Nederlandse Modelbouw en Luchtvaartsite

Dutch Modelling and Aviation

In Memoriam

Klaas Willem Jonker
† April 30, 2018

On Monday 30 April 2018, Wilko Jonker died after a long illness at the age of 58. He leaves behind a wife and two children. The Dutch military aviation and plastic modeling were his hobby and on this website he shared all the knowledge he has collected over the years. His hobby has been able to distract him from the persistent disease in his body until the last week of his life. The contacts with other hobbyists were a major support for him.

This website will be maintained by different people for as long as possible, so that other enthusiasts can continue to benefit from extensive content.

Ryan STM-2 and STM-2S


The Ryan Aeronautical Company was founded in 1934 by Claude T. Ryan and was more or less the successor to Ryan Airlines, the firm who had built the Ryan NYP "Spirit of St. Louis".

The first draft of the Ryan ST "Sports Trainer" made its first flight in June 1934.
The performance with the Menasco B-4 of 95 hp was very disappointing. So in 1935, the Ryan ST-A with a Menasco C-4 125 hp was released. One year later, the ST-A Special was released with a Menasco C-4S with turbo and a power of 150 bhp.

The single seat version was the Ryan ST-B.

In 1937 an order was placed by the Mexican Air Force for six ST-A Specials. These were referred to as STM (SportTrainer Military) and had a slightly enlarged cockpit openings because of the chutes the crew carried.

The Ryan STM S2 was a version equipped with EDO Model 1965 floats. Nationalist China received a version with a machine gun under the designation STM-2P.

The USAAC used a few dozen STMs. The Menasco engine proved to be unreliable and Ryan was commissioned to replace this engine with a 440 Kinner radial engine.

Ryan was also commissioned to design a version with the Kinner radial engine as the standard engine. This meant that especially the nose section had to be re-designed.

The hull was broader and rounder and furthermore the rudder, the ailerons and elevators were reviewed.

A version that was developed in the late 1941, early 1942 was the ST-3KR (Kinner Radial), with a more powerful Kinner R-5. Over thousand examples of this version were built under the military designation PT-22.

The ST-4 was a wooden version of the ST-3, designed to be prepared for a shortage of metals such as aluminium.


Ryan ST:
Prototype and first version with Menasco B-4 of 95 hp; five examples built.
Ryan ST-A:
Improved version with Menasco C-4 of 125 hp; 73 examples built.
  • Ryan XPT-16: One Ryan ST-A, purchased by the USAAC to be evaluated.
  • Ryan XPT-16A: Ryan XPT-16 fitted with a Kinner R-440 radial engine of 125 hp.
  • Ryan YPT-16: 15 pre-production aircraft for the USAAC.
  • Ryan PT-16A: 14 YPT-16s modified and fitted with a Kinner R-440 engine.
Ryan ST-A Special:
Improved ST-A, fitted with a Menasco C4S engine of 150 hp; 10 examples built.
Ryan ST-B:
A single-seat version of the ST-A with extra fuel tank.
Ryan STM:
22 examples of the military version of the ST-A Special including enlarged cockpits; a crash bracket incorporated into the front windshield.
  • Ryan STM-2: 95 pieces of a variant of the STM for NEIAF and RNlNAS.
    • Ryan STM-S2: Thirteen examples for RNlNAS with floats, which was interchangeable with the wheel base.
  • Ryan STM-2E: 48 examples of a version with a 165 hp Menasco C4S2, built for China.
    • Ryan TM-2P: Two pieces of a single application of the STM-2E with provision of a machine built for China.
  • Ryan PT-20: Thirty examples built for the USAAC.
  • Ryan PT-20A: USAAC designation for Kinner R-440 equipped PT-20s.
Ryan ST-W:
Modified experimental YPT-16 with a Warner Scarab radial engine of 125 hp and one modified USAAC PT-20A with a Super Scarab 160 hp.
Ryan ST-3:
Improved version with a wider, rounder body and a Kinner B-5 radial engine of 125 hp; one built.
  • Ryan PT-21: Military production version of the Ryan ST-3; Built 100 examples.
Ryan ST-3KR:
Version of ST-3 with a stronger Kinner R-5 radial engine of 160 hp; one built.
  • Ryan PT-22A: Designation for 25 by the NEIAF ordered examples that were not delivered and taken over by the USAAF.
  • Ryan PT-22C: 250 examples of a customized version, fitted with a Kinner R 540-3 engine.
  • Ryan PT-22 Recruit: Military production version of the ST-3KR with Kinner R 540-1 engine, 1048 examples built.
  • Ryan NR-1: 100 examples built for the US Navy.
Ryan ST-4:
One built ST-3 with a wooden hull.
  • Ryan YPT-25: Five evaluation examples for USAAC.


Technical information
Length: 6,52 m Wingspan: 9,12 m
Height: 2,11 m Wing area: 11 m2
Empty weight: 480 kg Max. start weight: 726 kg
Max. speed: 257 km/hr Climbing speed: - m/min
Cruising speed: 217 km/hr    
Range: 600 km Service ceiling:  
Engine type: One Menasco C-4S rated 150 hp
Crew: Two: one instructor plus one pupil
Armament: None