Narrative:

I just flew the departure from mslp runway 07 three days in a row. Each day the clearance was the same. The flight plan filed the comalapa 3 departure. ATC cleared us to fly the jiboa radar 3 departure relta transition; to cross 10 DME at or above 8000. Terrain is an issue when departing mslp. The jiboa radar 3 joins the CAT 092 radial until reaching 8000 feet then allows a turn direct to relta. The 092 radial is over the coastal plain and clear of terrain. The initial climb to 8000 feet insures that the airplane is above the highest nearby mountains prior to turning. The 10 DME crossing at 8000 feet is an ATC restriction. It's very difficult to comply with. At first glance the chart for the jiboa radar 3 departure appears to depict this restriction. Closer examination reveals that the restriction on the chart is conditional and not tied to 10 DME. I was the pilot flying on all three departures. When departing airports with terrain I fly an open climb at green dot speed until above the terrain. I briefed that I would maintain green dot until 12;000 ft (above the crossing restriction at relta).the first day the jiboa radar 3 was loaded in the FMS. CAT VOR was hard tuned and displayed on the nd (navigation display). The waypoint on the nd showed the crossing was magenta (satisfied). After takeoff; cross checking the DME against the waypoint I realized that it did not depict 10 DME. Monitoring raw data I believe we satisfied the crossing. The second day I set it up the same way; except that I also used the fix page to depict the CAT 10 DME. During the climb I was able to monitor the crossing much closer. Even with an expedited climb we were 200 feet low passing 10 DME. The third day I was very aware of this restriction. When loading the FMGC (flight management guidance computer) I created a waypoint on the departure at 10 DME. My plan was to verify the altitude prediction at this point. If it was close to 8000 feet I would request a different departure. After loading was complete the FMGC predicted the crossing at 9038 feet. (The planned takeoff weight was lighter than the previous day so it looked reasonable). During the initial climb I noticed the prediction had changed to 7500 feet. I flew 175 knots and kept the flaps at 1 to expedite the climb. We were within 250 feet of the restriction at 10 DME.I see several issues with this departure. First is that ATC is issuing a crossing restriction that is almost impossible to comply with. Second; the ATC restriction looks similar to the conditional crossing on the chart. Third; that when the waypoint was properly loaded in the FMGC it calculated a prediction indicating the crossing could be exceeded by 1000 feet. But after takeoff it changed significantly. I made several errors. The first day I missed that 10 DME crossing was not depicted on the chart. I did not ask for relief from ATC when I saw that the crossing was marginal. On the third day I relied on the FMGC prediction when the clearance was accepted. The performance capability of the [aircraft] might have made me a little complacent on cross checking the crossing restriction. To prevent this event from recurring I will not be accepting the crossing restriction. The comalapa 3 departure will provide the margin needed to make the crossing restriction. I will also be much more conservative when evaluating the performance of the [aircraft] related to crossing restrictions especially when they are not depicted.

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Original NASA ASRS Text

Title: An Airbus flight crew reported difficulty complying with a departure altitude restriction at MSLP due to several factors - an ambiguous depiction on the charted departure procedure which did not correspond with the verbal ATC clearance; and an erroneous performance prediction by the aircraft software.

Narrative: I just flew the departure from MSLP runway 07 three days in a row. Each day the clearance was the same. The flight plan filed the COMALAPA 3 departure. ATC cleared us to fly the JIBOA RADAR 3 departure RELTA transition; to cross 10 DME at or above 8000. Terrain is an issue when departing MSLP. The JIBOA RADAR 3 joins the CAT 092 radial until reaching 8000 feet then allows a turn direct to RELTA. The 092 radial is over the coastal plain and clear of terrain. The initial climb to 8000 feet insures that the airplane is above the highest nearby mountains prior to turning. The 10 DME crossing at 8000 feet is an ATC restriction. It's very difficult to comply with. At first glance the chart for the JIBOA RADAR 3 departure appears to depict this restriction. Closer examination reveals that the restriction on the chart is conditional and not tied to 10 DME. I was the pilot flying on all three departures. When departing airports with terrain I fly an open climb at Green Dot speed until above the terrain. I briefed that I would maintain Green Dot until 12;000 ft (above the crossing restriction at RELTA).The first day the JIBOA RADAR 3 was loaded in the FMS. CAT VOR was hard tuned and displayed on the ND (Navigation Display). The waypoint on the ND showed the crossing was magenta (satisfied). After takeoff; cross checking the DME against the waypoint I realized that it did not depict 10 DME. Monitoring raw data I believe we satisfied the crossing. The second day I set it up the same way; except that I also used the FIX page to depict the CAT 10 DME. During the climb I was able to monitor the crossing much closer. Even with an expedited climb we were 200 feet low passing 10 DME. The third day I was very aware of this restriction. When loading the FMGC (Flight Management Guidance Computer) I created a waypoint on the departure at 10 DME. My plan was to verify the altitude prediction at this point. If it was close to 8000 feet I would request a different departure. After loading was complete the FMGC predicted the crossing at 9038 feet. (The planned takeoff weight was lighter than the previous day so it looked reasonable). During the initial climb I noticed the prediction had changed to 7500 feet. I flew 175 knots and kept the flaps at 1 to expedite the climb. We were within 250 feet of the restriction at 10 DME.I see several issues with this departure. First is that ATC is issuing a crossing restriction that is almost impossible to comply with. Second; the ATC restriction looks similar to the conditional crossing on the chart. Third; that when the waypoint was properly loaded in the FMGC it calculated a prediction indicating the crossing could be exceeded by 1000 feet. But after takeoff it changed significantly. I made several errors. The first day I missed that 10 DME crossing was not depicted on the chart. I did not ask for relief from ATC when I saw that the crossing was marginal. On the third day I relied on the FMGC prediction when the clearance was accepted. The performance capability of the [aircraft] might have made me a little complacent on cross checking the crossing restriction. To prevent this event from recurring I will not be accepting the crossing restriction. The Comalapa 3 departure will provide the margin needed to make the crossing restriction. I will also be much more conservative when evaluating the performance of the [aircraft] related to crossing restrictions especially when they are not depicted.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.