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Supercruise allows aircraft to fly at supersonic speeds without afterburners, increasing fuel efficiency and reducing tactical drawbacks. Afterburners are still used to accelerate to supersonic speeds, but supercruise is necessary for modern air superiority. The Concorde and F-22/A Raptor are examples of supercruise-capable aircraft.
Supercruise is the ability of an aircraft to fly at supersonic speeds without the use of an afterburner. In practical terms, an aircraft is considered capable of true supercruise only if it can operate at supersonic speeds while carrying a payload load. Aircraft with supercruise capability have been commissioned in both civil and military roles. The ability to break the sound barrier without relying on prolonged use of afterburners greatly increases the fuel efficiency of supersonic flight and eliminates many of the tactical drawbacks of afterburner flight in a combat environment.
For much of the history of supersonic aviation, speeds greater than Mach 1, or the speed of sound, 1,126 feet (343.2 m) per second, required the use of an afterburner system. An afterburner injects fuel into the jet exhaust of an engine after it has already passed through the jet turbine, greatly increasing the heat and pressure within the jet piping and resulting in a jet exhaust stream. which has a much higher muzzle velocity. The drawback of such a system is that it burns fuel at a rate several times that of normal operation. An aircraft that is capable of utilizing a tactically significant afterburner duration suffers from a higher fuel fraction, the proportion of the craft’s loaded weight that must be devoted to carrying fuel. It also creates a large plume of exhaust that makes the plane more visible to infrared sensors, increasing the range at which enemies can easily spot the plane.
A supercruise aircraft typically uses afterburners to accelerate from subsonic to supersonic speed, although this is due to fuel efficiency concerns rather than strict necessity, in most cases. By breaking the sound barrier, an aircraft is subjected to drag-inducing forces caused by flying within its own sonic boom, making acceleration even more difficult. After the aircraft has reached Mach 1.1, or 1.1 times the speed of sound, it is no longer subject to these forces and takes on a much more efficient flight profile. By using an afterburner to minimize the amount of time it takes to overcome sonic shock, a supersonic aircraft can save fuel throughout the flight, even allowing greater use of afterburner fuel.
The Concorde supersonic transport jet used supercruise on transatlantic flights, cutting transit time approximately in half compared to subsonic aircraft. The F-22/A Raptor was the first military aircraft designed with sustained supercruise capabilities, although some earlier fighters were capable of limited supercruise with specialized payloads. Many next-generation combat aircraft have been designed to reduce their reliance on afterburners for supersonic flight, because supercruise capabilities are seen as a necessary component of modern air superiority.
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