A portion of the North American P-51B airplane was tested to devise a means of eliminating a rumble which occurred in the radiator duct system.

A portion of the North American P-51B airplane was tested in the 16-foot wind tunnel to devise a means of eliminating a rumble which occurred in the radiator duct system. The actual fuselage and center portion of the airplane was installed in the tunnel for this purpose as is shown. A change in the form of the duct was made and tested, which eliminated the rumble. The entrance to the original radiator duct is indicated in this photograph, and the revised form of the duct entrance in photographer AAL-3926.