Learn what an afterburner or jet reheat is, how it boosts thrust, when pilots use it, why it burns fuel and how simulators should model it.
An afterburner, or reheat, is a jet-engine thrust-augmentation system that sprays and ignites extra fuel in the hot exhaust behind the turbine. The resulting hotter, faster exhaust provides a large but inefficient thrust increase, used mainly for military take-off, rapid climb, combat acceleration and reaching or sustaining supersonic flight.
Are reheat and afterburner the same thing?
Reheat and afterburner are two names for the same jet-engine thrust-augmentation system; augmentor is another engineering term. Reheat is traditional British terminology. In our Aviation & Real-World Flying coverage, these terms mean the complete system, not merely the bright exhaust flame.
How does an afterburner produce extra thrust?
An afterburner produces extra thrust by burning fuel in the exhaust stream downstream of the turbine.
It supplements the main combustor rather than replacing it. Our explanation of the compressor-to-nozzle jet-engine cycle covers the core process into which reheat fits.
- Oxygen-rich exhaust enters the afterburner: The engine uses surplus air to keep combustion temperatures within limits, so oxygen remains after the turbine.
- Spray bars inject fuel: The engine meters extra fuel into the exhaust duct, sometimes through several selectable afterburner zones.
- Flameholders stabilise the flame: These create recirculation zones in which combustion can remain alight despite the fast-moving exhaust.
- The exhaust becomes hotter: Combustion expands the gas without sending the added heat through the turbine.
- The nozzle opens and accelerates the flow: A variable-area nozzle accommodates the expanded gas, prevents excessive back-pressure and converts its energy into exhaust velocity.
The thrust increase comes mainly from higher exhaust velocity, not substantially greater airflow through the compressor. In an afterburning turbofan, reheat often acts on mixed core and bypass flow downstream of the turbine, although layouts vary.
The plume is not a reliable thrust gauge. It may be hard to see in daylight, while diamond-shaped shock cells can appear in either wet or dry supersonic exhaust when nozzle pressure does not match atmospheric pressure.
When are afterburners used?
Pilots select afterburner when immediate performance matters more than fuel economy, range, noise or infrared signature.
- Take-off and carrier launch: When weight, runway length, temperature, obstacles or an approved procedure demand maximum acceleration. Reheat is not required for every take-off.
- Rapid climb and combat acceleration: To intercept, evade a threat, close on a target or recover energy after manoeuvring.
- Transonic acceleration: To push through the steep rise in drag near Mach 1.
- Supersonic flight and short dashes: To reach or maintain high speed when the aircraft cannot do so efficiently on dry thrust.
Selection commonly involves moving the throttles through a detent beyond maximum dry thrust. Engines with several reheat zones let the pilot choose less than maximum augmentation.
| Power setting | Meaning | Typical use |
|---|---|---|
| Partial power | No reheat | Cruise, descent and economical flight |
| Maximum dry or MIL power | Highest thrust without reheat | Climb, some take-offs and fuel-conscious combat |
| Afterburner or reheat | Additional downstream combustion | Maximum acceleration, climb or supersonic performance |
MIL power usually means maximum non-afterburning thrust, not maximum possible thrust. Detents, terminology and authorised uses vary, so the aircraft’s flight manual takes precedence.
Why do afterburners use so much fuel?
Afterburning is inefficient because the extra fuel burns downstream of the turbine at relatively low pressure. Fuel flow rises disproportionately to thrust, so claims that every afterburner doubles engine thrust are incorrect.
Reheat also produces exceptional noise, a stronger infrared signature and greater thermal stress on the tailpipe and nozzle. It is a designed operating mode rather than inherent engine abuse, but limits differ: some installations impose strict time or temperature restrictions, while others may remain in reheat while fuel and operating conditions permit. There is no universal five-minute limit.
Does afterburner always make an aircraft supersonic?
Afterburner does not guarantee supersonic flight because speed also depends on altitude, weight, drag, inlet performance and aircraft limits. Dense low-altitude air can keep an afterburning aircraft subsonic despite its high thrust.
An aircraft capable of supercruise can maintain supersonic flight without reheat under suitable conditions, although it may still use afterburner to accelerate through the transonic region.
Do all jet aircraft have afterburners?
No. Afterburners are fitted mainly to military turbojets and low-bypass turbofans designed for high-performance or supersonic operation. They add weight, length, fuel plumbing, controls and a complex nozzle, and cannot safely be added to an engine not designed for them.
Modern high-bypass passenger engines prioritise economy and lower noise, so airliners do not use reheat. Concorde was the notable civil exception: it used reheat for take-off and transonic acceleration, then cruised supersonically without it.
What happens if an afterburner fails to light?
A failed light normally leaves the engine producing dry thrust, while unstable combustion may make reheat drop out. Engine controls may inhibit augmentation when they detect unsuitable conditions.
On a twin-engine aircraft, one afterburner lighting without the other can cause strong yaw from asymmetric thrust. Incorrect nozzle scheduling is more serious because excessive back-pressure can affect engine stability. Indications and remedies are type-specific, so pilots follow the aircraft flight manual rather than a generic procedure.
Why will an afterburner not engage in a flight simulator?
In a flight simulator, failure to engage usually comes from aircraft modelling, throttle calibration or control bindings. A flame graphic alone does not prove that augmented thrust is being produced.
- Confirm the aircraft models reheat: A complete implementation changes thrust and fuel flow as well as flame, sound, nozzle animation and engine indications.
- Check the required control: Some aircraft engage reheat beyond a throttle detent; others require a separate command.
- Calibrate the throttle: An axis that stops short of full travel may never cross the activation threshold.
- Remove conflicting assignments: Duplicate throttle or reheat bindings can cause intermittent engagement or immediate cancellation.
- Verify performance: Check acceleration, fuel flow, nozzle movement and cockpit indications rather than judging the flame alone.
For older platforms, our tutorial on adding and aligning afterburner effects in FSX covers visual installation for single- and twin-engine aircraft. We also explain the difference between FS2004 afterburner effects and genuine augmented thrust; visual work may still require separate flight-model changes.