The DH.114 Heron is a stretched, four engined development of de Havilland's successful DH.104 Dove.
Only a few years later in development than the Dove on which it was based, design work on the Heron began in the late 1940s, resulting in the prototype's first flight on May 10 1950 (the Dove first flew in 1945). In designing the Heron, de Havilland made as much use of Dove componentry as possible, and so both types feature the distinctive slightly raised cockpit and separate main cabin and metal construction. Initial Heron production aircraft also featured fixed undercarriage (unlike the retractable gear Dove). Major differences include the four 185kW (250hp) Gipsy Queen engines (as opposed to two 255 to 300kW/340 to 400hp Gipsy Queen 70s), greater span wings, a longer and taller fuselage and greater seating capacity. The first Series 1 production Herons were delivered to New Zealand National Airways in 1952.
Also in 1952 the first Series 2 Heron first flew on December 14. The 2's main improvement over the 1 was retractable undercarriage, which for a weight penalty of 75kg (165lb) increased cruising speed by 32km/h (17kt), while other standard and optional improvements were minor in nature. The Heron 2A was certificated for use in the USA, and an equivalent 2B executive version was also offered. The 2C and equivalent executive 2D have greater weights.
The Heron has been the subject of numerous conversion programs. In the USA Riley converted 20 to be powered by Lycoming IO540s (eight more were converted in Australia), while Prinair converted a further 29 to Lycoming power.
The most ambitious Heron conversions were performed by Saunders, whose ST27 conversions feature two Pratt & Whitney Canada PT6 turboprops and a stretched fuselage. In addition, Tawron converted six Series 1 Herons with Continental engines.
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