King Air C90 E90
Air Traffic Control Fully Certified
Training / Qualification; Confusion
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Human Factors; Manuals; Procedure
I was conducting training. Aircraft X was on frequency (don't remember where he departed) at 14;000 feet. He stated '14;000 is right in the tops; requesting a climb to VFR-ON-TOP.' The radar trainee was unfamiliar with the procedures and their instructor directed them to use the EDST (ERAM Decision Support Tools). VFR-ON-TOP procedures are indexed on the ARTCC reference page; my trainee located the paragraph in the 7110.65 (kudos to whomever compiled the reference page. In this instance; it worked flawlessly and was a great help.) The four of us were able to discuss the VFR-ON-TOP clearance. The trainee fumbled through the phraseology the first time; then I corrected them and showed them the phraseology example listed in the 7110.65. We had no other traffic and the trainee issued the appropriate clearance. The pilot reported reaching VFR conditions on top; and after corrections from the instructor and myself; they issued the appropriate response. 'Roger; maintain VFR.' Aircraft X leveled at 14;500 feet.We initiated a handoff to [the next sector] and the Radar Controller transferred communications thusly 'For further VFR flight following; contact Chicago Center 120.12.' My trainee and I discussed VFR on TOP and its applications. I explained that it's an IFR clearance and the appropriate computer entries.Later the [neighboring sector] controller called and questioned Aircraft X's clearance. Based on the explanation; I believe Aircraft X did not fully understand his clearance that after reporting reaching VFR ON TOP and the clearance 'Maintain VFR;' he was VFR.I don't believe it's clear that while VFR-ON-TOP is an IFR clearance; once the pilot reports ON TOP and is instructed to maintain VFR; whose responsibilities are what? I don't think I've seen phraseology 'Cancellation of IFR received.' I thought it was odd an IFR aircraft requested an OTP (On Top) clearance; climbed to a VFR altitude; was told to maintain VFR.
A ZAU ARTCC Controller used incorrect clearance phraseology with a VFR-on-top clearance request. The Controller did not understand how to use the procedure and requested clarification.