Factual Information 2015:1.6 Aircraft Information/1.6.3/1.6.3.6 Technical Log/1.6.3.6.1
This page contains an extract from MH370/01/15 Factual Information which accompanied the (first) Interim Statement released by The Malaysian ICAO Annex 13 Safety Investigation Team for MH370 on 8th March 2015.
1.6.3.6.1 Oxygen System Replenishment
The crew oxygen system replenishment on 07 March 2014 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).
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.
The crew oxygen system is supplied by two cylinders; each holds 115 cubic ft. (3150 litres) of oxygen at 1850 psi. Table 1.6C below shows the expected duration of oxygen supply from the two cylinders with the dilution control of the crew oxygen masks in ‘Normal’ position and aircraft at 36,000 ft. with a normally pressurised cabin (cabin altitude of 8,000 ft.) and an unpressurised cabin (cabin altitude of 36,000 ft.).
| Aircraft Altitude: 36,000 ft. Cabin Altitude: 8,000 ft. |
Aircraft Altitude: 36,000 ft. Cabin Altitude: 36,000 ft. |
||
|---|---|---|---|
| No. of Crew Members |
Expected Duration (hour) |
No. of Crew Members |
Expected Duration (hour) |
| 1 | 42 | 1 | 27 |
| 2 | 21 | 2 | 13 |
| 3 | 14 | 3 | 9 |
| 4 | 10.5 | 4 | 6.5 |
Table 1.6C Expected Duration of Crew Oxygen
Note: Further details of the Crew Oxygen system, Passenger Oxygen system and Portable oxygen can be found in Appendix 1.6E – Aircraft Systems Description under Section: Oxygen Systems.
Source: Malaysian ICAO Annex 13 Safety Investigation Team for MH370, 8 March 2015, Factual Information MH370/01/15
The Factual Information was updated in 2018 by the Safety Investigation Report MH370/01/2018 which added new content but did not include all of the previous data.