View source for Operational Requirement F.155

{{short description|British military defense specification}}
{{Use dmy dates|date=October 2019}}
{{Use British English|date=December 2016}}
'''Operational Requirement F.155''' was a specification issued by the [[British Ministry of Supply]] on 15 January 1955 for an [[interceptor aircraft]] to defend the United Kingdom from [[Soviet Union|Soviet]] high-flying nuclear-armed [[supersonic]] [[bomber]]s.

Discussion about the need for a new supersonic interceptor had been ongoing for some time in the early 1950s, and several designs introduced, but improving [[radar]] systems and weapons mooted the need for better aircraft in the short term. Information about new Soviet supersonic bomber designs emerged in 1954, sparking serious consideration for the first time. The Requirement emerged as a much larger and longer-range system than previously studied. The Requirement called for aircraft to be in service by 1962, the same date as the [[Tupolev Tu-22]].{{efn|This risk turned out to be overblown; the Tu-22 suffered significant performance problems that so limited its range that only small numbers were deployed as bombers.}}

A number of designs were entered into the competition, many of them based on earlier projects. They generally featured two engines, mounted a powerful new [[aircraft interception radar|aircraft interception (AI) radar]], and would be armed with improved versions of the [[de Havilland Firestreak]] missile or an even larger radar-guided design known as "[[Red Hebe]]". In overall terms, the F.155 designs were similar to the [[Convair F-106]] or [[Avro Arrow]], although longer range was desired.

Serious design work had only just started when the entire effort was cancelled as part of the [[1957 Defence White Paper]]. This paper considered the introduction of new Soviet [[medium range ballistic missile]]s (MRBMs) that were being deployed in [[East Germany]]; these were armed with [[chemical weapon|chemical warhead]]s, but it was clear that nuclear-armed versions would be available by the mid-1960s. In this case, shooting down bombers would have no ultimate effect on the outcome of the battle. The paper led to the cancellation of nearly all crewed fighter projects as well as most other air defence programs as a radical change had occurred in strategic threats with the expectation that missiles and low-level strike would replace high-flying bombers.
 
[[File:Gloster.javelin.xh903.arp.jpg|thumb|right|[[Gloster Javelin]] all-weather fighter in service at the time.]]

==Background==
During the early 1950s, the RAF's front line defence was converting from [[Gloster Meteor]] (a design that first flew during the Second World War) to [[Gloster Javelin]] all-weather fighters with the anticipation of new interceptors coming into service in the near-future. These included the [[English Electric Lightning]] (point defence interceptor) and [[Saunders-Roe SR.177]] interceptors in development. While the Lightning embodied largely conventional jet engine technology, the SR.177 was a "mixed" rocket/jet design that used rocket power for delivering high speed and maximum altitude performance. Due to the length of design and development, for the interim the RAF also considered purchase of the Canadian [[Avro Canada CF-105 Arrow|Avro CF-105 Arrow]] projected to be operational by 1961.

==Requirement==
Operation Requirement F.155 specified exacting demands:
* The capability of making an intercept within 20 minutes of target contact (250 miles from the UK)
* target speed would be Mach 1+
* ceiling: {{convert|60000|ft|m|abbr=on}}
* Armament: a mixture of infra-red guided missiles and radar guided missiles
* Crew: Two (pilot, weapons systems/navigation); a crew of two was specified because of the anticipated workload.

The Ministry of Supply made clear in the requirement that the plane and missiles should be treated as a "weapon system" i.e., a cohesive whole. The armament specifications were covered by a separate Operational Requirement: OR.1131. Two missiles were identified in OR.1131:  
*[[Blue Vesta]] to be developed by [[de Havilland]] and
*[[Red Hebe]] by [[Vickers-Armstrong|Vickers]], a scaled down version of their [[Red Dean]] missile.

A smaller version of Red Hebe would eventually also come into the equation. Blue Vesta was a {{convert|150|kg|lb|abbr=on}} infra-red guided weapon for attack from a pursuit angle. The Blue Vesta was largely displaced by the development of [[Blue Jay missile|Blue Jay]] Mark 4 (which would enter service as [[Hawker Siddeley Red Top|Red Top]]). Red Hebe was nearly {{convert|600|kg|lb|abbr=on}} but being radar guided, it would be able to hit its target from any firing angle including a collision course intercept.

==Designs==
Most British manufacturers provided their own suggestions for planes that would meet the [[List of Air Ministry specifications|specification]]. At the same time the engine manufacturers were encouraged to develop the necessary powerplants. These included the [[de Havilland Gyron]] and [[Rolls-Royce RB.106]].

[[Saunders-Roe]] came up with the P.187: a logical progression from the [[SR.53]] and [[SR.177]] mixed power (rocket and jet engines) interceptors. This gave both rapid acceleration and the capability to operate at high altitudes where jets would be inefficient due to the thin air. Saunders-Roe judged that a big aircraft would be needed to carry 2 IR and 2 radar-guided missiles and the fuel required. A highly streamlined futuristic-looking design (using a [[Droop nose (aeronautics)|drooped nose]]) it would have been powered by 2 PS.52 jets, a projected development of the Gyron giving 35,000&nbsp;lb (155.6&nbsp;kN) of thrust, and 4 Spectre rockets, giving a speed of Mach 2.5 at 76,000&nbsp;ft (23,165 m). It was judged, at 98,000&nbsp;lb (3 times the weight of the SR.177) and {{convert|84|ft|m|abbr=on|adj=mid|long}}, as too big. 
[[File:Fairey F.155T 03.jpg|thumb| A projected fighter derivative of [[Fairey Aviation Company|Fairey]]'s successful FD2 experimental aircraft]]
[[Fairey Aviation Company|Fairey]] drew on their experience with the [[Fairey Delta 2]] (FD2). Their first proposal was a single-engined fighter development of the existing FD2, which was felt to have good export potential although it did not meet the RAF criteria laid down in O.R. F.155. A larger twin-engined design tailored to the operational requirement followed on from this, which became known simply as the "Delta III". A fighter-bomber derivative of this aircraft was also envisaged, with [[Bristol Olympus]] 21R engines coupled with a large ventral drop tank giving a much-improved radius of action at low altitude.{{Citation needed|date=July 2008}} Fairey, like some of the other manufacturers, felt that carrying 4 missiles was too onerous especially given the size of the radar guided Red Hebe and provided designs based on a payload of only two missiles. They also took the mixed power route for both the FD2 based and the new 'FD3' designs, with both making provision for the fitting of [[de Havilland]] rocket engines.
[[File:H-p1103.jpg|thumb|left| [[Hawker P.1103]] company schematic drawing]]
Going on the basis of the smallest aircraft that could do the job, [[Hawker Aircraft|Hawker]]'s design (the [[Hawker P.1103|P.1103]]) used a single, albeit powerful, engine – a 25,000&nbsp;lb (111.1&nbsp;kN) development of the Gyron. Alternative engines in the form of the [[Rolls-Royce Ltd|Rolls-Royce]] [[Rolls-Royce RB.122|RB.122]], [[Armstrong-Siddeley P.173]] and the [[Canada|Canadian]] [[Orenda Iroquois|Orenda PS.13]] were also options. Two detachable rocket boosters, to give a 3.7-minute boost, were carried in midwing nacelles.
[[File:Aw169.JPG|thumb|left|[[Armstrong-Whitworth]] AW.169 manufacturer's model]]
[[Armstrong-Whitworth]] put forward their AW.169. A razor-thin straight wing carried the engines in nacelles – two Gyron Juniors on each side – with a rocket booster under the long narrow fuselage. Two missiles were carried, one on each wingtip.<ref>{{cite web |url=http://www.strange-mecha.com/aircraft/Cancel/UK-AW.htm |title=Armstrong Whitworth Aircraft |access-date=27 September 2007 |date=30 October 2000 |work=The Strange Mechanism Museum |url-status=usurped |archive-url=https://web.archive.org/web/20070927105202/http://www.strange-mecha.com/aircraft/Cancel/UK-AW.htm |archive-date=27 September 2007  }}</ref>
[[File:Vickers559 03.jpg|thumb|[[Vickers Type 559]]]] 
[[Vickers-Armstrong]] submitted the [[Vickers Type 559|Type 559]]; an unorthodox [[canard (aeronautics)|canard]] design with a massive chin air intake, split vertically, for two [[afterburner|reheated]] Gyron engines placed, as in the [[English Electric Lightning]], one above the other.  Two Spectre Junior rockets were situated each side of the jets at wing level.  Two Red Hebe or Blue Jay missiles were mounted alongside the upper part of the fuselage between the canard and the mainplane, which had end-plates incorporating twin rudders.

[[De Havilland]] submitted a relatively small design when compared to the giants from Fairey and Saunders-Roe. The DH.117 was to be powered by two Gyron Junior turbojets and a Spectre booster rocket in the tail, with a crew of two seated in tandem. Provision was not made for Red Hebe, the de Havilland team preferring the company's own line of missiles that would culminate in [[Red Top (missile)|Red Top]].

[[English Electric]] submitted a design based on their successful P.1B short-range interceptor that would become the [[English Electric Lightning|Lightning]]. The P.8 was larger overall, carried a crew of two, moved the weapons to the wingtips and undercarriage to the fuselage but featured the same vertically-stacked engine and nose intake layout as the Lightning. The radar package was to be the same AI-23 AIRPASS system as the Lightning but with a larger scanner dish to improve detection range. At the time, English Electric engineers were far from convinced of the ability of fighter aircraft to carry both radar- and infrared-guided weapons, so designed the P.8 to only carry the de Havilland Blue Jay Mk.4, which would enter service as [[Red Top (missile)|Red Top]].

The AW.169 and Fairey's Delta III design were considered to be the best two contenders taking into account the design of the aircraft, the development risks, the capabilities of the design teams and the manufacturers' workloads – [[Bristol Aeroplane Company|Bristol]] had not been invited to tender because of the importance of the [[Bristol 188]] high speed research plane they were working on. Initially further work was contracted on both designs but by the end of the year the AW.169 was dropped and the Fairey design become a firm choice. However, in April the following year, the 1957 Defence White Paper terminated nearly all crewed fighter development projects.<ref>{{Cite web| title=The 1957 Defence White Paper - The Cancelled Projects | url=https://www.aerosociety.com/media/8134/the-1957-defence-white-paper-cancelled-projects.pdf | archive-url=https://web.archive.org/web/20181210111308/https://www.aerosociety.com/media/8134/the-1957-defence-white-paper-cancelled-projects.pdf | archive-date=2018-12-10}}</ref>

==Proposed specifications==

===SR.187===
{{Aircraft specs
|prime units? = met
|ref=<ref>{{cite web |archive-url=https://web.archive.org/web/20040827002243/http://www.spaceuk.org/sr53/f155/f155.htm |archive-date=2004-08-27 |url=http://www.spaceuk.org/sr53/f155/f155.htm |title=Saunders Roe's Proposal for the F.155 - the P.187 |website=spaceuk.org |date=5 July 2002 |url-status=dead }}</ref>{{rs|date=March 2022}}
|crew=2 (pilot and navigator)
|length ft= 83
|length in= 6
|length m= 25.5 
|span ft=51
|span in=7
|span m= 15.7 
|height ft=21
|height in=8
|height m= 6.6 
|empty weight lb= 54,700  
|empty weight kg= 24,810
|gross weight lb= 97,000  
|gross weight kg= 43,990
|eng1 name=[[de Havilland Gyron]] P.S.52
|eng1 type=afterburning turbojet
|eng1 number=2
|eng1 lbf=25,000  
|eng1 kn= 111.2 
|eng1 lbf-ab=35,000  
|eng1 kn-ab= 155.7 
|eng2 name=de Havilland developed [[de Havilland Spectre|Spectre]] 5
|eng2 type=rocket 
|eng2 number=4
|eng2 lbf= 10,000 
|eng2 kn= 44.5 
|max speed mach= 2.5
|range nmi= 260 
|range km= 480
|ceiling ft=76,000   
|ceiling m= 23,080 
|missiles=OR 3101 (2 radar- and 2 infrared-guided missiles)  
}}

===AW.169===
{{Aircraft specs
|prime units? = met
|ref=<ref>{{cite web|url=http://www.strange-mecha.com/aircraft/Cancel/UK-AW.htm  |title=Armstrong Whitworth Aircraft PAGE |website=strange mecha |date=2000-10-30  |url-status=usurped  |archive-url=https://web.archive.org/web/20070927105202/http://www.strange-mecha.com/aircraft/Cancel/UK-AW.htm |archive-date=27 September 2007 }}</ref>{{rs|date=March 2022}}<ref>[http://www.rp-one.net/f_155_t/f155t.html F155T Design Submissions]</ref>{{rs|date=March 2022}}
|crew=1
|length m= 25.60 
|span m=13.82 
|gross weight kg= 24,494
|fuel capacity= {{convert|11600|lb|abbr=on}} kerosene, {{convert|4500|lb|abbr=on}} [[High test peroxide|HTP]]
|eng1 name=[[de Havilland Gyron Junior]]
|eng1 type=turbojet
|eng1 number=4
|eng2 name=Armstrong Siddeley
|eng2 type=rocket
|eng2 number=1
|max speed mach= 2.5
|max speed kmh=3,580
|max speed note=&nbsp;at altitude
|missiles=2 x [[Red Dean]] air-to-air missiles 
|avionics=GEC X Band AI Mk 18 derivative, Q band ranging radar
}}

===Fairey 'Delta III'===
{{Aircraft specs
|prime units? = met
|ref=<ref>{{usurped|1=[https://web.archive.org/web/20010308163222/http://www.strange-mecha.com/aircraft/Cancel/UK-Feirey.htm strange mecha]}}</ref>{{rs|date=March 2022}}
|crew=2
|length m= 22.6 
|length ft= 74.3 
|span m=14.2 
|span ft= 46.8 
|wing area sqm= 102 
|wing area sqft= 1,100 
|gross weight kg=22,888
|gross weight note=with 2 Red Dean
|gross weight lb= 50,460  
|eng1 name=[[Rolls-Royce RB.122]] 
|eng1 type=turbojet 
|eng1 number=2
|eng1 lbf= 17,000
|eng1 lbf-ab= 20,000
|eng2 name=[[de Havilland Spectre Junior]]  
|eng2 type=rocket
|eng2 number=2
|eng2 lbf= 5,000
|max speed mach= 2.27 
|max speed kmh= 2,387 
|max speed note=&nbsp;at {{convert|36000|ft|m|abbr=on}}
|missiles=2 x [[Red Dean]] or 2 x [[de Havilland Firestreak#Blue_Jay|Blue Jay Mk.4]]
}}

== Notes ==
{{notelist}}

== References ==
{{reflist}}

== Bibliography ==
* Buttler, Tony. ''British Secret Projects: Jet Fighters Since 1950''. Leicester, UK: Midland Publishing, 2000, {{ISBN|1-85780-095-8}}.
* Buttler, Tony. "Futile Rivals: F.155T– The Quest for 'An Ultimate in Interceptors'." ''Air Enthusiast'' No. 61, January–February 1996.
* Wood, Derek. ''Project Cancelled: British Aircraft That Never Flew''. Indianapolis: The Bobbs-Merrill Company, 1975. {{ISBN|0-672-52166-0}}.

==External links==

*[http://prototypes.free.fr/fd2/fd2-3.htm Fairey Delta 2 and III] {{in lang|fr}}

[[Category:1950s British fighter aircraft]]
[[Category:Cancelled military aircraft projects of the United Kingdom]]