Imagine that a malfunction on an aircraft forces the captain to make an emergency crash landing in the middle of an unforgiving landmass, such as Siberia, a thousand miles from anywhere. There are survivors, but in the frozen wastes of the north, with roads at a premium, there is little hope and not much time. Even the nearest hospital is completely out of reach. Yet, within minutes, the location of the wreckage is fixed and the process of mounting a rescue effort begins.
It is dark and the water cold. From the seabed in this vast swirling ocean, a distress signal is picked up by ships in the area, which alter course and rush toward its location. Survivors desperately clinging to wreckage are winched to safety. It can be the same with an individual or group of people lost or stranded in hostile terrain.
Magic it is not, but the fact that the lucky ones owe their survival to a piece of equipment smaller than a shoe box may still be a surprise to many. There are three types of emergency locator beacons–ELTs (aviation), EPIRBs (maritime) and PLBs (personal)–sending signals to a group of satellites that provide a typical fix to a four- square-kilometer area (1.5 sq mi), and if GNSS (GPS) position is encoded in the message, down to 100 meters (328 feet).
The geostationary Earth orbit (GEO) and low-altitude Earth orbit (LEO) satellites were put into orbit by Cospas-Sarsat, an agency overseen by the U.S., France, Russia and Canada, and process signals in the 121.5-MHz frequency. It is estimated that there are some 700,000 121.5-MHz beacons in use worldwide, including 170,000 emergency locator transmitter beacons (ELTs) fitted to aircraft. Since its inception in 1982, the Cospas-Sarsat system has assisted in the rescue of over 19,000 people in more than 5,300 distress situations.
False Alarms
But there is a problem. The 121.5-MHz ELTs have proven rather ineffective, with, according to Cospas-Sarsat, a 97-percent false-alarm rate, and more worryingly, they activate properly in only 12 percent of crashes. They also provide no identification data.
These problems have now largely been overcome by the new 406-MHz ELTs, which were developed specifically to work with the Cospas-Sarsat satellite system. The 406-MHz beacons are said to offer several advantages over the older models, including a dramatically reduced false alert rate, higher accident survivability and a reduction of an average of six hours in the time required to reach accident victims. Furthermore, the 406-MHz ELTs can be individually encoded with, for example, the aircraft registration and country of origin, and owner contact details that will help to minimize false alerts.
Most aircraft operators currently have the option of installing either type, but the U.S. Federal Aviation Administration has considered mandating the 406-MHz ELTs, as its study indicated that 134 extra lives and millions of dollars in SAR resources could be saved each year. If there is a drawback, it is the cost–between $1,500 and $4,000 for a 406 MHz, compared to $500 for a 121.5-MHz ELT–but with still greater retrofit costs that generally range from $5,000 to $10,000 and more for larger aircraft.
New Regs Coming
While the equipment itself is relatively simple, the regulations governing their application on aircraft are complex, and are due to undergo further changes that will have a significant influence on the future of the ELT market.
Starting July 1, 2008, all airplanes operating internationally will need to carry at least one ELT, according to proposed amendments to ICAO Annex 6. The proposal, if enacted, also states that beginning July 1, 2008, “automatic” (406 MHz) ELTs must be carried on all international operations of both commercial aircraft (authorized to carry 19 passengers or less) and private aircraft manufactured after that date. Further, international operations of commercial airplanes authorized to carry more than 19 passengers and manufactured after July 1, 2008, would have to be equipped with at least two ELTs, one of which must be automatic. Current ICAO standards call for ELTs only on airplanes operated on extended overwater flights and on flights over designated land areas where search-and-rescue operations pose a special challenge.
Helicopters operating in Performance Class 1 and 2 would be required to carry at least one automatic ELT, and when operating over water, also an ELT(s) in a raft. There is some relief for operators of older commercial and general-aviation aircraft. The requirement for them to retrofit automatic ELTs has been deleted in the provisions, as the “cost/benefit of automatic activation has not clearly been demonstrated.”
An automatic ELT is generally installed in the rear of the aircraft, rigidly attached, and activated on impact by a crash sensor or “g” switch. The benefits are derived from the ability to transmit an emergency signal immediately upon the onset of crash impact forces, without having to be manually activated. However, such an automatic ELT may be destroyed on impact, or may not function under water if an aircraft is forced to ditch at sea, hence the added requirement for an ELT(s). The ELT(s) is designed to be readily accessible in the cockpit or overhead bin, for example, and can be taken out of the aircraft by a survivor and manually activated.
On Feb. 1, 2009, as now planned, Cospas-Sarsat will cease satellite processing of 121.5-MHz beacons. This decision was influenced by the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO) in response to the superior capabilities of the 406 MHz alerting system. From that date, the satellites will detect only 406-MHz beacons.
As the ICAO and Cospas-Sarsat deadlines near, the message is clear: aircraft owners and operators need to begin replacing their 121.5-MHz beacons. The costs may be high, but what price a life?
