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 used on regional and commuter routes. 150 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.
The first Heron, Series 1A suffered deficiencies, as NAC soon
discovered. Firstly, the aircraft was generally underpowered. Its quite
heavy engines (weighing about 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. Secondly the lightweight aluminium alloy wingspars were prone to
constant cracking due to the heavy loading on the wing caused by the
overweight engines and rough landings on non paved runways at the time.
NAC resolved this by replacing the aluminium spars with heavier steel
spars, reducing the performance of the Heron Series 1A (re-classified
1B) to uneconomic levels for the services required of them in New
Zealand. NAC disposed of them in 1957.
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 could provide reliable and comfortable
service with seating for 17 passengers, in individual seats on either
side of the aisle.
With its larger fuselage, passengers could stand up whilst moving
down the aisle 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 relatively "leisurely",
and after production at De Havilland's Chester factory 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 U.S. airline that carried out Riley conversions was Prinair, of Puerto Rico, 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 in Sweden as of 20 May 2012 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.
From Wikipedia, the free encyclopedia & Air Britain Photographic Images Collection
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