Brazilian aircraft manufacturer Embraer revealed that, the first prototype of the KC-390 military transport plane has sustained minor damages during flight testing on 12 October.
The incident happened while the aircraft was performing stall speed flight tests, which resulted in aircraft losing altitude due to decreased lift force.
The flight assessed low speed flying qualities with simulated ice shapes installed on wings of the prototype 001. It experienced an event beyond the planned limit for the test point with one of the several configurations tested.
According to reports, the aircraft lost control as an onboard equipment detached free during a maneuver, which suddenly caused change in Center of Gravity (CG) of the aircraft. But the pilots were able to regain the controls.
As being a stall test, the aircraft will lose altitude. According to Flightradar24 the aircraft flying at 20,000 lost more than 8,000 feet (2,400 meters) in altitude before leveling off at around 3,000 feet.
Reports indicate the aircraft was recovered at an altitude around 1000 ft (300 m), as the area its was flying do not have ADS-B transponder coverage below 2,800 ft. The 3000 ft indicated could have been after climbing to a safe altitude after recovery.
The crew applied the recommended recovery procedures and was able to bring the aircraft back to the normal flying angle of attack range but the maneouvre characteristics and duration resulted in a substantial altitude loss and exceeded both airspeed and load factor operating limitations.
The flight was interrupted and crew requested an early return to the base, landing safely at the company’s aerodrome in Gavião Peixoto (SP) where the flight test campaign is being carried out.
After detailed inspections, no damage to the primary aircraft structure was found. Some external fairings and access hatches were damaged and need to be repaired before the aircraft resumes flying.
Embraer said the KC-390 certification schedule is not affected and entry into service is confirmed for 2018 with the delivery of the first production aircraft to the Brazilian Air Force.
Following the incident, Embraer has grounded the aircraft. The two aircraft flight test fleet have accumulated more than 1,300 flight hours, since first flight in 2015.