Tuesday, May 7, 2013
Improving Search And Rescue
Enhanced technology is available, but aviators have been slow to adopt it
At the foundation of advanced search and rescue is the 406 MHz beacon and satellite system. The precise frequency is 406.028 MHz. As of February 1, 2009, satellite monitoring of emergency frequency 121.5 MHz was ended, although 121.5 still is monitored by FAA facilities and in aircraft when feasible, and can be used by search-and-rescue assets. Older ELTs that are approved under TSO-91a transmit on 121.5 and the military frequency of 243.0 MHz.
Newer ELTs complying with TSO-C126 still operate on 121.5 in addition to 406.028. Military models can use 121.5, 406.028 and 243.0. The newer satellite system provides for faster recognition of ELT signals and greater accuracy in determining their location. As far back as September 2007, the NTSB issued a safety recommendation to the FAA calling for the agency to seek Congressional authority to mandate replacing all old ELTs with the then-emerging 406 MHz variety.
One of the speakers at the NTSB's forum was Joan Goodman, President of Emergency Beacon Corp., in New Rochelle, N.Y. They manufacture ELTs for both military and civilian use in portable cabin-mounted as well as fixed-installation models. She told me that the military seems better attuned to the value of the improved satellite system than the civilian pilot population because the Pentagon mandated that all of its aircraft carry a digital ELT. Goodman suggested, "As costs come down, there will be a change in civilian consumer attitude."
Goodman told the NTSB forum that improper installation can defeat technology. "ELTs need to be installed in or on a rigid area—not attached to the back of a seat or to the soft fabric on the wall of an aircraft. An ELT approved as an automatic fixed (AF) transmitter should be installed as far back in the craft as possible, usually in the tail or baggage area. AF transmitters need a remote control unit in the panel to make it convenient for the pilot to test the unit and reset after testing," Goodman said.
The digital 406 MHz units need to be connected to an antenna mounted on the aircraft's surface, but also come with an auxiliary antenna that can be plugged directly into the device for use if the external antenna is disconnected accidentally, or if the ELT is removed for use outside the aircraft.
Goodman explained to the NTSB forum that incorrect antenna placement can defeat proper ELT operation. She said, "Antennas need a ground plane, and ideally, the cable should not cross a breakpoint in the aircraft's structure. There are many reported cases of antennas being torn off the craft in an emergency or the cable being pulled out of either the transmitter or antenna. An aircraft that comes down inverted will often either break or bury the external antenna."
The lack of an external ELT antenna on an older ELT was cited in the NTSB's report on the crash of a Maule M-5-235C near Springville, Calif. The airplane hit trees at the 8,300-foot level of a mountain. The aircraft was owned and operated by the pilot and was on a personal sightseeing flight in the Sierra Nevada Mountains. Based on witness and National Weather Service observations along the route of flight, visual meteorological conditions prevailed with generally clear skies and light wind conditions.
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