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 with afterburners. Aircraft such as the SR-71 Blackbird are designed to cruise at supersonic speed with afterburners enabled.

Some 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. Planes marketed as featuring supercruise usually have the ability to carry a combat load at low to medium altitudes; being able to break Mach 1 without afterburner does not necessarily show supercruise ability. For example, the Federation of American Scientists defined supercruise as "the ability to cruise at speeds of one and a half times the speed of sound or greater without the use of afterburner for extended periods in combat configuration" in discussing the F-22.

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 supersonic; more than all other aircraft combined.

History

A few early supersonic aircraft attained speeds just beyond the speed of sound without using afterburning.

On 3August 1954, a Gerfaut research aircraft powered by an SNECMA Atar 101D2A engine exceeded Mach1 in level flight without using afterburning.

The first production aircraft to exceed Mach1 in level flight without afterburning was the Lockheed F-104 Starfighter after its J65 engine was replaced with a J79. The maximum speed without afterburning was Mach1.05.

The P.1 prototype of the English Electric Lightning, powered by non-afterburning Armstrong Siddeley Sapphire engines, exceeded Mach1 on 11August 1954. A week previously, on 4August, the P.1, '' WG760'' flown by Roland Beamont on its maiden flight, had unknowingly exceeded Mach1 in a climb. During development testing at English Electric it was established that the Lightning had a stabilized speed capability in level flight, without afterburning, of about Mach1.2 and for the T.4 (2-seat trainer) 1.08. Flying just above the speed of sound without using afterburning, although done by the contractor as part of some flight trials does not appear to have been relevant to the operational capability of the aircraft. Service trials established intercept profiles for subsonic and supersonic targets at different altitudes with subsonic cruising at a maximum of Mach0.95 with all supersonic speeds beyond subsonic cruise attained with afterburning.

All the Fairey Delta 2 initial supersonic test flying to Mach1.1 was done without afterburning. Selecting the afterburner, which initially only had a maximum selection with no intermediate positions, would have caused an uncontrollable rapid acceleration to potentially hazardous speeds, ie too far beyond previously established flutter-free speeds.

Only the supersonic transports (SST), Concorde, and the second version of the Tu-144 (the Tu-144D) spent most of their time cruising at their design speeds without needing afterburning. Afterburning was added to Concorde for take-off to cope with weight increases that came after the initial design. It was also used to accelerate through the high-drag transonic speed range, not because the extra thrust was required, but because it was available and improved the operating economics. The redesigned Tu-144D used engines with no afterburners which, together with other improvements, increased the full payload range from (Concorde's operational range was ).

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. 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 theorized 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.

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 Mach1.5. Supercruise capability provides advantages for stealth aircraft, because an afterburner plume reflects radar signals and creates a significant infrared signature. Virtually all fighters prior to the F-22 cruise at Mach0.8–0.9 while carrying a normal weapons load.

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 makes it the most capable supercruise-capable fighter aircraft in service. The F-22 Raptor can supercruise above Mach 1.5 without external stores.General Jumper qualifies in F/A-22 Raptor
af.mil, January 13, 2005
* 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. Typhoon pilots have stated that Mach 1.3 is attainable in combat configuration with external stores.
* The General Electric F414G in the JAS 39 Gripen NG is designed for supercruise and has achieved Mach 1.2, or Mach 1.1 with an air to air missile load.
* The two Snecma M88s that power the Dassault Rafale enables the Rafale to supercruise with four missiles and a belly drop tank.

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 accelerate 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.

Aircraft with supercruise ability

References

Citations

Bibliography

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* {{cite book , last1=Gordon , first1=Yefim , last2=Komissarov , first2=Dmitry , last3=Rigmant , first3=Vladimir , title=Tupolev Tu-144: The Soviet Supersonic Airliner , date=May 2015 , publisher=Schiffer Publishing Ltd. , location=Atglen, PA , isbn=9780764348945

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