Editing Concorde (section)

===Structural issues===
[[File:Concorde fuel trim.svg|thumb|upright|Fuel pitch trim]]

Due to its high speeds, large forces were applied to the aircraft during turns, causing distortion of the aircraft's structure. There were concerns over maintaining precise control at supersonic speeds. Both of these issues were resolved by ratio changes between the inboard and outboard [[elevon]] deflections, varying at differing speeds including supersonic. Only the innermost elevons, attached to the stiffest area of the wings, were used at higher speeds.{{sfn|Owen|2001|p=78}} The narrow fuselage flexed,<ref name="nova" /> which was apparent to rear passengers looking along the length of the cabin.<ref name="popular">Kocivar, Ben. [https://books.google.com/books?id=lpiMSzja6W4C&lpg=PA142 "Aboard the Concorde SST."] {{Webarchive|url=https://web.archive.org/web/20210225182355/https://books.google.com/books?id=lpiMSzja6W4C&lpg=PA142 |date=25 February 2021}} ''Popular Science'', October 1973, p. 117.</ref>

When any aircraft passes the [[critical mach]] of its airframe, the [[Center of pressure (fluid mechanics)|centre of pressure]] shifts rearwards. This causes a pitch-down moment on the aircraft if the centre of gravity remains where it was. The wings were designed to reduce this, but there was still a shift of about {{convert|2|m}}. This could have been countered by the use of [[Trim tab|trim controls]], but at such high speeds, this would have increased drag which would have been unacceptable. Instead, the distribution of fuel along the aircraft was shifted during acceleration and deceleration to move the centre of gravity, effectively acting as an auxiliary trim control.<ref name='fueltrim'>{{cite journal |doi=10.1108/eb035344 |title=Flight Refuelling Limited and Concorde: The fuel system aboard is largely their work |journal=Aircraft Engineering and Aerospace Technology |volume=48 |issue=9 |date=September 1976 |issn=0002-2667 |pages=20–21}}</ref>