Editing Concorde (section)

===Heating problems===
Kinetic heating from the high speed boundary layer caused the skin to heat up during supersonic flight.<ref name="harpur176">{{cite journal |url=https://arc.aiaa.org/doi/abs/10.2514/3.43926?journalCode=ja |title=Concorde Structural Development |last1=Harpur |first1=N. F. |journal=J. Aircraft |date=22 May 2012 |volume=5 |number=2 |page=176 |via=Aerospace Research Council |doi=10.2514/3.43926}}</ref> Every surface, such as windows and panels, was warm to the touch by the end of the flight.<ref>Dalton, Alastair. [http://www.scotsman.com/news/transport/supersonic-the-enduring-allure-of-concorde-1-2415088 "Supersonic: The enduring allure of Concorde"] {{Webarchive|url=https://web.archive.org/web/20120728231129/http://www.scotsman.com/news/transport/supersonic-the-enduring-allure-of-concorde-1-2415088 |date=28 July 2012}}. Scotsman.com, 17 July 2012.</ref> Apart from the engine bay, the hottest part of any supersonic aircraft's structure is the [[nose cone|nose]], due to [[aerodynamic heating]]. [[Hiduminium]] R.R. 58, an aluminium alloy, was used throughout the aircraft because it was relatively cheap and easy to work with. The highest temperature it could sustain over the life of the aircraft was {{convert|127|°C|°F|abbr=on}}, which limited the top speed to Mach 2.02.<ref>{{cite journal |doi=10.2307/3951418 |title=When the SST Is Too Slow… |journal=Science News |first=Jonathan |last=Eberhart |volume=91 |issue=22 |date=3 June 1967 |pages=528–29 |jstor=3951418}}</ref> Concorde went through two cycles of cooling and heating during a flight, first cooling down as it gained altitude at subsonic speed, then heating up accelerating to cruise speed, finally cooling again when descending and slowing down before heating again in low altitude air before landing. This had to be factored into the metallurgical and [[fatigue (material)|fatigue]] modelling. A test rig was built that repeatedly heated up a full-size section of the wing, and then cooled it, and periodically samples of metal were taken for testing.<ref>{{cite journal |doi=10.1108/eb034143 |title=The Concorde takes shape: Test programme and construction proceeding according to schedule |journal=Aircraft Engineering and Aerospace Technology |page=38 |year=1966 |volume=38 |issue=4 |issn=0002-2667}}</ref><ref>{{cite journal |bibcode=1972NASSP.309..631N |volume=309 |title=Fatigue Tests on Big Structure Assemblies of Concorde Aircraft |page=631 |year=1972 |author=N'guyen, V.P. |author2=J.P. Perrais |journal=Advanced Approaches to Fatigue Evaluation. NASA SP-309}}</ref> The airframe was designed for a life of 45,000 flying hours.<ref>{{cite web|url=http://www.flightglobal.com/pdfarchive/view/1967/1967%20-%202250.html|title=Concorde – 1967–2250 – Flight Archive|work=flightglobal.com|access-date=11 July 2013|archive-date=7 April 2014|archive-url=https://web.archive.org/web/20140407090353/http://www.flightglobal.com/pdfarchive/view/1967/1967%20-%202250.html|url-status=live}}</ref>

[[File:Concorde - airframe temperatures.svg|thumb|Concorde skin temperatures. They depended on the balance of heat transfer from the boundary layer, heat picked up from solar radiation, heat radiated back from the surface to the atmosphere, and heat transferred to the internal structure.<ref name="harpur176" />]]
As the fuselage heated up it [[Thermal expansion|expanded]] by as much as {{cvt|300|mm}}. The most obvious manifestation of this was a gap that opened up on the flight deck between the [[flight engineer]]'s console and the bulkhead. On some aircraft that conducted a retiring supersonic flight, the flight engineers placed their caps in this expanded gap, wedging the cap when the airframe shrank again.<ref>{{cite news |url= http://www.seattlepi.com/business/147276_pilot07.html |first= James |last= Wallace |title= Those who flew the Concorde will miss it |work= Seattle Post Intelligencer |date= 7 November 2003 |access-date= 25 April 2010 |archive-date= 16 March 2020 |archive-url= https://web.archive.org/web/20200316023128/https://www.seattlepi.com/business/article/Those-who-flew-the-Concorde-will-miss-it-1129118.php |url-status= live}}</ref> To keep the cabin cool, Concorde used the fuel as a [[Thermal energy storage|heat sink]] for the heat from the air conditioning.<ref>{{cite journal |title= Introduction to Concorde: A brief review of the Concorde and its prospects |journal=Aircraft Engineering and Aerospace Technology |author=Gedge, G.T. |author2=M.I. Prod |volume= 40 |issue= 3 |year=1993}}</ref> The same method also cooled the hydraulics. During supersonic flight a visor was used to keep high temperature air from flowing over the cockpit skin.{{sfn|Owen|2001|p=14}}

Concorde had [[aircraft livery|livery]] restrictions; the majority of the surface had to be covered with a [[Anti-flash white|highly reflective white]] paint to avoid overheating the aluminium structure due to heating effects. The white finish reduced the skin temperature by {{convert|6|to|11|C-change|F-change}}.<ref>{{cite web |url=http://www.flightglobal.com/pdfarchive/view/1967/1967%20-%200821.html |title=1967 &#124; 0821 &#124; Flight Archive |publisher=Flightglobal.com |access-date=15 June 2013 |archive-date=3 September 2015 |archive-url=https://web.archive.org/web/20150903215336/https://www.flightglobal.com/pdfarchive/view/1967/1967%20-%200821.html |url-status=live}}</ref> In 1996, Air France briefly painted F-BTSD in a predominantly blue livery, with the exception of the wings, in a promotional deal with [[Pepsi]].<ref>{{cite web|url=http://www.highbeam.com/doc/1P2-4794332.html |title=Is this the colour of the new millennium? |work=The Independent |date=3 April 1996 |location=UK |url-status=dead |archive-url=https://web.archive.org/web/20130516143325/http://www.highbeam.com/doc/1P2-4794332.html |archive-date=16 May 2013}}</ref> In this paint scheme, Air France was advised to remain at {{convert|2|Mach|altitude_ft=60000|sigfig=3}} for no more than 20 minutes at a time, but there was no restriction at speeds under Mach 1.7. F-BTSD was used because it was not scheduled for any long flights that required extended Mach 2 operations.<ref>{{cite news |title=Azul contra rojo |work=El Mundo |date=5 April 1996 |first=Cristina |last=Frade}}</ref>