A320
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface
Aircraft Equipment Problem Less Severe
Flight Crew Requested ATC Assistance / Clarification
Aircraft; Human Factors
While descending via the Eagul5 Arrival into PHX; I noted a discrepancy in comparing the chart with the aircraft Navigation Display. Specifically; the chart directs crossing EAGUL intersection at or above FL180 (based on QNE; that is; aircraft altimeters set to standard 29.92 in Hg.) The aircraft navigation database; in contrast; directs crossing EAGUL intersection at or above 18;000 FT (based on QNH; that is; aircraft altimeters set to a local altimeter setting.) Please note that the upper clearance limit of FL230 at EAGUL intersection is not at issue here. I queried the Air Traffic Controller as to which lower limit was correct at EAGUL intersection: FL180 or 18;000 FT. He replied that the lowest clearance limit to cross EAGUL intersection is FL180; not 18;000 FT (that is; the chart is correct and the aircraft navigation database is incorrect.) I asked him if he was certain of this and he replied that the lowest clearance limit to cross EAGUL intersection is FL180 and has always been so. I believe; but I am not certain; that this aircraft navigation database discrepancy is present in all A320 series aircraft. It is important that this discrepancy is promptly corrected because a sufficiently low local altimeter setting could result in a clearance deviation/violation/aircraft accident. For example; a local altimeter setting of 29.62 in Hg could cause an A320 series aircraft to cross EAGUL intersection at FL177 - which is 300 FT below the clearance limit altitude of FL180. The performance standards for Airline Transport Pilots delineate a maximum tolerance of 100 FT.
The reporter states that his company reported to him that this is just the way the A320 is and that keeping QNE until past the fix will prevent an altitude deviation.
A320 Captain reports his FMGC database depicts crossing EAGUL between FL230 and 18;000 FT; on the EAGUL 5 arrival to PHX. The chart; which is correct; indicates the lower limit should be FL180.