encouraged by this engine's promise to order a fourth, fully armed Badger with this powerplant. After some testing the rudder was modified with a horn balance and larger ailerons were fitted. This aircraft was the sole Badger II and was loaned by the Air Board to Bristol for the development of the Jupiter and its cowling during 1920-1. The lateral stability problems of the Badger worried its designer Frank Barnwell, because a 1/10 scale model had been carefully tested in the NPL wind tunnel without showing any problems. Scaling from model to full size was a problem because the Reynolds numbers reached in the atmospheric pressure wind tunnels of the time were much lower than those encountered in full-size flight. Flight tunnel tests also often involved the use of simplified aircraft models, with no attempt made to model the fuselage shape in detail. Using a spare set of Badger wings and empennage, Barnwell designed a new single-seat flat-sided and very simple fuselage made from plywood on a wooden frame for a fifth and final Badger, the Badger X. This first flew on 13 May 1919 and was Bristol's first civil registered aircraft, initially as K110, then G-EABU, but was never able to provide the intended comparative data with tunnel models, crashing on 22 May. Specifications (Badger II) References Notes Bibliography 1910s British fighter aircraft Military aircraft of World War I Badger Aircraft first flown in 1919