Red Steer

EKCO

Industry	Electronics, Radar manufacturing
Products	Red Steer tail warning radar

Template:Infobox radar Red Steer, which is also identified as ARI 5919 or ARI 5952 depending on the variant, was a tail warning radar employed by the British V bomber fleet. Manufactured by EKCO, its design originated from the experimental AI.20 radar developed for the English Electric Lightning. Since the Lightning required a radar system installed remotely in the aircraft's nose, this architecture made the radar equally applicable for remote installation in bomber tail sections.

The Red Steer system monitored a 45-degree conical sector behind the aircraft, relaying detected signals to an electronic warfare operator’s display. It could consistently identify large fighter-sized targets at approximately 10 nautical miles (19 km; 12 mi). Without onboard weaponry, its primary function was to alert the operator to guide the bomber crew in evading interceptors and to optimize the timing of deploying various electronic countermeasures against enemy radar systems, particularly the Red Shrimp jammer.

Introduced in 1957 as a replacement for the earlier Orange Putter, Red Steer addressed crew concerns regarding limitations of its predecessor. However, operational experience revealed challenges with its display interface, prompting development of an enhanced Mark 2 variant featuring a significantly improved display and extended detection range up to 25 nautical miles (46 km; 29 mi). These upgraded units were installed across the Avro Vulcan and Handley Page Victor fleets during the 1960s and remained active until these bombers were retired in the 1980s and 1990s.

AI.20

Main article: AI.20 radar

During early development phases leading to the creation of the English Electric Lightning, Ferranti proposed a revolutionary new aircraft interception radar system. This design aimed to fully automate target detection, interception plotting, and weapons cueing processes through computerized control. Instead of a conventional dimly lit cathode ray tube (CRT), data would be projected directly onto the pilot’s gunsight. This advanced system later became known as AIRPASS, representing a significant leap beyond contemporary AI radars.

Some officials within the Air Ministry expressed concerns that AIRPASS’s complexity posed technical risks potentially delaying the Lightning program. Consequently, a backup system based on traditional electronics was commissioned in 1952. The contract was awarded to EKCO, leveraging their expertise from developing illuminator radars for the Fireflash missile. EKCO adapted their medium-range, narrow-angle radar technology to extend both range and coverage angle. A notable innovation was utilizing the high-voltage power supply—originally dedicated solely to powering the radar’s magnetron—to also energize the CRT display, ensuring sufficient brightness even under full daylight conditions.

Designated under the rainbow code "Green Willow," this radar underwent testing starting in 1955. By that time, initial AIRPASS units were also progressing through trials without major issues threatening their deployment. As a result, Green Willow—also known as AI.20—was ultimately discontinued.

Red Steer

Soon after the AI.20 program was discontinued, the initial V bomber models were introduced into squadron service. These bombers were fitted with a basic tail warning radar system called "Orange Putter", originally developed for the English Electric Canberra. Early operational experience with V-bombers revealed that this radar was largely ineffective at fulfilling its primary function of alerting the bomber to incoming interceptor aircraft in sufficient time to take evasive maneuvers.

Consequently, in 1956 a Request for Quotation was issued to develop an enhanced radar specifically for the tail warning role. The system needed to be compact enough to fit inside the tailcone, necessitating a small, self-contained design. Both AIRPASS and AI.20 radars, initially engineered for installation in the Lightning’s nose cone, were well suited for this application. Since the radar’s purpose was limited to providing directional and range data, the advanced processing capabilities of AIRPASS were unnecessary, making the simpler AI.20 an almost ideal candidate. The primary challenge involved extending the 30 kV power supply line from the rear of a large aircraft all the way to the front cockpit area, rather than just a short distance as previously done; this required new connectors and vacuum testing.

Designated under the rainbow code "Red Steer," the project likely honored RRE Project Officer Gerry Steer, rather than following the usual unrelated naming convention of Rainbow Codes. A Vickers Valiant was adapted to test this system. By January 1958, it demonstrated a 75% detection probability of a Hawker Hunter at 10 nautical miles (19 km; 12 mi), improving to 100% at 8 nautical miles (15 km; 9.2 mi).

Subsequent installations were performed on Avro Vulcan and Handley Page Victor bombers, where these systems were designated ARI 5919. Starting in 1960, these aircraft underwent modifications including enlarged tailcone sections to accommodate both Red Steer and an expanded electronic countermeasures suite.

Mk. 2

In operational deployment, interpreting Red Steer’s display proved challenging due to its spiral scan presentation. The display directly showed the target’s zenith angle relative to the bomber’s tail, but represented azimuth angle by the blip length and range by its distance from center. As an interceptor drew nearer, the blip lengthened and moved rapidly on screen. This erratic motion has been described as a "nightmare to interpret", prompting jokes that Soviet forces refrained from jamming it since such interference would not complicate reading it any further.

These difficulties led to development of Red Steer Mark 2 during the late 1960s; consequently, the original model was retrospectively labeled Mark 1. The Mark 2 dispensed with spiral scanning in favor of an X-Y scan (C-scope) that swept horizontally across 70 degrees azimuth before incrementally stepping vertically for another sweep at a different elevation angle. This cycle covered from 25 degrees above to below centerline over eight horizontal sweeps. It had an effective detection range against fighter-sized targets out to 25 nautical miles (46 km; 29 mi), providing ample time for tracking before missile engagement range was reached. In service, these were known as ARI 5952 units.

Mark 2 systems remained active throughout the V-force’s operational lifespan, leaving frontline bomber roles by 1984. Their only combat deployment occurred on Vulcans during Operation Black Buck in the 1982 Falklands War. On one occasion aboard XM607, the unit failed due to loss of radar pressurization after an extended high-altitude flight lasting 15 hours—significantly longer than its design parameters anticipated. The final combat use came with Victor air tankers during the Gulf War in 1992 before official retirement in 1994. The detailed operational characteristics of Red Steer signals remain classified today.

Mk 1/ARI 5919

The initial ARI 5919 model comprised two main components: the radar unit positioned in the tail section and the display console located at the Air Electronics Officer (AEO) station within the cockpit. The radar employed an 18-inch parabolic reflector, which was rotated in a spiral pattern at 1000 revolutions per minute, powered by a 0.5 horsepower electric motor. Its scanning sequence covered from directly behind the aircraft to 45 degrees off-axis over 18 rotations, then reversed direction to scan across a 90-degree sector in approximately 2.25 seconds.

The display system, designed during a period when phosphors had low brightness, demanded exceptionally high voltages to ensure visibility under the bright conditions of a fighter cockpit. To achieve this, a single 30 kV power supply was shared between the radar and the display, with a heavily insulated cable running the short distance from the aircraft’s nose to the cockpit display. Although this high voltage output was unnecessary for V-bomber configurations—where the electronic warfare (EW) station was not subject to intense lighting—the system remained unaltered. Consequently, a high voltage line extended nearly the full length of the aircraft from the tail to the EW station, raising safety concerns that prompted rigorous testing and the creation of specialized connectors.

The scanner’s beam-width measured roughly 5.5 degrees, causing distant targets to produce brief arcs on the cathode-ray tube (CRT) display as they moved within the scan area. The position of these arcs around the display's circumference indicated a target’s angle relative to dead astern; for example, a blip appearing near the 10 o’clock position signified a target located left and slightly above the bomber. As targets neared dead astern, they remained illuminated longer due to beam overlap, eventually appearing continuously and forming a ring on the display. The total angular extent of this blip reflected how close to center the target was; at an offset of 3 degrees, it created a 180-degree arc.

Adding complexity, this display operated in an inverted manner compared to other spiral-scan radars. The radar receiver amplifier’s output modulated the CRT’s brightness control, making an otherwise invisible beam visible by brightening it. Typically, such radars drew the beam from the center outward during pulse transmission and return, causing blips to appear farther from center as range increased but often resulting in loss of returns at close range due to a constant bright dot at center. In contrast, AI.20 reversed this approach by drawing the beam from outside inward, which prevented loss of close-range returns but produced a challenging display at short distances where blips expanded significantly and shifted rapidly with minor target movements.

Mk 2/ARI 5952

File:Avro 698 Vulcan B2, UK - Air Force AN1358039.jpg

Later Vulcan models incorporated a significantly enlarged tail section housing an enhanced array of electronic countermeasures, including the ARI 5952 dome positioned at the furthest rear point.

In the ARI 5952 variant, the original scanner and display were substituted while retaining the existing radar electronics such as the transmitter and receiver units. The scanner was adapted from the EKCO E190 weather radar system used in airliner aircraft. This updated M2269 scanner featured a 24 inches (610 mm) reflector, which narrowed the beam-width to 3.7 degrees, thereby improving gain.

Unlike the initial spiral rotation, this scanner oscillated laterally, sweeping 75 degrees on either side of the aircraft’s centerline, generating a 150-degree wide display behind the plane. Each lateral sweep was accompanied by an eight-step vertical "nod" movement, covering 25 degrees above and below the centerline. This produced a rectangular scanning area that was somewhat broader horizontally but offered reduced vertical coverage compared to its predecessor. Given that V bombers were now executing low-level target approaches, the decreased vertical range was acceptable. Additionally, the entire system was line-of-sight stabilized, ensuring that the radar image remained steady despite aircraft maneuvers—an important improvement over the original design.

The complementary M2212 display adopted a rectangular format measuring 3 by 5 inches (76 by 127 mm). It employed a modern yellow phosphor screen which eliminated the need for high voltage to maintain visibility under direct sunlight.

Units on display

• A Red Steer ARI-5952 unit is exhibited at the City of Norwich Aviation Museum located in Horsham St Faith, Norfolk