The Ryan STs are a series of two seat, low-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 ...

aircraft built in the United States by the

Ryan Aeronautical Company The Ryan Aeronautical Company was founded by T. Claude Ryan in San Diego, California, in 1934. It became part of Teledyne in 1969, and of Northrop Grumman when the latter company purchased Ryan in 1999. Ryan built several historically and tec ...

. They were used as sport aircraft, as well as

trainers Sneakers ( US) or trainers ( UK), also known by a wide variety of other names, are shoes primarily designed for sports or other forms of physical exercise, but are also widely used for everyday casual wear. They were popularized by compani ...

by flying schools and the militaries of several countries.

Design and development

T. Claude Ryan was the founder of the Ryan Aeronautical Company, the second incarnation of a company with this name, and the fourth company with which he had been involved to bear his nameRussell, Stuart
"Ryan Stm-S2."
''New Zealand Warbirds,'' 2002, 2014. Retrieved: 6 March 2015. (the first, Ryan Airlines, was the manufacturer of the Ryan NYP, more famously known as the ''

Spirit of St. Louis The ''Spirit of St. Louis'' (formally the Ryan NYP, registration: N-X-211) is the custom-built, single-engine, single-seat, high-wing monoplane that Charles Lindbergh flew on May 20–21, 1927, on the Charles Lindbergh#New York–Paris flight ...

''). He began the development of the ST (for "Sport Trainer", and also known as S-T), the first design of the company, in 1933. The ST featured two open

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 in

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 ...

in a

semi-monocoque The term semi-monocoque or semimonocoque refers to a stressed shell structure that is similar to a true monocoque, but which derives at least some of its strength from conventional reinforcement. Semi-monocoque construction is used for, among o ...

metal

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 ...

of two main frames – one steel, the other half of steel and half of aluminium alloy ( alclad) – to take the loads from the wing spars and six more alclad frames; and alclad skin. It had wings in three sections of hybrid construction; the center section integral with the fuselage had tubular steel spars, the front spar a simple tube with an external brace to the upper fuselage, and the rear spar in the form of a parallel chord

truss A truss is an assembly of ''members'' such as Beam (structure), beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so ...

. The two outer wing panels had wooden spars and alclad ribs, with diagonal rods bracing the wings internally. Alclad sheet was used to form the leading edges, and fabric covered the whole structure. When attached, the outer wings were braced with

flying wires In aeronautics, bracing comprises additional structural members which stiffen the functional airframe to give it rigidity and strength under load. Bracing may be applied both internally and externally, and may take the form of struts, which act in ...

to the fixed

conventional landing gear Conventional landing gear, or tailwheel-type landing gear, is an aircraft Landing gear, undercarriage consisting of two main wheels forward of the Center of gravity of an aircraft, center of gravity and a small wheel or skid to support the tail ...

and landing wires to the upper fuselage.Holcomb, Kevi
"Ryan ST Construction description."
''Holcomb's Aerodrome''. Retrieved: 23 January 2008. The fuselage only required eight bulkheads, and no longerons or stringers were required. According to Cassagneres, "The stressed skin, of heavy 18 and 20 gauge 24ST Alclad, was riveted to the drop-hammer formed dural bulkhead rings." The main fuselage bulkhead, "was of built-up welded sheet steel and carried the important spar fittings as well as attachment points for the diagonal wing bracing strut, the upper landing wires, and lower flying wires." Cassagneres goes on to state, "The wings were constructed of solid spruce spars, stamped aluminum alloy ribs, and steel compression members, and were fabric covered. Ailerons and flaps were steel and aluminum structure with fabric covering. All tail surfaces were constructed entirely of tubular aluminum alloy with stamped ribs, and fabric covered." Five STs were built, each powered with a 95HP Menasco B4 engine Taylor, M. J. H. ed. ''Jane's Encyclopedia of Aviation.'' London: Studio Editions Ltd., 1989. . before the follow-on ST-A (A for ''A''erobatic) was developed with a more powerful 125HP Menasco C4 engine. A single ST-B was produced, this being an ST-A with only one seat and an extra fuel tank where the front cockpit normally was; this aircraft was subsequently converted back to ST-A standard."Ryan."
''Aerofiles.com,'' 13 March 2009. Retrieved: 23 January 2008. The ST-A was further developed as the ST-A Special, with a super-charged 150HP Menasco C4-S engine of increased power. In 1937 the ST-A Special was developed into a military version, the STM (also ST-M) series. The first STMs were virtually identical to the STA-Special. The STM-2 was derived from the STM with changes including wider cockpits to enable military pilots to enter and exit while wearing

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, external stringers, and provision for a machine gun on some examples. The military also required a turnover brace and a hand-cranked intertia engine starter. Variants, designated the PT-16s and PT-20s, also had their wheel pants, fairings and tail cones removed. Variants in the series included the STM-2P single-seat version armed with a machine gun delivered to Nationalist China; and the STM-S2, which could be fitted with landing gear or with EDO Model 1965 floats.Orphan, Graham M. "The Ryan ''ST'' in Australia (and the survivors of the breed)". ''Classic Wings Downunder'' magazine, Volume 7, No. 4, September/October 2000, pp. 26–29. ISSN 1172-9643. After the ST-M came the ST-3, a substantial redesign in 1941 partly brought about by the unreliability of the Menasco engines fitted to STs to that point. The

United States Army Air Corps The United States Army Air Corps (USAAC) was the aerial warfare service component of the United States Army between 1926 and 1941. After World War I, as early aviation became an increasingly important part of modern warfare, a philosophical ri ...

(USAAC) had purchased several dozen ST-M variants under various designations and had Ryan Aeronautical re-engine most with Kinner R-440 radial engines. The USAAC found the modification to be beneficial and asked Ryan Aeronautical to design a variant with this engine as standard, and with airframe modifications considered desirable from in-service experience. The ST-3 that resulted featured a longer and more circular wider fuselage, this being suggested by the circular radial engine. Other changes included a revised rudder, balanced ailerons and elevators, and strengthened main landing gear with the legs spaced further apart. The streamlining spats covering the mainwheels, found on ST series aircraft to that point, were deleted as well. The ST-3 served as the basis for military versions ordered by the USAAC and the

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

(USN). The ST-3 gave rise to another model developed in 1941 and early 1942, this was the ST-3KR (for ''K''inner ''R''adial). The ST-3KR had a more powerful Kinner R-5 engine fitted and became the definitive model; more than 1,000 military versions were built during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

as PT-22 Recruits. According to Cassagneres, "The only noticeable difference between the PT-21 and PT-22 was the metal landing gear fairings which covered the main gear structure, leaving the wheels exposed. Otherwise the airframe and its parts and components were interchangeable with the PT-22. One other difference from the later 22 model is in the aileron balance ring. On the 21 it is mounted below the aileron and on the 22 it's on top." The final variant was the ST-4, which was a version of the ST-3 with a wooden fuselage, developed in case a shortage of "

strategic material Strategic material is any sort of raw material that is important to an individual's or organization's strategic plan and supply chain management. Lack of supply of strategic materials may leave an organization or government vulnerable to disrup ...

s" (i.e. of metal) developed. Such a shortage did not eventuate and the ST-4 was not put into mass-production. Some U.S. Navy versions of the ST-3, the NR-1, were converted to specialized ground trainers to teach cadets how to taxi aircraft when on the ground or after landing, and especially in crosswinds. The main wing was clipped back to the landing gear; a small nose wheel added to prevent ground loops; a roll cage between cockpits to protect the pilot and cadet; and the throttle modified so the engine could not go over a certain RPM. The first Ryan ST flew for the first time on 8 June 1934 and production began the following year, when nine aircraft were delivered. Except for 1937 (when 46 aircraft were built), production rates remained low for several years, at about one aircraft every two weeks. This changed in 1940 when deliveries to military forces began in earnest; production that year was just under three aircraft per week. Total production of civil and military aircraft prior to the entry of the United States into

amounted to 315."Ryan ST serial number list."
''Aerofiles,'' 13 March 2009. Retrieved: 23 January 2008. Another 1,253 military versions were produced in 1942 and 1943, for a total of 1,568 aircraft of all models.

Operational history

Most civil aircraft in the ST series were delivered in the United States, although a few were exported to South Africa, Australia and various countries in Latin America. An example of the ST-A was procured by the USAAC in 1939 for evaluation as the XPT-16. This was followed by 15 YPT-16s, the first time the USAAC had ordered a monoplane trainer. These were the first of more than 1,000 Ryan STs to serve the USAAC, its successor, the

United States Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...

(USAAF) and the USN.Holmes, Tony. ''Jane's Historic Military Aircraft Recognition Guide''. London: HarperCollins, 1998. . A large number of STMs were exported in the 1930s and early 1940s (prior to the entry of the United States into World War II) to various air forces, with the biggest customer being the military of the

Netherlands East Indies The Dutch East Indies, also known as the Netherlands East Indies (; ), was a Dutch Empire, Dutch colony with territory mostly comprising the modern state of Indonesia, which Proclamation of Indonesian Independence, declared independence on 17 Au ...

, now

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

. The Netherlands East Indies Army and Navy took delivery of 84 STM-2s and 24 STM-S2s in 1940 and early 1941."Ryan ST series pre-war production figures."
''airminded.net.'' Retrieved: 15 January 2008. Another 50 STM-2Es and STM-2Ps were exported to Nationalist China, while a number of STMs were exported to

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

Ecuador Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...

Guatemala Guatemala, officially the Republic of Guatemala, is a country in Central America. It is bordered to the north and west by Mexico, to the northeast by Belize, to the east by Honduras, and to the southeast by El Salvador. It is hydrologically b ...

Honduras Honduras, officially the Republic of Honduras, is a country in Central America. It is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Ocean at the Gulf of Fonseca, ...

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

and

Nicaragua Nicaragua, officially the Republic of Nicaragua, is the geographically largest Sovereign state, country in Central America, comprising . With a population of 7,142,529 as of 2024, it is the third-most populous country in Central America aft ...

. The STM was chosen by the South American Air-forces because of the superior performance of the super-charged Menasco engine at the high altitude airports encountered. After the Japanese invasion of the Netherlands East Indies many Ryans in that country were pressed into combat, especially in

reconnaissance In military operations, military reconnaissance () or scouting is the exploration of an area by military forces to obtain information about enemy forces, the terrain, and civil activities in the area of operations. In military jargon, reconnai ...

roles, and large numbers were shot down or destroyed on the ground. Surviving STM-2s and STM-S2s that were not captured by the Japanese were shipped to Australia, where 34 entered service in the

Royal Australian Air Force The Royal Australian Air Force (RAAF) is the principal Air force, aerial warfare force of Australia, a part of the Australian Defence Force (ADF) along with the Royal Australian Navy and the Australian Army. Constitutionally the Governor-Gener ...

as trainers. Many of those that survived until the end of World War II were then placed on the civil register in Australia and elsewhere, and some are still flying more than 70 years after they were built.

Variants

Manufacturer designations

;ST: Prototype and first model, fitted with a Menasco B4 engine of 95 hp; five built. ;ST-A: Improved ST designed for aerobatics, fitted with a Menasco C4 engine of 125 hp; 73 built. ;ST-A Special: Improved ST-A, fitted with a super-charged Menasco C4S engine of 150 hp; 10 built. ;ST-B: Single-seat variant of ST-A with extra fuel tank in place of front cockpit; one built, later converted to ST-A. ;STM: Military version of ST-A Special, some with provision for a machine gun; 22 built for various South American air-forces. ;STM-2: Variant of STM for Netherlands East Indies Army and Navy; 95 built. ;STM-2E: Variant of STM delivered to China, fitted with a Menasco C4S2 engine of 165 hp; 48 built. ;STM-2P: Single-seat variant of the STM-2E with provision for a machine gun, also delivered to China; 2 built. ;STM-S2: Variant of STM-2 with interchangeable wheel landing gear or floats for Netherlands East Indies Navy; 13 built. ;ST-W: Experimental conversions, with a

Warner Scarab The Warner Scarab is an American seven-cylinder radial engine, radial aircraft engine, that was manufactured by the Warner Aircraft Corporation of Detroit, Michigan in 1928 through to the early 1940s. In military service the engine was designate ...

radial engine; one converted from USAAC YPT-16 with Scarab of 125 hp; one converted from USAAC PT-20A with Super Scarab of 160 hp. ;ST-3: Variant with new fuselage shape and a

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 ...

radial engine of 125 hp; one built. ;ST-3KR: Variant of ST-3 with a Kinner R-5 radial engine of 160 hp, one built. ;ST-4: Variant of ST-3 manufactured with wooden fuselage; one built.

US military designations

USAAC/USAAF

PT-16 * XPT-16: A single ST-A bought by the USAAC for evaluation. * XPT-16A: XPT-16 re-engined with Kinner R-440 radial engine of 125 hp. * YPT-16: A total of 15 aircraft similar to the ST-M ordered for service trials. * PT-16A: 14 YPT-16s re-engined with Kinner R-440 engine. ;PT-20: Production version of PT-16; 30 built. * PT-20A: Designation of PT-20s that were re-engined with Kinner R-440 engines. ;PT-21: Military production version of ST-3; 100 built. ; PT-22 Recruit: Military production version of ST-3KR with Kinner R-540-1 engine; 1,048 built, including PT-22As. * PT-22A: Designation for 25 examples of ST-3KR built for the

Royal Netherlands Air Force The Royal Netherlands Air Force (RNLAF; , "Royal Air Force") is the military aviation branch of the Netherlands Armed Forces. It was created in 1953 to succeed its predecessor, the ''Luchtvaartafdeling'' () of the Dutch Army, which was founded ...

but not delivered, aircraft subsequently taken by the USAAF. * PT-22C: Aircraft re-engined with Kinner R-540-3 engines, 250 aircraft modified. ;YPT-25: Military version of ST-4, ordered for evaluation; five built.

USN

;NR-1: Naval production version of ST-3; 100 built.

Operators

Numbers used from ''World Air Forces'' Ryan STM-S2 YMPC Creek

;Australia *

operated 34 ex-Netherlands examples that had escaped capture by the Japanese from 1942 to 1945 ;Bolivia *

Bolivian Air Force The Bolivian Air Force (BAF; or 'FAB') is the air force of Bolivia and branch of the Bolivian Armed Forces. History By 1938 the Bolivian air force consisted of about 60 aircraft ( Curtiss Hawk fighters, Curtiss T-32 Condor II and Junkers ...

operated one from 1939 to 1944 ;China *

Republic of China Air Force The Republic of China Air Force ( Chinese, 中華民國空軍), or the ROCAF; known colloquially as the Taiwanese Air Force ( Chinese, 臺灣空軍) by Western or mainland Chinese media, or commonly referred as the National Military Air Force ...

operated 120 from 1940 to 1942 ;Ecuador *

Ecuadorian Air Force The Ecuadorian Air Force (; FAE) is the air branch of the Armed Forces of Ecuador. Mission To develop the military air wing, in order to execute institutional objectives which guarantee sovereignty and contribute towards the nation's security an ...

operated 10 from 1941 ;Guatemala * Guatemalan Air Force operated 12 STA specials from 1938 to 1958 ;Honduras * Honduran Air Force operated three STA specials from 1938 to 1943 ;Japan *

Imperial Japanese Army Air Service The Imperial Japanese Army Air Service (IJAAS) or Imperial Japanese Army Air Force (IJAAF; ) was the Military aviation, aviation force of the Imperial Japanese Army (IJA). Its primary mission was to provide tactical close air support for ground ...

operated an unknown number captured from the Netherlands ;Mexico *

Mexican Air Force The Mexican Air Force (FAM; ) is the air service branch of the Mexican Armed Forces. It is a component of the Mexican Army and as such overseen by the National Defense Secretariat (SEDENA). The objective of the FAM is to defend the integrity, in ...

operated six STA specials from 1937 to 1947 ;Netherlands East Indies * Royal Netherlands East Indies Army Air Force operated 60 STM-2/STM-S2 from 1940 to 1942 *

Royal Netherlands Navy The Royal Netherlands Navy (, ) is the Navy, maritime service branch of the Netherlands Armed Forces. It traces its history to 8 January 1488, making it the List of navies, third-oldest navy in the world. During the 17th and early 18th centurie ...

operated 48 STM-2/STM-S2s from 1941 to 1942 ;Nicaragua * Nicaraguan Air Force operated one STA special during 1938 ;South Africa *

South African Air Force The South African Air Force (SAAF) is the air warfare branch of South African National Defence Force, with its headquarters in Pretoria. The South African Air Force was established on 1 February 1920. The Air Force saw service in World War II a ...

operated three from 1939 ;United States *

and

operated 1,224 of all versions from 1939 until 1946 *

operated 100 NR-1s (PT-22) from 1940 until 1944

Surviving aircraft

There are a number of surviving Ryan ST series aircraft remaining. The survivors range from project aircraft in various stages of completion to restored flying examples. There are remaining examples of the ST, STA, STA-Special, STM, STM-2 and PT20. Many of these restored examples have had their Menasco C4 engines replaced with Menasco D4-87 engines. This change was often because of the shortage of parts available for the C4 engine.

Specifications (ST-A)

References

Notes

Citations

Bibliography

* Cassagneres, Ev. ''The New Ryan: Development and History of the Ryan ST and SC.'' Eagan, Minnesota: Flying Books, 1995. . * Donald, David, ed. ''Encyclopedia of World Aircraft''. Etobicoke, Ontario, Canada: Prospero Books, 1997. . * * * * * Mayborn, Mitch. ''Profile Number 158: The Ryan PT/ST Series''. Leatherhead, UK: Profile Publications, 1967. * Mondey, David. ''American Aircraft of World War II ''(Hamlyn Concise Guide). London: Bounty Books, 2006. . * ''Pilots Flight Operating Instructions for Army Model PT-22 Airplanes, T.O. NO. 01-100GC-1.'' Wright-Patterson AFB, Ohio: U.S. Army Air Forces, 1943. * ''United States Air Force Museum Guidebook.'' Wright-Patterson AFB, Ohio: Air Force Museum Foundation, 1975.

External links

The Ryan ST page

''Popular Mechanics'', February 1943, '' "Plywood Trainer Saves Metal for Warplanes" ''
shows ST-4 wooden construction {{DEFAULTSORT:Ryan St 1930s United States sport aircraft ST Aerobatic aircraft Low-wing aircraft Single-engined tractor aircraft Aircraft first flown in 1934 Aircraft with fixed conventional landing gear Single-engined piston aircraft