Poland

The pilot mistakenly retracted the undercarriage at rotation. There was no immediate decision of the pilot to abandon the takeoff procedure when both propellers contacted the runway surface.

The cause of the hydraulic leak and resulting failure was caused by the fracture of a flexible hydraulic hose connecting the brakes system of the right main gear with hydraulic system C. The fracture occurred in the area of a metal band around the tip of the hose. The nature of the crack suggests there was a stress relaxation resulting in material creep. The inner Kevlar lining of the pressure sleeve had signs of abrasions which according to the manufacturer suggests the hose had been repeatedly flexing as result of pressure changes, so that the manufacturer suspects the hose was not installed completely straight.
The hydraulic fluid was found to meet required specifications.
Following comparison of the alternate landing gear system with another aircraft with the circuit breaker C829 in both off and on positions, it was found that the alternate landing gear sequence would extend the gear with the circuit breaker in the on position, however, would not operate if the circuit breaker was in the off position.
The actuator was found operative.
The C829 circuit breaker was confirmed to not be indicated on the engine indications and crew alerting system (EICAS) and was not recorded by the black boxes.
Documentation (checklists) would turn attention towards that circuit breaker only if systems protected by the circuit breaker needed to be activated.
The checklist for loss of pressure in the central hydraulic system did not refer to the circuit breaker C829 leaving the crew without guidance if the first item to activate the alternate gear extension switch did not illuminate the "gear down" lights. The checklist did not include the possibility of the alternate gear extension failing at all.
The checklist for gear disagree also did not include the possibility of a failed alternate gear extension.
There was no checklist available at all in case of both primary and alternate gear extension had failed, e.g. a all gear up landing checklist.
Based on current technical evidence the investigation thus may conclude that the cause of the belly landing was the circuit breaker C829 in the off position. A separate issue will be to find out why the circuit breaker was off.

Source: AvHerald

Ground collision with a baggage vehicle.

The pilot in command was under instruction and was joining the circle to perform the final approach with one engine inoperative. He selected full flaps on final, which is against the procedure published in the AFM that requires a maximum flaps of 25°. It was also determined that the pilot in command failed to maintain directional control when power was added to attempt a go around. On his part, the flight instructor failed to take over the control of the aircraft.