Mitsubishi Aircraft is reviewing the MRJ regional jet's flight test plans, and estimates that the programme will now require around 500 extra flight hours and up to two additional aircraft to achieve certification.

Executive chief engineer Nobuo Kishi says this is due to necessary design changes, and says that the four flight test prototypes have so far logged 660 flight hours, both in Japan and at its Moses Lake flight test centre in the US. Its fifth flight test aircraft is still in final assembly in Nagoya.

"We had many achievements and successful results during the flight tests especially to the aircraft's structure and aerodynamics. For example in flutter tests, load surveys, stall handling characteristics. We were also able to do subsystem verification," he tells FlightGlobal in an interview at the manufacturer's headquarters in Nagoya.

The aircraft has also conducted natural icing, cold weather tests, and ground experiments such as initial smoke penetration in the cabin.

Kishi says no issues have surfaced concerning the aircraft structure, but that there is a need to tune the aircraft's flight control software, and to change some of the air management system's characteristics in the cabin and cockpit.

In January, Mitsubishi announced a two-year delay to the first delivery of the MRJ90 citing the need to relocate some components in the aircraft's avionics bay and to move wiring to meet certification requirements.

With the design change, the chief engineer expects the need for either one or two additional aircraft, with the changes incorporated, to join the flight test programme. The original plan was for 2,500 flight hours, and Kishi now expects it to be "less than 3,000 hours".

He adds that regardless of the design change, the majority of the 660 flight hours logged thus far are valid for certification of the structures and aerodynamics of the jet. Some tests related to the changed areas will however need to be repeated.

Asked if these additional flight test aircraft will be delivered to customers, Kishi says this "depends on the mindset of the customers".

"There are some small differences between production aircraft and test aircraft, so it depends on the airlines. On a contract viewpoint, there needs to be some discussions. Now I have to decide on the number of new aircraft we need for flight tests and after that the sales and marketing team will discuss with the airlines."

Mitsubishi is using five flight test and two ground test aircraft for MRJ certification. Delivery of the first aircraft to launch customer All Nippon Airways is now set for mid-2020.

Source: Cirium Dashboard