Citation X (C750)
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Aircraft
During descent we went 400 FT below a crossing altitude. The pilot flying caught the error as it was happening; disconnected the autopilot; and returned to the assigned altitude. At about the same time; ATC called to let us know that he noticed and let us know that there was no traffic/conflict noted. Background: we had loaded and double checked the altitudes in the FMS and were using the VNAV function. I had just put in the runway in use and was in the process of checking the FMS/IPAD to confirm the altitudes again when the error occurred. Upon further checking; we found that all the crossing altitudes (even the hard programmed ones) had been dropped from the FMS.
On the JAIKE THREE arrival I was the flying pilot. We check the FMS 3 times and all altitudes were correct for the arrival. Runway was selected at Morristown; New Jersey. FMS drop all altitudes for the arrival after JAIKE and started a gradual descent with auto pilot on with VNAV engage. We went from 13;000 to 12;600 when I saw the descent. Turn the autopilot off and went back to 13;000. ATC saw it and call to make sure we knew to stay at 13;000. We corrected and reprogram the FMS with correct altitudes again. No conflict.
Citation X flight crew descended below assigned crossing altitude.