Dassault Falcon 50, F-HAIR, operated on a check flight from Lyon-Bron to Paris-Le Bourget, France. The first officer was Pilot Flying on the preceding flight to Lyon. He experienced handling problems after selecting emergency braking. During the taxi phase the crew checked the operation of the braking system in normal and emergency modes, but did not find any faults. The first officer remained Pilot Flying for the flight to Paris. While on approach to Le Bourget, the first officer noted that the left main gear anti-skid was inoperative. The captain decided to use emergency braking because of the ineffective anti-skid system. After touchdown the aircraft deviated to the right and the first officer responded by using left rudder. When moving to the left, the pilot attempted to correct using right rudder but the airplane ran off the left side of the runway. The aircraft returned to the runway but the nosegear collapsed. Causes: The accident resulted from the undetected reversal of two hydraulic lines of the emergency braking system following maintenance actions. The following factors contributed to the accident: – The lack of a means to differentiate the two pipes; – Incomplete documentation on technical procedures in the application of Technical Instruction for the preparation and finalization of work for a return to service ; – The doubt expressed by the co-pilot on the handling of the aircraft on the ground that was not taken into account by the captain.