The prototype General Aircraft Monospar ST-4 was G-ABUZ.
The ST-4 went into series production by the newly-formed General Aircraft Ltd at Croydon. This four seat aircraft was powered by two 85hp Pobjoy radials and introduced the characteristic 'Monospar' look. Seven ST-4 Mk Is and 22 improved Mk IIs were built. A version with retractable undercarriage, the ST-6, attracted little interest, including a single conversion from an ST-4 Mk II.