A320
Flight Crew Flight Engineer; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Total 15000; Flight Crew Type 2000
Time Pressure; Human-Machine Interface; Situational Awareness; Training / Qualification; Confusion; Communication Breakdown
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance
Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Human Factors
This was a flight to LAS. Enroute to PGS ATC cleared us to FL260 and assigned us 280 KIAS. After we leveled off I re-cruised us at FL260. Our planned Cost Index was 36 which calculated a managed descent speed of 282 KIAS. However I had selected 280 on the FCU. East of PGS ATC cleared us to descend via the TYSSN THREE RNAV arrival for a visual approach to Runway 25L. I dialed in 8;000 to meet the restriction at PRINO. Both the First Officer and I had triple checked all the altitude constraints on the arrival; and we both had the constraints pb pushed. PGS has an 'at or above FL200' constraint and CEJAY has an 'at or below FL190' constraint. With a top of descent arrow displayed about halfway between our position and PGS; I engaged managed descent. I calculated we needed 21 miles to get below FL190 over CEJAY from FL260. PGS to CEJAY is 19 miles so I felt safe. I engaged managed descent; with the airplane starting a nominal 900 FPM descent; still in selected speed of 280. I selected the PROG (Progress) page on the MCDU and it showed I was approximately 2;400 FT low on the path but slowly decreasing deviation. The Descent Path Indicator (donut) on the Primary Flight Display (PFD) was at the top of the scale but moving down slowly. I felt very confident (not complacent) that we could meet all constraints without any problem. I was expecting a slower than normal descent since I had started down prior to the computed Top of Descent and we had a roughly direct headwind of 60 plus KTS. Prior to reaching PGS my very sharp First Officer remarked that we had an amber missed constraint circle around CEJAY on the Nav Display (ND). I acknowledged his concern; noted the PROG page showed we were still slightly low on the path with the donut slightly above center. In my mind we were intercepting the path from below. I did briefly check the VERT REV page for CEJAY (on the MCDU) and made sure it showed ALT CSTR -190. But for the life of me I did not think to cross check for an ALT ERROR. My mental math told me I had 19 miles to lose a bit over 5;000 FT. The First Officer again questioned me about the amber missed constraint circle. We were now past PGS still descending at approximately 1;000 FPM; but the donut was centered and the PROG page showed we were on the path. Not once did I think to check the FLT PLAN page and read the altitude over CEJAY. I was trying to come up with an answer as to why I was not getting a MORE DRAG message in the Flight Management Annunciator (FMA) since we had crossed one way point with a constraint. Or why I did not have a vertical discontinuity with a TOO STEEP PATH AHEAD message in the MCDU scratch pad. I became preoccupied with trying to diagnose the conflicting information between my Primary Flight Display (PFD) and my Nav Display (ND). I failed to recheck my mental math or aggressively correct our flight path. I erred in not advising ATC of my mistake. ATC did not mention my mistake. We crossed CEJAY in excess of 1;500 FT high. The First Officer reported he saw FL207 as we crossed. The MCDU showed FL209. At this point I assessed that the airplane would not meet the next restriction 22 miles ahead at KADDY. I disconnected the autopilot and selected full speedbrakes in order to cross KADDY at 250 KIAS and 12;000 FT. About 5 miles prior to KADDY at 12;000 FT and 250 KIAS I re-engaged the autopilot and managed descent. The rest of the profile from KADDY to PRINO was uneventful. PREVENTIVE MEASURES My First Officer deserves a great deal of credit for voicing his concerns about the amber missed constraints circle on the ND. We were anything but complacent. I was mentally scrambling trying to sort out conflicting information and determine a possible input error while thinking any moment the airplane is going to lower the nose and pick up the descent rate. For the life of me I cannot figure out what I did incorrectly.
An A320 Captain on the LAS TYSSN THREE RNAV calculated his descent constraint compliance incorrectly and failed to meet one of the constraints before realizing his error even though his First Officer was cautioning about the error.