Beatty-Johl BJ-2 Assegai
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The Beatty-Johl BJ-2 Assegai was a single seat, high performance competition glider built in South Africa in the early 1960s. Only one was built; it was optimised for South African conditions and performed well there, winning two nationals and setting several records, but was less successful under European conditions at the 1965
World Gliding Championships The World Gliding Championships (WGC) is a gliding competitions, gliding competition held roughly every two years by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are always held in the sum ...
.


Design and development

The BJ-2 was a successor to the BJ-1, a 60 ft (18.3 m) span glider on which design began in South Africa in 1945 but abandoned before completion as it became clear that the new
laminar flow Laminar flow () is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral m ...
airfoil An airfoil (American English) or aerofoil (British English) is a streamlined body that is capable of generating significantly more Lift (force), lift than Drag (physics), drag. Wings, sails and propeller blades are examples of airfoils. Foil (fl ...
sections offered better performance. The BJ-2 used one of the 65 series airfoils in conjunction with Fowler flaps. Its design, led by W.A.T. Johl, concentrated on high cross country glide speeds, achieved via a high
wing loading In aerodynamics, wing loading is the total weight of an aircraft or flying animal divided by the area of its wing. The stalling speed, takeoff speed and landing speed of an aircraft are partly determined by its wing loading. The faster an airc ...
and low camber, important in South African gliding conditions with strong
thermals A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...
and long flights between them. Design work started in 1955 but the BJ-2 was not flown until January 1961, piloted and chiefly built by P.J.Beatty. The BJ-2 was an almost entirely wooden aircraft, both internally and with a
plywood Plywood is a composite material manufactured from thin layers, or "plies", of wood veneer that have been stacked and glued together. It is an engineered wood from the family of manufactured boards, which include plywood, medium-density fibreboa ...
skin on all surfaces. The single spar, 50 ft (15.24 m) span,
shoulder The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder m ...
mounted wings had three pieces, the centre one with a span of 30 ft 1 in (9.17 m), rectangular in plan, the NACA 65 wing section and no dihedral. The outer pieces were
trapezoidal In geometry, a trapezoid () in North American English, or trapezium () in British English, is a quadrilateral that has at least one pair of parallel sides. The parallel sides are called the ''bases'' of the trapezoid. The other two sides are ...
and had 5° dihedral, changing to a non-laminar section at the tip, with the
aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement aroun ...
s filling all their
trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 1997. ...
. The centre panel trailing edge was filled with
Fowler flap 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 landin ...
s, which at maximum, 30° extension increased both the camber and the wing area, the latter by 19.5%, for low speed flight in thermals. Small wing tip bodies were added later. Its
fuselage The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...
was a semi-
monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...
structure, elliptical in cross-section and tapering uniformly towards the tail. The
fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. F ...
and
rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...
together were trapezoidal, with a
T tail A T-tail is an empennage wikt:configuration, configuration in which the tailplane of an aircraft is mounted to the top of the vertical stabilizer, fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs fr ...
and
elevator An elevator (American English) or lift (Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive traction cables and counterweight systems suc ...
of constant chord within tapered tips. Lacking the more usual wing mounted airbrakes, the BJ-2 had a pair of petal type, fuselage mounted brakes for glide angle control just aft of the wing. It also had two
cruciform A cruciform is a physical manifestation resembling a common cross or Christian cross. These include architectural shapes, biology, art, and design. Cruciform architectural plan Christian churches are commonly described as having a cruciform ...
braking
parachute A parachute is a device designed to slow an object's descent through an atmosphere by creating Drag (physics), drag or aerodynamic Lift (force), lift. It is primarily used to safely support people exiting aircraft at height, but also serves va ...
s deployable from the lower rear fuselage below the rudder. Forward of the wing the upper fuselage line blended smoothly into that of the single piece, sideways opening
canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an a ...
to limit dive speeds. The undercarriage combined a retractable
monowheel A monowheel or uniwheel is a type of one-wheeled, single-track vehicle. Unlike the unicycle, a monowheel consists of a large, hollow wheel that loops above and around the driver. Monowheels are typically powered by an engine as with a motorc ...
, fitted with a brake, and a co-retracting forward skid. The nose was of
glass reinforced plastic Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cl ...
. Camber changing Fowler flaps had been used before on gliders, notably on the 1938 Akaflieg Hannover AFH-4 and the 1948 Cijan-Obad Orao II, though not fitted to this design's later version. Whilst they provided the increased camber needed for low speed climbs, they also increased
drag Drag or The Drag may refer to: Places * Drag, Norway, a village in Tysfjord municipality, Nordland, Norway * ''Drág'', the Hungarian name for Dragu Commune in Sălaj County, Romania * Drag (Austin, Texas), the portion of Guadalupe Street a ...
, both by reducing the
aspect ratio The aspect ratio of a geometry, geometric shape is the ratio of its sizes in different dimensions. For example, the aspect ratio of a rectangle is the ratio of its longer side to its shorter side—the ratio of width to height, when the rectangl ...
, raising the
induced drag Lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, in aerodynamics, is an aerodynamic drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or ...
, and by the creation of extra vortexes at the outer ends of the flaps. This penalty was less costly in typically strong South African thermals than in the weaker ones found in northern
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
. The BJ-2 proved to have the intended high speed performance, demonstrated in a series of closed circuit and out and back flights. The fuselage mounted airbrakes proved rather ineffective.


Operational history

The BJ-2's first competitive appearance was at the South African Nationals held from late December 1961 to early January 1962. Flown by Pat Beattie, it came third overall but was the highest placed South African aircraft, making him the national champion. During the competition he set an unofficial world record round a 400 km triangular course at a speed of 102.3 km/h (63.6 mph) and made a 600 km (373 km) out and return flight at 90 km/h (56 mph). After this the BJ-2 was flown by Bert Dommisse, who completed a 500 km triangle, now an officially FAI recognised pattern, at a record speed of 107.5 km/h (66.8 mph) just before competing with it in the 1963/4 South African Nationals, when he became national champion. In 1965 the BJ-2 was flown by Dommisse at the
World Gliding Championships The World Gliding Championships (WGC) is a gliding competitions, gliding competition held roughly every two years by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are always held in the sum ...
at
South Cerney South Cerney is a village and civil parish in the Cotswold district of Gloucestershire, 3 miles south of Cirencester and close to the border with Wiltshire. It had a population of 3,074 according to the 2001 census, increasing to 3,464 at the ...
in the
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.
English English usually refers to: * English language * English people English may also refer to: Culture, language and peoples * ''English'', an adjective for something of, from, or related to England * ''English'', an Amish ter ...
conditions, with weak thermals, were not what it was designed for and it finished well down the field.


Specifications


Notes


References

* * * * * * {{refend Glider aircraft