A small fleet of Cessnas at NASA’s Langley Research Center in Hampton, Virginia, has not been having a breezy summer. The first, a model 172, carrying two dummies in the cabin, suffered a hard landing on July 1; the second took a nosedive into the dirt on July 29; and a third airplane got a hard tail strike as it crashed on August 26. Had people been in these accidents, they potentially could have survived. What NASA wanted to know was: Would help come in time?
The agency’s Search and Rescue Mission Office was testing the airplanes’ emergency locator transmitters, or ELTs—instruments the Federal Aviation Administration requires every aircraft to carry. In modern ELTs, which transmit at 406 megahertz, a protected frequency band for personal distress calls, a gravity-activated switch flips to transmit a signal when the airplane experiences an impact. A satellite detects the signal and a monitoring agency notifies a local search-and-rescue team. But ELTs have been notoriously unreliable (see “Lost in America,” Oct./Nov. 2011). And the FAA doesn’t give advice on where and how to install them so they best survive a crash.
“We’re trying to mimic real-world crashes,” says Lisa Mazzuca, NASA’s search-and-rescue manager. The data from the tests will help in building and verifying models that can predict what happens to every part of the ELT instrument when it goes through an impact. “Obviously we can’t keep buying airplanes and crashing them to see what happens,” says Mazzuca. Each aircraft was outfitted with a mix of four or five ELTs. “We’re trying to figure out…for any given make and model what would be the best way to install it,” says Chad Stimson, project manager for the crash tests. The ELT needs to be in the best location to both detect the crash and not be destroyed by the crash. “And those are sort of competing odds because your crash sensing is optimal towards the front of the airplane,” says Stimson. “But your crashworthiness, your crash survivability, is decreased.” The team is also studying the system itself: Are there materials that will better be able to survive the impact and the environment it creates—like a fire? Could the cables be designed better? Is the relay to the satellite working as best it can?
The team wants to be able to offer recommendations about all these points, but without imposing strict regulations on manufacturers. “We don’t want to tie their hands and [require] a specific technology or specific material,” says Stimson, which might prevent them from continuing to develop something “that’s better, faster, cheaper.” Though, strangely enough, it’s the vagueness of current regulations that plagues manufacturers. “We’ve heard from vice presidents at these companies that these requirements are hard to understand,” says Stimson, “they don’t make any sense, and nobody can explain to us why.” NASA is also working with other ELT testing facilities, so that when device makers are given clear standards that allow flexibility to design better products, they can also test them easily, not just at specialized facilities like NASA’s.
Next year, NASA will take the models it’s creating from the Cessna test crashes to an international group that’s developing standards for the second generation of ELTs. These members—including representatives from ELT and airplane manufacturers, pilot organizations, the FAA, the Coast Guard, NOAA (the agency that runs the database of ELT registrations), and NASA, among others—will discuss their reports and come to a consensus on recommendations that is scheduled to be published in 2017. That would put the next-gen models on track to be available by 2019, just after an upgrade in the satellite system that detects them. Over the next few years, Cospas-Sarsat, the multi-national program that runs the search-and rescue system, plans to move its instruments from low-Earth-orbit and geosynchronous satellites onto GPS satellites in medium Earth orbit. (Cospas-Sarsat also needs countries around the world to build new ground stations to accommodate the new orbits; construction is currently under way but will take a few years.) The stronger beacons and higher satellite altitude will enable location detection to within 100 square meters, down from one square kilometer today. The new ELT models will also be equipped with an improved terrestrial beacon. “The biggest issue today is that there isn’t a cheap 406 [megahertz] receiver that local search-and-rescue forces can use while searching,” says Mazzuca. “But that will soon change also.” Inexpensive receivers, ground signals that reach farther, and satellites that can narrow down a target site will hopefully lead to more pilots and passengers being rescued quickly when the worst happens in the air.
Meanwhile, however, there are still plenty of aircraft equipped with the original models of ELTs, which transmit at 121.5 megahertz; Cospas-Sarsat stopped monitoring this frequency band in 2009, dedicating its resources to the protected 406 megahertz band instead. The FAA can’t force pilots to upgrade—ELTs aren’t cheap, and search and rescue teams on the ground will still listen in on 121.5 megahertz, but only if they know a crash has happened. (That stronger ground transmitter that NASA is working on that transmits at 406 megahertz? A version will be available as a terrestrial homer only, as an inexpensive way for pilots to transmit on the protected search and rescue frequency if they can’t afford the ELT with the satellite signal.) Another problem is that some pilots never register their ELTs or update their information with NOAA—that means that when an ELT impact beacon is detected, search and rescue teams may not know what aircraft they’re even looking for. “We don’t know how to mandate [registering an ELT],” says Mazzuca. “You can’t withhold a beacon from coming on; you can’t supply consequences to the owner if they don’t register.” If you’re a pilot, consider this your opportunity to take advantage of the hard work being put into finding you if you ever need rescue, and register your ELT today.