Narrative:

Inbound on the TELLR2 RNAV arrival into den level at FL190 were approaching the fix crste and already established the arrival; we were cleared to descend via the TELLR2. We waited almost a full minute for the top of descent (TOD) to display and engaged VNAV/valt. Approximately 2 minutes later over crede intersection; ATC changed our runway so the pilot not flying (PNF) reloaded the FMS to 34L transition. When he executed the change; our TOD and all speed commands disappeared from the pfd. It took over 3 minutes for a TOD and VNAV to return; during this time I was very focused on manually making the altitude crossings while the PNF was desperately trying to determine why the FMS VNAV had failed. I was successful at making the altitude crossings manually; but due to task saturation caused by an inadequate and antiquated honeywell FMS; I did not catch the speed restriction of 250 KTS at powdr; about 3 miles past powdr; denver approach queried us about our current speed to which the PNF responded 'slowing for 250;' which was done immediately after the query. The rest of the arrival and landing was normal and there were no other excursions.the excel crews are getting sick and tired of the shortcoming of the underpowered and antiquated FMS system. It amazes me that our safety department can't figure out why this fleet is having so many altitude/navigation deviations; but it is very clear in our minds that there is a direct correlation between this substandard and outdated FMS system and the deviations; it simply cannot meet the demands of the latest generation of RNAV procedures and is very unpredictable. The worst case scenario for this FMS is an arrival comprised of multiple in between altitudes; it does not have the computing power to make these calculations in a timely fashion.to mitigate this in the future; I recommend the safety department and the FAA do not authorize the xl fleet to perform these complex RNAV procedures. We should be using only non-RNAV arrivals. I'm going to go out on a limb and assume the above recommendation will fall on deaf ears so I will also recommend that when between altitudes [that] are part of an RNAV arrival; the procedure is to replace every in between with a manual hard altitude that is in compliance with the published between range. For example; if the procedure specifies cross between FL190 and FL150; the crew would manually input FL170 as a hard altitude.

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Original NASA ASRS Text

Title: CE-560XL Captain reported the Honeywell FMS installed in this type of aircraft is; in his opinion; incapable of complying with the complex demands of modern RNAV arrival procedures.

Narrative: Inbound on the TELLR2 RNAV arrival into DEN level at FL190 were approaching the fix CRSTE and already established the arrival; we were cleared to descend via the TELLR2. We waited almost a full minute for the Top of Descent (TOD) to display and engaged VNAV/VALT. Approximately 2 minutes later over CREDE intersection; ATC changed our runway so the Pilot Not Flying (PNF) reloaded the FMS to 34L transition. When he executed the change; our TOD and all speed commands disappeared from the PFD. It took over 3 minutes for a TOD and VNAV to return; during this time I was very focused on manually making the altitude crossings while the PNF was desperately trying to determine why the FMS VNAV had failed. I was successful at making the altitude crossings manually; but due to task saturation caused by an inadequate and antiquated Honeywell FMS; I did not catch the speed restriction of 250 KTS at POWDR; about 3 miles past POWDR; Denver approach queried us about our current speed to which the PNF responded 'slowing for 250;' which was done immediately after the query. The rest of the arrival and landing was normal and there were no other excursions.The Excel crews are getting sick and tired of the shortcoming of the underpowered and antiquated FMS system. It amazes me that our safety department can't figure out why this fleet is having so many ALT/NAV deviations; but it is very clear in our minds that there is a direct correlation between this substandard and outdated FMS system and the deviations; it simply cannot meet the demands of the latest generation of RNAV procedures and is very unpredictable. The worst case scenario for this FMS is an arrival comprised of multiple in between altitudes; it does not have the computing power to make these calculations in a timely fashion.To mitigate this in the future; I recommend the safety department and the FAA do not authorize the XL fleet to perform these complex RNAV procedures. We should be using only NON-RNAV arrivals. I'm going to go out on a limb and assume the above recommendation will fall on deaf ears so I will also recommend that when between altitudes [that] are part of an RNAV arrival; the procedure is to replace every in between with a manual hard altitude that is in compliance with the published between range. For example; if the procedure specifies cross between FL190 and FL150; the crew would manually input FL170 as a hard altitude.

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.