Safety Investigation Report 2018:1 Factual Information/1.6/1.6.7 ELT
SAFETY INVESTIGATION REPORT MH370 (9M-MRO)
1.6.7 Emergency Locator Transmitter
An emergency locator transmitter (ELT) is a radio beacon that when activated will transmit digital distress signals. These signals can be tracked in order to aid the detection and localisation of an aircraft in distress.
The Fixed and Portable ELT radio beacons interface worldwide with the international Cospas-Sarsat satellite system for Search and Rescue (SAR). When activated and under satellite coverage, such beacons send out a distress signal which can be detected by satellites. The satellite receivers send this information to ground stations. This signal is transmitted to Mission Control Centres (MCC) located in six regions worldwide. The MCC covering the Indian Ocean is managed by the Australian Maritime Safety Authority based in Canberra, Australia.
ELTs are mandatory safety items carried on board the aircraft. The cabin and the technical crew attend compulsory safety emergency procedure (SEP) training and have to remain current by attending refresher SEP courses. Operation and functioning of the ELT is part of the SEP training module.
The specifications for the ELT are contained in FAA Technical Standard Orders TSO-C126 and TSO-C91A.
The ELT is a radio beacon; like all other radio equipment installed on-board, its usage is approved by the Malaysian Communications and Multimedia Commission through the Aircraft Radio Licence.
Appendix 1.6C - Copy of the Radio Licence issued for 9M-MRO.
9M-MRO had four ELTs installed. They were located as follows:
One FIXED ELT located above ceiling of the aft passenger cabin at STA 1880.
The aircraft was delivered without a fixed ELT; this component was added by MAS later (between December 2004 and July 2005). This unit is mounted to aircraft structure at the aft passenger cabin at STA 1880.
A control switch installed in the cockpit (flight deck) aft overhead panel provides the command signal. This switch is guarded in the ARMED position. If required, the flight crew can select the ELT to ON by moving the guarded switch from ARMED to ON.
The fixed ELT is manufactured by ELTA FRANCE and is of the 406 series, part number is 01N65900. The unit is connected to an Omni- directional, triple frequency blade antenna located at the rear fuselage forward of the vertical stabilizer at station 1881. The ELT will activate upon a sudden deceleration force per the Technical Standard Order.
This ELT has the provision to operate on the satellite frequency of 406 MHz when activated. The transmission includes the ELT identifier, aircraft nationality and registration markings. It will also transmit on 121.5 MHz and 243 MHz when activated and these signals may be detected by air, sea or ground receivers. Transmissions on VHF frequency (121.5/243 MHz) are line of sight and effective only in close proximity (about 20 km radius).
The battery expiry date for the FIXED ELT was November 2014.
One PORTABLE ELT located in the forward cabin right hand coat closet.
This closet is used by the cabin crew.
This unit is bracket-mounted to the inside of the coat closet door. A label fixed on the coat closet door identifies the ELT. The installation allows quick removal. The Portable ELT is manufactured by ELTA FRANCE and is of the 406 series. It is identical to the fixed ELT except that this unit has its own foldable antenna. The operations and function are the same. The manufacturer part number is 01N65910.
The portable ELT has a control switch on the front face. It is normally in the OFF position. When needed, the switch can be selected to the ON position to activate the ELT transmission.
The battery expiry date for the PORTABLE ELT was November 2014.
Two SLIDE RAFT mounted ELTs located at Door 1 Left and Door 4 Right (packed within the slide raft assembly).
The slide raft mounted ELT will only be available when the slide rafts at doors 1 Left or 4 Right are deployed. The ELT transmission is not satellite enabled. The transmission signal is on 121.5 MHz and 243 MHz which may be monitored with air, sea and ground-based receivers. The slide raft ELT is automatically armed when the slide raft is deployed and inflated. Once armed the ELT is automatically activated by a water sensor coming in contact with water. This ELT is not activated by deceleration. The slide raft ELTs (Part No.: P3-03- 0029-10) are manufactured by DME Corporation and the battery expiry dates are as follows:
- Door 1 Left - August 2016
- Door 4 Right - May 2017
No relevant ELT beacon signals from the aircraft were reported from the responsible Search and Rescue agencies or any other aircraft.
1) Review of Effectiveness of Emergency Locator Transmitters
In general, Emergency Locator Transmitters (ELT) are intended for use on land or on the surface of water, and neither portable nor fixed ELT signals are detectable when the ELT is submerged in deep water. Portable ELT is equipped with a floatation device and can be activated by immersion in water. For effective signal transmission, the antenna of the ELT must remain above water. Damage to an ELT or its associated wiring and antenna, or shielding by aircraft wreckage or terrain, may also prevent or degrade transmission. If the portable ELT is activated within a closed aircraft the shielding effect of the aircraft structure may degrade the transmission.
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a) A review of ICAO accident records over the last 30 years indicates that of the 114 accidents in which the status of ELTs was known, only 39 cases recorded effective ELT activation.
This implies that of the total accidents in which ELTs were carried, only about 34% of the ELTs operated effectively (Appendix 1.6D).
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b) The Cospas-Sarsat system has been helpful for search and rescue teams in numerous aircraft accidents on a world-wide basis. Despite these successes, the detection of ELT signals after an aircraft crash remains problematic. Several reports have identified malfunctions of the beacon triggering system, disconnection of the beacon from its antenna or destruction of the beacon as a result of accidents where aircraft was destroyed or substantially damaged. Even when the beacon and its antenna are functioning properly, signals may not be adequately transmitted to the Cospas-Sarsat satellites because of physical blockage from aircraft debris obstructing the beacon antenna or when the antenna is under water.
Source: Global Aeronautical Distress and Safety System (GADSS document)
Note:
In the aftermath of the disappearance of MH370, following a multi-disciplinary meeting in May 2014, ICAO formed an Ad- hoc Working Group on Flight Tracking with the mandate to develop a Concept of Operation on the sequence of events before and after the occurrence of an accident which should include all identified phases of such a sequence including detection of an abnormal situation, alert phase, distress phase, and search and rescue activities. This Concept of Operation is GADSS.
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c) ELT can be activated automatically by shock typically encountered during aircraft crashes or manually. It is possible for Flight Crew to manually activate the ELT; however existing flight operating procedures do not call for activation of the ELT until the incident has occurred.
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d) The Cospas-Sarsat system does not provide a complete coverage of the earth at all times. As a consequence, beacons located outside the areas covered by these satellites at a given moment cannot be immediately detected and must continue to transmit until a satellite passes overhead.
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e) The global distress beacon detection system, Cospas-Sarsat, no longer detects 121.5 MHz distress signals. Only 406 MHz digital distress beacons are now capable of detection by satellite. Analogue beacon signals may be received by other aircraft within VHF range but there may not be such aircraft within range at the time of beacon transmission and monitoring 121.5 MHz.