Boulton Paul Sidestrand The Boulton Paul P . 29 Sidestrand was a twin - engine biplane medium bomber of the Royal Air Force . Named after a village on the Norfolk coast near Boulton & Paul ' s factory in Norwich , the Sidestrand first flew in 1926 and entered service in 1928 . It remained in service until 1936 , only ever equipping one squadron ; No . 101 Squadron RAF . It was an agile and relatively fast aircraft that was capable of aerobatic manoeuvres such as loops , rolls and spins . Design and development . Boulton & Paul Ltd of Norwich built a series of twin - engined biplanes starting with the Bourges of 1918 , which although not ordered into production , had demonstrated excellent performance and manoeuvrability , followed by the all - metal Bolton of 1922 and the smaller Bugle of 1923 . In 1924 , the Air Ministry issued Specification 9 / 24 for an all - metal , twin engined medium bomber , with an order for two prototypes following early in 1925 . The first aircraft flew in 1926 by C A Rea , Boulton & Pauls first full - time test pilot . The village of Sidestrand , chosen for the aircraft name , was the home of the then Secretary of State for Air , Samuel Hoare Only 20 Sidestrands were ever built . The first two , essentially prototypes , were designated the Sidestrand Mk I . Originally intended to be powered by two Napier Lion inline engines , the Mk I was eventually fitted with 425 hp ( 317 kW ) Bristol Jupiter VI radial engines which also powered the first six production Sidestrands , designated the Sidestrand Mk II . The remaining 12 aircraft were powered by 460 hp ( 343 kW ) Jupiter VIIFs and were designated the Sidestrand Mk III . The six Mk IIs were also re - engined to bring them up to the Mk III specification . The Sidestrand had three open defensive gun positions ; nose , dorsal and ventral . The crew usually consisted of three personnel ; pilot , nose gunner and a single gunner for the dorsal or ventral positions , the choice depending on where each individual aircraft was intended to fly in a formation . Armament for each position was a single . 303 in ( 7 . 7 mm ) Lewis gun , the gun being moved between the two rear positions as required . The Sidestrand ' s bombload was limited to 1 , 050 lb ( 476 kg ) which did not compare favourably with its contemporaries such as the Martin B - 10 . Operational history . Deliveries to the newly re - formed No . 101 Squadron at Bircham Newton began in 1928 , the first batch of six aircraft being the Sidestrand Mk II with ungeared Bristol Jupiter VI engines . These were followed by nine of the Sidestrand Mk III variants with geared Jupiter VIII Fs , and the final three production aircraft were replacement Mk IIs . The squadron then moved to RAF Andover in 1929 . The Sidestrand inherited the good manoeuvrability of the Boulton Paul P . 7 Bourges , but despite proving to be an excellent aircraft for bombing and gunnery , only No . 101 Squadron was equipped . In the early 1930s a Sidestrand Mk III was fitted with Bristol Pegasus IM3 engines . This was intended to become the Sidestrand Mk IV , but eventually became the prototype for the redeveloped Boulton Paul Overstrand which would begin replacing the Sidestrand in service in 1936 . Four Sidestrands were eventually converted to Overstrand standard and essentially are considered Overstrands .