Articles

Emergency Locator Transmitters: Can you hear me now?

By Daryl Collins,
Transportation Safety Board of Canada

This article originally appeared in the November 2016 issue of COPA Flight magazine.

On May 31, 2013, shortly after midnight, a Sikorsky S-76 air ambulance helicopter operated by Ornge Rotor-Wing crashed just after taking off from the Moosonee Airport in Northern Ontario, killing all four on board: the captain, first officer, and two paramedics.

Although it did not play a role in the outcome of this tragic occurrence, a distress signal from the helicopter's emergency locator transmitter (ELT) was not received, thereby slowing search-and-rescue (SAR) efforts. Shortly after reaching the crash site, TSB investigators saw that the helicopter's external whip-style ELT antenna had broken off and the unit had come free from its hook-and-loop fastening straps. This led the investigation to examine current ELT requirements and design standards, ultimately identifying four ELT-related safety deficiencies that pose a significant risk to the travelling public.

406-MHz ELTs

Aircraft in Canada are not currently required to carry an ELT that transmits on 406 MHz—even though this has been the standard internationally since 2005, and even though 406 MHz is the only ELT frequency monitored by the international search-and-rescue satellite system (Cospas-Sarsat). This creates a significant risk. For instance, over half of the approximately 27 000 Canadian-registered aircraft that require an ELT don't carry one that can be detected by the SAR system. As a result, the TSB recommended that Transport Canada require those aircraft mandated to have an ELT be equipped with one that transmits on 406 MHz.

ELT crashworthiness standards

In this occurrence, the ELT's broken antenna prevented a distress signal from being detected by SAR satellites—an issue that has come up in numerous TSB investigations. Studies have shown that between 80-90% of ELT non-activations are a result of damage to the ELT.Footnote 1, Footnote 2 While the design standards for the ELT unit itself are robust, they are significantly less so for the components, such as external wiring and the antenna. As a result, the TSB is calling on Transport Canada and international bodies—including ICAO, the Radio Technical Commission for Aeronautics, and the European Organization for Civil Aviation Equipment—to establish rigorous crash-survivability standards to reduce the likelihood that an ELT system will be rendered inoperative as a result of impact forces.

First-burst delay

Under the current standards, 406-MHz ELTs are required to have a minimum delay of 50 seconds from the time of activation to the first transmission of a distress signal. However, if an ELT is rendered inoperative during this period (for example, due to damage or by being submersed), the signal will not be transmitted to the Cospas-Sarsat system. Given the advances in technology, the TSB feels it is time to reduce this delay to the lowest possible timeframe and maximize the likelihood that a distress signal will reach search-and-rescue.

Hook-and-loop fasteners

In 2015, Transport Canada adopted a new standard that prohibits the use of hook-and-loop fasteners when installing new ELTs; however, the new requirement did not apply to previously installed devices. As a result, there are a large number of ELTs currently being restrained by a system that has proven ineffective in a wide range of occurrences. To rectify this issue, the TSB recommends that Transport Canada prohibit the use of hook-and-loop fasteners as a means of securing any ELT to an airframe, regardless of its original installation date.

If adopted, the TSB's recommendations on ELTs will significantly enhance the safety of Canadian pilots, owners, and the travelling public. However, these were not the only issues to arise from our investigation into the tragic events of May 31, 2013. In fact, we issued a total of 14 recommendations. In follow-up articles, I will discuss some of these, particularly those related to instrument recency/currency requirements, and the regulations governing night visual flight rules (VFR).

Daryl Collins is a senior investigator within the TSB's Air Branch. More information about TSB recommendations can be found at the TSB website (www.tsb.gc.ca).

Footnotes

Footnote 1

Defence Research and Development Canada (DRDC), Emergency Locator Transmitter (ELT) Performance in Canada from 2003 to 2008: Statistics and Human Factors Issues (September 2009), part 5.1.1, p. 30.

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Footnote 2

National Aeronautics and Space Administration (NASA), Current Emergency Locator Transmitter (ELT) Deficiencies and Potential Improvements Utilizing TSO-C91a ELTs (1990).

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