| H.P.20 | |
|---|---|
 | |
| Showing open and closed slots and depressed aileron | |
| Role | experimental monoplane |
| National origin | United Kingdom |
| Manufacturer | Handley Page |
| First flight | 24 February 1921 |
| Number built | 1 |
The Handley Page H.P.20 was an experimental monoplane modification of a de Havilland DH.9A, built to study controllable slots and slotted ailerons as high lift devices. It was the first aircraft to fly with controllable slots.
Frederick Handley Page obtained his master patent for controllable slots on the edge of an aircraft wing on 24 October 1919. [1] He knew the lift coefficient of all wings increased linearly until the stall was approached, then fell away; he argued that if the stall could be delayed, higher lift coefficients could be reached. In Germany Gustav Lachmann had the same idea, though through a wish to avoid the dangers of stalling. [2] Rather than going to litigation an agreement was reached in which Lachmann, working with Prandtl at the advanced Goettingen air tunnel acted as consultant to Handley Page. Lachmann heard about the Handley Page work when they modified a standard DH.9A with fixed slots and demonstrated it dramatically at the Handley Page airfield at Cricklewood on 21 October 1920. That machine was retrospectively designated the H.P.17. The first aircraft with pilot controllable slots, designed by Handley Page and wind tunnel tested by Lachmann was called the X.4B in the company's contemporary notation but became, retrospectively, the H.P.20. [3] The Air Ministry met the cost.
Like the H.P.17 it used a D.H.9A engine, fuselage and empennage, but fitted with an entirely new wing. [3] [4] The H.P.20 was a high-wing monoplane, using a thick wing with a straight leading edge but taper on the trailing edge. It was a semi-cantilever structure bolted to a small cabane on the fuselage and braced to the lower fuselage longerons with a pair of steeply rising struts on each side. The heaviness of early cantilever wing structures is shown by a comparison of the loaded weight of the H.P.20 (6,500 lb) with that of the loaded standard biplane DH.9A (4,645 lb including fuel for over 5 hours of flight and a 460 lb bomb load). [5] The undersurface was flat and the front edge cropped to allow the full span slats, when closed, to form the true leading edge. The slats were hinged ahead of the wing and at their leading edges; their rotation formed the slots. In addition, slots opened in front of the ailerons when they were lowered. This was done via a groove in the wing just in front of the aileron hinge, narrowing towards the top surface. [3]
The spans and wing areas of the DH.9A and H.P.20 were about the same, [6] [7] so the wing chord of the monoplane was about double that of the biplane. As a result, the tailing edge extended aft beyond the DH.9A's pilot's cockpit and so the H.P.20 was flown from what had been the gunner's position. [5] There was a small cut-out in the trailing edge to enhance the pilot's view. As there was no upper wing to house the fuel, the H.P.20 had a slightly round-ended cylindrical tank mounted high over the centre section to provide gravity feed. Because high angles of attack were used in landing and take-off with the slots open, the undercarriage was lengthened, [5] as it had been on the H.P.17. [8] There was an airflow direction indicator mounted on a little boom which projected forward of the starboard wing.
The H.P.20 was first flown with slots closed on 24 February 1921 at Cricklewood. [3] About a month later it was flying with controllable slots. In one test it landed at 43 mphh (69 km/h) at a wing loading of 11 lb/ft2 (54 kg/m2), [9] about the same as a Cessna 152. This corresponds to a lift coefficient of 1.17. Aerodynamic loads made the slats hard to operate reliably. After manufacturer's tests, the Air Ministry agreed to take on the aircraft, but the Ministry's pilot made a heavy landing at Cricklewood during acceptance flights and the H.P.20 remained there for repairs until final delivery in February 1922. [3]
Data from Barnes & James 1987, pp. 229
General characteristics
Handley Page Limited was a British aerospace manufacturer. Founded by Frederick Handley Page in 1909, it was the United Kingdom's first publicly traded aircraft manufacturing company. It went into voluntary liquidation and ceased to exist in 1970. The company, based at Radlett Aerodrome in Hertfordshire, was noted for its pioneering role in aviation history and for producing heavy bombers and large airliners.
In aircraft design and aerospace engineering, a high-lift device is a component or mechanism on an aircraft's wing that increases the amount of lift produced by the wing. The device may be a fixed component, or a movable mechanism which is deployed when required. Common movable high-lift devices include wing flaps and slats. Fixed devices include leading-edge slots, leading edge root extensions, and boundary layer control systems.
A flap is a high-lift device used to reduce the stalling speed of an aircraft wing at a given weight. Flaps are usually mounted on the wing trailing edges of a fixed-wing aircraft. Flaps are used to reduce the take-off distance and the landing distance. Flaps also cause an increase in drag so they are retracted when not needed.
A leading-edge slot is a fixed aerodynamic feature of the wing of some aircraft to reduce the stall speed and promote good low-speed handling qualities. A leading-edge slot is a spanwise gap in each wing, allowing air to flow from below the wing to its upper surface. In this manner they allow flight at higher angles of attack and thus reduce the stall speed.
Gustav Victor Lachmann was a German aeronautical engineer who spent most of his professional life working for the British aircraft company Handley Page. He was, with Frederick Handley Page, the co-inventor of the leading edge slot.
Slats are aerodynamic surfaces on the leading edge of the wings of fixed-wing aircraft which, when deployed, allow the wing to operate at a higher angle of attack. A higher coefficient of lift is produced as a result of angle of attack and speed, so by deploying slats an aircraft can fly at slower speeds, or take off and land in shorter distances. They are usually used while landing or performing maneuvers which take the aircraft close to a stall, but are usually retracted in normal flight to minimize drag. They decrease stall speed.
The Bristol Type 123 was a single-seat, single-engine biplane fighter built to a United Kingdom Air Ministry specification for a four-gun fighter in the early 1930s. Only one was built.
The Handley Page Type G was a two-seat British biplane, designed by Handley Page that first flew in 1913. Only one was built.
The Handley Page H.P.22 and H.P.23 were single-seat sport monoplanes produced for the 1923 Lympne light aircraft trials. They were not successful.
The Handley Page Handcross was a single-engined biplane day bomber built to an Air Ministry specification. It was not put into production and only the three prototypes were built.
The Handley Page H.P.43 was a three-engined biplane bomber-transport built to an Air Ministry specification. It did not fly well and the biplane configuration was out-dated at completion; the only one constructed was later turned into a monoplane and led to the Handley Page H.P.54 Harrow.
The Handley Page H.P.51 was a monoplane conversion of the earlier, unsuccessful biplane bomber-transport aircraft, the Handley Page H.P.43. The Air Ministry ordered the production variant off the drawing board as the Handley Page H.P.54 Harrow bomber.
The Handley Page H.P.46 was a two-seat, single-engined biplane built to an Air Ministry specification for a carrier-based torpedo bomber. With an advanced combination of high lift, slow flying controls it was beset by handling problems and made few flights.
The Handley Page H.P.47 was a British single-engined low-wing monoplane built to an Air Ministry specification for a general-purpose bomber and torpedo bomber aircraft. Only one was built.
The Handley Page H.P.31 was a two-seat single-engined biplane built to a British specification for a carrier-based torpedo bomber and reconnaissance aircraft. After trials, the Blackburn Ripon was preferred, though the Harrow played a significant role in the development of automatic slots.
The Handley Page Type E was a two-seat, single-engined monoplane intended as a demonstrator. Though only one was built, it flew successfully from 1912 to 1914, carrying several hundred passengers and flying several thousand miles.
The Handley Page Type F was a two-seat, single-engined monoplane designed to compete for a War Office prize for a specified military machine in 1912. It crashed before the trials got under way and, although it flew well later, only one was built.
The Westland PV.7 was a private venture submission to a 1930s British specification for a general-purpose military aircraft with two crew. It was a single-engined, high-wing monoplane of promise, but was destroyed early in official tests.
The Villiers XXIV or Villiers 24 CAN2 was a French army night fighter most notable as the first French military aircraft to be fitted with leading edge slats.
The Bodiansky 20, a French four-seat touring aircraft flown in the early 1930s, was one of the first French aircraft to adopt Handley Page slots to delay the stall and lower landing speed.
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