The Emsco B-4 Cirrus was a

mid-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 ...

, two-seat trainer built in the US in the late 1920s. Six were built and three variants with more powerful engines flown.

Design

The two-seat B-4 trainer was a mid-wing

monoplane 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 con ...

with wings of rectangular plan out to blunted tips. Structurally, the largely wooden wings were based on pairs of box

spars SPARS was the authorized nickname for the United States Coast Guard (USCG) Women's Reserve. The nickname was derived from the USCG's motto, "—"Always Ready" (''SPAR''). The Women's Reserve was established by law in November 1942 during Wor ...

and

spruce A spruce is a tree of the genus ''Picea'' ( ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ecosystem, boreal (taiga) regions of the Northern hemisphere. ''Picea'' ...

and

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 ...

rib In vertebrate anatomy, ribs () are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the thoracic cavity, enabling the lungs to expand and thus facilitate breathing by expanding the ...

s, with

duralumin Duralumin (also called duraluminum, duraluminium, duralum, dural(l)ium, or dural) is a trade name for one of the earliest types of age hardening, age-hardenable aluminium–copper alloys. The term is a combination of ''Düren'' and ''aluminium'' ...

sheet stiffening the

leading edge The leading edge is the part of the wing that first contacts the air;Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, 1997. alternatively it is the foremost edge of an airfoil sectio ...

s. The rest of the wing was fabric covered. They were wire-braced from above and below with streamlined wires from pylons within 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 ...

to the spars. Its Frise ailerons were inset. The B-4's fuselage was based on a

chrome-molybdenum steel 41xx steel is a family of SAE steel grades, as specified by the Society of Automotive Engineers (SAE). Alloying elements include chromium and molybdenum, and as a result these materials are often informally referred to as chromoly steel (common v ...

frame. It had a American Cirrus III four-cylinder, upright inline engine in the nose with an aluminium

firewall Firewall may refer to: * Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts * Firewall (construction), a barrier inside a building, designed to limit the spre ...

and tanks in the wing roots. The two

tandem Tandem, or in tandem, is an arrangement in which two or more animals, machines, or people are lined up one behind another, all facing in the same direction. ''Tandem'' can also be used more generally to refer to any group of persons or objects w ...

cockpit A cockpit or flight deck is the area, on the front part of an aircraft, spacecraft, or submersible, from which a pilot controls the vehicle. The cockpit of an aircraft contains flight instruments on an instrument panel, and the controls th ...

s, fitted with dual controls, were over the wing. The view from the forward cockpit, placed around quarter- chord, was good and the instructor's view from the rear cockpit was improved with windows in the underside wing roots. The B-4's

empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third ed ...

was conventional, framed like the wings and fabric covered. The

tailplane A tailplane, also known as a horizontal stabilizer, is a small lift (force), 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 ...

was mounted at mid-fuselage height; its angle of incidence could be varied in-flight for trimming. It carried split, unbalanced

elevators An elevator (American English) or lift (English in the Commonwealth of Nations, Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive tracti ...

. There was a small

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 ...

with a curved-topped, straight-edged

balanced rudder Balanced rudders are used by both ships and aircraft. Both may indicate a portion of the rudder surface ahead of the hinge, placed to lower the control loads needed to turn the rudder. For aircraft the method can also be applied to elevator (air ...

which extended down to the keel between the elevators. It had conventional, split axle, fixed

landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for taxiing, takeoff or landing. For aircraft, it is generally needed for all three of these. It was also formerly called ''alighting gear'' by some manufacturers, s ...

with a track. The axles and drag struts were hinged from the same pylon used by the lower wing bracing wires.

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. A stay is sometimes used as a synonym for ...

s joined the wheels, enclosed in fairings, to

shock absorber A shock absorber or damper is a mechanical or hydraulics, hydraulic device designed to absorb and Damping ratio, damp shock (mechanics), shock impulses. It does this by converting the kinetic energy of the shock into another form of energy (typic ...

s within the wing root

aircraft fairing An aircraft fairing is a structure whose primary function is to produce a smooth outline and reduce drag.Crane, Dale: ''Dictionary of Aeronautical Terms, Third Edition'', page 206. Aviation Supplies & Academics Inc, Newcastle Washington, 1997. ...

s. At the rear the B-4 had a tripod tailskid with a vertical rubber shock absorbing extension of the rudder post.

Development

The exact date of the first flight of the Emsco Cirrus is not known, though it was flying in mid-November 1929. It was one of the aircraft taking part in the non-competitive First All-

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

Tour, which ended at

Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...

on 7 November. This event was intended to advertise the Western Aircraft Show held at Los Angeles from 9–17 November, where the Cirrus was on display. Its tests were complete by January 1930, though it never reached certification, partly because of the departure of its designer, Charles Rocheville, from the firm. His replacement Gerard Vultee, ex-Lockheed, decided to re-engine the sole B-4 with a five-cylinder

radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric), a line * Radius, adjective form of * Radial distance (geometry), a directional coordinate in a polar coordinate system * Radial set * A ...

, the

Wright J-6-5 Whirlwind The Wright R-540 Whirlwind was a series of five-cylinder air-cooled radial engine, radial aircraft engines built by the Wright Aeronautical division of Curtiss-Wright. These engines had a Engine displacement, displacement of 540 in³ (8.85& ...

. The modified aircraft was designated B-7 and received its Approved Type Rating (ATC) on 21 February 1931. It was longer than the B-4 and was about heavier empty. No other B-7s were built; instead it was followed by the newly built, solitary B-7-C, powered by a Continental A.70 seven-cylinder radial which produced the same power as the Whirlwind. It was longer than the B-4 but was otherwise similar to the B-7, with about the same empty weight, though it had various refinements such as a tailwheel. The B-7-C got its ATC in June 1931. Vultee left Emsco to set up

Vultee Aircraft Vultee Aircraft, Inc., was an aircraft manufacturer founded in 1939 in Los Angeles County, California, when the ''Vultee Aircraft Division'' of the aviation holding company AVCO was reorganized as an independent company. It had limited success b ...

and was replaced by T.V. van Stone, who built another airframe with a Curtiss Challenger six-cylinder radial. Designated B-7-CH, it flew late in 1931.

Operational history

Little is known about the six B-4s constructed apart from the B-7 conversion. The latter's subsequent career is also obscure. The B-7-C was scrapped in 1946 but its flying life is not recorded. The B-7-CH has a better recorded history. It was used for a time by Scott Flying Services of

Long Beach Long Beach is a coastal city in southeastern Los Angeles County, California, United States. It is the list of United States cities by population, 44th-most populous city in the United States, with a population of 451,307 as of 2022. A charter ci ...

until it was sold in 1936 and flown to

Haiti Haiti, officially the Republic of Haiti, is a country on the island of Hispaniola in the Caribbean Sea, east of Cuba and Jamaica, and south of the Bahamas. It occupies the western three-eighths of the island, which it shares with the Dominican ...

with the intention of starting an internal service there. It returned to

New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...

where a new owner took it back to the West Coast and sold it on. It was last recorded at the Multnomah School of Aviation in 1950.

Variants

;Emsco B-4 Cirrus: American Cirrus III engine. 6 built. ;Emsco B-7:

engine. 1 converted from a B-4. ;Emsco B-7-C:

Continental A70 Continental may refer to: Places * Continental, Arizona, a small community in Pima County, Arizona, US * Continental, Ohio, a small town in Putnam County, US Arts and entertainment * ''Continental'' (album), an album by Saint Etienne * Continent ...

engine. 1 built. ;Emsco B-7-CH: Curtiss Challenger engine. 1 built.

Specifications (B-4 Cirrus)

References

{{Emsco aircraft 1920s United States sport aircraft Mid-wing aircraft Single-engined tractor aircraft Aircraft first flown in 1929