Date: 201409
Local time of day: 0601-1200
Location: ATL.Airport, GA
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B ATL
ATC / advisory: TRACON A80
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Second reporter function: Pilot Not Flying; Captain
Anomaly: ATC Issue All Types; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: On arrival into Atlanta from the East Corridor; (East flow into ATL) we planned on an ILS PRM RWY 10. After checking in with ATL Approach Control; we are assigned ILS PRM RWY 8R. In addition to this assignment; we are given a clearance direct GAASS waypoint for the North downwind (which obviously is not in the FMS at this point). The Captain/PM asked for a vector so we could initiate a turn while we reprogram the FMS for the North downwind. We were assigned 'Right turn heading 235 and direct GAASS; when able'. We initiated the turn immediately and reprogrammed/verified the new route in the FMS and went direct GAASS. Less than one minute later ATC queries us about why we had not started our decent. The Captain responded by saying 'We were not given one' and we both confirmed never hearing; responding; or calling out any altitude change. ATC then gave us a clearance to 'descend and maintain one one thousand' and to try to help we expedited our descent for the departures out of ATL. The rest of the flight was uneventful.High task saturation; ATC seems to be unaware of the fact that we can not predict what approach they will give us until Approach Control assigns it. Poor communication on ATC's behalf. If you don't see us start a descent right away; an initial '...please start your descent' would correct this from happening so it isn't a last minute '...why have you not started your descent; I gave you a new altitude 8 miles ago!'I am not sure if this is a company policy issue or if this is an ATC issue. Our policies have us brief an approach as early as possible in flight to mitigate these types of scenarios. Yet; time and time again the clearance given to us when we check in with ATC/Approach Control is not the same as the planned/briefed. This has become the 'norm' and not the exception. And then; an immediate clearance to a waypoint that isn't even in the FMS is given; and had we not asked for a vector; we would have probably been queried about why we had not turn yet.


Second narrative: Checked in with ATL approach and given direct GAASS for ILS PRM 8R. PF had briefed RWY 10 so we asked for an initial heading for GAASS until PF could set up direct GAASS. We were given heading 235 when able GAASS. Just a moment later approach said he needed us to start our descent. I was pretty sure we had not been given the descent to 11000 ft. How could both of us miss setting it and reading the descent back? I said we were given direct GAASS for the ILS PRM 8R. We started our descent to 11000 ft.We were [originally] at 14000 ft with second controller. I should have expected to hear a descent given at the time of check in.


Synopsis: When inbound to ATL; the CRJ700 flight crew was given a new PRM runway assignment and direct to GAASS fix; which weren't associated with their previously briefed approach. As they descended through 14;000 FT; a further clearance to descend to 11;000 FT was either never given or was lost over the runway and arrival changes. ATC quickly asked why they hadn't started down and the issue was resolved.