Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Multiengine
Flight Crew Last 90 Days 220; Flight Crew Total 15350; Flight Crew Type 11250
Communication Breakdown; Confusion; Distraction; Human-Machine Interface; Situational Awareness; Workload
Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC Overrode Automation; Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Human Factors; Aircraft
Flight crew conducted RNAV STAR verification prior to descent; all constraints in database matched those charted; and no anomalies noted. ARTCC issued vectors for spacing during step-down (approximately FL290). First Officer left frequency to make descent PA. Upon First Officer's return to frequency; Captain was in the process of reading back the clearance to descend to FL240 and proceed direct to an intermediate fix on the arrival; which had a crossing window between FL220 and FL260. ARTCC issued 'descend via' clearance for the arrival as; '[Call Sign]; after [the subsequent fix]; descend via the [STAR].' First Officer read back clearance verbatim. Captain set the floor altitude of the arrival and managed the descent. First Officer queried Captain as to whether the descent should be initiated before the subsequent fix. Captain sarcastically said; 'Well; we have to start down now to make the constraints further down the road; right?' First Officer attempted to query ATC regarding the clearance; but radio chatter prevented a timely call. First Officer went 'heads-down' to compare the charted constraints with those shown on the Navigation Display to find why the FMS had initiated such a steep descent as though the aircraft were very high on profile (which simple observation did not support). Captain said; 'Hey; this is supposed to be above 220!' First Officer redirected attention to Primary Flight Display (PFD) to see aircraft descending through FL220 a couple miles before the fix. Captain abruptly set vertical speed to zero to arrest descent. Captain then noted that the floor of the next fix was also FL220; and that the FMS software would have the aircraft crossing about 3000 FT low. First Officer scrolled through the rest of the arrival on the MCDU and found that many of the fixes showed projected crossings 1;000 to 3;000 FT beneath their charted floors; which was not the case during the initial STAR verification. It is unclear what caused the problem because neither pilot noticed when the FMS descent profile changed. Captain flew the remaining step-downs manually to prevent deviations. Multiple vectors and step-downs along with heavy radio chatter prior to the 'descend via' clearance probably inhibited situational awareness to some extent. The clearance was unclear and inconsistent with what pilots are taught to expect; a concise clearance would have been either; '[Call Sign]; maintain FL240 until passing [the subsequent fix]; then descend via the [STAR]; or; '[Call Sign]; cross [the subsequent fix] at or above FL220; then descend via the [STAR].' The most significant reason the First Officer did not recognize the impending issue upon descent was the Captain's derisive attitude regarding the descent clearance and his unilateral decision to initiate the descent without ATC clarification. These factors compelled the First Officer (PNF) to divert his attention away from monitoring the flight path. Besides better coding in FMS software; which is a persistent issue with RNAV descent profiles ATC clearance should be more concise and better crew coordination on the part of the Captain.
A narrow body Airbus First Officer reported that after verifying the IVANE RNAV crossing restrictions the flight received spacing vectors then returned to the arrival where he discovered subsequent crossing restrictions were as much as 3;000 FT below the charted constraints. ATC Descend Via phraseology standardization was also questioned.