The Lincoln AP was a

U.S. The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

, single engine, high wing, general purpose (AP stood for All-Purpose) civil cabin aircraft first flown in 1930. Only four were built.

Design and development

The Lincoln AP, first flown in 1930, was a high wing, single-engine cabin monoplane with seats for three. The purchaser could chose between two five cylinder Kinner

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...

s of different powers but the two models were otherwise similar. It was of mixed construction but entirely fabric covered. The fuselage, tail and wing, apart from its twin

spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfami ...

spars The United States Coast Guard (USCG) Women's Reserve, also known as the SPARS (SPARS was the acronym for "Semper Paratus—Always Ready"), was the women's branch of the United States Coast Guard Reserve. It was established by the United States ...

, had welded Cr/Mo steel tube structures. The wing was rectangular in plan out to angled, rounded tips, though centrally there was a gentle reduction in chord to improve the pilot's upward field of view. Parallel chord

ailerons 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 Flight dynamics, roll (or ...

filled about half the

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 wings were braced to the fuselage with a parallel pair of

strut A strut is a structural component commonly found in engineering, aeronautics, architecture and anatomy. Struts generally work by resisting longitudinal compression, but they may also serve in tension. Human anatomy Part of the functionality o ...

s between spars and lower

longeron In engineering, a longeron and stringer is the load-bearing component of a framework. The term is commonly used in connection with aircraft fuselages and automobile chassis. Longerons are used in conjunction with stringers to form structural ...

s on each side. At the rear both

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. Fin ...

and

tailplane A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplane ...

had blunted triangular profile and plans. The fin carried a near semi-circular unbalanced

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...

which reached down to the keel and the tailplane, mounted on top of the fuselage and inflight adjustable for trim, carried parallel chord

elevators An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They are ...

separated by cut-outs for rudder movement. Behind the engine, mounted with cylinders exposed for cooling, the fuselage was rectangular in cross-section. The AP's cabin was largely under the wing but placed the pilot at the

leading edge The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...

ahead of the two passengers sitting side-by-side; each of the three bucket seats contained a

parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, who ...

space. Access was via a side door. The AP had fixed, tailskid

landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...

with the main wheels on split axles, each mounted together with a rear drag strut on the lower fuselage longerons. Vertical shock absorbing

oleo strut An oleo strut is a pneumatic air–oil hydraulic shock absorber used on the landing gear of most large aircraft and many smaller ones. This design cushions the impacts of landing and damps out vertical oscillations. It is undesirable for an airp ...

s were mounted on the forward wing struts at points strengthened with struts to both to the upper and lower longerons. Only four APs were built, including the prototype. One was powered by a

Kinner K-5 The Kinner K-5 was a popular engine for light general and sport aircraft developed by Winfield B. 'Bert' Kinner. With the boom in civilian aviation after Charles Lindbergh's transatlantic flight the K-5 sold well. The K-5 was a rough running but ...

and the other three by

Kinner B-5 The Kinner B-5 was a popular five cylinder American radial engine for light general and sport aircraft of the 1930s. Design and development The B-5 was a development of the earlier K-5 with slightly greater power and dimensions. The main change ...

s. Despite a service ceiling of Lincoln test pilot Malcolm S. Smith, piloting a B-5 equipped to set a light aircraft altitude record, claimed to have reached about . Both its

altimeter An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. The m ...

s failed at .

Variants

;AP-B5:

;AP-K5:

Specifications (Kinner B-5 engine)

References

{{reflist, refs= {{cite journal , title=Lincoln AP-B5 & AP-K5, journal= Aero Digest, date= April 1931, volume=18 , issue=4 , page=108 , url=https://archive.org/details/aerodigest1819unse/page/n607/mode/1up {{cite journal , title=Nebraska, journal= Aero Digest, date= January 1931, volume=18 , issue=1 , page=110 , url=https://archive.org/details/aerodigest1819unse/page/n115/mode/2up {{cite web , url=http://www.aerofiles.com/_la.html, title=Aerofiles: Lincoln, access-date=26 July 2020 Single-engined tractor aircraft High-wing aircraft 1930s United States civil utility aircraft