Ryan STM S-2

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Ryan STM S-2

Unable to find work after leaving the US Army Air Corps in January 1922 to pursue a civilian flying career, T. Claude Ryan purchased a Curtiss JN-4 Jenny biplane and began offering joyrides around San Diego, California. Shortly afterwards he established the Ryan Flying Company at Dutch Flats airfield, San Diego and began offering flying lessons and charter services. By 1925 Ryan had formed a partnership with Benjamin Mahoney, purchased six war surplus Standard J-1 biplanes and the Douglas Cloudster (the first aircraft designed by Donald Douglas) and, as Ryan Airlines, was operating the first regularly scheduled flights between San Diego and Los Angeles. This was also Ryan's first foray into aircraft design when he modified all seven aircraft to provide fully enclosed passenger cabins. The company's first original design was the Ryan M-1 mail/passenger plane, a high wing monoplane that first flew in February 1926. This was followed by a faster version, the M-2, and then the Bluebird, an M-2 with an enclosed cabin. However, by far the most famous aircraft to carry the Ryan name was a highly modified version of the M-2, the NYP "Spirit of St. Louis" used by Charles Lindbergh in his famous 1927 New York to Paris flight.

When the "Spirit of St. Louis" was built in April 1927, Ryan had sold his interests in Ryan Airlines to Mahoney and was acting as general manager. The two soon went their separate ways and in July 1927, Mahoney changed the name of the company from Ryan Airlines to the B.F. Mahoney Aircraft Corporation. Ryan, meanwhile, had formed the Ryan Aeronautical Company and was acting as an import agent for German built Siemens aircraft engines. After being bought out by Siemens for $75,000 in 1928, Ryan opened a flying school in San Diego which became the Ryan School of Aeronautics on June 5, 1931. Not entirely content with the training aircraft available at the time, his attention turned to aircraft design once more and consequently, the Ryan Aeronautical Company was reborn early in 1934.

The first design by the new company, the Ryan ST or "Sport Trainer", flew on June 8, 1934 at Lindbergh Field (now San Diego international airport). The ST was a low-wing monoplane powered by a 95 hp Menasco B-4 "Pirate" four-cylinder inline engine with seating for two in tandem open cockpits. Instead of the usual wooden construction used in many contemporary aircraft, the ST was built predominantly of metal. The entire fuselage consisted of elliptical steel bulkheads covered with an aluminium skin. The externally braced wings used a combination of steel tube and solid spruce spars, aluminium ribs and, apart from aluminium sheet leading edges, were fabric covered. Fabric also covered the metal framed control and tail surfaces and the fixed main landing gear was fully enclosed in streamlined fairings.

Despite having satisfactory handling in straight and level flight, the aircraft's aerobatic performance could best be described as mediocre. The obvious solution was to fit a more powerful engine so in 1935 the ST became the 125 hp Menasco C-4 powered ST-A and then a year later, the ST-A Special with a 150 hp supercharged Menasco C-4S. As was so often the case with aircraft of this era, the military showed an interest in Ryan's new trainer and in September 1937, the Fuerza Aérea Mexicana (Mexican Air Force) placed an order for six ST-A Specials. These were designated the Ryan Sport Trainer Military and had a slightly wider cockpit opening to accommodate the wearing of parachutes by the crew. Further orders for STMs were received in 1938 from the Aviación Militar Hondurena (Honduran Air Force), Fuerza Aérea Guatemalteca (Guatemalan Air Force) and Fuerza Aérea Ecuatoriana (Ecuadorian Air Force). Included in the Guatemalan and Honduran orders was a number of gunnery trainer STMs armed with 0.3 in machine guns.

The US Army Air Corps was also on the lookout for a new primary trainer so in 1939 they got hold of an ST-A, gave it the experimental designation XPT-16 and began evaluation testing at Wright Field, Dayton, Ohio. This led to a pre-production order in June 1939 for 15 YPT-16s, the first monoplane primary trainer to be ordered by the USAAC. At the request of the military, several modifications were made to the basic ST-A design. The 125 hp Menasco C-4 engine was retained but had a Bendix hand-cranked inertia starter fitted and, as with the STM, the cockpits were widened to allow easier entry and exit for a pilot wearing a parachute. A turnover mast or "roll bar" was added and projected through the windscreen of the forward cockpit, a very welcome addition considering that without it, the occupant of that cockpit would end up supporting over 1,000 lbs of aircraft with their head should a landing not go entirely to plan. Further testing followed and in October 1939, a production order was placed for 30 aircraft. Given the USAAC designation PT-20, it was the same as the YPT-16 apart from having a roomier cockpit thanks to the load-bearing cockpit longerons being moved from inside to outside the fuselage, an adjustable seat and a parking brake.

The daily demands of military training began to take their toll on the aircraft's Menasco engine with many of them experiencing problems. As a result, in 1940 the original XPT-16 was fitted with a 132 hp Kinner R-440-1 radial engine in a streamlined nose fairing through which its five cylinders projected and became the Ryan STK or USAAC XPT-16A. Other options were also tried such as the 160 hp Warner Scarab powered Ryan STW and the 125 hp Menasco D-4 powered P-20B but the Kinner engine proved to be the most reliable and was promptly fitted to 13 YPT-16s and 29 PT-20s, the two types being redesignated the YPT-16A (later to become the PT-16A) and PT-20A respectively. With a suitable engine now installed and the aircraft performing satisfactorily, the USAAC and US Navy placed orders in August 1940 for 100 aircraft each, albeit with yet more modifications. In response, Ryan fine-tuned the design of the PT-20 by lengthening the fuselage and giving it a wider, more circular cross-section to match the new radial engine. The shape of the rudder was changed slightly, balanced ailerons and elevators were fitted and the main gear was strengthened and its track widened to cope with student landings of dubious virtue. This model became the 132 hp Kinner R-440-3 powered Ryan ST-3 and entered service with the USAAC as the PT-21 and NR-1 with the USN. A year later, and with the demand for training aircraft growing, Ryan changed the engine of the ST-3 to a 160 hp Kinner R-540-1 and removed the landing gear fairings resulting in the ST-3KR. This was to become the most widely produced version of the Ryan ST series thanks to the US Army Air Force (as the USAAC had become in June 1941) placing an order for 1,023 examples in September 1941. They began entering service shortly after as the PT-22 Recruit and were later joined by 25 PT-22As, an undelivered order for the Koninklijke Luchtmacht (Royal Netherlands Air Force) and then 250 PT-22Cs, these being PT-22s that had been re-powered with a Kinner R-540-3 engine.

Meanwhile, exports of the STM had continued. Between 1940 and 1941 China took delivery of 50 aircraft comprising 48 STM-2E two-seat trainers and two STM-2P single-seat "pursuit" trainers armed with a single 0.3 in machine gun, all of which were powered by a 165 hp supercharged Menasco C-4S2 engine. Around the same time, the army and navy of the Netherlands East Indies (now Indonesia) became the biggest export customer when they took delivery of 84 Menasco C-4S powered STM-2s and 24 STM-S2 floatplanes. The aircraft were soon hard at work providing both primary and advanced training, tasks previously undertaken back in the Netherlands. Their use was to be short-lived however, as on March 1, 1942 Japanese forces invaded Java and destroyed or captured many of them. Despite this, 34 aircraft managed to be escape and were shipped to Australia where they entered service with the Royal Australian Air Force.

There are currently two Ryans flying in New Zealand, these being an STM-S2 and an ST-3KR (PT-22 Recruit). As the designation would imply, the STM-S2 (c/n 489) is one of the 34 surviving aircraft from the Netherlands East Indies. Entering service as a floatplane, it was given the Dutch serial number S-53 and then, following the aircraft's arrival in Australia, its floats were replaced by normal landing gear and it gained the RAAF serial number A50-13. After being released from the RAAF, it went through several owners in Australia before being imported to this country and registered as ZK-BEM in 1955. Once here, it passed through several further owners before the now derelict aircraft was donated to Auckland's Museum of Transport and Technology in August 1967. The donation was made on the proviso that it be restored to flying condition, however very little was done to the aircraft until 1994 when an agreement was reached between MOTAT and the NZ Warbirds association. Under the terms of the agreement, NZ Warbirds would restore the aircraft to airworthy condition in return for the exclusive use of it for a set time. Just over four years later (December 13, 1998 to be exact) the Ryan took to the air again as ZK-BEM by the founding NZ Warbird’s president, Trevor ‘TT’ Bland and presently carries its original S-53 wartime markings.

On 29 August 2004 a magneto drive gear failure started a chain of events leading to loss of oil pressure and engine seizure. Pilot Shane Papps skilfully force landed at the Clevedon polo field but the Ryan syndicate managed to source an alternative power plant and with the support of the Whitehouse Tavern Trust installed the replacement $50,000 LOM Prague M332A. The Ryan returned to the air in March 2012. It is now fitted with an electric start, new engine mounts, new frontal and right- hand side cowls, spinner and constant speed propeller unit 

Original Text © 2002 Stuart Russell

Revisions © 2014 NZ Warbirds Association Inc.



Power Plant: 

- Original: One 112kW (150hp) Menasco C-4S  

- Current Replacement: One  140hp LOM Prague M332A 4 cylinder in-line 

Wingspan: 9.17m (30ft 1in) 

Length: 6.83m (22ft 5in) 

Max T-O weight: 844kg (1,860lb) 

Max Level speed: 258km/h (160mph) 

Range: 566km (352miles)


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