[3] An L-4J was then modified by converting it into a low wing design with "V" lift struts and it was powered with an 85 hp Continental C-85 four-cylinder horizontally-opposed piston engine with Sensenich two-bladed fixed-pitch propeller.

[5] The improved NU-90A variant was powered with 100 hp Continental O-200 engine with 6 ft (1.8 m)-diameter McCauley metal fixed-pitch propeller.

[1] It retains many of the L-4J's features, although modified, such as its USA-35B airfoil but with the flaps removed, extended length of the ailerons, the split-axle mainwheels which was moved 10 cm forward, and also L-4Js original wing structures.

[5] The wings itself was braced with V-struts from the top section of the fuselage longerons and was set 1° 37’ incidence at the root and 5° dihedral.

Although the aircraft were still in the evaluation stage, eight cadets managed to solo fly after being trained with the three Belalangs.

The Indonesian Army Aviation School at Kalibanteng airfield in Semarang received 5 Belalangs to be used as primary trainers.

[3] As of 2017, a single incomplete Belalang still exist and used as a teaching tool at a vocational high school in Semarang.