over 90 percent of the span, in four sections. The flaps extended via electrical actuators, and had very small ailerons. Each wing had five spoilers made of perforated magnesium alloy. The engine air intakes were flat oval inlets, with a duct curving downward in a flat “S” to the engines, which were mounted behind the leading edge of the wing. The unusual flight control system utilized a system of pneumatic piping to transmit the pilot's control inputs and actuate various systems, rather than the more typical hydraulic, manual or electrical control lines and systems of most aircraft of the era. Production versions were to be equipped with a pair of .50 caliber Browning M2 machine guns in a tail turret designed by Emerson Electric Company and provision was made for an APG-27 remote control optics and sighting system, but no weaponry was fitted into the prototype. Likewise, production aircraft were intended to be built with the General Electric J47 engines with static thrust rather than the J35s used on the prototype. Testing The XB-46's first flight occurred 2 April 1947 after a month of taxi testing, and lasted ninety minutes as the bomber departed the Convair plant in San Diego, California for Muroc Army Airfield in the high desert. The pilot praised its handling qualities. Basic flight testing took place for five months, and by September 1947 it was concluded after 127 hours aloft on 64 flights by both the Convair company and AAF test pilots. Stability and control were excellent but there were engineering problems with engine de-icing, the cabin air system, and vertical oscillations caused by harmonic resonance between the wing and spoilers. There was also concern regarding the ability of the three man crew to exit the aircraft in case of an emergency, since the exit plan relied on the pneumatic system to hold the main door open against the airstream. The aircraft was accepted on 7 November and delivered on 12 November 1947. Cancellation The B-46 program was cancelled in August 1947, even before flight testing had been completed, because it was already obsolete. The North American B-45 Tornado already had production orders, and even it would be eclipsed by the Boeing B-47 Stratojet's superior performance. Furthermore, the bulky radar fire-control system which was not installed in the XB-46 prototype would have undoubtedly forced an expensive redesign of the slender fuselage. Subsequent testing investigated excessive noise,