The two 15,000-lb. static thrust (lb.s.t.) General Electric YJ01 turbofans which powered the YF-17 were replaced by their F404-GE-400 derivatives, each rated at 16,000 lbs.s.t. with afterburner. The F404 is an augmented, dual rotor, low-bypass "true" turbofan, rather than a "leaky" turbojet as the YJ101. It has essentially the same thrust as the J79 turbojet, yet weighs half as much.
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Fed by a non-variable air intake with splitters, the engine has a three-stage titanium fan, with one row of fixed inlet guide vanes and one row of variable guide vanes. It is of modular construction, comprised of the fan, high pressure compressor, combustor, low pressure turbine and afterburner modules, plus an accessories gearbox. The unit is slightly toed to align the nozzles.
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In addition, the combustor is a through-flow annular type, and the augmentor is fully modulating from minimum to maximum augmentation. The engine control system regulates speeds, temperature levels and fuel flow for afterburning and non-afterburning operation. The lubrication and ignition system are self-contained on the engine. The tailpipes are of variable area type.