A refined version of the S-3 with revised strutting carrying the centre section of the upper wing and the root attachments of the centre wing, a modified undercarriage and other changes. The S-6 triplane of 1917 was the first US "scout" to be fitted with twin forward-firing machine guns, these being gas-operated Lewis guns (which were mounted side-by-side on inverted and inclined "V" struts immediately beneath the centre section of the upper wing and firing outside the propeller disc.
Only a single example of the S-6 was built and tested.
Take-off weight: 625 kg / 1378 lb
Wingspan: 7.62 m / 25 ft 0 in
Length: 5.94 m / 19 ft 6 in
Height: 2.62 m / 8 ft 7 in
Wing area: 13.25 sq.m / 142.62 sq ft
Max. speed: 177 km/h / 110 mph