Safety Investigation Report 2018:1 Factual Information/1.6/1.6.4 Airworthiness and Maintenance
SAFETY INVESTIGATION REPORT MH370 (9M-MRO)
1.6.4 Airworthiness and Maintenance
The aircraft, Serial Number 28420, was issued with a Federal Aviation Administration (FAA) Export Certificate of Airworthiness No: E370249 on 29 May 2002 and placed on the Malaysian aircraft register as 9M-MRO on 03 June 2002. Ownership of the aircraft, as stated on the Certification of Registration (C of R), was Malaysian Airline System Berhad. The ownership was subsequently changed to Aircraft Business Malaysia Sdn. Bhd., as the lessor, and leased and operated by MAS. A new C of R to reflect the new owner was issued on 17 June 2002.
A Certificate of Airworthiness (C of A) in the ‘PRIVATE’ category was initially issued on 03 June 2002. The aircraft was then flown to Kuala Lumpur, Malaysia where a C of A in ‘TRANSPORT PASSENGER’ category was issued by the DCA Malaysia on 12 June 2002 after the pre-service modifications were accomplished.
The C of A was subjected to annual renewal by DCA Malaysia and its renewal was subjected to compliance to the DCA Malaysia Airworthiness Notice No. 2 - Certificate of Airworthiness Renewal Procedure. The operator was required to declare the aircraft, engine, APU and equipment maintenance status as per the approved Maintenance Schedule, and that they complied with all the mandatory inspections and modifications originating from the State of Manufacture and State of Registry. The Quality Assurance Department of MAS was required to submit an ‘Aircraft Physical Inspection for the Purpose of C of A Issue/Renewal’ prior to the expiry of the C of A. An ‘Aircraft Survey Report for Certificate of Airworthiness’ will be issued by the DCA Inspector after a satisfactory physical inspection on the aircraft has been carried out. At times, the physical aircraft inspection has to coincide with the aircraft scheduled check at base or line maintenance.
The last C of A document review by DCA Inspector was carried out on 15 May 2013 for the C of A renewal and the aircraft physical inspection was carried out by MAS Quality Assurance Engineer (QAE) on 12 April 2013. The only inspection defect noted was a torn left hand flaperon inboard seal which was subsequently replaced. The aircraft C of A was renewed with no airworthiness issues identified.
1) Aircraft Maintenance Schedule
Brief description of the sections follows:
a) Section 1
The definition and introduction of the routine check types. Check intervals and limitations at which the maintenance tasks are to be carried out.
b) Section 2
Task Maintenance Requirements relating to on-wing tasks or tasks to be performed on parts after removal from the aircraft, their intervals and control in the routine maintenance check or independently.
c) Section 3
Component Maintenance Requirements on tasks to be performed on components, their intervals and controlled independently.
d) Section 4
Registers all the applicable job cards which are tied up to the maintenance Checks or Phases of inspections or tasks. The job cards/task cards cover the system, power plants, structural and zonal tasks.
The Master document of the approved Maintenance Schedule is stored in the Engineering Maintenance System (EMS) computer system bank and subject to regular revisions.
In addition to the Maintenance Schedule, a Supplementary Maintenance Schedule covered MAS’ own generated tasks, non-mandatory manufacturer/vendor recommended tasks and non-airworthiness items.
The Maintenance check cycles are translated into the routine Transit Check, Stayover Check, Equalised ‘A’ Check, ‘C’ Check, ‘C Extended’ Check and ‘D’ Check. Table 1.6A (below) summarises the maintenance check intervals.
| Transit | Stay-over | A Check | C Check | CX (Extended Check) | D Check |
|---|---|---|---|---|---|
| Whenever aircraft is on transit | 6 hours planned or 12 hours unplanned |
In 4 parts A1 thru A4 |
In 2 parts C1 and C2
|
52 months | 8 years |
Table 1.6A - Maintenance Check Intervals
| No. | Type of Aircraft Checks |
Date of Aircraft Checks |
Airframe Hours |
Landing Cycles |
|---|---|---|---|---|
| 1 | A1 | 23 February 2014 | 53,301:17 | 7,494 |
| 2 | A4 | 14-16 January 2014 | 52,785:37 | 7,422 |
| 3 | A3 | 13 December 2013 | 52,323:00 | 7,359 |
| 4 | A2 | 04 November 2013 | 51,766:29 | 7,282 |
| 5 | C1 and A1 | 29 August - 26 September 2013 | 51,270:15 | 7,208 |
| 6 | A4 | 24-25 July 2013 | 50,810:19 | 7,132 |
| 7 | A3 | 19 June 2013 | 50,372:07 | 7,069 |
| 8 | A2 | 14 May 2013 | 49,840:28 | 6,994 |
| 9 | A1 | 04 April 2013 | 49,331:52 | 6,910 |
| 10 | A4 | 19-20 February 2013 | 48,836:23 | 6,840 |
| 11 | A3 | 10 January 2013 | 48,291:37 | 6,766 |
| 12 | A2 | 03 December 2012 | 47,749:39 | 6,693 |
| 13 | A1 | 25 October 2012 | 47,214:27 | 6,617 |
| 14 | A1, A4 and C2 | 06-22 July 2012 | 46,727:16 | 6,552 |
| 15 | A4,C2, CX and D | 25 May - 26 June 2010 | 37,014:15 | 5,304 |
Table 1.6B Recent Aircraft Checks
A review of the maintenance records for 9M-MRO revealed the following sequence of recent checks (Table 1.6B [above]) carried out by MAS prior to the disappearance of the aircraft on the 08 March 2014. No significant defects were noted during the checks including the turn-around transit checks.
The Maintenance Schedule incorporated the Structural Inspection Programme based on the B777 Maintenance Review Board Report and B777 Maintenance Planning Document, which are categorised as Structural Inspection Items, Corrosion Prevention and Control Items and Fatigue Related Inspection Items. Inspection findings would be evaluated by the MAS Reliability Section of the Technical Services Department and the department would recommend any follow-up actions as necessary and report to Boeing Company of all significant structural discrepancies.
The Maintenance Schedule also included compliance procedures for Airworthiness Directives5, Airworthiness Limitations (AWL)6 and Structural Inspections with Provisions for Damage Tolerance Rating. It also included Certification Maintenance Requirement Compliance to the Extended Twin Engine Operations (ETOPS)7 operational approval, which was obtained from DCA Malaysia. The MAS B777 ETOPS Maintenance Manual specified the maintenance policies, procedures and requirements for ETOPS operations. A policy to prevent the same personnel to perform or certify certain tasks on multiple similar systems at the same downtime is stipulated. ETOPS task intervals cannot be exceeded. If a concession is given for a check that contains ETOPS task or for individual ETOPS task, the aircraft must be downgraded to non-ETOPS status. 9M-MRO was approved and had no limitations for ETOPS operations at the time of departure from Kuala Lumpur to Beijing. It was not on an ETOPS flight plan. MAS and its fleet of B777 were approved for Reduced Vertical Separation Minimum (RVSM) operation.
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5 An AD is a notification to owners and operators of certified aircraft that a known safety deficiency with a particular model of aircraft, engine, avionics or other system exists and must be corrected. It is mandatory in nature.
6 AWLs are items that the Certificate process has defined as critical from a fatigue or damage tolerance assessment.
7 ETOPS is an aviation rule that allows twin-engine airliners to fly long distance routes that were previously off- limits to twin-engine aircraft.
2) Major Repair
There was an entry in the Aircraft Log Book on 09 August 2012 that the aircraft right wing tip was damaged during taxiing at Pudong, Shanghai Airport. The aircraft collided with a China Eastern Airlines A340-600, registered B-6050. The right wing tip of 9M-MRO ran into the left horizontal stabilizer of B-6050. Part of the aircraft wing tip was ruptured and stuck at the left elevator of the B-6050. Figures 1.6A and 1.6B (below) show the wing tip damages.
Figure 1.6A - Right Wing Tip Damage
Figure 1.6B - Damaged Wing Tip
Boeing produced an Aircraft Survey Report reference WB175/W8134/LN404 on 15 August 2012 and the repair was carried out by Boeing Aircraft-On-Ground (AOG) Team at Pudong, Boeing Shanghai facility from 22 September to 03 October 2012. The Boeing repair scheme was approved under DCA Malaysia’s Statement of Compliance (SOC) Reference Number SC/2012/081 issued on 03 September 2012. At the time of the incident, the recorded airframe hours were at 46,975:43 and landing cycles at 6,585.
There was a requirement for damage tolerance8 information to be incorporated in the aircraft maintenance programme within 24 months from 02 October 2012 as stated in the FAA Form - Organization Designation Authorization (ODA). This damage tolerance information was not yet included in the maintenance programme for the aircraft at the time of the occurrence.
3) Cabin Configuration Change
The fleet of B777 of MAS went through a cabin interior retrofit programme which converted the configuration from 12 First Class seats/33 Business Class seats/233 Economy Class seats to 35 Business Class and 247 Economy Class seats. On 9M-MRO, this re- configuration started on 17 August 2006 and was completed on 08 September 2006. The modification was approved under FAA Supplemental Type Certificate (STC) No. STO1493SE dated 24 January 2005 and DCA’s SOC No. SC2004/98.
4) Mandatory Occurrence Reports
A A review of the Mandatory Occurrence Reports (MORs) for the B777 fleet raised by the Engineering & Maintenance Quality Assurance Department of MAS revealed that only one was raised for 9M-MRO, and this was related to the right wing tip damage stated above. A total of 77 MORs were raised for the MAS fleet of 17 B777 aircraft. MORs raised by the Quality Assurance department are primarily related to technical issues with the fleet. The average age of the B777 fleet as of 01 March 2014 was 14.35 years. 9M-MRO was 11.75 years old.
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8 Damage tolerance means that the structure has been evaluated to ensure that should serious fatigue, corrosion or accidental damage occurs within the operational life of the aircraft, the remaining structure can withstand reasonable loads without failure or excessive structural deformation until the damage is detected.
5) Airworthiness Directives
Maintenance and Inspection records provided by MAS indicated that at the time the aircraft 9M-MRO went missing, the aircraft and engines were fully compliant with all applicable Airworthiness Directives (AD).
The most recent AD, which was accomplished on 17 January 2014, was FAA AD 2012-13-05 which made mandatory the accomplishment of Boeing Service Bulletin 777-35A0027 which requires replacement of low pressure oxygen hoses in the cockpit. The changes provided in the service bulletin are to prevent damage to the low pressure oxygen hoses that may be subjected to electrical current. An electrical current condition in the low pressure oxygen hose can cause the low pressure oxygen hose to melt or burn. This could result in smoke and/or fire in the flight compartment. An operator (not MAS) reported that a fire originated near the first officer's area which caused extensive damage to the cockpit. One scenario of the causes being considered is that an electrical fault or short circuit resulted in electrical heating of the low pressure oxygen hoses in the flight crew oxygen system. This service bulletin is to replace low pressure oxygen hoses with non-conductive low pressure oxygen hoses located in the cockpit. The replacement of the low pressure oxygen hoses will prevent electrical current from passing through the low pressure oxygen hose internal anti-collapse spring which can cause the low pressure oxygen hose to melt or burn.
An FAA AD 2014-05-03 was issued and became effective on 09 April 2014. This AD made mandatory the accomplishment of Boeing Service Bulletin 777-53A0068 which addresses a crack in the fuselage skin under the SATCOM antenna adapter. The Service Bulletin was issued on 12 June 2013. The AD was issued to detect and correct cracking and corrosion in the fuselage skin, which could lead to rapid decompression and loss of structural integrity of the aircraft. However, this AD was not applicable to 9M-MRO as the location and configuration of the antenna on the aircraft, as delivered by Boeing ex- production, were different and not affected by the issues highlighted in the Service Bulletin.
6) Technical Log
a) MR1 and MR2
The MAS Technical Log Book was divided into Maintenance Report 1 (MR1) and Maintenance Report 2 (MR2). The MR1 has provision for the flight crew to enter any aircraft defects for each flight phase. It can also be used to enter maintenance required and rectifications by the Licenced Aircraft Maintenance Engineers (LAME) or Approval Holders, or defer defects within the Minimum Equipment List (MEL) procedures to the Maintenance Report 2 (MR2) section.
A review of the Technical Log entries for 9M-MRO since the last D check in June 2010 did not reveal any significant defects or trend.
The most recent entries made in the Technical Log Book for 9M-MRO are listed in Appendix 1.6A.
b) Oxygen System Replenishment
A Technical Log entry of interest, made on 07 March 2014, is the replenishment of crew oxygen system. This replenishment was reviewed in detail together with information gathered from the interview of the LAME who performed the task. Replenishment (servicing) of the crew oxygen system is a routine procedure, carried out before the minimum pressure required for departure is reached, usually carried out during a Stayover check. The minimum pressure for despatch as per the MAS Minimum Equipment List (MEL) is 310 psi at 35°C for 2-man crew and with a 2-cylinder configuration (as installed on MAS B777 fleet).
It has been the practice of the airline to service the oxygen system whenever time permits, even if the pressure is above the minimum required for despatch.
During the Stayover check on 07 March 2014, the servicing on 9M-MRO was performed by the LAME with the assistance of a mechanic, as the pressure reading was 1120 psi. The servicing was normal and nothing unusual was noticed. There was no leak in the oxygen system and the decay in pressure from the nominal value of 1850 psi was not unusual. The system was topped up to 1800 psi. Before this servicing, maintenance records showed that the system was last serviced on 14 January 2014 during an A4 check.
A small amount of oxygen is normally expended during pre-departure checks of the oxygen masks by the flight crew.
Oxygen pressure is also dissipated by a bleed valve in the system for a few seconds during engine start following the end of a flight.
7) Deferred Defects (Maintenance Report 2)
A review of the aircraft records from the MAS Maintenance Control Centre (MCC) showed that the following defects were outstanding on 9M-MRO and deferred to the Deferred Defect Log (Table 1.6C, [below]). The hole found on the right engine acoustic panel, mentioned below in item 7, was of dimension of approximately 1 inch by 1 inch and is allowed to be deferred by the B777 Maintenance Manual until permanent repair is carried out within 500 flight hours. This minor damage is considered normal wear and tear of the engine nacelles and does not pose any hazard to the engine.
| No. | Deferred Date | Defect |
|---|---|---|
| 1 | 25 Sep 2013 | To carry out installation test for aft water quantity gauge. |
| 2 | 31 Oct 2013 | In-Flight Entertainment (IFE)
Airshow does not show arrival time/time |
| 3 | 07 Nov 2013 | FrFrom Daily Engineering Operations
Report (DEOR) |
| 4 | 21 Jan 2014 | Toilet 3F-1L mirror light lens broken |
| 5 | 30 Jan 2014 | Pre-departure F/O seat power adjustment (fwd/aft) found inoperative. |
| 6 | 05 Mar 2014 | Please check alignment for left runway turn/off light. |
| 7 | 05 Mar 2014 | Hole found at 6 o'clock position of the right engine acoustic panel. |
Table 1.6C - Deferred Defects
8) Engine Health Monitoring
Engine Health Monitoring (EHM) was contracted out to Rolls Royce, the engine manufacturer. Engine data ‘snapshot’ reports were generated by the Aircraft Condition Monitoring System (ACMS) and transmitted via ACARS to MAS, who then submitted them to Rolls Royce for analysis on its behalf. The transmitted engine parameters primarily used to assess engine health are:
- Turbine Gas Temperature
- Shaft Speeds
- Shaft Vibration (Low Pressure, Intermediate Pressure and High Pressure)
- Oil Pressure
- Oil Temperature
The EHM system trend reports over the last 3 months which covered ‘snapshot’ data points gathered at take-off, climb and cruise received through the ACMS show no evidence of unusual engine behaviour for both engines. On the occurrence flight, 2 EHM reports were transmitted; the first was a Take-off report generated at 1641:58 UTC, 07 March 2014 [0041:58 MYT, 08 March 2014] and the second was a Climb report at 1652:21 UTC, 07 March 2014 [0052:21 MYT, 08 March 2014]. Reports are transmitted by ACARS at convenient times during the flight (not necessarily at the time of generation/data capture). Both reports did not show any unusual engine behaviour. The data transmitted on these reports are shown in Appendix 1.6B - Engine Health Monitoring Decoded Data for Take-off and Climb Reports. The ACMS will also generate other pre-defined engine reports including engine parameters’ exceedance reports. However, no such EHM reports were received during the flight. Position reports are also transmitted, via ACARS, every 30 minutes. Refer to Section 1.9.4 for further details.
9) Central Maintenance Computing System
The Central Maintenance Computing System (CMCS) collects and stores information from most of the aircraft systems. It can store fault histories as well as monitor and conduct tests on the various systems. The fault history contains details of warnings, cautions and maintenance messages.
At regular intervals, during flight, the CMCS transmits any recorded fault messages, via the ACARS, to the Maintenance Control Centre (MCC) of MAS. This helps in the planning and preparation for the rectification of any potential aircraft defects at the main base or line stations.
The traffic log of maintenance messages transmitted for the last 10 flights on 9M-MRO were reviewed. There were messages transmitted, indicating that the CMCS was functioning prior to the occurrence flight. However, no maintenance messages were transmitted during the occurrence flight. These messages are transmitted in real time that is, as the faults occur.
Maintenance messages are not displayed on the Engine Indicating and Crew Alerting System (EICAS) in the cockpit and they are not used to determine the airworthiness of the aircraft. They provide diagnostic information useful in troubleshooting or maintenance planning. Only maintenance messages which trigger EICAS Alert messages require maintenance action (including deferment, if allowable) prior to despatch.