One of Embraer’s KC-390 prototypes returned to flight over Brazil on 2 March, after being grounded for several months due to unexpected altitude loss during a stall test flight conducted last October, several flight tracking websites report.

Embraer confirms that the tactical transport involved in last year's mishap has resumed testing. The company’s first production aircraft is expected to enter service with the Brazilian air force’s 11th Wing in Rio de Janeiro later this year: a schedule that Embraer says will not be delayed by the prototype’s stall test incident and subsequent months of unavailability.

The company has two KC-390 prototypes, with the stall test issue having grounded aircraft 001 (PT-ZNF). The other example continued to fly and conduct tests, Embraer says.

KC-390 - Marcio Jumpei

Marcio Jumpei

During the testing incident, the twinjet “experienced an event beyond the planned limit” while conducting a simulated icing test, which took the aircraft beyond its airspeed and load factor operating limitations, the company said last November. The crew was forced to apply recovery procedures and return the aircraft to Embraer’s test base at Gavião Peixoto.

Embraer says the aircraft showed no damage to its primary structure, but some external fairings and access hatches had to be replaced before it could resume testing. The company confirms that aircraft 001's performance envelope has not been changed as a result of the incident.

The KC-390 is designed to be used for troop transport, cargo airlift and air tanker operations. Powered by International Aero Engines V2500 turbofans and with a gross weight of 68,500kg (151,000lb), it is the heaviest aircraft Embraer has manufactured to date.

On order for the Brazilian air force – which will take 28 examples – the KC-390 is an upstart challenger to the Lockheed Martin C-130, which has been in continuous production since 1954 and dominates the tactical airlift market.