Date: 201507
Local time of day: 1201-1800
Location: A90.TRACON, NH
Flight conditions: Marginal
Weather elements / visibility: 10
Light: Daylight
Aircraft: Small Aircraft
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Training
Flight phase: Initial Approach
Airspace: Class E A90
ATC / advisory: TRACON A90
Reporter organization: Personal
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Commercial
Human factors: Confusion; Situational Awareness; Communication Breakdown
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Contributing factors: Chart Or Publication; Human Factors
Primary problem: Ambiguous

Narrative: I was flying an instrument proficiency flight. The flight was to fly practice approaches under IFR at CON (Concord; NH); MHT (Manchester; NH) and terminate with a practice approach and some VFR takeoffs and landings at ASH. The [flight] was flown under IFR because marginal VFR conditions existed over the route; with ceilings ranging from 2;200 feet to 3;500 feet AGL; depending on location. Good visibility existed beneath the cloud deck. A safety pilot was on board and a view limiting device was used; because conditions were not solid IMC. Departing out of ASH; I contacted Boston Approach and was cleared to climb to my assigned altitude of 4;000 feet MSL. After some vectoring for traffic; I was cleared to proceed direct to KERSY; which is an IAF for the RNAV Runway 17 Approach at CON. Since the aircraft was equipped with the G1000 System; much of the leg to KERSY was flown on autopilot; while I tended to other tasks such as obtaining ASOS at CON; briefing the approach; etc. Approximately 5 miles from KERSY; I took over manual control and received the following clearance from Boston Approach: 'Cross KERSY at 4;000; cleared RNAV Runway 17 Approach at Concord.'  Looking at my chart; the minimum altitude for the published segment from KERSY to INKOW (the next fix) was 4;400 feet MSL. It struck me odd that the controller would issue a crossing restriction that was LOWER than the minimum altitude for the segment I was about to enter. I was also aware that there was hilly terrain in that area and that there was likely good reason for the published altitude for that segment. I decided that AFTER crossing KERSY at 4;000 feet; I would then climb to 4;400 feet MSL; because I was cleared for the approach; and should be cleared to fly the procedure as published after making the requested crossing restriction.I climbed to 4;400 feet MSL and about 4 miles into the segment; the controller called me and advised: 'I see you have climbed to the published altitude of 4;400 feet. Just for future reference; when I assign a crossing altitude; I'm expecting you to fly that altitude for the segment.' He didn't sound upset; nor did he ask me to contact him on the ground after the flight. Based on the controller's tone; it did not appear as if any conflict was created by my action. He just made it clear that I did something he was not expecting. Needless to say; I immediately descended to 4;000 feet and proceeded with the approach to CON.  The rest of the flight was uneventful; and nothing further was said about the altitude situation at KERSY.Needless to say; I was a bit rattled by the incident. I pride myself on flying precisely and interacting as professionally as possible with ATC. I realize that it is not just my reputation that is on the line; but also that of the organization. In my previous experience; the only time I had ever been given an altitude assignment that was BELOW published safe altitudes was while being vectored...never on a published approach segment. In addition; it has always been my understanding that once cleared for the approach; I was cleared to fly the procedure as published. Whenever a controller needed me higher than published on an approach segment; the controller would typically say: 'Intercept and fly the route; maintain X thousand; expect approach clearance in X miles'; meaning once cleared; I could then fly the procedure at the published altitudes. Clearly; I need to get back with the AIM and reread the material on approaches. At any rate; the deviation wasn't done maliciously; it was done for safety and because I believed at the time that it was the correct thing to do.




Synopsis: While on a practice instrument approach; there was a disagreement between the pilot and the Controller about the assigned altitude being below the published approach segment altitude.