Safety Concern
Decision making and response during non-normal situation
• No cockpit indication of fire
• Flight crew informed of fire by ATC
• Flight crew depended on fire commander (FC) as primary
information source
o In line with operator’s training
• 1st communication, FC informed flight crew
o trying to contain fire, described fire as “pretty big”
• FC assessed no risk of fire spreading, recommended
disembarkation
Areas of Safety Concern
Decision making and response during non-normal situation
• Pilot-in-command aware decision to evacuate lay with
him
• After over 2 minutes
o FC confirmed fire under control
o Maintained initial recommendation for disembarkation
• Swifter decision on evacuation desired
• Possible resources to aid decision making not utilised:
o Cabin crew
o Taxiing camera system
o Cockpit escape window
Areas of Safety Concern
Decision making and response during non-normal situation
• Research has shown:
o Decision making under stress may become less
systematic and more hurried
o Fewer alternative choices are considered
• Not possible for checklists to include all possible
emergency/abnormal situation
• Critical to have ability to consider alternatives/ available
resources not dealt with by any checklist
Safety Improvements
• 25 Jul 16, TSIB (then AAIB Singapore) made safety
recommendations to:
o Accelerate MFOHE SB implementation
o Review need for interim operational procedures should
flight crew encounter similar fuel leak in-flight
Previously Now
MFOHE SB implementation
- By next engine shop visit - By August 2017
Operationalprocedures for in-flight fuel leak
None - Interim in-flight procedure availablein event of MFOHE fuel leak
- Reduce likelihood of fire after landing
Engine manufacturer diagnostics algorithm
- Developed based on 2014 event- High false alarm rate- No real time detection
- Improved detection capability- Reduced false alarm rate- Real time monitoring by integration
into B777 ACMF
Safety Improvements
• No instance of leak in MFOHEs incorporated with SB
• FAA working with engine manufacturer
o Monitor analysis and design issues affecting MFOHE
o Implement improvements where necessary
Safety Recommendations
• 13 further safety recommendations made
• Areas of concern includes:
o Study to understand if cracks may develop in crimped
tubes that have no history of cracking
o Evaluate need to periodically inspect MFOHE internal
components
o Evaluate need for guidance to perform leak check with
engines operated at unequal thrust
o Improve sensitivity of fuel leak detection during
maintenance checks
Safety Recommendations
• Areas of concern includes (continued):
o Review airworthiness control system ensure expeditious
implementation of corrective actions
o Ensure emergency and non-normal checklists are
performed correctly
o Develop flight crews’ ability to consider alternatives/
resources in situations no dealt with by any checklist
• Final report available at:
https://www.mot.gov.sg/About-MOT/Air-
Transport/AAIB/Investigation-Report/
Thank You
Questions?