37000 Feet

Browse and search NASA's Aviation Safety Reporting System

ZAB controller expressed concern regarding the confusion reference the 'descend via' phraseology and the apparent uncertainty by both controllers and flight crews as to the required/expected published airspeed/s.

Narrative:

An A321 came over from ZLA60 assigned 300 KTS or greater. Published speed at scole is 280 KTS. I gave a CRJ9 the 'descend via' clearance with the 25L transition and told them to comply with the speeds starting at hydrr (published 250 KTS); pilot read it back questioning what I had given. I said it mostly the same way; but gave comply with the speeds from hydrr inbound. When the A321 was past hydrr; they were still showing 450 ground speed. I asked them if they were at 250 KTS; they said they were slowing. The next aircraft on the arrival was the CRJ9; they were also assigned 300 KTS or greater. I gave them the 'descend via' clearance without any other guidance; expecting them to comply with the snrra speed (265 KTS) and the rest. The pilot subsequently asked me if they needed to comply with the speeds; I said yes. Even though our expectation as controllers is that the 'descend via' cancels any previous ATC assigned speed; the pilots still aren't sure what to do. Recommendation; our RNAV procedures are fairly simply when we have a single stream or aircraft in isolation. However; you start mixing in turns; sequencing; or speed control; and things get very confusing for both the pilots and controllers. Training was extremely poor; worse it would appear for the pilots than us. Phraseology needs to be addressed and I believe this is a national systemic problem and should be addressed.

	Enter your search terms Submit search form
	Web www.37000feet.com

Original NASA ASRS Text

Title: ZAB Controller expressed concern regarding the confusion reference the 'descend via' phraseology and the apparent uncertainty by both controllers and flight crews as to the required/expected published airspeed/s.

Narrative: An A321 came over from ZLA60 assigned 300 KTS or greater. Published speed at SCOLE is 280 KTS. I gave a CRJ9 the 'descend via' clearance with the 25L transition and told them to comply with the speeds starting at HYDRR (published 250 KTS); pilot read it back questioning what I had given. I said it mostly the same way; but gave comply with the speeds from HYDRR inbound. When the A321 was past HYDRR; they were still showing 450 ground speed. I asked them if they were at 250 KTS; they said they were slowing. The next aircraft on the arrival was the CRJ9; they were also assigned 300 KTS or greater. I gave them the 'descend via' clearance without any other guidance; expecting them to comply with the SNRRA speed (265 KTS) and the rest. The pilot subsequently asked me if they needed to comply with the speeds; I said yes. Even though our expectation as controllers is that the 'descend via' cancels any previous ATC assigned speed; the pilots still aren't sure what to do. Recommendation; our RNAV procedures are fairly simply when we have a single stream or aircraft in isolation. However; you start mixing in turns; sequencing; or speed control; and things get very confusing for both the pilots and controllers. Training was extremely poor; worse it would appear for the pilots than us. Phraseology needs to be addressed and I believe this is a national systemic problem and should be addressed.

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.