Editing Concorde (section)

===Powerplant===
[[File:Concorde.highup.arp.750pix.jpg|thumb|The four powerplants mounted in two nacelles under the wings.]]
[[File:Concorde Ramp.jpg|thumb|Twin air intake assembly for each nacelle.]] 
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[[File:Rolls-Royce-Snecma Olympus - Musée Safran.jpg|thumb|Engines and twin exhaust system for each nacelle.]]
{{Main|Rolls-Royce/Snecma Olympus 593}}

A symposium titled "Supersonic-Transport Implications" was hosted by the [[Royal Aeronautical Society]] on 8 December 1960. Various views were put forward on the likely type of powerplant for a supersonic transport, such as podded or buried installation and turbojet or ducted-fan engines.<ref>{{cite magazine |title=Supersonic – Transport Implications |magazine=Flight International |date=23 December 1960 |page=971 |url=https://www.flightglobal.com/pdfarchive/view/1960/1960%20-%203039.html |via=FlightGlobal Archive |archive-url= https://web.archive.org/web/20171222052952/https://www.flightglobal.com/pdfarchive/view/1960/1960%20-%203039.html |archive-date=22 December 2017}}</ref><ref>{{cite magazine |magazine=Flight International |date=30 December 1960 |page=1024 |url=https://www.flightglobal.com/pdfarchive/view/1960/1960%20-%203108.html?search=supersonic%20transport%20implications |title=Supersonic – Transport Implications |via=FlightGlobal Archive |access-date=26 February 2017 |url-status=dead |archive-url=https://web.archive.org/web/20170226132358/https://www.flightglobal.com/pdfarchive/view/1960/1960%20-%203108.html |archive-date=26 February 2017}}</ref> Concorde needed to fly long distances to be economically viable; this required high efficiency from the powerplant. [[Turbofan]] engines were rejected due to their larger cross-section producing excessive drag (but would be studied for future SSTs). Olympus turbojet technology was already available for development to meet the design requirements.<ref>{{cite web|url=http://papers.sae.org/760891/Olympus |title=SAE International – mobility engineering |website=Papers.sae.org|access-date=21 December 2017|url-status=dead|archive-url=https://web.archive.org/web/20170801033212/http://papers.sae.org/760891/Olympus/ |archive-date=1 August 2017}}</ref> Rolls-Royce proposed developing the RB.169 to power Concorde during its initial design phase,<ref>{{cite magazine |title=Aero Engines 1962 |magazine=Flight International |date=28 June 1962 |page=1018 |url=http://www.flightglobal.com/pdfarchive/view/1962/1962%20-%201020.html |access-date=29 December 2013 |archive-url=https://web.archive.org/web/20131231002631/http://www.flightglobal.com/pdfarchive/view/1962/1962%20-%201020.html |archive-date=31 December 2013 |url-status=live}}</ref> but developing a wholly-new engine for a single aircraft would have been extremely costly,<ref>{{cite journal |last1=Parker |first1=R. |title=Aircraft engines: a proud heritage and an exciting future |journal=The Aeronautical Journal |date=2016 |volume=120 |issue=1223 |pages=131–69 |doi=10.1017/aer.2015.6 |s2cid=18375144}}</ref> so the existing BSEL [[Rolls-Royce Olympus variants#Bristol Olympus (BOl) 22R (Mk. 320)|Olympus Mk 320]] turbojet engine, which was already flying in the [[BAC TSR-2]] supersonic strike bomber prototype, was chosen instead.{{sfn|Owen|2001|p=50}}

Boundary layer management in the podded installation was put forward as simpler with only an inlet cone, however, Dr. Seddon of the RAE favoured a more integrated buried installation. One concern of placing two or more engines behind a single intake was that an intake failure could lead to a double or triple engine failure. While a ducted fan over the turbojet would reduce noise, its larger cross-section also incurred more drag.<ref>{{cite book |last=Birtles |first=Philip |title=Concorde |pages=62–63 |place=Vergennes, Vermont |publisher=Plymouth Press |year=2000 |isbn=1-882663-44-6}}</ref> Acoustics specialists were confident that a turbojet's noise could be reduced and SNECMA made advances in silencer design during the programme.<ref>{{citation |magazine=Flight International |url=https://www.flightglobal.com/pdfarchive/view/1971/1971%20-%200616.html |year=1971 |title=Noise and Environment |page=xxi |via=FlightGlobal Archive |access-date=26 February 2017 |url-status=dead |archive-url=https://web.archive.org/web/20170226212746/https://www.flightglobal.com/pdfarchive/view/1971/1971%20-%200616.html |archive-date=26 February 2017}}</ref> The Olympus Mk.622 with reduced jet velocity was proposed to reduce the noise<ref>{{cite magazine |magazine=Flight International |url=https://www.flightglobal.com/pdfarchive/view/1974/1974%20-%200593.html |title=Up to date with Rolls-Royce Bristol |date=11 April 1974 |page=463 |via=FlightGlobal Archive |access-date=26 February 2017 |url-status=dead |archive-url=https://web.archive.org/web/20170226132427/https://www.flightglobal.com/pdfarchive/view/1974/1974%20-%200593.html |archive-date=26 February 2017}}</ref> but was not pursued. By 1974, the spade silencers which projected into the exhaust were reported to be ineffective but "entry-into-service aircraft are likely to meet their noise guarantees".<ref>{{citation |magazine=Flight International |url=https://www.flightglobal.com/pdfarchive/view/1974/1974%20-%201690.html |title=Commercial Aircraft of the World |via=FlightGlobal Archive |page=546 |date= 24 October 1974 |access-date=26 February 2017 |url-status=dead |archive-url=https://web.archive.org/web/20170226132353/https://www.flightglobal.com/pdfarchive/view/1974/1974%20-%201690.html |archive-date=26 February 2017}}</ref>

The powerplant configuration selected for Concorde highlighted airfield noise, boundary layer management and interactions between adjacent engines and the requirement that the powerplant, at Mach 2, tolerate pushovers, sideslips, pull-ups and throttle slamming without surging.{{sfn|Talbot|2013|p=131}} Extensive development testing with design changes and changes to intake and engine control laws addressed most of the issues except airfield noise and the interaction between adjacent powerplants at speeds above Mach 1.6 which meant Concorde "had to be certified aerodynamically as a twin-engined aircraft above Mach 1.6".{{sfn|Talbot|2013|p=48}}

Situated behind the wing leading edge, the engine intake had a wing boundary layer ahead of it. Two-thirds were diverted and the remaining third which entered the intake did not adversely affect the intake efficiency{{sfn|Talbot|2013|p=21}} except during pushovers when the boundary layer thickened and caused surging. Wind tunnel testing helped define leading-edge modifications ahead of the intakes which solved the problem.<ref>{{cite journal |title=Concorde Airframe Design and Development |author=D. Collard |date=April 1999 |journal=Swiss Association of Aeronautical Sciences |publisher=ETH-Zentrum |issue=8092 |place=Zürich |page=6}}<br/>* {{cite journal |author=Collard, D. |title=Concorde Airframe Design and Development |journal=SAE Transactions |series=SAE Technical Paper Series |volume=100 |pages=2620–41 |id=912162 |year=1991 |doi=10.4271/912162 |jstor=44548119}}</ref> Each engine had its own intake and the [[nacelle]]s were paired with a splitter plate between them to minimise the chance of one powerplant influencing the other. Only above {{convert|1.6|Mach}} was an engine surge likely to affect the adjacent engine.{{sfn|Talbot|2013|p=48}}

The air intake design for Concorde's engines was especially critical.<ref>{{cite conference |conference=Aerospace Technology Conference and Exposition |url=https://www.sae.org/publications/technical-papers/content/912180/ |title=Concorde Propulsion{{snd}}Did we get it right? The Rolls-Royce/Snecma Olympus 593 Engine reviewed |publisher=SAE International |author=Ganley, G. A. |date=September 1991 |doi=10.4271/912180 |series=SAE Technical Paper Series |access-date=27 August 2018 |archive-date=27 August 2018 |archive-url=https://web.archive.org/web/20180827142352/https://www.sae.org/publications/technical-papers/content/912180/ |url-status=live}}</ref> The intakes had to slow down supersonic inlet air to subsonic speeds with high-pressure recovery to ensure efficient operation at cruising speed while providing low distortion levels (to prevent engine surge) and maintaining high efficiency for all likely ambient temperatures in cruise. They had to provide adequate subsonic performance for diversion cruise and low engine-face distortion at take-off. They also had to provide an alternative path for excess intake of air during engine throttling or shutdowns.<ref>{{cite journal |title=Design and Development of an Air Intake for a Supersonic Transport Aircraft |author1=I. H. Rettie |author2=W. G. E. Lewis |journal=Journal of Aircraft |volume=5 |issue=6 |pages=513–21 |date=November–December 1968 |doi=10.2514/3.43977}}</ref> The variable intake features required to meet all these requirements consisted of front and rear ramps, a dump door, an auxiliary inlet and a ramp bleed to the exhaust nozzle.{{sfn|Talbot|2013|loc=plate 4}}

As well as supplying air to the engine, the intake also supplied air through the ramp bleed to the propelling nozzle. The nozzle ejector (or aerodynamic) design, with variable exit area and secondary flow from the intake, contributed to good expansion efficiency from take-off to cruise.<ref>"An experiment on aerodynamic nozzles at M=2" Reid, Ministry of Aviation, R. & M. No. 3382, p. 4.</ref> Concorde's Air Intake Control Units (AICUs) made use of a digital processor for intake control. It was the first use of a digital processor with full authority control of an essential system in a passenger aircraft. It was developed by BAC's Electronics and Space Systems division after the analogue AICUs (developed by [[Ultra Electronics]]) fitted to the prototype aircraft were found to lack sufficient accuracy.<ref>{{cite journal|last1=Page|first1=N.|last2=Dale|first2=R. S.|last3=Nelson|first3=N.|title=Engine intake-control|journal=Flight|date=8 May 1975|pages=742–743|url=https://www.flightglobal.com/FlightPDFArchive/1975/1975%20-%200828.PDF|access-date=19 January 2016|archive-date=26 January 2016|archive-url=https://web.archive.org/web/20160126153712/https://www.flightglobal.com/FlightPDFArchive/1975/1975%20-%200828.PDF|url-status=live}}</ref> Ultra Electronics also developed Concorde's thrust-by-wire engine control system.<ref>{{cite web |url=http://www.flightglobal.com/pdfarchive/view/1976/1976%20-%201835.html |title=1976 &#124; 1835 &#124; Flight Archive |publisher=Flightglobal.com |date=4 September 1976 |access-date=15 June 2013 |archive-date=3 September 2015 |archive-url=https://web.archive.org/web/20150903215336/https://www.flightglobal.com/pdfarchive/view/1976/1976%20-%201835.html |url-status=live}}</ref>

Engine failure causes problems on conventional [[subsonic aircraft]]; not only does the aircraft lose thrust on that side but the engine creates drag, causing the aircraft to yaw and bank in the direction of the failed engine. If this had happened to Concorde at supersonic speeds, it theoretically could have caused a catastrophic failure of the airframe. Although computer simulations predicted considerable problems, in practice Concorde could shut down both engines on the same side of the aircraft at Mach 2 without difficulties.<ref>{{cite web |url=https://www.flightglobal.com/news/articles/concorde-special-the-test-pilot-john-cochrane-172657/ |title=Concorde Special&nbsp;– The test pilot&nbsp;– John Cochrane |work=[[Flight International]] |date=21 October 2003 |access-date=2 April 2018 |archive-date=2 April 2018 |archive-url=https://web.archive.org/web/20180402225635/https://www.flightglobal.com/news/articles/concorde-special-the-test-pilot-john-cochrane-172657/ |url-status=live}}</ref> During an engine failure the required air intake is virtually zero. So, on Concorde, engine failure was countered by the opening of the auxiliary spill door and the full extension of the ramps, which deflected the air downwards past the engine, gaining lift and minimising drag. Concorde pilots were routinely trained to handle double-engine failure.<ref>{{cite news |url=http://www.highbeam.com/doc/1G1-63710463.html |archive-url=https://web.archive.org/web/20120207015537/http://www.highbeam.com/doc/1G1-63710463.html |url-status=dead |archive-date=7 February 2012 |title=How a Concorde pilot would handle a nightmare failure |newspaper=Birmingham Post |first=Peter |last=Woodman |date=27 July 2000}}</ref> Concorde used [[reheat]] (afterburners) only at take-off and to pass through the [[transonic]] speed range, between Mach 0.95 and 1.7.<ref>{{cite conference |url=http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=A9110958AH&q=Rolls-Royce%2FSnecma+Olympus+593&uid=788858323&setcookie=yes |url-status=dead |archive-date=21 September 2011 |archive-url=https://web.archive.org/web/20110921053303/http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=A9110958AH&q=Rolls-Royce%2FSnecma+Olympus+593&uid=788858323&setcookie=yes |title=The Rolls Royce/SNECMA Olympus 593 engine operational experience and the lessons learned |conference=European Symposium on the Future of High Speed Air Transport, Strasbourg, France; 6–8 Nov 1989 |author=Ganley, G. |author2=Laviec, G. |year=1990 |pages=73–80 |access-date=30 June 2011}}</ref>