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By
Wikipedia,
the free encyclopedia,
http://en.wikipedia.org/wiki/De_Havilland_Heron
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DH.114 Heron 2 restored in the United States |
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De Havilland Heron Instrument Panel |
The de Havilland DH.114 Heron was a small, propeller-driven British airliner that first flew on 10 May 1950. It was a development of the twin-engine de Havilland Dove, with a stretched fuselage and two more engines. It was designed as a rugged, conventional low-wing monoplane with tricycle undercarriage that could be utilised on regional and commuter routes. One hundred and fifty were built, exported to around 30 countries. Herons later formed the basis for various conversions, such as the Riley Turbo Skyliner and the Saunders ST-27 and ST-28.
Design and development
Immediately after the Second World War, the aircraft manufacturer de Havilland developed the DH.104 Dove, a small, two-engined passenger aircraft intended as a replacement for the earlier Dragon Rapide, and which soon proved to be successful. As a further development, the company basically enlarged the Dove; the fuselage was lengthened in order to provide room for more passengers or freight, and the wingspan was increased to make room for two additional engines. The Heron was of all-metal construction, and was laid out as a conventional design; the resulting aircraft was able to use many of the parts originally designed for the Dove, thus simplifying logistics for airlines employing both types.
The emphasis was on rugged simplicity in order to produce an economical aircraft for short to medium stage routes in isolated and remote areas which did not possess modern airports. The Heron was designed with a fixed undercarriage and reliable ungeared, unsupercharged Gipsy Queen 30 engines.
The Heron prototype registered to the de Havilland Aircraft Company, Hatfield, UK as G-ALZL undertook its first flight with Geoffrey Pike at the controls on 10 May 1950 . The aircraft was unpainted at the time, and after 100 hours of testing, was introduced to the public on 8 September 1950 at the Farnborough Airshow, still glistening in its polished metal state. By November, the prototype had received its formal British Certificate of Airworthiness and had embarked to Khartoum and Nairobi for tropical trials.
The prototype was then painted and "prepped" as a company demonstrator, undergoing a trial in 1951 with British European Airways on their Scottish routes. Following the successful completion of the prototype trials as a regional airliner, the Heron began series production. The first deliveries were to National Airways Corporation (NAC, later part of Air New Zealand).
Operational service
The first Heron, Series 1A suffered from a number of deficiencies, as NAC soon discovered. First of all, the aircraft was generally underpowered. Its quite heavy engines (weighing approximately 882 lb/400 kg each), had an output of only 250 hp (190 kW) each. By comparison, later modifications or rebuilt aircraft had as much as 50% more power (in the case of the Saunders ST-27). Unlike the Dove, the Heron came with a fixed undercarriage and no nosewheel steering, which simplified maintenance, but reduced top speed.
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15 Herons have been operated in Australia since 1952 by carriers such as Butler Air Transport (Tamworth), Connellan Airlines (Alice Springs), Southern Airlines (Melbourne), Kendall Airlines (Wagga Wagga), Heron Airlines (Sydney) and Airlines of Tasmania (Launceston). VH-NJI see here at Australia's Museum of Flight in 2006, has had a long and varied career. Serving initially with Turkey’s national carrier, THY, from 1955 to 1966, it subsequently served with Royal Air Canada (1966 - 1969) and the North American operators Fleet Air (1969 – 1971), Swift Air (1971 – 1978) and Susquchanna Airlines (1978 – 1985) who then sold it to Fiji Air (1985 – 1991). |
After 51 Series 1 aircraft had been built, production switched to the Series 2, featuring retractable landing gear, which reduced drag and fuel consumption, and increased the top speed marginally. The 2A was the equivalent of the 1A, the basic passenger aircraft while the 1B and its successor the 2B had higher maximum takeoff weight, the 2C featured fully-feathering propellers, the Heron 2D had an even higher maximum takeoff weight, while the Heron 2E was a VIP version.
In service, the Heron was generally well-received by flight crews and passengers who appreciated the additional safety factor of the four engines. At a time when smaller airliners were still rare in isolated and remote regions, the DH.114 was able to provide reliable and comfortable service with seating for 17 passengers, in individual seats on either side of the aisle. With its larger fuselage, customers could stand up and large windows were also provided. Baggage was stored in an aft compartment with an additional smaller area in the nose. A few peculiarities cropped up; passengers who filled the aft rows first would find that the Heron gently "sat down" on its rear skid. Pilots and ground crews soon added a tail brace to prevent the aircraft from sitting awkwardly on its tail.
Performance throughout the Heron range was "leisurely", and after production ceased in 1963, several companies, most notably Riley Aircraft Corporation, offered various Heron modification "kits," mainly related to replacing the engines, which greatly enhanced takeoff and top speed capabilities. Riley Aircraft replaced the Gipsy Queens with horizontally-opposed Lycoming IO-540 engines. One airline that carried out conversions was Prinair, which replaced the Gipsy Queens with Continental IO-520 engines. Connellan Airways also converted its Herons, using Riley kits. When available aircraft reached the end of their service lives, the engine conversions gave the elderly airliner a new lease on life as a number of examples were converted in the 1970s and 1980s including N415SA, a Riley Heron still flying as of 2005 and a Riley Turbo Skyliner, tail number N600PR currently registered in the United States (this example appeared in the 1986 movie Club Paradise).
The most radical modification of the basic Heron airframe was the Saunders ST-27/-28, that basically changed the configuration as well as the "look" of the whole aircraft with two powerful turboprop engines replacing the lethargic four-engine arrangement, the easily recognisable "hump" over the cockpit disappearing, the shape of the windows changed and the wingtips being squared instead of rounded.
Fictional usage
The De Havilland Heron is used in the book series Flight 29 Down [2]. A Heron also features in the Khufra Run by Jack Higgins [3].
Variants
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DH.114 Heron 1B of Morton Air Services in 1965. Note fixed undercarriage of this version |
- Heron 1: Four-engined light transport aircraft. Fitted with fixed landing gear.
- Heron 1B: This model had an increased take-off weight of 13,000 lb (5,897 kg).
- Heron 2: Four-engined light transport aircraft. Fitted with retractable landing gear.
- Heron 2A: This designation was given to a single Heron 2, which was sold to a civil customer in the USA.
- Heron 2B: This model had the same increased takeoff weight as the Heron 1B.
- Heron 2C: Redesignation of the Heron 2Bs, which could be fitted with optional fully-feathering propellers.
- Heron 2D: Four-engined light transport aircraft. This model had an increased takeoff weight of 13,500 lb (6,123 kg).
- Heron 2E: VIP transport aircraft. One custom-built aircraft.
- Heron C.Mk 3: VIP transport version for the Queen's Flight, Royal Air Force (RAF). Two built.
- Heron C.Mk 4: VIP transport aircraft for Queen's Flight, RAF. One built.
- Sea Heron C.Mk 20: Transport and communications aircraft for the Royal Navy. Three ex-civil Heron 2s and two Heron 2Bs were acquired by the Royal Navy in 1961.
- Riley Turbo Skyliner: Re-engined aircraft. A number of Herons were fitted with 290 hp (216 kW) Lycoming IO-540 flat-six piston engines. The modifications were carried out by the Riley Turbostream Corporation of the USA.
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Japanese DH.114 Tawron |
- Saunders ST-27: The fuselage was lengthened by 8 ft 6 in (2.59 m), to accommodate up to 23 passengers. It was powered by two 750 shp (559-kW) Pratt & Whitney Canada PT6A-34 turboprop engines. 12 Herons were modified by the Saunders Aircraft Corporation of Gimli, Manitoba, Canada.
- ST-27A and ST-27B : The original designations of the ST-28.
- Saunders ST-28: Improved version of the ST-27. One prototype built.
- Tawron: Toa Domestic Airline(Japan); Continental IO-470s replaced the original engines.
Operators
Military operators
Civil operators
Specifications (Heron 2D)General characteristics
- Crew: two (pilot and co-pilot)
- Capacity: 14 passengers
- Length: 48 ft 6 in (14.78 m)
- Wingspan: 71 ft 6 in (21.80 m)
- Height: 15 ft 7 in (4.75 m)
- Wing area: 499 ft² (46.4 m²)
- Empty weight: 8,150 lb (3,700 kg)
- Max takeoff weight: 13,500 lb (6,100 kg)
- Powerplant: 4× de Havilland Gipsy Queen 30 Mk.2 6-cylinder inverted inline piston engine, 250 hp (186 kW) each
Performance
See also
Related development
Bibliography
External links
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Published in July 2009.
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