De Havilland Express
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| de Havilland Express | ||
|---|---|---|
| ||
| Description | ||
| Role | Passenger transport / trainer | |
| Crew | 2 | |
| Passengers | 10-12 | |
| First flight | 1933 in aviation | |
| Entered service | ||
| Manufacturer | de Havilland | |
| Dimensions | ||
| Length | 46 ft 1 in | 14.1 m |
| Wingspan | 64 ft 6 in | 19.7 m |
| Height | 13 ft 3 in | 4 m |
| Wing area | 638 ft² | 59.3 m² |
| Weights | ||
| Empty | 6,250 lb | 2,830 kg |
| Loaded | 10,250 lb | 4,650 kg |
| Maximum takeoff | lb | kg |
| Powerplant | ||
| Engine | 4 × de Havilland Gipsy Six | |
| Power (each) | 200 hp | 150 kW |
| Performance | ||
| Maximum speed | 166 mph | 267 km/h |
| Combat range | 748 miles | 1,200 km |
| Ferry range | km | miles |
| Service ceiling | 17,400 ft | 5,300 m |
| Rate of climb | 925 ft/min | 280 m/min |
Contents |
[edit] Development
During 1933 talks between the governments of Great Britain, India, Malaya, the Straits Settlements and Australia resulted in an agreement to establish an Empire Air Mail Service. The Australian Government called tenders on 22 September 1933 for the Singapore-Australia legs of the route, continuing as far south as Tasmania. On the following day Qantas, anticipating success in contracting for the Singapore-Brisbane leg, placed an order with de Havillands for an as yet undesigned aircraft to be designated the de Havilland 86, the prototype to fly by the end of January 1934. This order was soon followed by one from Holymans Airways of Launceston, Tasmania to operate the Bass Strait leg of the service. The DH 86 was initially styled the Express or Express Air Liner although the name was soon discontinued.
The DH 86 was conceptually a four-engined enlargement of the successful de Havilland 84 Dragon, but of more streamlined appearance with a plywood box section fuselage instead of the tubular steel framework of the earlier aircraft. The most powerful engine made by de Havilland, the new 200 horse power Gipsy Six, was selected. For long-range work the aircraft was to carry a single pilot in the streamlined nose, with a wireless operator behind. Maximum seating for ten passengers was provided in the long-range type, however the short-range Holyman aircraft were fitted with twelve seats.
The prototype DH 86 first flew on 30 January 1934, but the Qantas representative Lester Brain immediately rejected the single pilot layout because he anticipated pilot fatigue over long stretches, and the fuselage was promptly redesigned with a dual-pilot nose. Only four examples of the single-pilot DH 86 were built, and of these the prototype was rebuilt as the dual-pilot prototype. When she entered service in October 1934 the first production aircraft, Holymans' single-pilot DH 86 Miss Hobart, was the fastest British-built passenger aircraft operating anywhere in the world - the dual pilot type with its lengthened nose proved to be even faster.
Investigations in 1936 following a series of fatal crashes resulted in late production aircraft being built with "Zulu Shield" extensions to the tail planes to improve lateral stability - these aircraft were designated DH 86Bs.
[edit] Operational History
Dual pilot DH 86s were built for Imperial Airways and given the class name Diana. They were used on European and Empire air routes including the run from Khartoum to Lagos.
DH 86s were also built for New Zealand's Union Airways, flying between Auckland, Palmerston North and Wellington. During World War II, the New Zealand aircraft fitted with bomb racks, were used to hunt German raiders and Japanese shipping by the Royal New Zealand Air Force. The survivors served with NAC post war.
A total of 15 DH 86s and DH 86Bs operated commercially within Australia and New Guinea up till the outbreak of World War II. Eight DH 86s served in the RAAF as A31-1 to A31-8 during the War. Some served as air ambulances in the Middle East, while others did sterling work as transport aircraft in New Guinea.
A total of 62 DH 86s of all types were built. Most of those still flying in Europe at start of World War II were taken also into military service, mostly for communications and radio navigational training. Few survived the war.
[edit] Technical Deficiencies
Seriously lacking in directional stability, the DH 86s were frequently in trouble. Holymans' VH-URN Miss Hobart and VH-URT Loila were lost in Bass Strait with all on board on 19 October 1934 and 2 October 1935, respectively. At the time Miss Hobart disappeared the design of the aircraft was not suspect, and it was thought that an accident may had occurred when Captain Jenkins and the wireless operator and assistant pilot Victor Holyman were swapping seats in mid flight. Following the loss of Qantas' VH-USG near Longreach four weeks later, however, it was found that the fin bias mechanisms of the crashed aircraft and at least one other were faulty, although it is doubtful that this had any direct bearing on the accidents other than perhaps adding to the aircraft’s lack of inherent stability. Investigation of the wreck of the Loila revealed a section of charred carpet on the floor just ahead of the lavatory door. It was thought possible that a small fire from a dropped cigarette had led to someone running aft suddenly to stamp it out – the sort of sudden change in weight distribution that could set up a fatal loss of directional control while the aircraft was on a low-speed landing approach.
The Royal Air Force’s Aeroplane and Armament Experimental Establishment’s tested the DH 86 design in 1936 following three fatal crashes in Europe. It would be forty years before the report was published – one of the most damning inditements ever written on the design of a commercial airliner put into series production. The DH 86 had been rushed from design concept to test flight in a record four months to meet the deadlines set by the Australian airmail contracts, and a lot of attention to detail had been ignored. It was a big aircraft for its power, and as a result very lightly built. The wings were inclined to twist badly if the ailerons were used coarsely and, most seriously, the vertical tail surface was of inadequate area. The result was an aircraft that, although quite safe under normal conditions, could rapidly get out of control under certain flight regimes.
Although the control problems were overcome on later-manufactured DH 86Bs, the results of the tests do not appear to have been communicated to Australia and the DH 86s already in use were never modified to improve their safety. This may have prevented many later accidents including at least one of two further fatal disasters in commercial service : the mid-air break-up of Qantas' VH-USE Sydney in a thunderstorm near Brisbane in 1942 with the loss of nine lives was probably unavoidable, but MacRobertson Miller Airline’s ex Qantas VH-USF at Geraldton on 24 June 1945 most likely was not. On its first commercial flight for its new owners after military service, the pilot and a passenger were killed in a classic loss-of-control accident while taking off with a heavy load in gusty conditions. The eleven year-old Lepena was the last of the type to fly in Australia, but was abandoned in India in an "unsafe state" while on her delivery flight to English owners in 1946.
[edit] The Political and Commercial Consequences
Following three fatal Australian DH 86 accidents and a forced landing to VH-USW Lepena when the pilot believed his aircraft was about to break up in mid-air (it was later found that only a metal faring had worked loose), the Australian Government temporarily suspended the type's Certificate of Airworthiness. This caused outrage in Britain as it reflected on the whole British aircraft industry. In fact, the DH 86 had approached the limits to which traditional "plywood and canvas" aircraft construction could be taken, but was obsolete compared to all-aluminium stressed-skin aircraft like the Boeing 247 and the Douglas DC-1 that were already flying before it was even designed. Under pressure from Holymans and other companies, the Australian Government rescinded its ban on the import of American aircraft during 1936, and for the next 25 years most large commercial aircraft imported into Australia were of American manufacture.
[edit] References
- A. J. Jackson, De Havilland Aircraft since 1909, Putnam, 1978.
- Macarthur Job, Air Crash, Volumes One and Two, Aerospace Publications of Australian Capital Territory, Australia, 1991 & 1992.
| Related content | |
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| Related development | de Havilland Dragon - de Havilland Dragon Rapide |
| Similar aircraft | |
| Designation series | |
| Related lists | |
