Medium Transport; Low Wing; 2 Turbojet Eng
Communication Breakdown; Confusion; Time Pressure; Workload
ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Procedure
Enroute we received a new clearance from ATC that changed our arrivals. This was expected as is common now for the new IAH RNAV STARs. We were assigned the GUSHR ONE RNAV ARRIVAL starting at MQP VOR. The Captain and I confirmed all the waypoints in the FMS and all the crossing restrictions. We briefed the arrival expecting a 'descend via' clearance as we got a little bit closer. Around MQP area we got a pilots discretion descent to somewhere in the 30's. The Captain started down and as we leveled off they gave us another pilot's discretion descent to FL240. We sat at FL240 for a while and saw that we were becoming close of not being able to make any of the crossing restrictions if ATC assigned them to us. We thought maybe they were changing arrivals or had something else in mind and that was the reason for keeping us so high; instead of just having us descend via the arrival. After a few more minutes ATC tells us to descend via the arrival. This happened at around waypoint DPLAN. So we were at FL240 when we should have been much; much lower. Even the FMS gave us an error saying it would exceed VNAV limitations; which I had never seen before. Even without the FMS I knew we would never make it and immediately told ATC unable and that they gave us the clearance way too late. They then gave us a heading vector off the arrival and descent. We started thinking we were going to just get vectors now all the way in. After we got a little bit lower they then tried to have us go direct to MPORT and descend via the arrival. MPORT was more than a 90 degree left turn for us and it was so close the FMS wanted to auto cycle to the next waypoint. We were also still too high. We had to once again tell ATC this wouldn't work. They then gave us new vectors and new altitudes and were going to vector us all the way into the airport now. A few minutes later we passed abeam GUSHR at 8;000 FT; realizing that there was no way we would have ever made any of the crossing restrictions as ATC wanted to give them to us. The biggest threat here was ATC. Instead of just giving us a 'descend via' clearance right away as we started the arrival; they decided to give us pilot discretion descents and then ultimately forgot about us. Once they decided to give us the proper clearance of 'descend via' for an RNAV arrival; it was too late. We thought we mitigated this threat by saying unable; but as soon as ATC thought we could; they tried to give us the 'descend via' again throwing up another huge threat. ATC should be giving these clearances before you even begin the arrival so you can plan ahead of time and know exactly what is going on. These arrivals were devised and planned to take the workload of ATC; which they did none of. Denver gives you this clearance right away so there is no confusion. There was no behavior that the flight crew could have changed. This is something that ATC needs to change in Houston. The only thing we could have done is possibly asked ATC if they wanted the descent instead of staying up at FL240 like they wanted. But with all these new procedures; we assumed they were going to change something on us; and that is why we hadn't received the 'descend via' clearance.
ZHU issued an air carrier a late DESCEND VIA GUSHR ONE RNAV Arrival clearance descent to IAH and then began issuing vectors when the crew advised unable to meet waypoint altitude constraints.