Handley Page HP.28 Handcross

The Handley Page Handcross was a single-engined biplane day bomber built to an Air Ministry specification. It was not put into production and only the three prototypes were built.

Development
In August 1923 the Air Ministry issued specification 26/23, which called for a day bomber powered by a Rolls Royce Condor III engine which could carry a 550 lb (250 kg) bomb load with a 500 ml (800 km) range. In response Handley Page designed what was known at the time as the C/7 Handcross but retrospectively became the H.P.28 Handcross after the introduction of the familiar H.P. type numbers in about 1927.

The Handcross was constructed from wood and canvas throughout. It was a three bay biplane with equal span wings without stagger or sweep. The wings had parallel chord but the lower planes were significantly narrower than the upper; only the lower planes carried dihedral. Ailerons, with back set hinges to provide aerodynamic balance were mounted on the upper planes alone. The wide track divided main undercarriage had legs mounted on the wing front spar below the innermost interplane struts, braced to the fuselage. The fuselage was flat sided with a pronounced dorsal fairing or decking and a similar ventral fairing below. The pilot sat in an open cockpit below the upper wing, with the gunner in a dorsal position behind him. The gunner could also access two spaces in the belly: a prone position below the pilot for bomb aiming, or a rearward firing gun position behind this. The tail surfaces were conventional, rudder and elevators being horn balanced; the rudder reached down below the fuselage bottom, protected by a small tailskid. The V-12 watercooled Condor engine was cooled by a radiator in the nose below the boss of the two bladed metal Leitner-Watts propeller.

Handley Page were awarded an order for three prototypes and the first of these flew at the company's Cricklewood base on 6 December 1924, piloted by Hubert Broad. After test flights there it went to RAF Martlesham Heath on 1 January 1925 for Air Ministry tests and eventually in June for competitive trials against other manufacturers' entrants. Meanwhile the other two machines had been completed, the second going to RAE Farnborough for use in an experimental radio programme and the third retained at Cricklewood. It was used to find solutions to several problems that the Martlesham flights had revealed. The original fuel tanks, mounted just outboard of the innermost interplane struts and projecting both above and below the upper wing were found to be the source of aerodynamically induced vibration at high angles of attack, so they were modified to have a top face matching the upper wing surface. The exhaust pipes were modified to avoid flame dazzle and flow into the cockpit by discharging at the forward end via "rams horn" exits; and the ventral gun position was canvassed over, for there was such a draught through the dorsal and ventral openings that neither position was usable.

The Hawker Horsley won the specification trials, so no more Handcrosses were built. The last one stayed at Cricklewood until 1926, serving as a test machine and the second, moved from Farnborough to Martlesham, remained with the Armaments Trial Flight until 1928. The first machine was fitted with several different wooden two- and four-bladed propellers for comparison with the original metal two-bladers.