In 1961, de Havilland began work upon a small business jet, then known as the DH.125 Jet Dragon, which was intended to replace the piston engined de Havilland Dove, a successful business aircraft and light transport. Prior to the start of the project, de Havilland had determined that a successful business jet would require several variables to be met, including a range of at least 1,000 miles, the speed and cost factors of a suitable jet engine to outperform turboprop-propelled competitors, and an engineering philosophy that favored reliability and conventionality. The design team settled on a twin-engine aircraft with the engines mounted on the rear fuselage, the Armstrong Siddeley Viper turbojet powerplant was also selected to power the type.
On 13 August 1962, the first of two prototypes conducted its first flight, a second aircraft followed it on 12 December that year. The second prototype was more aerodynamically-representative of a production aircraft, and was fitted out with more equipment than the first prototype; the subsequent production-standard aircraft incorporated several changes and improvements from the prototypes, such as a longer fuselage and a greater wingspan. The first production-standard aircraft performed its first flight on 12 February 1963. The first delivery to a customer took place on 10 September 1964.
The aircraft went through many designation changes during its service life. Hawker Siddeley had bought de Havilland the year before the project had started, but the legacy brand and "DH" designation was used throughout development. After the jet achieved full production, the name was changed to "HS.125" except for American exports which retained the DH.125 until it was replaced by BH.125 for Beechcraft-Hawker. When Hawker Siddeley Aircraft merged with the British Aircraft Corporation to form British Aerospace in 1977, the name changed to BAe 125. When British Aerospace sold its Business Jets Division to Raytheon in 1993, the then-main variant of the jet became widely referred to as the Hawker 1000.
While the two prototypes were assembled at de Havilland's Hatfield site, final assembly of all production aircraft would take place at the Broughton factory near Chester until the 1990s. By the 2000s, the fuselage, wings and tailfin of the aircraft were still being assembled and partially equipped in the Broughton site, now being owned and managed by Airbus UK; various sub-assemblies were also produced in Airbus UK's Buckley facility. From 1996 onwards, the assembled sections and components were shipped to Wichita, Kansas in the United States, to undergo final assembly. Writing in 1993, Flying Magazine said of the type "In numerical terms, the 125 series is the most successful British commercial aircraft ever built, and the world's longest in-production business jet".
Production of the aircraft came to an abrupt halt in 2013 due to the bankruptcy of owner Hawker Beechcraft, who has suffered during the Great Recession of the late 2000s in which demand for business jets had slumped for a number of years. The type had been in production for more than 50 years when manufacturing stopped, during which time over 1,600 aircraft had been produced. In April 2013, the type certificate and support responsibility for all 125s built was transferred to the reformed Beechcraft Corporation. As of October 2012, Beechcraft does not intend to restart production of its business jet lines; instead the company intends to alternatively sell or dismantle the production facilities for the 125 family.
The DH.125 is a low-winged monoplane, powered by two engines mounted on the rear fuselage. The wing is slightly swept, being based upon the larger de Havilland Comet's wing planform, and employs large slotted flaps and airbrakes to better enable operations from small airfields; the aircraft can be flown from hardened grass airstrips. The type has a perfectly cylindrical fuselage with the one-piece wing mounted upon the underside of the fuselage; this design allows for the majority of manufacturing and assembly work of the wing and fuselage to be performed as separate sections with the two being joined together late in the production process. The wing also houses integral fuel tanks which contain the majority of the aircraft's fuel.
Early models of the aircraft were powered by several versions of the Bristol Siddeley Viper turbojet engine, while later aircraft have adopted more recent turbofan powerplants such as the Garrett TFE731 and Pratt & Whitney Canada PW300. As well as providing the propelling thrust of the aircraft, each of the engines are connected to independent gearboxes which provide electrical power via generators and drive the onboard fuel, oil and hydraulic pumps and a generator for electrical power. The design is redundant so that in the event of a single engine failing, all aircraft systems shall continue to operate normally.
All control surfaces of the aircraft are aerodynamically balanced via set-back hinges and geared tabs. The flaps and airbrakes are operated using the aircraft's hydraulics, while the ailerons, elevators, and rudder are manually-actuated. The design of the control circuits allows for an Collins-built A.P.103 autopilot to be incorporated. Each aircraft is typically equipped with a de-icing system, which uses a mixture of bleed air from the engines, TKS fluid for general airframe, and AC electric windshield heating to prevent ice formation. From the type's introduction to service, weather radar was incorporated into the aircraft's avionics fit out. Some operators, such as the Royal Air Force, have equipped their 125s with electronic countermeasures to defend against hostile missile attacks upon the aircraft.
The pressurised fuselage was designed to accommodate two pilots and six passengers. Various interiors were offered for the aircraft, the standard interior offered a high degree of comfort to the passengers. In an executive configuration, the flight desk is separated from the main passenger cabin; the single entrance of the aircraft, located directly behind the cockpit and forward of the passenger cabin, forms a vestibule area in which luggage can be stored and meals prepared during flight. An unobstructed cabin floor with 5 ft 9in of headroom and a 3 ft wide cabin door also allowed the loading of bulky equipment, which was seen as particularly attractive to military operators. In addition to the entrance door, an emergency escape door is also located in the passenger cabin midsection over the wing. The rear of the fuselage is occupied by a large equipment bay and, on some aircraft, two additional fuel tanks for extended operations.
- Series 1
- Series 2
- Series 3
- Series 400
- Series 600
- Series 700
- Series 800
- Series 1000
- Handley Page HP.130