B307 - VertFin Rudder -- design REVOLUTION
About two slots above BA shows a Boeing B307 Stratoliner -- but that modern Vertical Fin and Rudder in that photo is AFTER the fatal upset/breakup of 18Mar1939.
Since Ralph Cram (Aero) was killed in that upset/breakup, Boeing brought George S up from Consolidated. GS and Eddie Allen worked through several iterations from the tiny Vertical Stab' with initial HUGE RUDDER aft of hinge.
AB -- ?maybe you can find IMAGES of the pre-mishap fin-rudder design on the web?? I have the early magazine images, the iterations were shown in the IAeS magazine:
Schairer, George S. "Directional Stability and Vertical Surface Stalling." Presented at IAeS Aerodynamics session, Ninth Annual Meeting, NY, 31Jan 1941. Published in IAeS' Journal of Aeronautical Sciences, May'41; pg 270-75; paper describes directional instability of prototype's Fin-Rudder design and excess Rudder Hinge Moment during flight with large Beta.
Cook, William H. Road to the 707. Bellevue WA: TYC Publishing, '91. pg 57, "rudder locked full over".
Regarding research on directional control: subsequent modifications of Vertical Fin (added dorsal fin) and Rudder (specifics on sizing to reduce hinge moments); and then added Rudder hydraulic boost). Later B-17s and other aircraft adopted lesson learnt, with the Fin-Rudder sizing to inhibit Rudder "lock-over". This was one of the major lessons in design, and measurement (with the knowledge that Sideslip Angle did NOT merely equal Yaw Angle).
Seattle P-I Sunday March 19th, 1939 front page headline, shown in large type spread across the top, reads "STRATOLINER FALLS, 10 DIE". Under the headline on that front page is a large photograph of the Stratoliner wreckage ...
P-I page two shows a photograph of NX19901 apparently in flight with #3 and #4 Props BOTH stopped, and the RUDDER deflected to the left (correcting for asymmetric thrust); no photo caption shown (perhaps a Boeing photo taken during a prior test flight). [This configuration, thrust asymmetry and associated sideslip angle, was described by WHC as likely at initial mishap-upset: with Rudder "lock-over" causing an unexpected yaw-rotation and spin in the direction of the "good" engines.]
Last edited by IGh; 16th Mar 2009 at 15:55.