1931 Lanier XL-4 Vacuplane.
One of the rare, and quite unknown, experiments undertaken in 1928-33 period to explore Edward H Lanier’s ideas on low-speed flight. Lanier’s basic idea was to use a vacuum principle (reduced air pressure) to achieve inherent stability, especially at the challenging near-stalling conditions. He achieved that thanks to a concave cell on the centre section of the aircraft, some slots were also involved. Easy said than done…
The 1931 XL-4 was built with the help the University of Miami aeronautics department (hence the “U M” on its fuselage). It was powered by a 85hp LeBlond 5DF and it was, in essence, the previous XL-3 modified with these quite huge stabilizing wingtip “endplates”. Data about those Vacuplanes is scarce.
By the way, Edward H Lanier was also the inventor of the definitely more well-known ice cream cone.