Enroute controller described a loss of separation likely caused when an aircraft initiated an unauth...

Narrative:

I may have transposed the call signs of the aircraft in this report; I only have the call signs right now and I'm not sure which pilot made the deviation. That said; I believe that it was aircraft X that was at four thousand; requesting higher. I had stopped him at 040 for traffic at 050. I advised the pilot that it would be a while before I could issue his requested altitude of 070 because of said traffic; and inquired whether he would like 040 as a final or prefer a vector to continue his climb. He advised that he would take a vector. I issued a heading of 220 to separate him from the 050 traffic and gave the reason for the vector as 'for your climb.' I did not clear the pilot to leave 040; however he accepted the vector and began to climb immediately. As soon he left 040 the pilot lost minimum separation with the other aircraft. I saw that he was climbing through 044 and told the pilot 'maintain four thousand.' the pilot returned to 040. Recommendation; while the pilot clearly deviated from his altitude clearance; I could have restated his assigned altitude when issuing the vector so as to preclude any ambiguity. Particularly with general aviation pilots; it is sometimes best to take additional precautions to ensure separation.

Original NASA ASRS Text

Title: Enroute Controller described a loss of separation likely caused when an aircraft initiated an unauthorized climb into an occupied altitude; the reporter acknowledging additional precautions might be necessary when controlling general aviation aircraft.

Narrative: I may have transposed the call signs of the aircraft in this report; I only have the call signs right now and I'm not sure which pilot made the deviation. That said; I believe that it was Aircraft X that was at four thousand; requesting higher. I had stopped him at 040 for traffic at 050. I advised the pilot that it would be a while before I could issue his requested altitude of 070 because of said traffic; and inquired whether he would like 040 as a final or prefer a vector to continue his climb. He advised that he would take a vector. I issued a heading of 220 to separate him from the 050 traffic and gave the reason for the vector as 'for your climb.' I did not clear the pilot to leave 040; however he accepted the vector and began to climb immediately. As soon he left 040 the pilot lost minimum separation with the other aircraft. I saw that he was climbing through 044 and told the pilot 'maintain four thousand.' The pilot returned to 040. Recommendation; while the pilot clearly deviated from his altitude clearance; I could have restated his assigned altitude when issuing the vector so as to preclude any ambiguity. Particularly with general aviation pilots; it is sometimes best to take additional precautions to ensure separation.

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	967148
Time
Date	201108
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Aircraft 1
Make Model Name	Bonanza 36
Flight Phase	Climb
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Published Material / Policy

Enroute controller described a loss of separation likely caused when an aircraft initiated an unauthorized climb into an occupied altitude; the reporter acknowledging additional precautions might be necessary when controlling general aviation aircraft.