B737 Next Generation Undifferentiated
Flight Crew Last 90 Days 372
Distraction; Human-Machine Interface; Situational Awareness; Confusion
Aircraft Equipment Problem Less Severe; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Aircraft
We were cleared direct SAILZ and to descend and maintain 3;000 FT. We were LNAV/VNAV established and had 3;000 FT set in Altitude window and 3;000 FT restriction set in CDU for SAILZ. We initiated a descent to 3;000 FT and the pilot not flying verified it. We did not notice the aircraft level off at 3;300 FT. ATC queried our altitude we admitted 3;300 FT and descended to 3;000 FT and were established prior to the fix. After landing; the Captain of another flight came over to us. He was following us in an -800 with the same clearance and reported to us his aircraft level led off at 3;300 FT too. We suspect an -800 software issue.
The reporter stated they were flying the PANGG 1 RNAV arrival and that the aircraft was level; (forgot what altitude) with LNAV/VNAV engaged. When the descent to 3;000 FT was issued; he simply selected ALT INTV to initiate the descent. He was not directly looking at the FMA during the level off but does remember when ATC called about the 3;300 FT level off altitude; the FMA indicated ALT HLD and they were level.
[Report narrative contained no additional information.]
After selecting ALT INTV to initiate a descent to the MDW PANGG1 RNAV SAILZ waypoint; a B737-800 leveled at 3;300 FT with the FMA indicating ALT HLD but 3;000 FT set in both the MCP and FMC. ATC alerted the crew about the error.