The flying prototype of Russia’s Irkut МС-21 narrowbody airliner commenced the second stage of factory tests on September 13 with a two-hour flight.

Flights continue after adjustments to the aircraft’s software and systems based on the results of the first stage of the program, an Irkut representative told Russian Aviation Insider. In particular, strain gauges have been mounted on the airframe to measure structural loads.

The main aim of the second stage is to further test the airliner’s weight, center-of-gravity, speed, and altitude envelopes.

The prototype, which is representative of the МС-21-300 version, first flew in late May 2017. The current series of tests is expected to continue until October, to be followed by certification tests.

As reported earlier, Aviastar-SP, a participant in the MC-21 program, was to begin assembling accessories for the pilot batch of five production airliners in August 2017.

The МС-21-300 is designed to carry 163 to 211 passengers. The prototype is being tested with Pratt & Whitney PW1400G engines. The Russian-made powerplant option, the Aviadvigatel PD-14, will become available later on. Irkut is also planning the МС-21-200 version, which will seat between 132 and 165 passengers.