B737-700
Flight Crew Last 90 Days 166
Training / Qualification; Situational Awareness; Human-Machine Interface; Communication Breakdown
Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Aircraft; Human Factors
We had the FMC programmed with the correct altitudes for the MOTIF 4 Arrival into MDW. We were given our initial descent from FL390 to FL330. During the descent; we were given a crossing restriction of 50 west of BFD at FL240. I put FL240 in the MCP and programmed the crossing restriction in the FMC. The aircraft was in a 1000 fpm descent as we were still below the path. At FL280 Chicago Center called and asked where we were. We responded FL280 with the restriction of FL240 50 west of BFD. I then noticed that we had left VNAV PATH and had arrived at the restriction of 50 west of BFD 4;000 FT high.
VNAV must have gone to Speed and we did not catch the change.
After receiving a crossing clearance 50W of BDF at FL240; the flight crew of a B737-700 failed to monitor autoflight performance and crossed at FL280.