B757 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 180; Flight Crew Total 19100; Flight Crew Type 2550
Human-Machine Interface; Distraction; Confusion; Situational Awareness; Workload; Time Pressure
ATC Issue All Types; Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Other / Unknown
Chart Or Publication; Procedure; Human Factors; Company Policy
The new RNAV STAR procedures are a significant detriment to safety; passenger comfort; on time performance; and efficiency. Additionally; from a Human Factor's perspective they increase the threats faced on every flight. Until they can be corrected; they should not be flown by our company's flight crews. The arrivals compromise our four Flight Operations Priorities in the following ways. 1) Safety: Both pilots spend the vast majority of their time ensuring compliance with the crossing restrictions. Due to time constraints other important duties are completely ignored; with traffic watch at the top of this list. Both pilots MUST continually monitor the FMA to insure it remains in or; as necessary; is returned to VNAV PTH to insure compliance with crossing altitude and/or airspeed restrictions. Large altimeter changes make many restrictions nearly impossible. The technology of the FMC does not allow programming altimeter setting information. This leads to large path deviations when the altimeter varies from 29.92. The B757 fleet has a specific limitation when leveling off within 2;000 FT after changing altimeter setting from QNE to QNH; or QNH to QNE; 'DO NOT use VNAV to execute the level off if QNH is less than 29.70.' There are several approach constraints that legally can't be flown in VNAV to DEN with such a low altimeter setting. The B757 FMC eliminates restrictions that are at or below the cruise altitude. Hence; even previously briefed approaches are subject to errors if the aircraft climbs due to turbulence; or if an intersection had a speed constraint when the cruise altitude was changed. This is compounded by not having speed constraints depicted on the ND [moving map Nav Display]. Cross checking the ND and the Approach Plate is required; regardless of the effort to brief in advance. Since arrivals have many restrictions; large amounts of time are spent in this process. Denver Approach Control frequently issues speed changes on the arrivals. This cannot be anticipated or planned and is compounded significantly when done several miles from a restriction with a 'top side' altitude constraint. Per SOP; this requires the pilot not flying to research and reset the MCP altitude; wait for the pilot flying to confirm and point to the most restrictive altitude as VNAV PTH reverts to VNAV SPD; and the pilot not flying hurriedly tries to change the FMC in an effort to return to VNAV PTH. All this while the pilot flying usually disconnects the autopilot; and extends the speed brakes in an effort to make the 'top side' restriction. This same process happens when Approach Control issues a runway change [but with an even greater increase in workload] which includes: the gathering of the new approach plate; tuning frequencies; checking performance; and re briefing; all while the procedures of the above bullets are being followed. This is happening with intersections that are as little as seven miles apart; while traveling at 5 miles per minute; and while VNAV has not caught up to display [the new] VNAV PTH. 2) Passenger Comfort: The use of Speed Brakes (including full application) is required multiple times on most arrivals. This is very uncomfortable for passengers and is often accompanied on the same arrivals with major power additions required at different constrained fixes. VNAV PTH can be quite aggressive; when passing a fix where the next segment requires a steep descent angle. In addition to the B757 fleet; I have; as a jump seat observer on the A-320; noted that the attitude changes at different segments were quite severe. On several recent arrivals; the autopilot had to be disconnected; full speed brakes extended and an aggressive level off accomplished in order to meet a restriction more than 30 miles from the airport. 3) On Time Performance: The arrivals don't take into account traffic or the actual runway in use. Slowing; to 250 KTS when operating behind schedule is of concern. The speed restriction at SAYGE Intersection when landing to the North; for instance; seems unreasonable. 4) Efficiency: The arrivals require extensive; unprecedented use of Speed Brakes. This is not just at DEN. IAD; DCA; and PHX all require significant speed brake usage. Power increases are often required on arrivals alternating with speed brake extension. Altitudes are much lower than required for a power off descent to the airport. Crossing windows are too tight. Speeds as slow as 210 KTS on the arrivals can require the use of flaps far from the airport. On the B757 fleet the manual advises 'When multiple constraints are entered; the FMC may construct straight line vertical path segments where an idle descent path would be inappropriate. If fuel is the number one cost for our airline; how can consuming more for the same segment be justified? In addition to these concerns the new arrivals compromise the threat and error section of our FOM. The goal of the CRM enhancement program remains singularly focused; to maximize flight safety by minimizing incidents and accidents caused by human factors. Our training's 'ALERT' words are frequently used on these complex arrivals. Each restriction brings its individual 'ALERT' and multiple restrictions increase the 'Alert' level to an uncomfortable state. Safety is definitely compromised as previously reported. Recently; a DEN Controller issued a speed reduction so close to an intersection I had to reply 'unable.' Such judgments shouldn't have to be made on a routine basis. Our FOM advises that threats are encountered; on average; three times per flight. Realistically; each waypoint with a restriction is a threat. The threat becomes more severe if a 'top side' altitude is added; and even more severe if a speed restriction; altimeter change or runway change is thrown in. Each procedural or ATC directed restriction occurs outside the pilots' influence and increases operational complexity in that it requires greater crewmember attention to maintain safety margins. While such threats begin as anticipated and are programmed in advance; they typically revert to unanticipated with each speed or runway change. The FOM advises that effective strategies include preparation and adhering to SOP. These procedures actually lead to increased threats as the consequent reversion to manual flight and the accompanying loss of VNAV PTH only increases workload and flight crew distraction.
A B757 Captain discussed the impact of the new OPD (Optimized Profile Descent) RNAV STARs on flight crew workload; distraction; flight path management and the consequent degradation in operational safety that results. An important facet not specifically addressed in prior similar reports is the effect of company SOPs that require modification of VNAV Path operations under certain conditions.