Narrative:

[We were instructed] to change the FMS to reflect hard altitudes on the new mem RNAV stars; we did just that and changed the 'at or below FL230' at jyson to a hard altitude of FL230 while descending into mem on the monaa RNAV STAR for runway 27. Approximately 10 miles from jyson we realized that we weren't going to make the restriction at monaa of at or below 10;000 ft and 250 KTS. If we hadn't changed jyson to a hard altitude; we would have made the restriction. We started our descent and told ATC that we may not make the speed at monaa. We were told to try to make the altitude before the speed. Crossing monaa we were approximately 290 KTS instead of 250. Approach handed us off and told us to tell the next controller our speed. We did and the next controller gave us a pilot discretion descent to 4;000 ft; with speed at our discretion.I don't think we should ever change at or below altitudes on the FMS [line selectable procedures] to hard altitudes. You may make the first restriction; but will you make the next one? This was my first time flying this arrival. I was the pilot not flying; I should have realized sooner that the distance between jyson and monaa is only 16 miles. Consider changing the 'at or below' altitude at jyson to something more like 15;000 ft; instead of FL230. Unfortunately it was our mistake; and it was a stupid one.

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Original NASA ASRS Text

Title: After the flight crew was cleared for the MONAA RNAV STAR to MEM; they reprogrammed the 'at or below FL230' at JYSON to 'at FL230/' As they approached JYSON they realized they would be unable to comply with the 'between 6;000 and 10;000 FT at 250 KTS' restriction at MONAA only 16 NM beyond JYSON.

Narrative: [We were instructed] to change the FMS to reflect hard altitudes on the new MEM RNAV STARS; we did just that and changed the 'at or below FL230' at JYSON to a hard altitude of FL230 while descending into MEM on the MONAA RNAV STAR for Runway 27. Approximately 10 miles from JYSON we realized that we weren't going to make the restriction at MONAA of at or below 10;000 FT and 250 KTS. If we hadn't changed JYSON to a hard altitude; we would have made the restriction. We started our descent and told ATC that we may not make the speed at MONAA. We were told to try to make the altitude before the speed. Crossing MONAA we were approximately 290 KTS instead of 250. Approach handed us off and told us to tell the next Controller our speed. We did and the next Controller gave us a pilot discretion descent to 4;000 FT; with speed at our discretion.I don't think we should ever change at or below altitudes on the FMS [line selectable procedures] to hard altitudes. You may make the first restriction; but will you make the next one? This was my first time flying this arrival. I was the pilot not flying; I should have realized sooner that the distance between JYSON and MONAA is only 16 miles. Consider changing the 'at or below' altitude at JYSON to something more like 15;000 FT; instead of FL230. Unfortunately it was our mistake; and it was a stupid one.

Data retrieved from NASA's ASRS site as of July 2013 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.