The Acme Aircraft Co S-1 Sierra was an experimental aircraft of unusual configuration built in the US in 1948 to investigate the advantages of a pusher propeller configuration. Apart from this engine installation, the aircraft was unusual in having an X-shaped tail incorporating ruddervators on the upper fins. The wing was mounted midway up the fuselage and was unswept. During the 1960s, the US aerospace manufacturer Northrop used the aircraft as a technology demonstrator for boundary layer control concepts. Specifications (S-1 Sierra) See also References External links Aircraft Ab – Ak#Acme Aerofiles Acme Sierra website 1940s United States experimental aircraft Aircraft manufactured in the United States V-tail aircraft Single-engined pusher aircraft