A319
Flight Crew Last 90 Days 100; Flight Crew Total 10000; Flight Crew Type 8000
Workload; Human-Machine Interface; Confusion; Communication Breakdown; Distraction
Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Aircraft; Human Factors
This was the first flight of a four day trip. It is ironic that the Captain and I had a lengthy discussion about the threat of complacency just prior to this flight. KEPEC arrival LAS; assigned to cross CLARR at 13;000 FT; 210 KTS. Altitude of 13;000 FT captured before CLARR and all altitude constraints checked prior to the arrival. Assigned to descend via KEPEC arrival; I set 8;000 FT as the lowest altitude on the descent. After passing CLARR the Captain initiated a managed descent; a magenta 11;000 FT altitude constraint was displayed and DESC was boxed as the descent mode. Upon descent mode initiation; the aircraft started descending out of 13;000 FT. All appeared normal. Unfortunately; there is a 13;000 FT altitude constraint at KEPEC; approximately 20 miles or so from CLARR; we should have been in level flight. I didn't determine that we should be in level flight; not descending; until we were already at 11;800 FT or so. I had my range scale in either 10 or 20 NM (to de-clutter the upcoming restraints) and didn't see the 13;000 FT restriction at KEPEC initially; although I should have known having just verified the altitude constraints. It took me a bit to recheck the approach plate; then the map display and verbalize to the pilot flying that we were below our KEPEC altitude. L30 Approach queried us; then gave us direct to IPUMY (which has an 11;000 FT constraint) and we proceeded with the approach and landing. As the pilot not flying; I should have caught the descent much sooner. I was lured into a flight myth versus flight reality by seemingly normal managed descent indications. I didn't cross check fast enough; I took too much time trying to reconcile what looked OK as a managed descent with the approach criteria. I admit I am puzzled by the aircraft's managed descent below a clearly indicated altitude constraint on the map display and with all seemingly normal managed descent indications. We do this procedure many times during any given trip. From a systems perspective; I really have no answers as to why our managed descent deviation occurred; although I'm sure there is a simple explanation.
The First Officer and I had a lengthy preflight briefing concerning complacency. We have flown together over a hundred times over the last decade or more without incident. I was excited to see that I was flying with him because he is an excellent pilot.On the KEPEC arrival into Las Vegas; we were cleared to cross CLARR at 210 KTS and 13;000 FT. At 13;000; we were cleared to descend via the KEPEC arrival. We set 8;000 for the lowest altitude on the arrival. The pilot flying; the Captain; pushed the altitude knob 'in' to enter the DESC mode for the RNAV arrival. Passing 11;700 FT the First Officer noticed we were descending to 11;000 FT with ALT CNST* displayed. KEPEC had an altitude crossing of 13;000 FT. IPUMY was the next fix after KEPEC and the altitude was 11;000. We spoke with ATC and they gave us direct IPUMY. The pilot flying failed to confirm that the aircraft stayed at 13;000 FT after selecting the DESC mode by pushing the altitude knob in.
An A319 crew monitoring the FMGC in the DESC Mode failed to see that the aircraft did not remain level to the KEPEC 13;000 FT constraint even though the system was in the Managed Descent Mode with next constraint illuminated magenta.