Pratt & Whitney J58

<p>The Pratt & Whitney J58 (company designation JT11D-20) is an American <a href="/facts/Jet_engine/CJjFpeqt">jet engine</a> that powered the <a href="/facts/Lockheed_A-12/0nJX004R">Lockheed A-12</a>, and subsequently the <a href="/facts/Lockheed_YF-12/7kvHhpfI">YF-12</a> and the <a href="/facts/Lockheed_SR-71_Blackbird/ESfv9oFq">SR-71</a> aircraft. It was an afterburning turbojet engine with a unique compressor bleed to the afterburner that gave increased thrust at high speeds. Because of the wide speed range of the aircraft, the engine needed two modes of operation to take it from stationary on the ground to 2,000 mph (3,200 km/h) at altitude. It was a conventional afterburning turbojet for take-off and acceleration to Mach 2 and then used <a href="/facts/Bleed_air/kY6jz4X4">permanent compressor bleed</a> to the afterburner above Mach 2. The way the engine worked at cruise led it to be described as "acting like a <a href="/facts/Turboramjet/koKP4mUu">turboramjet</a>". It has also been described as a turboramjet based on incorrect statements describing the turbomachinery as being completely bypassed.
</p><p>The engine performance that met the mission requirements for the <a href="/facts/CIA/U7urmQYL">CIA</a> and <a href="/facts/USAF/7MxWBYlc">USAF</a> over many years was later enhanced slightly for <a href="/facts/NASA/TIMCV0yV">NASA</a> experimental work (carrying external payloads on the top of the aircraft), which required more thrust to deal with higher aircraft drag.
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Pratt & Whitney J58 open-in-new

Pratt & Whitney J58