The Handley Page H.P.42 and H.P.45 were four-engine biplane airliners designed and manufactured by British aviation company Handley Page, based in Radlett, Hertfordshire.
It held the distinction of being the largest airliner in regular use in the world upon the type’s introduction in 1931.
The H.P.42/45 were designed in response to a specification issued during 1928 by British airline Imperial Airways; the two models share considerable similarities, the H.P.42 being optimised towards greater range at the expense of payload while the H.P.45 had these priorities inverted, allowing the latter to carry more passengers over shorter distances.
Imperial Airways approved of Handley Page’s proposals and ordered four aircraft of the two variants to serve as the new land-based long-distance flagships of its fleet.
On 14 November 1930, the prototype, named Hannibal, conducted its maiden flight.
Following their introduction into Imperial Airways, they formed the backbone of the airliner’s land-based fleet through most of the 1930s and, along with the company’s numerous flying boats, have been considered to be icons of their era.
A total of eight aircraft were built, four of each type; all were named, with names beginning with the letter “H”. Three of the survivors were pressed into Royal Air Force (RAF) service at the outbreak of the Second World War.
By the end of 1940, all of the aircraft had been destroyed as a result of several accidents.
The Handley Page H.P.42 was a large unequal-span sesquiplane.
It was a relatively unorthodox aircraft, even beyond its size, having incorporated numerous original features throughout its design.
As observed in an official evaluation by the American National Advisory Committee for Aeronautics (NACA), amongst the uncommon elements included is a fuselage which extended more forwards beyond its wings than that of most contemporary aircraft.
It used an all-metal approach in its construction, except for a few areas such as the fabric coverings present on the wings, tail surfaces and rear fuselage.
The fuselage comprises two sections, the forward section being a metal monocoque and the rear formed from welded steel tubes; their construction was noted as seemingly quite strong, but also relatively expensive.
The wings were braced by a Warren truss.
Automatic slots are fitted to the top wing, the auxiliary airfoils of which benefiting from a new construction approach involving single z-section spars and planking, both composed of duralumin.
Slot-type ailerons are also present, each being installed upon four hinges and supported by four box-section brackets; these ailerons are both statically and aerodynamically balanced, making them relatively light to control.
Inboard of the lower engines, the lower wings slope upwards to pass above the fuselage rather than through it, thus keeping the spars from obstructing potential cabin space.
Both the elevators and ailerons are controlled via a large diameter Y-tube; the core controls being duplicated.
The tailplane was of a biplane configuration, being furnished with three separate fins.
The H.P.42 was powered by an arrangement of four Bristol Jupiter XIFs, each capable of producing up to 490 hp (370 kW), while the H.P.45 variant instead used four Jupiter XFBM supercharged engines, which could generate a maximum of 555 hp (414 kW) each.
Both models placed their engines in the same positions: two engines on the upper wing and one on each side of the fuselage on the lower wing; while this arrangement was uncommon, it was not an original innovation, having been previously used on aircraft produced by Blériot.
The upper engines are placed as close together as permissible by the diameter of their propellers.
The engines are mounted on rigid duralumin plates that are attached to rear wing spar via welded steel tubing; fuel for the engines is housed within the upper wing and is gravity-fed to all four engines.
The throttle controls for the engine includes a ‘lost motion’ mechanism, which uses the first degrees of movement from the idle position to turn on the fuel.
The crew compartment, which was located at the very front of the aircraft, was fully enclosed, then a relatively new and uncommon feature.
There were two separate passenger cabins, one forward of the wings and the other aft.
The H.P.42E carried six (later 12) in the forward compartment and twelve in the aft.
There was also substantial space allocated for storing baggage.
The improved H.P.42W variant seated 18 passengers forward and 20 aft, at the cost of a reduced baggage capacity over the preceding model.
The cabins featured a high degree of luxury, having been intentionally styled to resemble Pullman railway carriages akin to the Orient Express; other features intended to increase passenger comfort were a high level of spaciousness, relatively wide windows, and full onboard services.
Initially, there were no seatbelts present upon any of the seating until an unrelated air accident motivated Imperial Airways to instate this feature.
On the ground, passengers could both embark and egress without using steps or ladders due to the low position of both the doors and the fuselage overall.