The Leonard Annebula is an American
high-wing
A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple wings.
A monoplane has inherently the highest efficiency and lowest drag of any wing config ...
, single-seat
FAI Standard Class
Competition classes in gliding, as in other sports, mainly exist to ensure fairness in competition. However the classes have not been targeted at fostering technological development as in other sports. Instead classes have arisen because of:
* t ...
glider designed by Bob Leonard of
Wichita, Kansas
Wichita ( ) is the List of cities in Kansas, most populous city in the U.S. state of Kansas and the county seat of Sedgwick County, Kansas, Sedgwick County. As of the 2020 United States census, 2020 census, the population of the city was 397, ...
, based on the
Hall Cherokee II.
[Said, Bob: ''1983 Sailplane Directory, ]Soaring Magazine
''SOARING'' is a magazine published monthly as a membership benefit of the Soaring Society of America. It was first published in 1937. The headquarters is in Hobbs, New Mexico. The magazine's article topics include safety issues and accounts of i ...
'', page 36. Soaring Society of America
The Soaring Society of America (SSA) was founded at the instigation of Warren E. Eaton to promote the sport of soaring in the USA and internationally. The first meeting was held in New York City in the McGraw–Hill Building on February 20, 193 ...
, November 1983. USPS 499-920
Design and development
The Annebula design is derived from the Cherokee II, but while retaining the basic Cherokee structure, Leonard incorporated many changes and new features. The aircraft is built from wood and
fiberglass
Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...
, with
aircraft fabric covering
Aircraft fabric covering is a term used for both the material used and the process of covering aircraft open structures. It is also used for reinforcing closed plywood structures. The de Havilland Mosquito is an example of this technique, as are ...
.
The Annebula uses a completely new single-
spar wing with Prue-type
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. ...
dive brake
Dive brakes or dive flaps are deployed to slow down an aircraft when in a dive. They often consist of a metal flap that is lowered against the air flow, thus creating drag and reducing dive speed.Crane, Dale: ''Dictionary of Aeronautical Terms, ...
s. The
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 ...
is a
NACA
The National Advisory Committee for Aeronautics (NACA) was a United States federal agency that was founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its ...
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 ...
type of varying section over the span, starting at the
wing root
The wing root is the part of the wing on a fixed-wing aircraft or winged-spaceship that is closest to the fuselage,Peppler, I.L.: ''From The Ground Up'', page 9. Aviation Publishers Co. Limited, Ottawa Ontario, Twenty Seventh Revised Edition, 1 ...
as a NACA 64(3)-618, becoming a NACA 64(3)-615 by mid-span and then a NACA 4412 at the tip. The wing is constructed from
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 ...
and fiberglass and is responsible for the Annebula's performance increase from the Cherokee II's 23:1
glide ratio
In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under give ...
to 31.5:1. The Annebula also has more span, wing loading and a higher
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 ...
than the Cherokee II.
The
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 also extensively redesigned, with a new shaped nose, a new vertical fin with twice the area and a new fuselage shape aft of the wing. Landing gear is a monowheel.
Only one Annebula was built.
Operational history
Completed in 1967, the Annebula is registered as a US
experimental amateur-built.
By 1983 the sole example had flown over 700 hours and had been used to complete
Diamond badge distance and altitude flights. It also once held the
Kansas
Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...
state records for speed attained in , and triangles, goal distance, altitude and altitude gain. Aside from the designer himself, Leonard's three sons have also flown the aircraft.
Specifications (Annebula)
See also
References
{{reflist
1960s United States sailplanes
Aircraft first flown in 1967