A privately registered Bombardier Challenger 605, was conducting a flight from Palm Beach International Airport, Florida USA (KPBI) to Calgary Intl., AB (CYYC), with three crew members and 10 passengers on board. During the final descent into CYYC, the flight crew selected flaps 20 and immediately received a flaps fail caution message. The decision was made to abandon the approach, and the crew received clearance from ATC to proceed NW of the CYYC airport and troubleshoot the issue. The crew executed the applicable QRH procedure and subsequently received clearance from ATC to proceed with the landing. A flaps 0 landing was then executed. During the landing roll, after ground spoiler and thrust reverser deployment, the nose of the aircraft attained a significant nose high attitude. The rear fuselage of the aircraft struck the runway, and during the recovery, the nose landing gear subsequently impacted the runway. The aircraft taxied clear of the runway and to the intended parking area. Subsequent inspection revealed that the aircraft sustained significant structural damage to the forward fuselage and minor damage to the rear fuselage. There were no injuries. Findings as to causes and contributing factors 1. Moisture entered the flap flexible drive shaft casing, likely through the undetected puncture holes and the drive shaft casing to flap actuator interface, which led to the subsequent corrosion and failure of the inner drive shaft. 2. As the occurrence aircraft’s actual annual utilization was approximately half of that expected by the manufacturer, the calendar time interval between maintenance inspections increased. As a result, the corrosion that developed was not detected because the shaft had not yet reached the 2400 flight-hour maintenance interval. 3. The Challenger 605 flight simulator used for recurrent training did not accurately represent the zero-flap handling characteristics of the aircraft when the thrust reversers are deployed, nor was it required for certification. As a result, the flight crew was inadequately prepared to prevent, or recover from, the nose pitch-up that occurred when the thrust reversers were deployed. 4. The pilot monitoring did not read the cautions included on the flaps fail checklist out loud to the pilot flying during the completion of the Quick Reference Handbook procedure. As a result, information critical to the safe operation of the aircraft was not brought to the pilot flying’s attention. 5. Insufficient pressure was applied to the control column to maintain the nose on the runway while using maximum reverse thrust; as a result, the nose pitched up, the aft fuselage contacted the runway, and the aircraft transitioned to a partial weight-off-wheels state. 6. When the left main wheel left the runway surface and the angle of attack reached 28.9ø, the stick pusher activated and commanded a rapid nose-down pitch input. As a result of this rapid nose-down pitch, the forward section of the aircraft was damaged when the nose wheel contacted the runway.