DC-9 10
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew Landed As Precaution
Aircraft
After takeoff I noticed the cabin pressure indicator was at zero. After confirming with the PIC he took over the flight controls and radios as I ran the checklist. We maintained an altitude below 10;000 MSL. The checklist was ineffective at regaining pressurization. After discussion between the PIC; Operations; Chief Pilot; ATC and I we elected as a crew to divert and we landed normally. After landing we noticed nothing out of the ordinary on the exterior or interior of the aircraft. While flying we noticed that as speed increased; a 'rumble' in the floor behind us became louder. We both agreed that the air stair door was likely opened. There was no indication of any open doors or any other irregularity from the annunciator lights.
DC9 First Officer experiences a pressurization anomaly during initial climb and the aircraft is leveled below 10;000 FT to troubleshoot. A rumbling is felt and thought to be the result of the forward air stair door being open but no annunciator lights are illuminated and the aircraft cannot be pressurized. Flight diverts to a suitable airport.