Narrative:

I was pilot monitoring; descent plan and RNAV arrival verification and brief had been completed. Early in the decent from 37000 feet I was communicating with the cabin and doing a passenger PA. As I returned my attention to my duties and later in the descent; center began issuing descent instructions close in to boove that was off the script of the arrival descent profile. We were given 'descend 20 south of boove FL190 or below'; while our profile had us at cross zzzzz 19000-17000 feet; 20 more miles further at 19000 feet. ATC additional instructions were 'at boove descend via the arrival.' sounds simple enough; but not when we were too close to make it. I went heads down to rebuild the parameters in the FMS for the pilot flying. I had to correct the initial entry for an error and by the time the FMS calculated the vertical path it confirmed we were well above it to make the requested crossing restriction. The pilot flying increased the descent with full speed brakes but the 4000 FPM rate of descent was still going to put us about 1000 to 2000 feet too high. It took a while to get a word in to the controller to advise them of this problem. By the time I did controller complicated matters rather than just provide relief so I requested a heading and altitude. Rather than help simplify the matter for us during an ATC induced complicated high stress maneuver; controller kept with his conditioned modified RNAV arrival script that these new arrival procedures have morphed in to. To simplify the situation I then stated 'unable RNAV'; but then more untimely questions ensued and wasted time rather than simply giving us a more direct route with fewer restrictions. Controller finally gave us relief. We accepted the instructions to descend via at zzzzz and were switched to approach control without incident. ATC does not understand how much planning and preparation goes in to setting up an RNAV arrival and what we have to do to ensure we adhere to it. This controller also doesn't understand what the aircraft; crew; and FMS is capable of with too little time to perform the requested maneuvers. Typically we are issued instructions from controllers that have a basic understanding of how fast our planes can descend and we don't have a problem complying. However; in this instance this controller gave us an unrealistic task with regard to what we had to do with the FMS and the aircraft to meet his expectations. If ATC cannot coordinate to keep us on an RNAV arrival as written; then I strongly recommend they issue vectors; altitude; and airspeeds for the remainder of the arrival. I have had many instances like this that just complicated our duties because what was supposed to be a procedure to simplify things for pilots and controllers; has now morphed in to something that takes more time to set up; brief and comply with which causes more distraction from flying duties. In the past we were only distracted by briefing the approach; now we have to both. But to add more problems; distractions; and frustration is when the controller takes us off the profile and or lateral navigation for their separation requirements; and then expect us to rejoin mid arrival; or not rejoin. Which then begs the question of why are we wasting our time and attention with something that doesn't work for ATC 50% or more of the time. For this particular instance; when we are too close in or it seems tight; the controller has a bigger picture of what controller needs and if we can do it before controller issues the instructions; controller should be aware of that and ask us if we can do it first before rapidly giving instructions and just expect or hope we can do it. If it is tight like that; it would help if controller could just as us to begin a descent with the required minimum rate and try to use waypoints on our route rather than have us rebuild new waypoints.

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Original NASA ASRS Text

Title: A319 Captain reported ZFW Center gave them a crossing restriction which they could not comply with.

Narrative: I was Pilot Monitoring; descent plan and RNAV arrival verification and brief had been completed. Early in the decent from 37000 feet I was communicating with the cabin and doing a passenger PA. As I returned my attention to my duties and later in the descent; Center began issuing descent instructions close in to BOOVE that was off the script of the arrival descent profile. We were given 'descend 20 South of BOOVE FL190 or below'; while our profile had us at cross ZZZZZ 19000-17000 feet; 20 more miles further at 19000 feet. ATC additional instructions were 'at BOOVE descend via the arrival.' Sounds simple enough; but not when we were too close to make it. I went heads down to rebuild the parameters in the FMS for the Pilot Flying. I had to correct the initial entry for an error and by the time the FMS calculated the vertical path it confirmed we were well above it to make the requested crossing restriction. The Pilot Flying increased the descent with full speed brakes but the 4000 FPM rate of descent was still going to put us about 1000 to 2000 feet too high. It took a while to get a word in to the Controller to advise them of this problem. By the time I did Controller complicated matters rather than just provide relief so I requested a heading and altitude. Rather than help simplify the matter for us during an ATC induced complicated high stress maneuver; Controller kept with his conditioned modified RNAV arrival script that these new arrival procedures have morphed in to. To simplify the situation I then stated 'UNABLE RNAV'; but then more untimely questions ensued and wasted time rather than simply giving us a more direct route with fewer restrictions. Controller finally gave us relief. We accepted the instructions to descend via at ZZZZZ and were switched to Approach Control without incident. ATC does not understand how much planning and preparation goes in to setting up an RNAV arrival and what we have to do to ensure we adhere to it. This Controller also doesn't understand what the aircraft; crew; and FMS is capable of with too little time to perform the requested maneuvers. Typically we are issued instructions from controllers that have a basic understanding of how fast our planes can descend and we don't have a problem complying. However; in this instance this Controller gave us an unrealistic task with regard to what we had to do with the FMS and the aircraft to meet his expectations. If ATC cannot coordinate to keep us on an RNAV arrival as written; then I strongly recommend they issue vectors; altitude; and airspeeds for the remainder of the arrival. I have had many instances like this that just complicated our duties because what was supposed to be a procedure to simplify things for pilots and controllers; has now morphed in to something that takes more time to set up; brief and comply with which causes more distraction from flying duties. In the past we were only distracted by briefing the approach; now we have to both. But to add more problems; distractions; and frustration is when the Controller takes us off the profile and or lateral navigation for their separation requirements; and then expect us to rejoin mid arrival; or not rejoin. Which then begs the question of why are we wasting our time and attention with something that doesn't work for ATC 50% or more of the time. For this particular instance; when we are too close in or it seems tight; the controller has a bigger picture of what Controller needs and if we can do it before Controller issues the instructions; Controller should be aware of that and ask us if we can do it first before rapidly giving instructions and just expect or hope we can do it. If it is tight like that; it would help if Controller could just as us to begin a descent with the required minimum rate and try to use waypoints on our route rather than have us rebuild new waypoints.

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.