Regulatory Brief -- Emergency Locator Transmitters (ELTs)

Regulatory Brief

Emergency Locator Transmitters (ELTs)

The issue

ELTs are emergency transmitters that are carried aboard most general aviation aircraft in the U.S. In the event of an aircraft accident, these devices are designed to transmit a distress signal on 121.5, 243.0-megahertz frequencies (and for newer ELTs, on 406 MHz). Currently, ELTs are required to be installed in almost all U.S.-registered civil aircraft, including general aviation aircraft, as a result of a congressional mandate. The mandate resulted from the 1972 loss of U.S. Representative Hale Boggs and Nick Begich in Alaska after their aircraft crashed and was never found.

When ELTs were mandated in 1973, most GA aircraft were equipped with an ELT that transmits on the 121.5 MHz frequency, the designated international distress frequency. The original ELTs were manufactured to the specifications of an FAA technical standard order (TSO-C91) and have an activation rate of less than 25 percent in actual crashes and a 97 percent false-alarm rate. In 1985, a new TSO-C91A ELT was developed, which substantially reduces or eliminates many problems with the earlier model. The TSO-C91A provides improved performance and reliability (with an activation rate of 73 percent in actual crashes) at a reasonable cost to users ($200-$500 including installation). Since then, an even more advanced model of ELT has been developed — the C126 ELT (406 MHz). This newest model activates 81-83 percent of the time and transmits a more accurate and near-instantaneous emergency signal by utilizing digital technology. This digital 406-MHz ELT also allows search and rescue personnel to have vital information specific to you and your aircraft. These ELTs are more expensive, however, with the current cost around $1,000 or more per unit, not including installation.

ELTs were originally intended for use on the 121.5-MHz frequency to alert air traffic control and aircraft monitoring the frequency. In 1982 a satellite-based monitoring system was implemented (COSPAS-SARSAT) to provide a better receiving source for these signals. As of February 1, 2009, the international COSPAS-SARSAT satellite system will discontinue satellite-based monitoring of the 121.5/243-MHz frequencies, in part because of a high number of false signals attributed with these frequencies. While there's no requirement in the United States to replace the first- and second-generation 121.5-MHz ELTs, after this date, 121.5/243-MHz distress signals transmitted from ELTs operating on the lower frequency will only be detected by ground-based receivers such as local airport facilities and air traffic control facilities or by overflying aircraft. It is important to note that after 2009, existing 121.5-MHz ELTs, although still legal from the FAA's perspective, will provide extremely limited assistance if an aircraft crashes, especially in a remote location.

AOPA's position

AOPA opposes any attempt to mandate or otherwise require the replacement of existing 121.5/243-MHz ELTs with 406-MHz units. AOPA recognizes the benefits that can be derived from the advanced ELTs available today. However, the benefits of advanced ELTs must be balanced against cost and the needs of the individual aircraft owner. AOPA supports the installation of these more advanced ELTs on a voluntary basis. General aviation is an industry already struggling under the weight of increased regulation and mandated equipage, and the decisions to replace an existing ELT should be left to the discretion of the aircraft owner. The association supports the education of pilots and aircraft owners as to the limits of 121.5/243-MHz ELTs and the benefits of 406-MHz units.

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Updated Thursday, January 22, 2009