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| AN/APN-59 | |
|---|---|
| Name | AN/APN-59 |
| Caption | AN/APN-59 airborne radar set |
| Origin | United States |
| Type | Aircraft approach radar / transponder navigation aid |
| Service | 1950s–1960s |
| Used by | United States Air Force; United States Navy; NATO allies |
| Designer | Collins Radio Company; Bendix Corporation |
| Manufacturer | General Dynamics; Magnavox |
| Production date | 1953–1961 |
| Weight | approx. 45 lb (unit only) |
| Dimensions | standard rack-mount |
| Power | vacuum tube electronics; 115V AC |
| Range | up to 30 nmi for beacon interrogation |
| Wavelength | UHF band |
AN/APN-59 is a mid-20th century airborne navigation and approach radar set developed in the United States for use on transport, bomber, and reconnaissance aircraft. It served as an instrument landing system complement and transponder interrogator during the 1950s and early 1960s, integrating radio-navigation and landing-aid functions into a compact airborne package. The set saw service with multiple branches and allied air arms and influenced subsequent generations of airborne navigation electronics.
The AN/APN-59 was developed in the early Cold War era as part of a modernization effort that included programs influenced by Hobson Committee, United States Air Force, United States Navy, Federal Aviation Agency, North Atlantic Treaty Organization, and industrial partners such as Collins Radio Company, Bendix Corporation, General Dynamics, Magnavox, RCA Corporation, Raytheon, and Westinghouse Electric Corporation. Drawing on research from Massachusetts Institute of Technology, Stanford Research Institute, Caltech, and engineering groups at MIT Lincoln Laboratory, the design emphasized compatibility with ground-based aids like Instrument Landing System, Ground Control Approach, and Tactical Air Navigation. Prototype trials involved test units installed on aircraft types including Lockheed Constellation, Boeing B-47 Stratojet, Douglas DC-6, Convair CV-240, and North American B-45 Tornado, with evaluation flights conducted at Edwards Air Force Base, Patuxent River Naval Air Station, and Wright-Patterson Air Force Base facilities. Development drew on avionics standards promulgated by Joint Electronics Type Designation System committees and incorporated vacuum tube and early transistor hybrid circuits informed by wartime advances from Bell Laboratories, MIT Radiation Laboratory, and Harvard University researchers.
The electronics architecture combined an antenna assembly, receiver-transmitter modules, indicator consoles, and power supplies using components supplied by Sylvania Electric Products, Philco, and GE Aviation. Frequency allocation placed the system in the UHF range adjacent to allocations used by Identification Friend or Foe and VHF omnidirectional range systems. The unit employed pulse-modulated interrogation and reply processing similar to contemporary Secondary Surveillance Radar concepts developed in conjunction with work at MITRE Corporation and Lincoln Laboratory. Indicators were influenced by displays used on B-52 Stratofortress and C-130 Hercules navigation suites and incorporated plan-position indicator styling used in AN/APQ-13 and AN/APN-4 sets. Dimensions and installation interfaces adhered to standards used by Bendix racks and Air Transport Association guidelines. Cooling and ventilation were engineered with input from National Advisory Committee for Aeronautics precedents and NACA-era practices.
The AN/APN-59 entered squadron service during the Korean War aftermath and widespread NATO rearmament, operating on tactical airlift, bomber, and reconnaissance platforms assigned to units within United States Air Forces in Europe, United States Air Forces in the Pacific, Fleet Air Wing One, and transport wings supporting United Nations logistic operations. It was deployed in Europe alongside Berlin Airlift-era navigation upgrades and in Cold War deployments such as the Suez Crisis contingency staging and NATO air exercises including Operation Mainbrace and North Atlantic Treaty Organization joint training. Units fitted with the set performed non-precision approaches, beacon homing, and beacon identification tasks in weather conditions similar to those encountered during Operation Market Garden recovery training and in Arctic operations comparable to Operation Pike. Maintenance and logistics were supported through supply chains tied to Defense Logistics Agency procedures and depot overhauls at Ogden Air Logistics Complex and Jacksonville Naval Air Depot.
Production and service life spawned field modifications and contractor-updated versions produced by Hughes Aircraft Company, Garrett AiResearch, and Honeywell affiliates. Variants included ruggedized installations for maritime patrol aircraft such as Lockheed P-2 Neptune conversions, low-profile antenna adaptations for Sikorsky H-19 helicopter trials, and compatibility packs to interface with AN/ARN-6 and AN/ARN-8 navigation receivers. Upgrade programs paralleled developments in AN/APN-59B-style designation practices with enhanced receiver sensitivity, reduced tube count, and improved frequency stability influenced by oscillator work at Bell Labs and Rockwell International.
Installation required bench alignment, rack mounting, antenna removal and bonding procedures coordinated with airframe manufacturers like Douglas Aircraft Company, Boeing, and Lockheed Corporation. Flight crews received training at service schools such as Sheppard Air Force Base and Naval Air Technical Training Center with syllabi referencing instrument procedures from Instrument Flight Rules publications and guidance from Civil Aeronautics Authority-era manuals. Preflight checks included calibration against ground beacons maintained by Federal Aviation Administration field offices and interaction tests with Air Route Traffic Control Center equipment and intercept controllers at Holloman Air Force Base training ranges.
Operational performance typically provided reliable beacon interrogation out to 20–30 nautical miles under standard atmospheric conditions; sensitivity and range were constrained by antenna size, transmitter power, and atmospheric ducting effects encountered in North Atlantic and Pacific Ocean operations. Reliability was limited by tube life and maintenance cycles influenced by supply disruptions during heavy-use deployments; improvements in solid-state electronics by Texas Instruments and Fairchild Semiconductor rendered the set obsolete by the late 1960s as fleets transitioned to systems like AN/APN-59 replacement-class solid-state navigational suites and integrated inertial systems developed by Litton Industries and Sperry Corporation. Interference with emerging Civil Aeronautics Board microwave links and spectrum reallocation posed operational constraints addressed in coordination with Federal Communications Commission planners.
Examples and components survive in aviation museums and restoration collections at institutions such as the National Museum of the United States Air Force, Smithsonian National Air and Space Museum, National Naval Aviation Museum, Imperial War Museum, The Museum of Flight, Science Museum London, and specialized collections maintained by Collings Foundation and Commemorative Air Force. Individual units appear in restoration projects for aircraft like Douglas DC-3, Convair 240, and Lockheed Constellation at sites including Pima Air & Space Museum, Fantasy of Flight, Historic Aircraft Restoration Museum, and regional aviation heritage centers in Duxford and Bletchley Park. Preservation efforts are often coordinated by volunteer groups linked to Experimental Aircraft Association chapters and aviation history organizations such as Air Britain.
Category:Aircraft radars