B737-800
Flight Crew Last 90 Days 152
Confusion; Situational Awareness; Communication Breakdown
Airspace Violation All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert
Procedure; Human Factors; Chart Or Publication
DEN Approach cleared us on a vector to intercept the ILS 35R final at 8000 FT MSL; and cleared to cross DEANE at 8000 FT and contact Tower. I deleted the crossing restrictions of 9000 FT at DEANE and DRUMM since our clearance was at 8000 FT. We intercepted final at 8000 FT and set 7000 FT in the MCP ALT window which was FAF Altitude. After passing DEANE; PF announced and began descent to 7000 FT MSL. We had not passed DRUMM when DEN Tower stated; 'Low Altitude alert; the MVA is 7500 FT .' We initiated an immediate climb to 7500 FT MSL; passed DRUMM and then resumed the ILS 35R Arrival without further incident.When vectored below a fix required altitude; it would be a good idea to set that altitude as a hard altitude until the earliest fix we can descend from; which in this case was DRUMM. ATC's clearance led me down the path of deleting hard altitude requirements we were already below. DEN Approach Control could have also stated maintain 8000 FT until DRUMM which would have been a better clearance.
A better clearance from Approach would have been helpful. Perhaps; '...maintain 8000 FT till DRUMM; cleared approach'. We still should have stayed at 8000 FT until DRUMM.  My bad.
When they misinterpreted Approach Control's clearance to intercept 'the final approach course at 8;000 FT; cross DEANE at 8;000 FT' as a clearance to fly the DEN ILS 35R approach the flight crew of a B737NG began a descent to the glideslope intercept altitude after passing DRUMM.