| Lachassagne AL 3 | |
|---|---|
 | |
| Role | Experimental aircraft |
| National origin | France |
| Designer | Adolphe Lachassagne |
| First flight | mid-December 1925 |
| Number built | 1 |
| Variants | Lachassagne AL 5 |
The Lachassagne AL 3 was an experimental 1920s French aircraft designed to test a camber-changing wing meant to extend speed ranges. It was flown only briefly but led to a second design with similar features.
Early aircraft designers appreciated that whilst low take-off speeds required wings with high lift, high camber sections, more symmetric, low camber sections produced less drag at speed. One solution was to make a wing sufficiently flexible chordwise that the section could be altered in flight. This was the approach taken by Adolphe Lachassagne; his AL 3 was the first French monoplane with such a wing. [1]
Details of the profile changing mechanism for the AL 3 are sparse, though each two spar wing was in two parts, a forward rigid metal structure and a rear flexible wooden structure. Both were fabric covered. [2] On the later Lachassagne AL 5 the leading edge ahead of the forward spar was rigid but rotatable and the AL 3 may have had a similar feature. [1] Its "minimum incidence" could be altered from 2° to 5°. [2]
Apart from the camber-changing system the two wings were unremarkable; they were rectangular in plan, with a low aspect ratio of only 4.3, each joined low down onto the fuselage. On each side a pair of near-parallel struts braced the wing from the spars beyond half span to the upper fuselage. Very short and broad balanced ailerons were mounted at the tips. [2]
The AL 3 had a flat-sided fuselage with rounded decking, built around ash longerons and covered with 3 mm (0.12 in) plywood. The pilot sat in an open cockpit between the wing spars. It was initially powered by an 13–15 kW (18–20 hp) Darracq flat twin engine, mounted with its cylinder heads exposed for air-cooling. [2] This, like parts of the fuselage and its landing gear were not new; Lachassagne was not well funded. [1] At the rear the trapezoidal tailplane had, like the wings, a rigid forward part and a camber changing rear section, though the latter had a wider range of angular movement than the wing and carried the elevators. The vertical tail was conventional, with a triangular fin and an unbalanced, round topped and straight edged rudder which reached down to the keel, working between the elevators. [2]
The AL 3's 1.3 m (4 ft 3 in) track undercarriage seen from ahead formed a splayed M-form set of rigid, longitudinally wire braced struts. The large diameter wheels were mounted on half axles, hinged at the centre of the M and joined to its outer members by rubber shock absorbers. A tall tailskid protected the rudder. [2]
The AL 3 took a long time to build, partly for financial reasons. Though it was entered into a 1923 event, it was not completed until 1925. [1] It flew just before Christmas 1925, even though the Darraq engine was underperforming. [3] By mid March 1926 the Darraq had been replaced by an Anzani engine of similar power presented to Lachassagne by the Association Française Aérienne in January to enable his work on the AL3 to continue. [4] On 20 March 1926 AL 3 flew with this engine for the first time. [5] Testing of the effects of camber changing began the next day; the Al 3's handling was good over a speed range of around 45–130 km/h (28–81 mph) but about a week later it was badly damaged when its wire braced undercarriage collapsed on landing. [6] Despite the short testing period, Lachassagne felt the flight trials had demonstrated that the variable camber approach worked so, rather than rebuild the AL 3, he decided to build a development, the AL 5. [1]
Data from Les Ailes 26 March 1925 [2]
General characteristics
The Aero A.23 was a Czechoslovakian airliner of the 1920s. Aero Vodochody had produced the first Czech airliner, the A.10, four of which had served with ČSA, the national airline. The A.23, another biplane, was bigger, more powerful and could carry more passengers.
The Potez 40 was a French three-engine, braced high-wing monoplane designed and built in response to a French government programme for colonial transport and policing aircraft duties.
The Potez 27 was a French reconnaissance biplane first flown in 1924. 175 were operated by the Polish Air Force, most built in Poland by PWS under licence. Others went to Romania, where they were also used as light bombers.
The Feiro Dongó was a Hungarian side-by-side trainer biplane. It was notable for its high aspect ratio wings, aerodynamic clearness and high lift/drag ratio.
The de Marçay Limousine was a two-seat French touring biplane introduced at the 1919 Paris Aero Salon. A smaller but otherwise very similar single-seater was also there.
The Les Mureaux 3 C.2 and Les Mureaux 4 C.2 were French two seat, parasol winged fighters, flown in 1927-8, which differed only in their engines. They were developed into near identical army co-operation types, the ANF Les Mureaux 130 A.2 and ANF Les Mureaux 131 A.2, in 1929-31.
The Buscaylet-de Monge 7-5 was a twin engine, twin-boom aircraft without a fuselage but with pilot, passenger and fuel accommodated in a thickened wing centre-section. It was designed by Belgian pioneer Louis de Monge and built in France in the mid-1920s.
The Lachassagne AL 5 was a French low power, single seat sports aircraft with novel, in-flight variable camber wings and tailplane. It first flew in 1930; at least two were built.
The Salmson-Béchereau SB-5 was a two-seat fighter aircraft built for a French government programme in 1925. Despite a powerful engine it did not perform well and only one was built.
The Peitz 101, aka Peitz Avionette, was a French, amateur-built, all-metal light aircraft, first flown during the winter of 1931–32.
The Peyret Avionette was a low power, single seat French monoplane which won several first-place prizes at the Congrès Experimental contest of 1923.
The SABCA Demonty-Poncelet monoplane, Demonty-Poncelet limousine or SABCA-DP was a Belgian light aircraft first flown in 1924. It had two comfortable side-by side seats in a glazed cabin. Though it had competition successes in 1924 and 1925, it did not go into production.
The Caproni Ca.66 was an Italian night bomber designed to reequip the post-World War I Italian Air Force. Only two examples of the four-engined biplane were built.
The Dewoitine 14 was a mid-1920s French civil transport, capable of carrying mixture of passengers and freight. The sole example was used in commercial trials.
The Caspar C 17 was a mid-1920s German, low power, two seat ultralight aircraft with a cantilever wing of unusually high aspect ratio, flexibly attached to the fuselage to moderate gust effects.
The Magni PM.2 Vittoria was an Italian experimental, single seat, parasol wing aircraft built in the mid-1920s. It had a large area aerofoil on each of its single wing bracing struts which could be rotated together or independently to give lift or drag.
The CPA 1 was a French twin-engined, parasol-winged bomber designed and built in the mid-1920s.
The Hanriot H.25 was a French, single-engined, six passenger airliner built in 1926. Only one was flown.
The Skraba S.T.3 was a two-seat Polish biplane built in 1928. It was the first all-metal aircraft designed in Poland; only one was completed.
The Peyret-Nessler Libellule (Dragonfly) was a French two-seat, low-powered parasol wing light aircraft built in 1927 to provide practical but economical flying. It was one of the first of these French avionettes.