Narrative:

When cleared for the RNAV descent profile for runway 25L; ATC told us to maintain 250 KTS. After a point that I figured that we needed to slow our speed to configure for the approach; I told ATC we needed to slow. He told us to maintain 250 KTS. I told him we needed to slow. He asked if we had a problem because he had our aircraft profiles or something to that effect. I informed him that our aircraft does not slow down and go down at the same time and that we were slowing to 210 KTS. As it was; it took over 10 miles to slow at idle power while descending on the profile just to get to our initial flap speed for configuring.the problem is two fold. RNAV descent profiles are made to descend at the same angle all the way to the ground. Most airbus aircraft will not normally slow down and go down while on the RNAV descent in less than 10-20 miles depending on weight; speed and winds. More spacing for descents needs to be allowed without using speed brakes or lowering gear. These aircraft are highly automated and in order for them to stay on the automation they need to be at altitude and speed prior to intercepting the glide slope and not fighting the aircraft to get down to meet the glide slope.[we need] more spacing on aircraft and more time for the aircraft to descend on automation (without speed brakes extended as the norm). ATC and descent profiles should end 5 miles before the initial glide slope intercept altitude. This would allow aircraft to keep their speed up knowing that they have ample time to slow at level flight 5 miles from the glide slope intercept.

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Original NASA ASRS Text

Title: A321 Captain reports being instructed to maintain 250 KTS during the RNAV arrival to Runway 25L at LAX. When the reporter deemed it necessary to slow for approach and flap extension; he was denied by ATC. Reporter became adamant and slowed to 210 KTS.

Narrative: When cleared for the RNAV descent profile for Runway 25L; ATC told us to maintain 250 KTS. After a point that I figured that we needed to slow our speed to configure for the approach; I told ATC we needed to slow. He told us to maintain 250 KTS. I told him we needed to slow. He asked if we had a problem because he had our aircraft profiles or something to that effect. I informed him that our aircraft does not slow down and go down at the same time and that we were slowing to 210 KTS. As it was; it took over 10 miles to slow at idle power while descending on the profile just to get to our initial flap speed for configuring.The problem is two fold. RNAV descent profiles are made to descend at the same angle all the way to the ground. Most Airbus aircraft will not normally slow down and go down while on the RNAV descent in less than 10-20 miles depending on weight; speed and winds. More spacing for descents needs to be allowed without using speed brakes or lowering gear. These aircraft are highly automated and in order for them to stay on the automation they need to be at altitude and speed prior to intercepting the glide slope and not fighting the aircraft to get down to meet the glide slope.[We need] more spacing on aircraft and more time for the aircraft to descend on automation (without speed brakes extended as the norm). ATC and descent profiles should end 5 miles before the initial glide slope intercept altitude. This would allow aircraft to keep their speed up knowing that they have ample time to slow at level flight 5 miles from the glide slope intercept.

Data retrieved from NASA's ASRS site as of April 2012 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.