Editing Saab 37 Viggen (section)

=== Wings and airframe ===
With the performance requirements to a large extent dictating the choice of the engine, the airframe turned out to be quite bulky compared to contemporary slimmer designs with turbojet engines. The first prototypes had a straight midsection [[fuselage]] that was later improved with a "hump" on the dorsal spine for reduced drag according to the [[area rule]].<ref name="Vectorsite">{{Citation | url = http://www.vectorsite.net/avvig.html | title = The Saab 37 Viggen | publisher = Vector site | access-date = 15 September 2007 | archive-url = https://web.archive.org/web/20071013164709/http://www.vectorsite.net/avvig.html | archive-date = 13 October 2007 | url-status=usurped | df = dmy-all}}</ref> The wing had the shape of a double delta with a dogtooth added to improve longitudinal stability at high incidence angles.<ref>Riebe, J. and William C. "Low-Speed Stability Characteristics of a Cambered-Delta-Wing Model", ''NACA RM-L55L21a'', 1956.</ref>{{Page needed |date=April 2016}}

[[File:JA 37D tail.jpg|thumb|Vertical stabilizer]]
A consequence of a tailless delta design, such as in the Viggen, is that the elevons, which replace more conventional control surfaces, operate with a small effective [[torque|moment arm]]; their use adds substantial weight to the aircraft at takeoff and landing. Hinged leading edge surfaces can help counteract this, but an even more effective tool is the canard. The canard surfaces were positioned behind the inlets and placed slightly higher than the main wing, with a higher stall angle than the wing, and were equipped with flaps. The lifting canard surfaces act as a vortex generator for the main wing and therefore provide more lift. An added benefit was that they also improved roll stability in the transonic region.<ref>Peake, D. and Tobak M. "Three-Dimensional Interactions and Vortical Flows with Emphasis on High-Speed Vehicles", ''AGARD AG-252'', 1980.</ref> The canard flaps were deployed in conjunction with the landing gear to provide even more lift for takeoff and landing.{{Sfn | Gunston | Spick | 1983 | pp = 22–23, 244}}

To withstand the stresses of no-flare landings, Saab made extensive use of [[aluminium]] in the airframe of the Viggen, which was constructed using a bonded metal [[honeycomb structure]]; the entire rear section of the fuselage, downstream of the engine nozzle, formed a heat-resistant ring composed of [[titanium]].{{Sfn | Gunston |Spick | 1983 | p = 245}}<ref>Warwick 1980, pp. 1260–61.</ref> The main landing gear, manufactured by Motala Verkstad, was highly strengthened as well; each leg held two small wheels fitted with [[anti-lock braking system|anti-skid brake]]s placed in a tandem arrangement. The design requirements imposed by the large anti-ship missiles employed upon the Viggen necessitated that both the undercarriage and [[vertical stabilizer]] be quite tall.<ref name = "warwick 1261" /> To accommodate this, and to allow the main landing gear to be stowed outside of the wing root, the undercarriage legs shortened during retraction.{{Sfn | Gunston | Spick | 1983 | p = 245}}  The [[vertical stabilizer]] could also be folded via an [[actuator]] in order that the aircraft could be stored in smaller hangars, [[hardened aircraft shelter]]s, and [[underground hangar]]s, the latter of which were employed by the Swedish military to limit the damage of preemptive attacks.{{Sfn | Gunston | Spick | 1983 | p = 245}}

The six tanks in the fuselage and wings held approximately 5,000 litres of fuel with an additional 1,500 litres in an external drop tank. The specific fuel consumption was only 0.63 for cruise speeds{{Sfn | Gunston | Spick | 1983 | p = 245}}<ref name="Nativi" />{{Page needed | date = January 2014}} (fuel consumption was rated 18&nbsp;mg/Ns dry and 71 with afterburner).<ref name = "Nativi" />{{Page needed | date = January 2014}} The Viggen's consumption was around 15&nbsp;kg/s at maximum afterburner.<ref name = "Nativi" />{{Page needed | date = January 2014}} A pair of inlets placed alongside the cockpit feed air to the engine; simple fixed-geometry inlets were adopted, similar to the Draken, except for being larger and standing clear of the fuselage.{{Sfn | Gunston | Spick | 1983 | pp = 244–45}}