sentences:  The gearbox produced unacceptable amounts of vibration in ground testing, delaying the aircraft's first test flight for months.Flight testing of the V-173 went on through 1942 and 1943 with 190 flights, resulting in reports of UFOs from surprised Connecticut locals.Charles Lindbergh piloted the V-173 during this time and found it surprisingly easy to handle and exhibiting impressive low-speed capabilities.