Taking the Search Out of Search and Rescue

May 2001
By Henry S. Kenyon

High-technology beacons and positioning devices speed aid to stranded fliers.

An advanced personnel-location and communications system will allow U.S. and allied air forces to more easily locate downed pilots and crews. The technology consists of a warfighter-worn personal transceiver with a global positioning system capability and a signal interrogator carried on a search aircraft to query the beacon, and it could expedite efficient wartime aircrew recovery.

Locating and recovering crash victims in wartime presents dangers not found in civilian and peacetime rescue efforts, as hostile forces may be actively searching for the crew. Under such circumstances, covert activity is necessary to hide the aircrew’s location and to protect search aircraft. Modern global positioning system (GPS) technology incorporated into communications and survival equipment now allows rescuers to locate the proverbial needle in a haystack quickly.

Motorola Incorporated, Scottsdale, Arizona, has developed a family of beacons and transceivers for use in search and rescue operations. The GPS-112 personnel-location system is the latest addition to this product line. According to Arne Olson, program area manager with Motorola’s communications enterprise in Scottsdale, the device is an evolutionary extension of the firm’s successful line of AN/PRC-112 personnel-locator systems, of which more than 30,000 have been built.

The original device relied solely on the search aircraft’s instruments to triangulate the distress radio signal to locate downed aircrews. However in 1995, an appliqué kit was created for the radio to provide it with a GPS capability, two-way messaging and encryption, Olson says. This modification resulted in the PRC-112B al GPS satellites and calculate its latitude, longitude and altitude.

The GPS-112 uses a more sensitive 12-channel parallel GPS receiver that features up to 250 navigational waypoints and is accurate to 25 meters, Olson explains. The device can operate as a stand-alone GPS receiver for navigation and route management as well as a very high frequency-ultrahigh frequency amplitude modulated transceiver for ground-to-air communications. When it is turned on, it automatically acquires GPS satellites and allows over-the-air reprogramming and waypoint downloads. Messaging occurs through short, encrypted data bursts backed up by forward error correction algorithms. Other features include low power consumption and flexible power source capabilities.

The pocket-sized, lightweight device also serves as a navigational tool for the downed pilot by providing location data based on GPS coordinates. The transceiver’s display allows users to send and receive pre-formatted and free text encrypted messages.

The GPS-based transceiver is an improvement on previous radio triangulation location methods, Olson says. In the past, the ground device would use distance-measuring equipment to send out a signal that would provide a search aircraft with bearing and distance. A radio interrogator aboard the aircraft would then calculate the estimated direction and approximate distance to the missing pilot. This process often had to be repeated several times to get an accurate fix. Because the aircraft and the soldier on the ground were generating radio signals, their chances of being detected by the enemy increased.

In comparison, the brief data bursts from the new device provide all the necessary location data. “When you do your interrogation with the GPS-112, you get the latitude and longitude of the radio. You just put that information into your navigational computer, and it will calculate the bearing, distance and flight path for the aircraft. It adds a level of refinement and takes the search out of search and rescue,” Olson says.

The GPS-112 works in concert with the Motorola-manufactured Quickdraw handheld interrogator device, which can plug into a variety of aircraft communications systems and allows almost any type of jet or helicopter to conduct search and rescue operations, Olson claims. The Quickdraw interrogator is currently in use on F/A-18 and A-10 attack aircraft and various helicopters, he says.

The interrogator operates by using an aircraft’s ultrahigh frequency radio to send out a signal to the GPS-112 on the ground. The GPS-112 replies with its GPS location and an optional message from the pilot on the ground in an encrypted line-of-sight short-burst transmission. When this message is received by the aircraft radio, the data is relayed to the pilot’s Quickdraw unit on which the GPS location and message are displayed.

Olson notes that because the interrogator device is carried by the pilot—usually in a leg holster for high-performance jet crews—no additional equipment needs to be installed on the aircraft. “This means no new radio, no new antenna, no internal cabling, and we don’t even access the aircraft’s power supply because it uses AA batteries,” he says. No installation costs or aircraft certification and no required ground maintenance for the device translate into cost savings. Users do not have to carry a GPS device and a search and rescue radio because these functions are combined in one unit.

The GPS-112 is backward-compatible with current personnel-locator radios that are built into many aircraft. This flexibility allows searchers to use either their radios or the Quickdraw interrogator to locate crewmen on the ground. The GPS-112 appliqué kit will enable the 30,000 existing transceivers to be upgraded to GPS or improved GPS capabilities. Olson adds that the transceiver will provide customers who do not already own a search and rescue radio with a new GPS-capable unit.

Quickdraw devices were recently used by U.S. Air Force units during Operation Northern Watch missions over Iraq. According to Lt. Col. Robert Stenevik, USAFR, director of operations training, 10th Air Force, Fort Worth, Texas, pilots laud the Quickdraw interrogator because it provides the survivor’s exact location as soon as line-of-sight contact is made with the downed flier. The colonel notes that, even in the best conditions, during combat search and rescue training exercises involving up to 35 aircraft, it often takes more than an hour to locate survivors. However, the combination of the airborne interrogator and the GPS-112 dramatically reduces search time, which is significant for aircraft trying to locate a soldier behind enemy lines. “Five to seven minutes after takeoff, you know where you’re going. This capability is something that we never had,” he explains.

According to Col. Stenevik, 13 Quickdraw units were sold to the U.S. Navy and three went to the Air Force. He notes that while some modifications to cockpit interface cables were necessary to integrate the interrogation devices, they performed very well. “The Air Force Reserve people are 100 percent convinced that if they had a choice to fly with it, they would take it,” the colonel says. He adds that the Air Force is considering the purchase of additional GPS-112s and Quickdraws so that front line units will have sufficient numbers to train with and to take to war.

Motorola is currently conducting negotiations with other potential customers. Olson notes that clients include previous PRC-112 purchasers such as the U.S. military and North Atlantic Treaty Organization countries. The transceiver and its complementary devices may also have some use with law enforcement and intelligence organizations, Olson says. The first GPS-112 and Quickdraw shipments are scheduled to begin this July.