Mem approach controller reports pilot usage of group form for speed readback leads to confusion and ...

Narrative:

I was working final monitor west with aircraft X; on final descending inside the step down fix (blews). Aircraft X was overtaking a CRJ2 that was ahead on final. I instructed aircraft X to reduce speed to one-five-zero knots and maintain that speed to the outer marker (elvis). Aircraft X read back that they were reducing to one-fifty which sounded to me like one-fifteen. I repeated; to clarify; my instruction again using phraseology 'one-five-zero.' the pilot for aircraft X again read back the speed assignment in group form. I then advised aircraft X that when they read back 150 in group form; it sounded like they were saying 115. Aircraft X again said they were slowing to 150 in group form. I was aware that tower needed the frequency; so I let it go. Aircraft X never read back the speed assignment in single digit form despite its requirement in the faao 7110.65. The pilot even mentioned that maybe we shouldn't use call signs in group form when the tower controller passed along the sense of confusion I had with his read back. I did not respond at this point; but I would remind all pilots that there is phraseology for similar sounding call signs on the same frequency; just as there is proper phraseology for the read back of numbers depending on what the numbers refer to.

Original NASA ASRS Text

Title: MEM Approach Controller reports pilot usage of group form for speed readback leads to confusion and is contrary to rules.

Narrative: I was working final monitor west with Aircraft X; on final descending inside the step down fix (BLEWS). Aircraft X was overtaking a CRJ2 that was ahead on final. I instructed Aircraft X to reduce speed to one-five-zero knots and maintain that speed to the outer marker (ELVIS). Aircraft X read back that they were reducing to one-fifty which sounded to me like one-fifteen. I repeated; to clarify; my instruction again using phraseology 'one-five-zero.' The pilot for Aircraft X again read back the speed assignment in group form. I then advised Aircraft X that when they read back 150 in group form; it sounded like they were saying 115. Aircraft X again said they were slowing to 150 in group form. I was aware that tower needed the frequency; so I let it go. Aircraft X never read back the speed assignment in single digit form despite its requirement in the FAAO 7110.65. The pilot even mentioned that maybe we shouldn't use call signs in group form when the tower controller passed along the sense of confusion I had with his read back. I did not respond at this point; but I would remind all pilots that there is phraseology for similar sounding call signs on the same frequency; just as there is proper phraseology for the read back of numbers depending on what the numbers refer to.

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.

Attributes
ACN	866794
Time
Date	200912
Local Time Of Day	1201-1800
Place
Locale Reference	MEM.Airport
State Reference	TN
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Other ILS
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Non Radar 6 Air Traffic Control Radar 14 Air Traffic Control Time Certified In Pos 1 (yrs) 6
Events
Anomaly	Deviation - Procedural Published Material / Policy

Mem approach controller reports pilot usage of group form for speed readback leads to confusion and is contrary to rules.