 The first XF6U @-@ 1 prototype was powered by a Westinghouse J34 @-@ WE @-@ 22 turbojet with 3 @,@ 000 lbf ( 13 @.@ 34 kN ) thrust , one third of the weight of the aircraft . To help improve the underpowered aircraft 's performance , the third prototype , which first flew on 10 November 1947 , was lengthened by 8 feet ( 2 @.@ 4 m ) to use a Westinghouse J34 @-@ WE @-@ 30 afterburning engine of 4 @,@ 224 lbf ( 18 @.@ 78 kN ) thrust , the first United States Navy fighter to have such a powerplant . 
