An ATC instructor reports a loss of separation between a cpr G4 and a B737 air carrier near mxe.

Attributes
ACN	484026
Time
Date	200008
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : mxe.vor
State Reference	PA
Altitude	msl bound lower : 18000 msl bound upper : 18600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zny.artcc
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zny.artcc
Operator	general aviation : corporate
Make Model Name	Gulfstream IV
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : handoff position controller : radar instruction : instructor
Qualification	controller : radar
Experience	controller limited radar : 5 controller military : 0 controller radar : 5 controller supervisory : 0 controller time certified in position1 : 5
ASRS Report	484026
Person 2
Affiliation	government : faa
Function	controller : radar instruction : trainee
Qualification	controller : developmental
Events
Anomaly	conflict : airborne critical non adherence : far non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera other controllerb
Resolutory Action	none taken : anomaly accepted
Miss Distance	horizontal : 24000 vertical : 600
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Trainee appeared to have situation under control due to his performance in prior instances and amount of time he had to correct situation. At last moment to ensure separation trainee keyed microphone and I thought he was going to assign the air carrier FL180 however, he xferred communications with an aircraft and before I could react pilot was acknowledging frequency change and separation was lost.

Original NASA ASRS Text

Title: AN ATC INSTRUCTOR RPTS A LOSS OF SEPARATION BTWN A CPR G4 AND A B737 ACR NEAR MXE.

Narrative: TRAINEE APPEARED TO HAVE SIT UNDER CTL DUE TO HIS PERFORMANCE IN PRIOR INSTANCES AND AMOUNT OF TIME HE HAD TO CORRECT SIT. AT LAST MOMENT TO ENSURE SEPARATION TRAINEE KEYED MIKE AND I THOUGHT HE WAS GOING TO ASSIGN THE ACR FL180 HOWEVER, HE XFERRED COMS WITH AN ACFT AND BEFORE I COULD REACT PLT WAS ACKNOWLEDGING FREQ CHANGE AND SEPARATION WAS LOST.

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.