The ARJ21-700 regional jet has made new flight tests following some design optimisation of the aircraft, says Comac.

These include crosswind tests, testing of an upgraded flight control system software, as well as an evaluation of the VHF antenna’s vibration during flight.

The Chinese manufacturer says the aircraft has since successfully completed crosswind tests, which took five rounds over 13 days.

It adds that the various tests were conducted concurrently, greatly improving utilisation of resources. Previously, only a single module was done each time.

Aircraft 103 spent 25 days making the tests at Dongying and Xilinhot airports. The aircraft has since returned to Shanghai.

Last September, Comac told FlightGlobal that the ARJ21 still needs to be optimised in areas including reducing cabin noise, simplify the aircraft’s warning systems, resolving a door pressure issue as well as to ensure that the aircraft is safe for operations even in heavy rain.

Comac is targeting for these changes to be completed by the end of 2017, thereafter it will work to upgrade the aircraft’s systems and functions, and reduce its weight.

The ARJ21 received type certification from the Civil Aviation Administration of China in December 2015, but has yet to receive a production certificate. Sources tell FlightGlobal that the regulator has given Comac a list of seven or eight improvements it must make to the jet before it will provide a production certificate for the type.

Flight Fleets Analyzer shows that Comac has delivered three ARJ21 to launch customer Chengdu Airlines.