The airborne search and rescue (SAR) capability of the U. S. Coast Guard has improved since the introduction, one year ago, of the HH-3F, an all-weather search and rescue utility helicopter. The first three aircraft were assigned to the Coast Guard Air Station (CGAS) New Orleans in January 1969, expanding SAR coverage in the Gulf area. The next three aircraft were assigned to the Basic Operating Training Section (comparable to Navy’s Replacement Air Group) at CGAS Mobile, Alabama.
The HH-3F, which is a modification of the U. S. Navy’s SH-3 (HSS-2) “Sea King,” has an SAR radius of 300 nautical miles and is capable of operating on the water. The increased reliability of dual engines and an expanded fuel capacity, allows the aircraft to assume a search and recovery mission three-fold in comparison to the range of HH-52 single-turbine helicopters, which have been in service with the Coast Guard for several years. It has an average cruise speed of 130 knots at sea level.
Since the Coast Guard must operate in all types of weather and also over water, a navigation capability was required. The demands were clear—provide the helicopter with the capability to fly, unescorted, to a known position, offshore, make the recovery, and then proceed to the desired destination while placing minimum demands on the crew. In achieving this goal, the Coast Guard now has one of the most advanced airborne search and rescue systems flying in the world today.
The heart of the new rescue system is the AN/AYN-1 navigation computer. The basic design objective of this computer system was to relieve the pilot and aircrew of the navigation computation problem, by providing an automatic processing of navigation information. Navigation parameters are displayed, and automatic flight direction is derived from a central navigation computer having a multi-sensor input capability.
The navigation information that is available to the computer includes Tacan range and bearing, doppler ground speed and drift angle, Loran A time-difference readings, magnetic heading, true air speed, and Loran C time-difference readings. Constant present position, course, track, along track distance, arrival at destination, and other related information is presented on a digital display in the helicopter’s cockpit. Simultaneously, present position data and a permanent track record are provided on a map display. Any standard air navigation chart may be used. The aircraft position is indicated by a lighted “bug” which moves under the chart. All of this capability is contained in four units on board the craft, which weigh 65 pounds.
The pilot programs the computer through the controller located on the center console in the cockpit. The computer has an automatic search mode, with several preselected search patterns in permanent memory. This allows the pilot to fly accurately a search pattern with little navigational effort.
The Loran A information, supplied to the computer, is provided by the AN/APN-180 automatic tracking loran receiver. This micro-miniature, fully-transistorized receiver was developed for this particular installation. It is actually two receivers in one, with updated time-difference readings automatically fed to the computer.
Another search and navigation aid not often found on rotary-wing aircraft is the radar. The AN/APN-195 radar set with its 10, 30, and 60-mile ranges provides the aircraft with weather avoidance, terrain mapping, and search capability. The helicopter is provided with communication equipment that covers the full spectrum of UHF, VHF, VHF(FM), and HF ranges, as well as homing capability throughout these frequencies. The craft also has all standard en route and terminal navigation aids, such as VOR, Tacan, ILS, and the latest IFF transponder, AN/APX-72. The cockpit arrangement of the HH-3F enables the pilot to control the radar scope which is located on the center panel.
While performing its actual rescue mission, the automatic hovering and positive altitude retention equipment can control the aircraft. The HH-3F is equipped with 240 feet of rescue hoist cable to permit rescue regardless of sea state or terrain. The craft is capable of carrying six passengers in addition to its regular three-man crew.