Communications:9M-MRO APU Report

MH370 DECODED
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9M-MRO APU Report

Background

The Boeing 777 is fitted with an Auxiliary Power Unit (APU). It supplies the auxiliary power system for the aircraft pneumatic and electrical power. This permits independent operations from the ground external power sources or the main engines.

The APU generator supplies 120 KVA electrical power at any altitude. The APU can start at all altitudes up to the service ceiling of the aircraft (43,100 ft/13,100 m). Electrical power is available up to the service ceiling and pneumatic power is available up to 22,000 ft (6,700 m).

Source: Safety Investigation Report MH370/01/2018


This means that if the aircraft is on the ground, before the engines are started, and with no external source of electricity, the APU can supply the power needed to operate all electrical systems. The APU can also supply power during flight, for example if the engines have failed, until fuel is exhausted.

The APU is located in the aircraft tail. Passengers boarding can often hear (and smell) the APU running.

The APU Report for MH370 was sent by ACARS after the aircraft was 'Out of the gate' but still on the ground at KLIA. The report shows total number of hours that the APU has been running.


1. APU Report


Time
16:29:33
Trans
46818489
Direction
Incoming Downlink
AN
9M-MRO
FI
MH0370
Medium
IOR2
Machine
MHKULKJACM001
Raw DTG
071629
SMI
DFD
Application
RELAY
Status
Normal
Message Type
B777 APU Report
Source/Destination
QXSXMXS

QU DPCCAMH
.QXSXMXS 071629
DFD
FI MH0370/AN 9M-MRO
DT QXT IOR2 071629 D00A
- MAS002A0     B777 APU OPS REPORT         332

ACID FLT FM FLCT DATE GMT DPT DST
MRO S370 PO 318 07/03/14 16:29:12 WMKK ZBAA
SWID SFC
316A-BSM-710-02 17911
APU CYC APU TOT HRS APU PREV FLT HRS
15699 22093 4


Source: Safety Investigation Report MH370/01/2018 Appendix 1.9A

Note: Additional ACARS messages related to this transmission are included in the ACARS Traffic Log for MH370 (9M-MRO).



2. Auxiliary Power Unit Hours

The following Table was included in the Safety Investigation Report MH370/01/2018 .

Note that the total APU Hours 22093 matches the data in the ACARS message.

1.6.3 Auxiliary Power Unit
ManufacturerAllied Signal
Model GTCP 331-500B
Serial Number P1196
APU Hours 22,093 (as of 07 March 2014)

Source: Safety Investigation Report MH370/01/2018 1.6 Aircraft Information