Editing Boeing 707 (section)

===Engines===
<gallery mode="packed" heights="160">
File:Boeing 707-328, Air France AN1634050.jpg|An early [[JT4A]] [[turbojet]]
File:Boeing 707-338C, Australia - Royal Australian Air Force (RAAF) JP5845779.jpg|A later [[JT3D]] low-bypass [[turbofan]]
</gallery>

The initial {{convert|145|ft|m|adj=mid|-long}} {{not a typo|707-120}} was powered by Pratt & Whitney JT3C turbojet engines.

The JT3D-3B engines are readily identifiable by the large gray secondary-air inlet doors in the nose cowl. These doors are fully open (sucked in at the rear) during takeoff to provide additional air. The doors automatically close with increasing airspeed.

The 707 was the first commercial jet aircraft to be fitted with clamshell-type [[thrust reverser]]s.<ref>[https://books.google.com/books?id=zSADAAAAMBAJ&pg=-PA124 "Boeing's Jet Stratoliner."] ''Popular Science'', July 1954, p. 124.</ref>

====Turbocompressors====
The 707 uses engine-driven [[gas compressor|turbocompressors]] to supply compressed air for [[cabin pressurization]]. On many commercial 707s, the outer port (number 1) engine mount is distinctly different from the other three, as this engine is not fitted with a turbocompressor. Later-model 707s typically had this configuration, although American Airlines had turbocompressors on engines 2 and 3 only. Early 707 models often had turbocompressor fairings on all four engines, but with only two or three compressors installed.<ref>{{cite web |url=http://www.airlinercafe.com/page.php?id=72 |title=Ultimate Boeing 707 Guide |website=Airliner Cafe |access-date=February 17, 2016 |archive-date=March 17, 2021 |archive-url=https://web.archive.org/web/20210317031322/https://www.airlinercafe.com/page.php?id=72 |url-status=dead}}</ref>

====Upgraded engines====
[[File:Pratt-707re-N707HE-071126-03-16.jpg|thumb|Omega Air's 707-330C testbed for the 707RE program takes off from the [[Mojave Air & Space Port|Mojave Airport]], 2007]]

Pratt & Whitney, in a joint venture with Seven Q Seven (SQS) and Omega Air, selected the [[Pratt & Whitney JT8D|JT8D-219]] low-bypass turbofan as a replacement powerplant for Boeing 707-based aircraft, calling their modified configuration a 707RE.<ref name=flug>[http://www.flug-revue.rotor.com/FRNews1/FRNews02/FR020512.htm "Boeing 707."] {{webarchive|url=https://web.archive.org/web/20071107044727/http://flug-revue.rotor.com/frnews1/FRNews02/FR020512.htm |date=November 7, 2007}} ''Flug Revue'', May 12, 2002. Retrieved December 27, 2009.</ref> Northrop Grumman selected the -219 to re-engine the [[United States Air Force|US Air Force's]] fleet of 19 [[E-8 Joint STARS]] aircraft, which would allow the J-STARS more time on station due to the engine's greater fuel efficiency. [[NATO]] also planned to re-engine their fleet of E-3 Sentry AWACS aircraft. The -219 is publicized as being half the cost of the competing powerplant, the [[CFM International CFM56]], and is 40&nbsp;dB quieter than the original JT3D engines.<ref name=flug/>