FPS-24

FPS-24 Long range search Radar Set - A Long range frequency diversity search Radar set designed for select SAGE System radar sites built by General Electric. Twelve units were built for the United States Air Force between 1958 and 1962 by General Electric. Malmstrom AFB FPS-24 Radar Site (center) circa 1964-1971. These radar sets, like the FPS-35, were installed in and on five story towers that were each capped with a 70 to 80 ton rotating antenna. Two types of towers were used, the most common was a five story concrete tower that rose 84' 6" high with a 60' 3" square footprint. This configuration was used in eight of the FPS-24 installations with the other four installations using steel framed towers. The rotating antennas were very large and only two were covered with a radome, Mount Hebo Air Force Station and Cottonwood Air Force Station. FPS-24 Radar Set Locations (edit list) Site State Unit SAGE From To GPS Type Twr Status Rev Notes Eufaula AL 609th Z-119 1959 1968 31.8814, -85.2536 Steel Gone * Prototype Bearing failure 1968 closed the site Point Arena CA 776th Z-37 1961 1976 38.8886, -123.5497 Concrete Exists 1st production unit Almaden CA 682nd Z-96 1962 1980 37.1605, -121.8976 Concrete Exists 2nd production unit Designated historic Cottonwood ID 822nd Z150 1962 1964 46.0667, -116.4643 Steel Exists * Bearing failure 1964 closed the site early Bucks Harbor ME 907th Z-110 1963 1979 44.6294, -67.3953 Concrete Gone * Port Austin MI 754th Z-61 1962 1982 44.0303, -83.0025 Concrete Exists Bearing failure 1982 FPS-24 replaced by FPS-91A Baudette MN 692nd Z-132 1962 1979 48.6707, -94.6201 Concrete Exists Malmstrom MT 801st Z-147 1964 1970? 47.5018, -111.2034 Steel Gone * Winston-Salem NC 810th Z-130 1962 1970 36.0435, -80.1366 Concrete Exists Mount Hebo OR 689th Z-100 1962 1969 45.2158, -123.7578 Steel Gone * Oakdale PA 662nd Z-62 1963 1969 40.3991, -80.1566 Concrete Exists Blaine WA 757th Z-46 1963 1979 48.9119, -122.7346 Concrete Exists * FPS-24 Bearing Lives Table. The initial installations of the FPS-24 revealed many problems that caused a delay in operational status. The problems were resolved and the radar was operational in 1962. The antenna system provided another set of operational problems mostly due to failures of the bearing that the 85.5-ton antenna rotated upon. Catastrophic bearing failures sometimes caused secondary damage to the support towers, sails, and feed horns. Some sites were actually closed due to catastrophic failure of the antenna system and others were forced install other search radar sets when the damage could not be repaired. At Mount Hebo Air Force Station fears that the high winds would dammage the FPS-24 antenna led to three attempts to enclose it in a radome. All three radomes were destroyed by the high winds and the last radome failure also damaged the antenna sail. The FPS-24 was removed and replaced with a FPS-27. AN/FPS-24 and ÄN/FPS-35 Air Defense Radars were designed for continuous, highly reliable operation in the SAGE (Semi-Automatic Ground Environment) system. It was intended that these radars should operate 365 days a year, 23 hours a day, for ten years, one hour a day being allowed for preventive maintenance. However, it soon became apparent that this degree of reliability was not to be realized. Azimuth bearings began to fail at an average rate of once a year on each AN/FPS-24, and once every two years on each AN/FPS-35. Because this high failure rate was not anticipated, ease of replacement had not been given major consideration in the design. Consequently, bearing changes required radars to be shut down for as long as three months, with costs as high as $ 175,000 for a single bearing change. This situation was intolerable to the user, Aerospace Defense Command (ADC), and to the Air Force Logistics Command (AFLC), which was responsible for supplying replacement bearings. As a result, direction was received to take immediate action to alleviate the urgent problems of supply and replacement time and to undertake concurrently a long range program of general improvement in the large antenna bearing area. RADC-TR-71-81 Technical Report December 1971, Bearing Improvement Program For Large Rolling Element Bearings, Pdf The cure for the bearing problem was the development of a hydrostatic bearing for the AN/FPS-24 by Goodyear Aerospace Corp. The prototype was tested at Oakdale Air Force Station. Test terminated after 7821 hours with a catastrophic failure caused by human error. That bearing is shown on the chart above in line 9.That FPS-24 was not supplied with another bearing and it shut down in 1969. No other sites had received the the hydrostatic bearings as of the date of this report (1970). Current Status All of the radar sets have now been dismantled and removed from the buildings and although many of the towers remain there are no antennas still installed. FPS-24 Search Radar FPS-24 Search Radar Element Value Notes Nomenclature FPS-24 Origins Variants Manufacturer General Electric Type Search Number Made 12 IEEE Band VHF Frequency 214 to 236 MHz PRF Pulse Width 20 us Power 7.5 mw max 5 mw normal Range Long range Altitude Rotation Speed 5 rpm Reflector Width 120' Reflector Height 44' Rotating Weight 178,000 lbs 218,000lbs with ice Bearing Type 4 point Contact Ball & Crossed Roller Bearing Pitch Diameter 10' Number of Balls 84 Number of Rollers 116 Ball Diameter 3.5" Roller Diameter 2.68" Introduced 1961 See Also: FPS-35 US Radar Sets Sources: Winkler, David F., Searching the Skies: the Legacy of the United States Cold War Defense Radar Program, USAF Hq Air Combat Command, 1997, 192 pages, Pdf MIL-HDBK-162A, 15 Dec 1965. Links: Radomes - Radar Equipment Wikipedia - FPS-24