Shortly after the L-39NG training version certification, an important initial step in the preparation of its armed version has been completed. A series of L-39NG tests took place in the low-speed wind tunnel of the Czech Aerospace Research Centre in Prague (VZLU), this time the tests were focused on the ability of the aircraft to carry various weapon systems.

"In cooperation with the VZLU, we have completed the data collection phase from the wind tunnel before the aircraft will be converted to the armed version and before the flight tests will begin next year. Our goal was to experimentally verify the expected deviations of aerodynamic performance that might be different from the training version," said the head of the L-39NG program Vojtech Labuda from Aero Vodochody. For the needs of measurement, a model of the aircraft was 3D printed using the scale of 1:6.6. The model was subsequently measured using six-component internal strain gauge balance in a low-speed wind tunnel (wind tunnel measuring space has a diameter of three meters).

At first, measurements on the aircraft without pods took place, and then the aircraft with different types of pods, weapons, flap settings and different types of wing ends was measured. All weapon models were also made by 3D printing.

The L-39NG aircraft has five pods for carrying a wide range of weapons, starting with a machine gun calibre 12.7 millimetres or cannons calibre 20 millimetres, bombs up to 250 kilograms, unguided air-to-ground missiles or air-to-air missiles. The integration of laser guidance of weapons is also in consideration.

Before the flight tests, it was necessary to verify the effect on flight characteristics and performance by tests in the wind tunnel. During the measurements, the influence of the angle of attack and the angle of sideslip on the aerodynamic characteristics of the aircraft with different variants of weapons and settings of the flaps was investigated.

In addition to static measurements, which determine the forces and momentum strengths on the aircraft, dynamic measurements were also performed. This determines the aerodynamic damping for the flying qualities purposes.

"In a half a year, we have performed more than 200 measurements, in 30 different configurations, from a clean aircraft to a fully equipped aircraft with tilted flaps. During these measurements, it turned out that the aerodynamic model is fully capable of carrying a wide range of weapons in various configurations," said Pavel Hospodar from VZLU. The measured data will be used for calculations of flight performance.