The PT-22’s fuselage is a simple monocoque structure, with thick gauge alclad skin.
The wings feature spruce spars, aluminium alloy ribs, steel compression members, with aircraft fabric covering aft to the trailing edge and aluminium alloy sheet covering from the leading edge to the spar.
The wings have 4° 10′ of sweep back, 3° of incidence and 4° 30′ dihedral.
The PT-22 fuel system consists of a single tank mounted forward of the front cockpit.
Fuel is gravity fed to the carburettor.
The oil system is a dry-sump type, with all oil stored in a tank located on the front side of the firewall in the upper section of the fuselage.
The wing flaps are mechanically operated from a lever located on the left side of each cockpit.
Adjustable elevator trim is provided via an elevator trim tab controllable from a handwheel mounted on the left side of each cockpit.
In its original configuration, the aircraft was not equipped with an electrical system.
Hydraulic brakes are provided for each wheel, controllable via the rudder pedals in each cockpit.
In order to simplify maintenance, the wheel spats and landing gear fairings were deleted in the production examples
Prototype and first model, fitted with a Menasco B4 engine of 95 hp; five built.
Improved ST designed for aerobatics, fitted with a Menasco C4 engine of 125 hp; 73 built.
Improved ST-A, fitted with a super-charged Menasco C4S engine of 150 hp; 10 built.
Single-seat variant of ST-A with extra fuel tank in place of front cockpit; one built, later converted to ST-A.
Military version of ST-A Special, some with provision for a machine gun; 22 built for various South American air-forces.
Variant of STM for Netherlands East Indies Army and Navy; 95 built.
Variant of STM delivered to China, fitted with a Menasco C4S2 engine of 165 hp; 48 built.
Single-seat variant of the STM-2E with provision for a machine gun, also delivered to China; 2 built.
Variant of STM-2 with interchangeable wheel landing gear or floats for Netherlands East Indies Navy; 13 built.
Experimental conversions, with a Warner Scarab 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.
Variant with new fuselage shape and a Kinner B-5 radial engine of 125 hp; one built.
Variant of ST-3 with a Kinner R-5 radial engine of 160 hp, one built.
Variant of ST-3 manufactured with wooden fuselage; one built.
US military designations
A single ST-A bought by the USAAC for evaluation.
XPT-16 re-engine with Kinner R-440 radial engine of 125 hp.
A total of 15 aircraft similar to the ST-M ordered for service trials.
14 YPT-16s re-engine with Kinner R-440 engine.
Production version of PT-16,
Designation of PT-20s that were re-engine with Kinner R-440 engines.
Military production version of ST-3; 100 built.
Military production version of ST-3KR with Kinner R-540-1 engine, 1,048 built, including PT-22As.
Designation for 25 examples of ST-3KR built for the Royal Netherlands Air Force but not delivered, aircraft subsequently taken by the USAAF.
Aircraft re-engine with Kinner R-540-3 engines, 250 aircraft modified.
Military version of ST-4, ordered for evaluation; five built.