Editing Grumman A-6 Intruder (section)

===Test program===
The first prototype YA2F-1, lacking radar and the navigational and attack avionics, made its first flight on 19 April 1960,<ref>Jenkins 2002, p. 11.</ref><ref name="wapj12 p40">Dorr ''World Air Power Journal'' Spring 1993, p. 40.</ref> with the second prototype flying on 28 July 1960.<ref name="wapj12 p41">Dorr ''World Air Power Journal'' Spring 1993, p. 41.</ref>

The test program required to develop the aircraft was prolonged. The very advanced navigation and attack equipment required substantial development, and changes had to be made to correct aerodynamic deficiencies and remove unwanted features.<ref>Francillon 1990, p. 431.</ref> Extending the [[Air brake (aeronautics)|air brakes]], which were mounted on the rear fuselage, changed the downwash at the horizontal [[tailplane]] which overloaded its actuator so the tailplane was moved rearwards by {{convert|16|in|cm}}. Later evaluation of the aircraft showed that the airbrakes were not effective enough in controlling the speed of the aircraft and they were moved to the wing-tips.<ref>https://archive.org/details/202417484a6intruder/page/n5/mode/2up, p.5</ref> Early production aircraft were fitted with both the fuselage and wingtip air brakes, although the fuselage-mounted ones were soon disabled, and were removed from later aircraft.<ref name="wapj12 p41"/> The trailing edge of each wing-tip split to form a much more effective speed-brake which projected above and below the wing when extended.

The rudder needed a wider chord at its base to give greater exposed area to assist spin recovery.{{citation needed|date=February 2025}}

A major difference between the first six production aircraft and subsequent aircraft were the jet nozzles; the close-air support role sought by the U.S. Marine Corps required STOL performance to operate from forward airstrips. Jet deflection using tilting tailpipes was proposed. The performance benefits from varying the angle were not worthwhile, whether operating from short strips or carriers, thus they were fixed at a seven degree downward angle.<ref>Gunston 1974, p. 225.</ref>