Some aircraft, such as aircraft used in combat, are equipped with one or more ejection seats. While an aircraft with an ejection seat is in use, the aircrew member operating the aircraft is strapped to the ejection seat with seatbelts. In some emergency situations in which the aircraft becomes inoperative, the ejection seat, together with the aircrew member strapped thereto, is ejected from the aircraft so that the aircrew member can parachute to the ground.
It is conventional for an ejection seat to carry an emergency locator transmitter (ELT) that is automatically activated when the ejection seat is ejected from the aircraft. Once activated, the ELT transmits a beacon signal, which can be characterized as providing both an indication of the ejection and the location of the ejection seat.
The ELT is typically releasably tethered to the aircraft. More specifically, the ELT is activated by a lanyard having one end connected to the aircraft and an opposite end that pulls a mechanical or magnetic activation pin away from the ELT upon ejection, so that the ELT is automatically activated. It is important for the ELT to be automatically actuated, because in some circumstances the associated aircrew member will be disabled and unable to activate their primary handheld rescue radio, which is typically carried in the aircrew member's vest pocket. In addition to transmitting a beacon signal, a primary handheld rescue radio can provide for two-way verbal communication.
Aircrew members that eject from aircraft are often not disabled. An aircrew member that has parachuted to the ground with their ejection seat can remove the ELT from the ejection seat and extend an antenna to increase the effectiveness of the ELT. Nonetheless, it is common for an aircrew member that has parachuted to the ground to turn off the ELT and turn on their primary handheld rescue radio.
Whereas having both an ELT and a primary handheld rescue radio for each aircrew member ensures that a beacon signal is automatically transmitted when an aircrew member is ejected and provides the aircrew member with a handheld rescue radio, providing both of those radios may not be cost effective in some situations. In addition to the cost of the two separate radios, costs are also incurred in maintaining and servicing the two radios.