B737-700
Distraction; Communication Breakdown; Human-Machine Interface; Workload
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew FLC Overrode Automation; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Clearance
Chart Or Publication; Human Factors; Procedure; Weather
We [were] cleared to descend via the HAWKZ RNAV STAR landing south. Halfway through the arrival we asked SEA Approach to deviate 10 degrees right for weather. Approach cleared us for deviation 10 degrees right and instructed us to follow the descent path of the arrival. We asked Approach for a specific hard altitude 'hard' altitude because we were no longer on the arrival; since we were deviating off course. Approach would not give us a specific altitude and cleared us to maintain the descent profile of the arrival. At this time multiple airplanes were requesting a similar deviation because of weather near the arrival and therefore the radios were very busy. At no time was the airplane more than a mile or two to the right of course. After deviating for weather the Approach Controller then cleared us direct to the last fix on the arrival and instructed us to maintain the descent profile of the remainder of the arrival (which included 2-3 additional fixes between us and the last fix on the arrival.) We preceded direct to the last fix but also overlaid the remainder of the arrival over our path to maintain awareness of the arrival and the descent profile. We landed in SEA shortly after. Approach was assigning us a bogus clearance. There is no way to maintain the descent path of an arrival if we are not flying on the arrival path. Once we deviated from the HAWKZ arrival; approach should have issued us a specific altitude to maintain and provided us our descent clearance. We as a crew should have refused to descend via the descent profile and required a specific altitude for further descent.
When weather forced a B737NG flight crew to deviate from the HAWKZ RNAV STAR to SEA they were unable to 'descend in compliance with the descent path of the complex procedure as requested by ATC. When they so advised ATC they were given the same clearance.