Handley Page HP.115
| Industry | Aerospace |
|---|---|
| Founded | 1909 |
| Headquarters | Cricklewood , United Kingdom |
The Handley Page HP.115 was a British experimental aircraft featuring a delta wing configuration, developed by the manufacturer Handley Page to evaluate the low-speed flight characteristics of a slender delta wing design intended for upcoming supersonic airliner projects.
Conceived during the 1950s as part of the Ministry of Supply's supersonic research initiatives, the HP.115 sought to demonstrate that a narrow delta wing could perform effectively not only at supersonic velocities but also maintain controllability during takeoff and landing phases. Originally envisioned as an unpowered glider, the concept evolved into a jet-powered design to achieve cost efficiency. Handley Page constructed the jet-driven HP.115 at their Cricklewood facility.
The only HP.115 took to the skies for its maiden flight on 17 August 1961, initiating an extensive flight test program centered on low-speed aerodynamic behavior of the wing. Together with the high-speed experimental aircraft BAC 221, it supplied essential data confirming the operational viability of slender delta wings. The HP.115 was retired in 1974 and is currently exhibited at the Fleet Air Arm Museum. Its research outcomes contributed significantly to shaping the wing architecture of the Anglo-French supersonic airliner Concorde.
Background
Research into supersonic transport (SST) aircraft during the 1950s revealed difficulties in balancing efficient supersonic cruise capabilities with sufficient low-speed lift necessary for takeoff and landing operations. Supersonic wing designs typically require short spans to minimize drag but tend to produce inadequate lift at lower speeds, potentially leading to impractical runway lengths or demands for excessive engine thrust.
Within the United Kingdom, engineers Johanna Weber and Dietrich Küchemann at the Royal Aircraft Establishment discovered that delta wings generate strong vortices over their surfaces at high angles of attack, which substantially enhance lift during low-speed flight. This vortex-induced lift effect intensifies with increased wing length and leading-edge sweep angles exceeding 65 degrees, indicating that a slender delta wing extending along much of the fuselage could reconcile supersonic efficiency with manageable low-speed performance.
Nonetheless, this approach necessitated flying the aircraft at pronounced nose-up attitudes during takeoff and landing, requiring extended landing gear to preserve proper wing angle contact with the runway during rollout. Early American wind tunnel results had cast doubt on control and handling, but further investigations affirmed the feasibility of this concept.
Glider
At the inaugural Supersonic Transport Committee meeting in 1956, it was agreed that a dedicated low-speed test aircraft was required. The initial plan called for an unpowered glider, resulting in Slingsby Sailplanes developing the Slingsby T.48. However, cost assessments demonstrated that operating a powered aircraft would yield approximately double the flight time while reducing hourly expenses by about 95%, since glider operations depended on being towed to altitude by bombers such as the English Electric Canberra. Furthermore, officials preferred a metal airframe capable of exploring phenomena like Dutch roll and performing takeoffs—capabilities only feasible with powered flight. Consequently, the T.48 project was abandoned and a new specification for a self-sustaining aircraft was issued in December 1959.
Powered
British aerospace firm Handley Page obtained approval to construct a single aircraft derived from their HP.115 concept, primarily developed at their Cricklewood site. The HP.115 incorporated a delta wing with an exceptionally low aspect ratio, swept back at 75°, and featured trailing edge elevons, spring-loaded servo-tabs, and anti-balance tabs to enhance control precision. Pneumatic split-flap air brakes located at mid-chord allowed for adjustable drag. The wing utilized a modified bi-convex airfoil with its thickest point at 4% chord, selected for minimizing wave drag and aligning with supersonic transport requirements. A distinctive plywood leading edge permitted interchangeable camber sections, although this capability was never employed.
The cockpit accommodated a pilot seated on a Martin-Baker ejector seat beneath a sliding canopy, outfitted with fundamental instruments such as an airspeed indicator, altimeter, yawmeter, turn-and-slip indicator, artificial horizon, directional gyro, and a backup compass. Flight controls were manually operated via a differential gearbox; hydraulically powered wheel brakes were controlled by foot pedals. Additional slowing capability was provided by a drogue parachute mounted at the base of the rudder. Flight parameters including airspeed and altitude were captured by synchronized flight recorders.
The fixed tricycle landing gear incorporated components sourced from the BAC Jet Provost Mk 1 and Mk 2 variants. The fuselage was constructed from aluminium alloy featuring a shallow rectangular girder frame with a nose pod enclosing the cockpit. Propulsion came from a single Bristol Siddeley Viper turbojet engine positioned above the wing near the tailfin's base. Fuel capacity reached up to 150 gallons distributed across three wing tanks. The tailfin and rudder were swept at 60°, with an upturned segment near the exhaust designed to mitigate thrust-induced pitching moments. A bullet-shaped fairing atop the fin housed a cine-camera used for airflow visualization experiments employing smoke generators on the wing leading edges.
Testing and evaluation
The HP.115, registered XP841, achieved its maiden flight on 17 August 1961 at the Royal Aircraft Establishment Bedford, piloted by J.M. Henderson who reported positive impressions following the flight.[1] Prior extensive ground taxi trials established optimal takeoff trim, while pilots underwent comprehensive simulator training that initially forecasted more difficult handling characteristics than those actually encountered.[2]
Approximately one month after its inaugural flight, the HP.115 participated in an aerial demonstration at the 1961 Society of British Aerospace Companies (SBAC) airshow; contractor testing was completed by 29 September. Subsequently, the aircraft was utilized for low-speed research contributing to the supersonic transport programme that culminated in Concorde. Simultaneously, the BAC 221, derived from a modified Fairey Delta 2, conducted high-speed investigations. The HP.115 exhibited outstanding performance, enabling swift banking maneuvers while retaining control at speeds as low as 69 mph (60 kn, 111 km/h), approximately one-third that of the contemporary Lockheed F-104 Starfighter.[3]
Neil Armstrong was slated to pilot the HP.115 in 1962 but was initially restricted by NASA due to his astronaut responsibilities; he ultimately flew it on 22 June 1970.[4]
Despite some minor setbacks, the experimental programme continued until its last flight on 1 February 1974, providing valuable insights into delta wing behaviour during takeoff and landing operations.[3] Complementary research involved radio-controlled scale models, and after installation of Hartmann noise generators, the aircraft also supported acoustic investigations.[2] By the time of retirement, the HP.115 had logged around 500 flight hours, reaching its initial design endurance.[1][2]
Aircraft on display
Following its decommissioning at RAE Bedford, XP841 was initially exhibited at the museum located at RAF Colerne. After the closure of that facility, the aircraft was transferred to the Royal Air Force Museum Cosford. When the Concorde exhibit was inaugurated at the Fleet Air Arm Museum, XP841 was moved to RNAS Yeovilton, where it is showcased within "The Leading Edge Exhibition" alongside the BAC 221 and a Concorde prototype.
Operators
External links
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