In 1927, Ryan designed and built one of the most famous aircraft in U.S. aviation history, the Ryan Model NYP for Charles A. Lindbergh. Lindbergh named the aircraft Spirit of St. Louis and flew it from New York to Paris in May 1927. Later in 1927, the airline service was terminated and Ryan sold his interest in the manufacturing company to B. Franklin Mahoney. The company was renamed the B.F. Mahoney Aircraft Company although the Ryan name was used in advertising. After the sale, Ryan continued to operated the Ryan School of Aeronautics, a flight training school; the corporate name was changed to The Ryan Aeronautical Company in 1934. The school operated biplanes but Ryan began designing a modern primary trainer that incorporated all the desirable qualities needed for a trainer. The result was the Ryan Sport Trainer (ST).

The Model ST was a single-engine, two-seat, open cockpit, low wing, wire braced monoplane. The wings were constructed of spruce with thirteen aluminum ribs; the leading edge back to the front spar was metal and final fabric covering overall. The fuselage was all metal and covered with six pieces of Alclad; the tail unit, ailerons and flaps was were metal frames covered with fabric. The wheels of the fixed main landing gear were enclosed with aluminum fairings or wheel pants. The ST, powered by a 95 hp (71 kW) Menasco B-4 Pirate four-cylinder in-line engine, was one of the most esthetically pleasing aircraft of the 1930s. The ST was originally equipped with a two-bladed Story ground-adjustable metal propeller but this was insufficient and was later replaced with a wooden propeller. The Menasco B-4 engine was satisfactory for normal level flight but the aircraft was mediocre in aerobatics and only five STs were built. The ST was superseded by the Model ST-A equipped with a 125 hp (93 kW) Menasco C-4 Pirate four-cylinder, in-line engine and the majority of civil aircraft were ST-As. Another version was the ST-A Special powered by a 150 hp (110 kW) supercharged Menasco C-4 Pirate engine.

Several overseas air forces purchased ST-A Specials prior to the U.S. military. In September 1937, the Mexican Air Force ordered six trainers which were delivered to Mexico City in December 1937 and used for advanced training. In 1938, the Guatemalan Air Force bought twelve and the Honduran Air Force bought three aircraft; the front cockpit of these aircraft was covered to accommodate an extra fuel tank to permit ferrying. The Honduran ST-As also had a machine gun mounting bracket and suitable synchronization gears installed so that a machine gun could fire through the propeller. The twelve Guatemalan aircraft were purchased in two batches; the first six were standard, unarmed trainers while the second six had the machine gun mountings plus a 30-caliber (7.62 mm) machine gun in each wing.

The first order by the U.S. military for the ST-series was placed in May 1939 when one Model ST-A-1 was ordered for evaluation by the U.S. Army Air Corps (USAAC), which was superseded by the U.S. Army Air Forces (USAAF) on 20 June 1941. Designated XPT-16, this aircraft was powered by the 125 hp Menasco C4 engine, designated L-365-1 by the U.S. military. This was the first primary training monoplane ordered by the USAAC. This initial order was followed by a subsequent order in June 1939 for 15 YPT-16s. These latter aircraft were redesigned in accordance with military specifications, e.g., the cockpit openings were cut larger, a turnover mast was located at the front cockpit windshield, a Bendix hand-cranked direct-drive inertia engine starter was fitted and toe brakes and a parking brake were provided. The first production contract was signed in October 1939 for 30 Menasco C-4 powered PT-20s. These aircraft featured cockpit load-carrying longerons moved from inside to outside the fuselage permitting easier access for a pilot wearing a seat-pack parachute. These also had a parking brake and adjustable seats.

Use of the PT-16s and PT-20s revealed that the Menasco engine did not hold up to the daily training demands and the USAAC asked Ryan to modify the aircraft to accept an air-cooled radial engine. A 132 hp (98 kW) Kinner R-440-1 five-cylinder, single-row, air cooled, radial engine was fitted to the XPT-16 in early 1941 and the re-engined aircraft was redesignated XPT-16A. The radial engine was fitted in a streamlined nose fairing with projecting, uncowled cylinders. Thirteen of the XPT-16s were also re-engined with the Kinner engine and became XPT-16As and later, PT-16As; and 29 of the 30 PT-20s were re-engined becoming PT-20As. Two PT-20s were tested with the 125 hp Menasco D-4 engine and were redesignated PT-20Bs but this engine was not any more successful that the C-4 engine and both were re-engined with the Kinner R-440-1 and redesignated PT-20As. Now that the selection of the radial engine had been finalized, both the USAAC and the U.S. Navy (USN) each placed orders for 100 aircraft in August 1940, 100 PT-21s for the USAAC and 100 NR-1s for the USN. These Model ST-3s were powered by a 132 hp Kinner R-440-3 engine and were modified to meet military requirements. These modifications included a wider and more rugged landing gear to accommodate student pilots; elimination of the wheel pants; a wider cockpit; balanced ailerons and elevators; redesigned lower rudder area; and military equipment, e.g., fire extinguisher, map case, adjustable cockpit bucket seats, baggage compartment; large hanging rudder pedals with toe brakes, larger flap handle, dual controls and instruments; and fighter-type handles on the control sticks, were included.

The Model ST-3KR, powered by a 160 hp (120 kW) Kinner R-540-1 five-cylinder, single-row, air-cooled, radial engine, was the final ST ordered by the U.S. military. The first order for 1,023 PT-22-RYs was placed in September 1940. The 25 PT-22A-RYs had originally been ordered as seaplanes by the NEI Navy and were completed for the USAAF equipped with the R-540-1 engine. Finally, the PT-22C-RYs were 250 PT-20-RYs re-engined with the Kinner R-540-3 engine.

Three other military units operating the Ryan STs were the Chinese Air Force and the Netherlands East Indies (NEI) Army and Navy. All used the Ryan Model STM which was an ST-A Special with the same modifications used for the PT-20s described above. In November 1939, China placed an order for 48 STM-2Es and two STM-2Ps, all powered by a 165 hp (120kW) upgraded, supercharged Menasco C-4S2 engine. The STM-2Ps were single-seat pursuit trainers, equipped with one 30-caliber (7.62 mm) machine gun firing through the propeller, while the STM-2Es were two-seat trainers. These aircraft were shipped via a circuitous route to Rangoon, Burma between February 1940 and spring 1941. After assembly in Rangoon, they were flown to China.

In June 1940, the Netherlands East Indies (NEI) Army purchased 60 STM-2 aircraft and the NEI Navy ordered 35 Model STM-2s; the Navy also ordered 13 STM-S2 seaplanes with two Edo floats. These aircraft were initially used as trainers but were pressed into service as reconnaissance aircraft during the Japanese invasion of the NEI in 1941/1942. Thirty three of the aircraft were shipped to Australia in February 1942 for a relocated NEI flying school and were later transferred to the Royal Australian Air Force (RAAF) when the school moved to the U.S. Of the others, many were shot down or destroyed on the ground by Japanese aircraft but some were captured by the Japanese and used as trainers for aerobatics and formation flying.

OPERATIONAL HISTORY

The USN placed its first order for 100 NR-1s on 19 August 1940; the aircraft were delivered to Naval Air Station (NAS) Jacksonville, Florida between 4 August and 8 October 1941. NAS Jacksonville was the site of primary flight training for the USN until 1943 when the training moved to NAS Memphis, Tennessee. The NR-1s remained in squadron service until September 1943.

SPECIFICATIONS

Power Plant: A 132 hp (98.4 kW) Kinner R-440-3 five-cylinder, single-row, air cooled, radial engine.

Wing Span: 30 feet (9.14 meters)

Length: 22 feet 6 inches (6.86 meters)

Height: 6 feet 11 inches (2.11 meters)

Wing Area: 124 square feet (11.52 square meters)

Gross Weight: 1,825 pounds (828 kg)

Maximum Speed: 115 mph (185 km/h)

Armament: None