M03 controller described potential conflict event with two departures being transferred to ZME with ...

Attributes
ACN	860384
Time
Date	200911
Local Time Of Day	1201-1800
Place
Locale Reference	MEM.TRACON
State Reference	TN
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Climb
Route In Use	SID MEM7
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Climb
Route In Use	Airway J66 SID MEM7
Flight Plan	IFR
Person 1
Function	Approach Departure
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Non Radar 6 Air Traffic Control Radar 14.5 Air Traffic Control Time Certified In Pos 1 (mon) 1 Air Traffic Control Time Certified In Pos 1 (yrs) 7
Events
Anomaly	ATC Issue All Types

Narrative:

I was working east departure and arrival combined. Aircraft X departed eastbound on the mem 7 departure followed by aircraft Y. As each aircraft approached 10;000 in the climb; I asked each their airspeed above that altitude. Both answered 290 knots. Memphis center (ZME) took the hand-off on aircraft X; and I switched him to their frequency. As aircraft Y climbed through 14;000; still indicating 10 knots slower than aircraft X ahead; I called ZME and told them that both aircraft advised a speed request of 290 knots. ZME replied that aircraft Y was indicating 15 knots faster; but he would still take the hand-off. I said that my scope showed aircraft X going ten knots faster. ZME replied that now aircraft Y was indicating 35 knots faster while my display showed the aircraft at like speeds. After the situation; another controller at my facility said that there was a spot east of memphis that would give ZME a false overtake read-out because aircraft were transitioning from one radar feed to another. I have no way of knowing when ZME will see this false overtake; so I assume that I am giving them a clean situation that needs no coordination.

Original NASA ASRS Text

Title: M03 controller described potential conflict event with two departures being transferred to ZME with an overtake situation developing; reporter noting differing RADAR equipment types may display different speeds.

Narrative: I was working East departure and arrival combined. Aircraft X departed eastbound on the MEM 7 departure followed by Aircraft Y. As each aircraft approached 10;000 in the climb; I asked each their airspeed above that altitude. Both answered 290 knots. Memphis Center (ZME) took the hand-off on Aircraft X; and I switched him to their frequency. As Aircraft Y climbed through 14;000; still indicating 10 knots slower than Aircraft X ahead; I called ZME and told them that both aircraft advised a speed request of 290 knots. ZME replied that Aircraft Y was indicating 15 knots faster; but he would still take the hand-off. I said that my scope showed Aircraft X going ten knots faster. ZME replied that now Aircraft Y was indicating 35 knots faster while my display showed the aircraft at like speeds. After the situation; another controller at my facility said that there was a spot east of Memphis that would give ZME a false overtake read-out because aircraft were transitioning from one radar feed to another. I have no way of knowing when ZME will see this false overtake; so I assume that I am giving them a clean situation that needs no coordination.

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.

M03 controller described potential conflict event with two departures being transferred to ZME with an overtake situation developing; reporter noting differing radar equipment types may display different speeds.