Supercruise

The English Electric Lightning was one of the first aircraft capable of supercruise.

Supercruise is sustained supersonic flight of a supersonic aircraft with a useful cargo, passenger, or weapons load without using afterburner (also known as "reheat"). Many supersonic military aircraft are not capable of supercruise and can only maintain Mach 1+ flight in short bursts, typically with afterburners. Aircraft such as the SR-71 Blackbird are designed to cruise at supersonic speed with afterburners enabled.

Many 4th generation fighter jets are technically capable of supercruise, but only at high altitudes and in a clean configuration. For an aircraft to be deemed capable of true supercruise, it must be able to carry a normal load for an extended distance without diving or using an afterburner.^[1] Optimally, qualifying for "true supercruise" would involve demonstrating the ability with a combat load at low to medium altitudes; being able to break Mach 1 without afterburner does not in itself show supercruise ability.

One of the best-known examples of an aircraft capable of supercruise was Concorde. Due to its long service as a commercial airliner, Concorde holds the record for the most time spent in supercruise; more than all other aircraft combined.^[2]

History[]

Concorde routinely supercruised most of the way over the Atlantic, enabling it to travel from London to New York in three hours, a record which has yet to be surpassed by any other commercial aircraft.

On 3 August 1954, a Gerfaut research aircraft powered by an SNECMA Atar 101D2A engine exceeded Mach 1 on level flight without using afterburners.^[3][4] The first production aircraft intended to exceed Mach 1 in dry level flight was the Lockheed F-104 Starfighter which featured a radical design, with razor-thin, stubby wings attached substantially farther back on the fuselage than most contemporary aircraft. The wing provided excellent supersonic and high-speed, low-altitude performance, but resulted in poor turning capability and high landing speeds. It was the first production aircraft to achieve Mach 2, and the first aircraft to reach an altitude of 100,000 feet after taking off under its own power. The Starfighter established world records for airspeed, altitude, and time-to-climb in 1958, becoming the first aircraft to hold all three simultaneously. The non-afterburning Armstrong Siddeley Sapphire powered P.1 prototype of the English Electric Lightning, exceeded Mach 1 on 11 August 1954. A week previous, on 4 August, the P.1, WG760 flown by Roland Beamont on its maiden flight, had unknowingly exceeded Mach 1 in a climb, although, due to position error, the Machmeter had only shown a maximum of Mach 0.95. Beamont, who had not noticed any change in behavior of the aircraft, was surprised when informed after the flight data had been analysed.^[5] However, this early demonstration of supersonic flight was extremely limited, as the Lightning could only cruise without afterburner at approximately Mach 1.02,^[6] while later versions were able to achieve much higher speeds, but only for very short time periods. Since it could not sustain supersonic speed for 20 minutes, as specified in the original definition of "supercruise", inclusion of the EE Lightning in the category has remained controversial.^{[citation needed]}

The BAC TSR-2 strike and reconnaissance aircraft, which first flew on 27 September 1964, was one of the first military aircraft specifically designed to cruise supersonically; one of the planned mission profiles was for a supersonic cruise at Mach 2.0 at 50,000–58,000 ft (15–18 km).^[7] Supersonic cruise at lower levels was at Mach 1.1 at 200 ft (61 m).^[8] The TSR-2 used Bristol Olympus engines, a later version of which would also power Concorde.

Qualitative variation in Cd factor (drag coefficient) with Mach number (speed) for aircraft; supercruising above Mach 2 is efficient.

Only the supersonic transports (SST), Concorde, and the last version of the Tu-144 (the Tu-144D) spent most of their time cruising at their design speeds without needing afterburning. Afterburner was added to Concorde for take-off to cope with weight increases that came after the initial design, and was used to push through the transonic drag barrier. The upgraded Tu-144D had engines with a more-advanced intake design, which did not require afterburners during cruise, increased the full payload range from 3,080 to 5,330 km (1,910 to 3,310 mi) (Concorde's operational range was 6,470 km or 4,020 mi), and were more economical than the engines of the Tu-144.^[9]

Military use[]

The term "supercruise" was originally used to describe a fighter performance requirement set forth by USAF Col. John Boyd, and Col. Everest Riccioni, proponents of the F-16 Falcon.^{[citation needed]} Following the entry into production of the F-16, they began work on an improved fighter design with the ability to cruise supersonically over enemy territory for a minimum of twenty minutes. As air combat is often the result of surprise, and the speed of combat is determined by the speed of the surprising aircraft, this would have given a supercruise-capable design a worthwhile performance advantage in many situations. The postulated fighter would have had a top speed of just over Mach 1, and a fuel fraction in excess of 40%, the minimum required to meet the twenty-minute requirement. The fuel fraction requirement necessitated a very austere design with few advanced electronics. The United States Air Force showed no interest in the proposal at that time, but years later revived the term and redefined it to apply to the requirements for the Advanced Tactical Fighter, which resulted in the F-22 Raptor.^[10]

The F-22 Raptor is capable of supercruise at Mach 1.8 (but is seen here running afterburner).

The Dassault Rafale is capable of supercruising with four missiles and a belly drop tank.^[11]

The Eurofighter Typhoon is capable of supercruise at Mach 1.5.^[12]

The F-22 Raptor's supercruise capabilities are touted as a major performance advantage over other fighters, with supercruise being demonstrated up to at least Mach 1.8.^[13] Supercruise capability provides advantages for stealth aircraft, because an afterburner plume reflects radar signals and creates a significant infrared signature.^[14] Virtually all fighters prior to the F-22 cruise at Mach 0.8–0.9 while carrying a normal weapons load.^[15]

Supercruising uses more fuel to travel the same distance than at subsonic speeds. The Air Force Association estimates that use of supercruise for a 100-nautical-mile (120 mi; 190 km) dash as part of a mission would cut the F-22's combat radius from about 600 nautical miles (690 mi; 1,100 km) to about 450 nautical miles (520 mi; 830 km), but because of the F-22's flight dynamics being classified, this is unconfirmed.^{[citation needed]}

There are a few engines in production that are designed to facilitate tactically significant supercruise:

• The two Pratt & Whitney F119 that power the F-22 Raptor make it the most capable supercruise-capable fighter aircraft in service. The F-22 Raptor can supercruise up to Mach 1.8 without external stores.^[16][17]
• The EJ200 engine built by EuroJet Turbo GmbH mounted in the Eurofighter Typhoon. It is capable of supercruising at Mach 1.5 with an air superiority missile load.^[12] Typhoon pilots have stated that Mach 1.3 is attainable in combat configuration with external stores.^[18]
• The General Electric F414G in JAS 39 Gripen NG is designed for supercruise and has been shown to achieve Mach 1.2.^[19]
• The two Snecma M88s that power the Dassault Rafale enables the Rafale to supercruise with four missiles and a belly drop tank.^[11]

Independently, Russia is working on Izdelje 30 (after AL31F and AL41F derivatives modifications, like 117S turbofan) and RD33MKRU Morskaja Osa; an all new AL-41 engine with a complete redesign is underway to add supercruise ability to the Sukhoi Su-57. This has yet to bear fruit, but the stop-gap 117S engine, produced by this program, may achieve the supercruise goal already. During testing of a Su-35BM fighter equipped with these engines, it managed to accelerated past Mach 1 without the use of the afterburner, suggesting that it had supercruise capability. It has yet to be seen whether this will be possible with a combat load.^[20]

Aircraft with supercruise ability[]

References[]