Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 2900; Flight Crew Type 1300
Distraction; Situational Awareness; Time Pressure; Workload; Confusion
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural FAR
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Procedure; Company Policy
During [descent] to SFO the flight descended below an assigned altitude at a fix. During this flight I was the pilot flying and I was assisted by first officer as pilot monitoring. The conditions of the flight were daylight; clear sky; moderate wind from the west. The SFO airport was landing and departing from 28L and 28R. During the initial descent from FL280 we received ATIS and planned to execute the SERFR1 arrival followed by the Tip Toe Visual 28L. Initially we were cleared to descend from FL280 to FL240. We began the descent and were cleared to descend via the SERFR1 arrival; runway 28 transition. The bottom altitude is 4000 feet at the transition fix of MENLO per the Arrival. However the FMS was loaded to reflect an Altitude of 5000 feet at MENLO per the Tip Toe Visual approach minimum altitude. While descending our instructions were changed to Descend VIA SERFR1 except maintain 10;000. At this point we were told to expect Tip Toe visual 28L. All FMS entries were completed prior to this point and we identified that we would be continuing as briefed. Descending through 11;000 feet we were told to Descend and maintain 8000 feet. Quickly after we were instructed to expedite descent. Green FLCH was selected via the Guidance panel and speed brakes were deployed to increase the rate of descent. ATC instructed to continue descent maintain 6000 Feet; increase rate of descent. We gave the best rate down via Green FLCH and speed brakes. At 7000 feet approximately we were cleared to cross MENLO at 4000 feet (the FMS was loaded at 5000 feet per instructions that we would be cleared TIP TOE VISUAL 28L) and then Cleared for the Tip toe Visual 28L. However it was only seconds later that ATC amended the instruction yet again to add another altitude. They instructed us to cross 9 miles from the runway at 3100 feet. The Altitudes loaded into the FMS were currently; MENLO 5000/230 Knots First bridge 2500 At or above and final bridge 1800 feet. The first officer quickly read back the instruction and began trying to input a distance into the FMS so that we could identify where 9 miles would be. While he was loading the FMS and we were trying to determine the best way to identify this point the aircraft descended below 4000 feet. Because we were expediting the descent the altitude deviation was noticed immediately before 4000 feet but we were unable to arrest the descent rate until 3700 feet. Power was added and the auto pilot removed to climb the aircraft to 4000 feet. ATC was notified immediately that we were returning to our assigned altitude. A TCAS traffic advisory was presented for an aircraft at 2500 feet and 10:00 from our aircraft position. We saw traffic; were instructed to continue and returned to 4000 feet as soon as possible. I believe the aircraft crossed the MENLO intersection at 4000 feet but due to workload and task saturation I can't confirm it. The first officer also quickly finished locating the 9DME point from the runway. We Crossed this point at 3100 feet and continued to descend across the bridges at our assigned altitudes. I understand that this report will be complicated to read due to the incredible amount of altitude assignments and changes that were given. I attribute the situation that we encountered to this directly. The automation was operating correctly and I as pilot flying did fail to select VNAV to support us in our descent across the MENLO interception. However; all of these complicated instructions were given approximately 4 miles from the MENLO fix. At the assigned aircraft speed it was nearly impossible to load the FMS correctly in that short amount of time. In addition first officer did an excellent job monitoring my flying and trying to input information into the FMS; However I needed to look away to confirm his entries. I also needed to pay special attention to the entry as the first officer is still within his first 100 hours in the aircraft. Although he did an excellent job; I needed to back him up with his entry as well. Due to the short period of time; the aircraft speed and the instruction to expedite the descent; I failed to cross the MENLO intersection at the assigned altitude. In a time critical situation our communication was good. We also did our best to back each other up in our decisions. I feel like as a flight crew we did well to work together to recover our altitude and fix the problem that we encountered due to incorrect FGP usage while trying to comply with company policy. Although I feel that we failed to follow company SOP by having two pilots' heads down at the same critical moment; I feel that we are also instructed to confirm FMS entries and confirm navigation plans. I know that having two pilots heads down directly lead to our failure in allowing the aircraft to descend beyond our assigned crossing altitude. However I feel that not verifying the entire into the FMS is just as dangerous. I don't know that we acted incorrectly or actually violated a company SOP; however I know the time we had was not adequate to confirm our entries as well as keep one pilot heads up. I also feel that the charting procedures for SFO airport and particularly the SERFR1 arrival and TIP TOE VISUAL 28L should be reviewed. This is a common clearance and procedure used in SFO. However the altitudes for the procedures conflict between the two charts and the FMS at the MENLO intersection. This is a HIGH WORKLOAD environment that is extremely saturated with aircraft. I also feel that SFO approach exercised extremely poor air traffic management. Completing abnormal FMS entries during a turn to final is a poor time for ATC to assign a non-routine clearance. In addition the constant changing of descent clearances makes arriving into SFO a constant challenge. SFO is nearly impossible to plan for because the clearances are changed constantly; expedite is often used and regularly you're told to expect the charted Visual approach and then cleared for the ILS during a turn to final. This is common practice in SFO. In our particular situation; the weather was beautiful and this increased general aviation traffic. The increase and locations of these VFR targets makes the approach control give the crossing restrictions in a very complicated and time critical location. After this approach to 28L we were then required to side step to another runway 28R. In such a close proximity to all these other things it is very complicated to make complicated FMS entries which are required to navigate to lateral points with vertical restrictions.
Automation setup: auto pilot on; auto throttle on; coupled PIC side. On arrival to SFO; NorCal approach cleared us to descend and maintain FL240. The pilot flying selected FL240 in the preselect window; verified altitude restrictions as pre-loaded in the FMS and commanded a descend now VNAV descent from the autopilot. SOP checklist usage and cabin announcements accomplished at appropriate time. Further clearance to descend via the SERFR1 Arrival into SFO was received. The bottom altitude of 4000 feet was selected in the altitude preselect and verified. Continuing the descent we were re cleared to descend via except maintain 10;000 feet after EPICK. 10;000 feet was selected in the altitude preselect. Then clearance was received to expedite descent and maintain 8;000 feet. FLCH green guidance was commanded with usage of speed brakes and 8;000 feet was selected in the altitude preselect. Then further clearance was received to descend maintain 6;000 feet. 6;000 feet was selected in the altitude preselect. Then further clearance was received to descend via and cleared the tiptoe visual approach to 28L cross MENLO 4;000; cross the SFO 9DME at or above 3;100 feet. 1;800 feet set in the altitude preselect with FLCH green guidance still engaged. Descending through 4;000 feet 4NM prior MENLO the First Officer verbalized the pending deviation and manipulated the flight controls through the use of the TCS button and the yolk to arrest the descent. The PIC responded immediately with a verbal confirmation of the deviation and manipulation of the flight control through use of the auto pilot disconnect button and the yolk. The altitude deviation was 300 feet down to 3700 feet before the descent could be arrested. A Traffic Advisory was sounded where a TCAS target was displayed 10 o'clock relative to aircraft position 2;500 feet below. The First Officer notified ATC of the deviation and notified again when return to 4;000 feet was accomplished. Task saturation; mismanagement of automation and a failure to crosscheck instrumentation left the aircraft in an undesirable state. I do believe a flaw of the compass procedures of setting the absolute bottom of the approach is flawed because it would only keep the aircraft on a proper descent path in magenta FMS vertical guidance. A better method would be to set the hard altitude restrictions in the altitude preselect and readjust the altitude selector once the restrictions are assured to be met.
A flight crew cleared on the SFO SERFR ONE RNAV with multiple set down altitudes managed in Flight Level Change. When cleared to 3;100 feet; the MCP was set but the flight descended below the MENLO 4;000 foot constraint resulting in an airborne conflict with lower crossing traffic.