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COSPAS-SARSAT, Distress Beacons, DO Standards, ELT

Pharus ELT Didyma

Emergency Locator Transmitter (ELT) devices are the versions of distress beacons used in aircraft. For information about distress beacons, see here.

Emergency Locator Transmitter (ELT) devices are satellite communication systems mandated on manned aircraft by international civil aviation regulations. These devices are designed to transmit location and identification information to COSPAS-SARSAT satellites during emergencies involving helicopters or airplanes, enabling search and rescue teams to respond without delay. In emergency scenarios, ELT devices can be manually activated by the aircraft crew or automatically triggered when the ELT detects the impact forces of a crash. Pharus Tech’s Pharus ELT Didyma, currently under development, not only sends signals to satellites but also broadcasts terrestrially, enabling urgent distress calls to be received by nearby radio receivers.

Pharus ELT Didyma is designed in compliance with the latest aviation standards. According to these standards, it is capable of broadcasting an audio sweep tone signal on 121.5 MHz and 243.0 MHz channels, enabling distress calls to nearby radios. Additionally, it can transmit a distress signal containing location and identification information on the 406 MHz channel to satellites. The Didyma ELT can detect crashes exceeding a certain acceleration threshold and activate automatically. Furthermore, it features a portable design that allows it to be detached and carried by the crew if needed, qualifying it as an “Automatic Portable” type ELT device. For more detailed technical information about the product, you can review the brochure.

 

The Pharus ELT-AP Didyma is equipped with a battery capable of broadcasting for up to 50 hours. With a 5-year battery lifespan, the Didyma ELT batteries offer a significant advantage for aircraft manufacturing and maintenance companies by simplifying their maintenance processes. The ELT-AP Didyma features a modular design consisting of two modules, as seen in the accompanying illustration. The first module is the main module, containing all the electronic and software functions of the device. The second module is the battery module, housing the device’s batteries and the battery management system. This modular structure eliminates the need for aircraft manufacturing and maintenance companies to send the ELT device back to the supplier when the battery requires replacement or lifecycle renewal. Instead, integration with a new battery module acquired from Pharus Tech is sufficient.

Thus, with its modular battery design, the Pharus ELT Didyma aims to provide its customers with the utmost convenience in “Calendar Management” and “Maintenance Management,” both of which are critical aspects in the aviation sector.

A long-standing issue with Emergency Locator Transmitter devices is the problem of false alarms, which has been a persistent and serious concern, occupying national search and rescue centers. For example, reports published by the Canada Mission Control Centre (CMCC) and the French Mission Control Centre (FMCC) provide the following statistics on ELT incidents over the past six months in Canada and France:

 

Period

 

Location

Actual ELT Activations

False ELT Activations

People Rescued via ELT

November 2024

Canada

6

71

21

October 2024

Canada

5

83

11

September 2024

Canada

7

72

11

August 2024

Canada

10

104

24

July 2024

France

10

161

33

June 2024

France

9

154

11

CMCC (Canada Mission Control Center) Activity Reports –November 2024 to January 2024 & FMCC (French Mission Control Centre) Activity Reports – July 2024 to June 2024.

As observed, ELT devices have an average false alarm rate exceeding 90%. These false alarm incidents can result from human factors (e.g., unintentional manual activation by flight crew due to negligence) or from automatic activation during hard landings or abrupt flight maneuvers. For more detailed information on the automatic activation performance of ELTs and the issue of false alarms, you can review our article. In such cases, the flight crew quickly confirms via radio that the ELT was unintentionally activated and that there is no emergency requiring the involvement of national search and rescue teams. However, there is no doubt that this process, occurring with a frequency of over 90% each month, translates into a significant loss of time for the relevant units and personnel. Indeed, the Australian government’s 2024–2027 National Aviation Safety Plan has identified reducing the false alarm problem and the labor loss caused by false alarms as one of its primary goals.

The Pharus ELT-AP Didyma incorporates two design innovations to minimize the false alarm issue. First, using its electrical interface, it can receive inputs in ARINC-429 and Discrete formats to verify whether the aircraft has truly crashed (“isAlive” port). The second approach involves the use of state-of-the-art G-Switch technology for its automatic activation feature. This significantly reduces the likelihood of accidental activation, particularly during accelerations below the threshold required by the standard. In addition to receiving “isAlive” information via the ARINC-429 interface, the Pharus ELT Didyma device can also obtain real-time location data. A schematic of the current electrical interface in the prototype is provided alongside.

When selecting equipment for use in aviation vehicles, the Design Assurance Level (DAL) adopted during the certification process is a highly significant factor. Within this context, the DAL level of the equipment is determined according to the DO-178 standard for software design and the DO-254 standard for hardware design. All design, verification, and quality qualification processes are shaped based on this level. For more details about these aviation standards, you can review our articles on the DO-178 software standard and the DO-254 hardware standard. The Pharus ELT Didyma equipment has been designed with a focus on DAL-D level and is undergoing its certification process accordingly.

Over the years, ELT devices have become increasingly critical for saving lives. According to COSPAS-SARSAT data, ELT equipment was solely responsible for saving 379 lives in 206 aviation accidents last year. Through its ELT Didyma product and the high-quality standards embraced in its design, Pharus Tech strives to contribute to global efforts in saving human lives.

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