Commercial Fixed Wing
Flight Crew Last 90 Days 120; Flight Crew Total 9500; Flight Crew Type 4500
Distraction; Fatigue; Human-Machine Interface; Situational Awareness; Workload
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Procedure; Human Factors; Chart Or Publication; Aircraft
We were level at 37;000 FT and given a descent to cross BRNDN at FL270. This was set into the altitude window and put into the FMC and VNAV PATH was annunciated. Just prior to the top of descent; ATC asked us if we would like a 'descend via' clearance or altitude restrictions for the GIBBZ RNAV STAR into IAD. The Captain (pilot flying) answered 'descend via'. ATC then issued the clearance 'after BRNDN you are cleared to descend via the GIBBZ arrival; except delete speed restrictions'. The Captain started to change the descent speeds in the FMS; but soon realized it would involve quite a lot of typing with high workload. So we left the speeds as they were. During this time; we started our descent to BRNDN; but then realized that the FMC had reverted to VNAV SPEED and that we were now going to be quite high. The Captain deployed the speed brakes to catch the path - which he eventually did at around FL300. At that point; with 3;000 FT to go for our restriction; the Captain stowed the speed brake; however; the aircraft was descending at such a great rate that the aircraft started to pitch up so as to go above the path again. We realized that we weren't going to make the restriction of FL270 and I advised ATC. The Controller said; 'No problem; - just cross BRNDN at 29;000 FT - which we did. I am sure that a factor in not catching the deviation sooner was pilot fatigue as it was past midnight for us and we had been on duty for almost 9 hours.
The flight crew of an FMS equipped Boeing jet enroute to IAD -- cleared direct to cross BRNDN at FL270 -- was further cleared to 'descend via the GIBBZ RNAV STAR; except delete speed restrictions.' When the crew got involved in deleting the waypoint speed restrictions they failed to note the jet had not initiated the descent for the BRNDN crossing and were; ultimately; unable to comply. ATC re-cleared them to cross at FL290.