Editing Lockheed SR-71 Blackbird (section)

===Airframe, canopy, and landing gear===
Titanium was used for 85% of the structure, with much of the rest being [[polymer]] [[composite material]]s.<ref>{{harvp|Merlin|2009}}</ref> To control costs, Lockheed used a more easily worked titanium alloy, which softened at a lower temperature.{{refn|While titanium ores are cheap and abundant, converting those ores into metallic titanium is laborious and expensive. Soviet production of metallic titanium was several times US production, so the CIA{{snd}}without Soviet knowledge{{snd}}used dummy intermediary firms to obtain Soviet-produced metallic titanium for US military use.<ref>{{cite report |url=https://www.cia.gov/readingroom/docs/CIA-RDP86T00591R000200170005-0.pdf |title=The Soviet Titanium and Its Role in the Military Buildup |publisher=Directorate of Intelligence |access-date=15 January 2025}}</ref><ref>{{harvp|Rich|Janos|1994}}</ref><ref>{{cite web |url=https://nationalinterest.org/blog/buzz/titanium-russia-was-secret-ingredient-sr-71-blackbird-207691/ |title=Titanium from Russia Was the Secret Ingredient in the SR-71 Blackbird |date=3 December 2023 |first1=Maya |last1=Carlin |work=National Interest |accessdate=27 January 2025}}</ref>|group=N}} The challenges posed led Lockheed to develop new fabrication methods, which have since been used in the manufacture of other aircraft. Lockheed found that washing welded titanium requires [[distilled water]], as the chlorine present in tap water is [[corrosion|corrosive]]; [[cadmium]]-plated tools could not be used, as they also caused corrosion.<ref>{{harvp|Rich|Janos|1994|p=213-214}}</ref> Metallurgical contamination was another problem; at one point, 80% of the delivered titanium for manufacture was rejected on these grounds.<ref>{{harvp|Rich|Janos|1994|p=203}}</ref><ref>{{harvp|McIninch|1971|p=5}}</ref>

The high temperatures generated in flight required special design and operating techniques. Major sections of the skin of the inboard wings were corrugated, not smooth. Aerodynamicists initially opposed the concept, disparagingly referring to the aircraft as a Mach 3 variant of the 1920s-era [[Ford Trimotor]], which was known for its corrugated aluminum skin. But high heat would have caused a smooth skin to split or curl, whereas the corrugated skin could expand vertically and horizontally and had increased longitudinal strength.

Fuselage panels were manufactured to fit only loosely with the aircraft on the ground. Proper alignment was achieved as the airframe heated up, with [[thermal expansion]] of several inches.<ref>{{harvp|Graham|1996|p=47}}</ref> Because of this, and the lack of a fuel-sealing system that could remain leak-free with the extreme temperature cycles during flight, the aircraft leaked [[JP-7]] fuel on the ground prior to takeoff,<ref>{{harvp|Graham|1996|p=160}}</ref> annoying ground crews.{{r|iwm20211103}}

The outer windscreen of the cockpit was made of three layers of glass with cooling sections between them.{{citation needed|date=December 2024}} The ANS navigation window was made of solid [[quartz]] and was [[ultrasonic welding|fused ultrasonically]] to the titanium frame.<ref>{{cite journal |last1=Burrows |first1=William E. |title=The Real X-Jet |journal=Air & Space Magazine |date=1 March 1999 |url=https://www.airspacemag.com/military-aviation/the-real-x-jet-12377380/ |access-date=16 January 2018}}</ref> The temperature of the exterior of the windscreen could reach {{convert|600|°F|°C|abbr=on|sigfig=2}} during a mission.<ref>{{harvp|Graham|1996|p=41}}</ref>

[[File:16 19 037 SR71.jpg|thumb|Detail of SR-71A at the [[Museum of Aviation (Warner Robins)|Museum of Aviation]], [[Robins AFB]] showing red lined no-step areas. Not shown on this museum exhibit is the additional NO STEP wording on operational aircraft which showed to which side of the line the warning was applicable.]]
The Blackbird's tires, manufactured by [[Goodrich Corporation|B.F. Goodrich]], contained aluminum and were inflated with nitrogen. They cost $2,300 each and generally required replacing within 20 missions. The Blackbird landed at more than {{convert|170|kn|mph km/h|sigfig=2}} and deployed a drag parachute to reduce landing roll and brake and tire wear.<ref>Blackbird diaries, Air & Space, December 2014/January 2015, p. 46.</ref>