De Havilland DH.89 Dragon Rapide

Design and development

Origins

During summer 1933, the de Havilland aircraft company commenced work upon an aircraft to meet an Australian requirement, producing a four-engined faster passenger aircraft capable of seating ten passengers, the DH.86 Dragon Express. An important feature of the DH.86 was the newly developed and powerful Gipsy Six engine, a six-cylinder variant of the four cylinder Gipsy Major engine. The DH.86 would serve as the a key starting point for the later DH.89.

During late 1933, a team at de Havilland, led by aircraft designer Arthur Ernest Hagg, began working on a new design, intended to be a faster and more comfortable successor to the earlier DH.84 Dragon. The new aircraft was, in effect, a twin-engined, scaled-down version of the four-engined DH.86 Express. It shared many common features with the earlier DH.86 Express, including its tapered wings, streamlined fairings and fuselage, as well as the same Gipsy Six engines. However, the DH.89 demonstrated none of the operational vices of the Express.

On 17 April 1934, the prototype conducted its maiden flight at Hatfield Aerodrome, Hertfordshire. Flown by senior de Havilland test pilot H.S. Broad, it was powered by a pair of 200 horsepower (150 kW) Gypsy Six engines. Even prior to the prototype's first flight, plans to proceed with serial production of DH.89 had already received the go-ahead from management. During May 1934, airworthiness trials commenced at RAF Martlesham Heath using the prototype; during one such flight, upon attaining a speed of roughly 175 mph (282 km/h), the tip of the aircraft's nose buckled. In response to this event, a maximum permissible speed of 160 mph (260 km/h) was implemented for all DH89s. Upon the conclusion of trials, the prototype was sold.

By November 1934, series production of the Rapide had reached full swing. Originally referred to as the "Dragon Six", the aircraft was first marketed as the "Dragon Rapide", although the type later came to be popularly referred to as simply the "Rapide". Prior to the outbreak of the Second World War, 205 aircraft were manufactured for airlines and other private owners all around the world. The Rapide is perhaps the most successful British-built short-haul commercial passenger aircraft to be produced during the 1930s.

Further development

In response to the issuing of Specification G.18/35 by the British Air Ministry, de Havilland decided to design and produce a single prototype of a modified Rapide for undertaking coastal reconnaissance. Trials using the prototype, K4772, were performed between April and June 1935 at RAF Martlesham Heath and RAF Gosport. However, it ultimately lost out to its rival, the Avro Anson. K4772 was later used by the Royal Aircraft Establishment (RAE) in automatic landing trials before being broken down for spares. Work on a militarised version of the Rapide was not wasted as multiple sales were soon completed with other military customers, the first of which being to the Spanish government in December 1935.

Sensing demand for the type, de Havilland continued to modify the Rapide's design following its entry to service, creating both refinements and entirely new derivatives as a result. Aiming to produce a faster version of the Rapide, a smaller, lighter and externally cleaner version, designated as the DH.90 Dragonfly, emerged; first flying in August 1935, the DH.90 failed to achieve a similar rate of sales to the Rapide and production was terminated in 1938 after 67 aircraft had been completed. In November 1935, the 60th airframe to be produced, G-ADWZ, was modified and used by de Havilland as a trials aircraft. Fitted with elongated rear windows, cabin heating, thickened wing tips, and a strengthened airframe to allow for an elevated gross weight of 5,500 pounds (2,500 kg), G-ADWZ later participated in trials at Martlesham Heath, after which the higher gross weight was cleared for service.

In response to the announcement of an air race between Britain and Johannesburg, South Africa, de Havilland's design team produced a specialised variant of the Rapid, designated as the DH.92 Dolphin. This one-off derivative featured a retractable undercarriage, an expanded wingspan of 53 feet 7 inches (16.33 m), a modified nose section, and an increased all-up weight of 6,600 pounds (3,000 kg); however, flight tests in August 1936 revealed there to be no performance improvement over the standard Rapide, leading to the sole Dolphin being scrapped months later.

In November 1936, in response to suggestions that the addition of flaps would aid in landing, a single Rapide was modified in order to explore their functionality. Based on this performance, in February 1937, de Havilland announced that flaps would be fitted to all production aircraft from that year onwards, while other improvements such as a downwards-facing recognition light and metal propellers could be fitted as options. From 1937, to signify the fitting of improved trailing edge flaps, aircraft thus equipped were accordingly re-designated as DH.89A; earlier-built Rapides were commonly retrofitted to this standard during their service life as well.