Scramble says the OH-58E designation was "skipped in favour of the OH-58F, possibly to resemble the latest Chinook designation." The fine folks over at Designation Systems provide a listing of USAF and DOD basic aircraft designators which are not listed in standard reference sources on the subject, but this does not get into the weeds of variants such as the OH-58E.
The Army expressed interest in an advanced scout helicopter in 1974. The Advanced Scout Helicopter (ASH) would search, locate, and report the presence of enemy materiel and personnel. It would acquire and designate targets for Hellfire missiles, permitting the Advanced Attack Helicopter (AAH - what became the AH-64) to stay out of range ot enemy air defenses, reduce its vulnerability, and increase its effectiveness. The Army envisioned buying 723 ASHs, costing about $2.5 billion.
Efforts to establish an advanced scout helicopter (ASH) program first met with delays. Then Congress declined to provide fiscal year 1977 funding for the project. For fiscal year 1977 the Army requested $26.0 million for the ASH program; however, the Congress disapproved the request, which led to the closing down of the ASH Project Manager?s Office on 30 September 1976. Due to cost considerations plans were made to modify an existing observation helicopter to satisfy the ASH requirement. This modified helicopter will become an interim scout helicopter. The Army requested $19 million in fiscal year 1978 and plans to request $15 million in fiscal year 1979 to support this program.
The Army made a decision on 30 November 1979 to defer development of an advanced scout helicopter system, and pursue development of a near term scout helicopter (NTSH) based upon modification of an existing inventory airframe. The Advanced Scout Helicopter Special Study Group (ASH SSG) was tasked in 1980 by the Army with defining and demonstrating the need for an ASH, with selecting an effective and affordable ASH program, and with demonstrating that the chosen ASH alternative is more cost effective than the other alternatives considered.
The ASH SSG must build support for the ASH based upon an understanding of basic operational and organizational concepts. Their studies must be requirements rather than hardware oriented. In particular, the ASH SSG must demonstrate that the ASH need cannot simply be met by the current Light Observation Helicopter (LOH) being used for the ASH role.
An evaluation of thirteen candidate Advanced Scout Helicopter (ASH) designs and mixes of these designs was concluded in early 1980. The first four candidates were completely new developments. These candidates were the result of design studies that started from scratch with a "clean sheet of paper," unconstrained by current helicopter designs. All of these designs incorporated a full complement of mission equipment; they differ mainly in the number and power of engines -- although all designs incorporate an Advanced Technology Engine (ATE) -- and in the seating arrangement for the crew.
BTA was a single-engine helicopter that configures the crew in a side-by-side seating arrangement. BT2 had twin engines and a side-by-side configuration. BTT had twin engines and a tandem configuration (with a frag barrier that provides the crew with protection against a 23 millimeter high explosive round). B4K had twin engines and a tandem configuration; it also had the capability to operate under 4,000 feet/95 F conditions with one engine inoperative.
The next six candidates were modifications of existing attack helicopters. The first three candidates were variations of the OH-58C. The OH-58D was a minimal modification that involved principally the addition of a mast-mounted sight (MMS), with day-only capability, and some extra mission equipment (the OH-58D did not meet the specified ASH maneuverability requirement).
The OH-58E was a more substantial modification that included a four-bladed rotor, a mast-mounted sight (MMS), equipped with day-television and forward-looking infrared (FLIR) -- for night operations -- and an upgraded transmission and engine. The next two candidates were modifications of the AH-l attack helicopter. The OH-64 is a modification of the YAH-64 attack helicopter that left the weapons systems intact but removed the weapons.
The final three candidates were derivatives of helicopters that are currently in existence or under development. These included the Aerospatial AS-350 (350), the Agusta A-129 (129), and the Hughes 500D (500). The Army decided that an entirely new helicopter was not affordable. In 1980, the Army began planning for a scout helicopter that would bolster the capabilities of an existing model. The primary aspect of the NTSH program was to put a mast-mounted-sight (MMS) on the aircraft to improve its mission performance capability. The MMS will enable the aircraft to perform its reconnaissance, surveillance, and target acquisition functions while remaining hidden behind masking obstacles such as trees and terrain.
The Army conducted an evaluation of the UH-1 and OH-58 as NTSH candidates. Based upon the results of the relative detectability of the two, the UH-1 was dropped from consideration as a candidate airframe. The results of this evaluation showed that there was a dramatic reduction of the detectability of the OH-58 as a result of the MMS. A 10 July 1980 decision by the Army made the near term scout helicopter (NTSH) a competitive modification program. Independently from the Army, industry had developed a commercial helicopter similar to the OH-6. Actions are continuing to solicit industry for technical proposals that address the Army's needs for a near term scout helicopter.
Full-scale engineering development for Army Helicopter Improvement Program (AHIP) started in 1981, under the direction of the Aviation Systems Command in St. Louis, Missouri.
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