Potential conflict between two air carrier aircraft. Non comply with speed restriction.

Attributes
ACN	166596
Time
Date	199012
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : aml
State Reference	VA
Altitude	msl bound lower : 21000 msl bound upper : 21000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc artcc : zny
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport
Flight Phase	cruise other
Route In Use	enroute airway : j220
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	166596
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : clearance other anomaly
Independent Detector	other other : unspecified atc
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 36000 vertical : 0
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X was assigned 'maximum forward speed, what will it be?' pilot replied, '320'. I told X to maintain 310 KTS or greater and report passing through 300 KTS in acceleration. Air carrier Y was 10 mi in trail, same route of flight, I issued, 'do not exceed 300 KTS.' two mins passed when air carrier X stated that due to turbulence, moderate, he could not do 320 KTS. I replied, 'what speed can you do?' air carrier X stated '280.' I reassigned X to do 280 KTS or greater. The readback was 'we'll try.' I now had 8 mi and closing rapidly with air carrier Y driving on. I immediately slowed Y to 280 KTS and put a 5 mi conflict alert electronic cursor around X. All looked okay, so I switched communications on both aircraft to new york center, N27, middletown. A couple of mins later, middletown called me on the landline. To my surprise, he said that air carrier X declared that he did not acknowledge the assigned speed of 280 KTS and that he, the new york controller, just 'pried them apart.' no sep error occurred, however, I believe that air carrier X deceived me by saying he could do 280 KTS. Then when assigned 'will try' I should have know better. Terrible readback.

Original NASA ASRS Text

Title: POTENTIAL CONFLICT BETWEEN TWO ACR ACFT. NON COMPLY WITH SPEED RESTRICTION.

Narrative: ACR X WAS ASSIGNED 'MAX FORWARD SPD, WHAT WILL IT BE?' PLT REPLIED, '320'. I TOLD X TO MAINTAIN 310 KTS OR GREATER AND RPT PASSING THROUGH 300 KTS IN ACCELERATION. ACR Y WAS 10 MI IN TRAIL, SAME RTE OF FLT, I ISSUED, 'DO NOT EXCEED 300 KTS.' TWO MINS PASSED WHEN ACR X STATED THAT DUE TO TURB, MODERATE, HE COULD NOT DO 320 KTS. I REPLIED, 'WHAT SPD CAN YOU DO?' ACR X STATED '280.' I REASSIGNED X TO DO 280 KTS OR GREATER. THE READBACK WAS 'WE'LL TRY.' I NOW HAD 8 MI AND CLOSING RAPIDLY WITH ACR Y DRIVING ON. I IMMEDIATELY SLOWED Y TO 280 KTS AND PUT A 5 MI CONFLICT ALERT ELECTRONIC CURSOR AROUND X. ALL LOOKED OKAY, SO I SWITCHED COMS ON BOTH ACFT TO NEW YORK CTR, N27, MIDDLETOWN. A COUPLE OF MINS LATER, MIDDLETOWN CALLED ME ON THE LANDLINE. TO MY SURPRISE, HE SAID THAT ACR X DECLARED THAT HE DID NOT ACKNOWLEDGE THE ASSIGNED SPD OF 280 KTS AND THAT HE, THE NEW YORK CTLR, JUST 'PRIED THEM APART.' NO SEP ERROR OCCURRED, HOWEVER, I BELIEVE THAT ACR X DECEIVED ME BY SAYING HE COULD DO 280 KTS. THEN WHEN ASSIGNED 'WILL TRY' I SHOULD HAVE KNOW BETTER. TERRIBLE READBACK.

Data retrieved from NASA's ASRS site as of July 2007 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.