Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 236; Flight Crew Type 14895
Confusion; Communication Breakdown
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings; Procedure; Human Factors
During our visual approach to Runway 04 in AMA; the Approach Controller directed us to 'remain at 5;300 or above until established on final.' The reason given was to ensure separation from traffic at TDW airport (north of PANDE) since AMA Approach's primary radar was down and they were using secondary Center radar with no Mode C altitude information. The First Officer flew the visual approach in compliance with this instruction (at least in our view) by delaying descent below 5;300 FT until we were nearly aligned with final (LOC alive); although we were still in the turn to final. After rolling wings level on final; AMA Tower asked our altitude which I believe was either 4;400 FT or 4;600 FT MSL at the time. I'm not sure. We had rolled wings level about 4;800 FT - 4;900 FT. Although I was unable to talk to the Tower Controller further about this; it occurred to me that the reason for his question might have been that he thought we had descended earlier than instructed; since we were below 5;300 FT when we were first wings level on final and fully aligned with the runway.I'm concerned that confusion may exist between controllers and pilots in this situation which might result in a loss of separation event if we're not doing what they expect us to do. For pilots; we consider ourselves established on final (and able to descend in accordance with the approach procedure) when the LOC is alive; as it was in this case. However; it may be that the Controller expected us to be wings level on final and aligned with the runway before descending below 5;300. If that is what the Controller wants; a better instruction in this case might have been to cross PANDE at 5;300 then clear us for the visual approach. Since the Controller told us that their radar may be out of service for a couple more weeks; this may be something worth discussing.
Confusion between Approach Control and an air carrier flight crew may have resulted in a premature descent on a visual approach to Runway 04 at AMA.