Handley Page HP.21
S-2 (left), S-1 (right)
The 1923 HP.21 Ship’s Fighter Type S cantilever monoplane was designed to meet a US Navy requirement.
The first machine, the S-1, had major directional stability problems, The S-2 wings were given dihedral to resolve the problem.
The prototypes were powered by 230 hp Bentley B.R.2 rotaries. The HP.21 had full span droopable ailerons to enhance carrier takeoffs and landings.
It nwas intendedd for production aircraft to be powered byArmstrong Siddeley radials.
When the S-2 was wrecked during trials the US Navy cancelled its contracts for three prototypes, the S-3 saplane being uncompleted.