I already suspect this will not be a popular opinion (especially among CFI’s), but here goes my logic and my “armchair legal opinion” (I am not a lawyer). Sorry for the length, but this is complicated:
1) A controller can NOT authorize you to do something illegal. They may say "go ahead and buzz the field", but that doesn't make it legal. Your mother may say the same thing, but that doesn't make it legal, either.
2) If you are cleared to land, and you abort the landing in the interests of safety, you have violated your ATC clearance (you were cleared to LAND), but it's totally okay to do so in the interests of safety. By aborting your landing, you have, in effect, performed a routine “emergency “action, as you deviated from 91.123b (requiring adherence to ATC clearances), per the allowance given to you in 91.3 (“an in-flight emergency requiring immediate action”).
91.123b: "Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised."http://www.aeromanual.com/%C2%A791.123
91.3: "In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency."http://aeromanual.com/%C2%A791.3
3) You MUST tell the controller, once it's safe to do so, that you're "going around", per 91.123c:
91.123c: "Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible."
4) ATC should NEVER complain about you aborting a landing (or doing ANYTHING, for that matter), in the interests of safety. If an overwhelmed and flustered controller ever does complain, be sure to non-defensively clarify on the radio (this is being recorded) that you aborted your landing in the interests of safety. It'll look good on the tape transcript later, if they make a beef.
....now, the trouble...
5) If you intend to PRACTICE a "go-around" (meaning that you never had any intention of touching the ground), you are technically breaking the minimum altitude rule.
FAR 91.119 begins "Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:"http://www.aeromanual.com/%C2%A791.119
..this means that if you approach the field for, let's call it a "practice go-around", in which you've already decided that you're not going to land, then really you're just flying too low (unless you're a helicopter, which has different minimums), since you were never intending to land. Even if the controller is okay with it, that doesn’t make it legal.
For this reason, if I want to practice my go-arounds (a critical pilot skill to keep sharp on), I WILL NOT WARN THE CONTROLLER. I know this doesn’t sound good; the system works best when everyone is “on the same side” and works together, but the law unfortunately left us with this unhandled problem. I will usually ask for “the option”, giving no indication that I’m not intending to touch the ground, then announce that I’m “going around” on my way up. Warning the controller that I’m not going to land would be admitting to an intentional violation of the 91.119 minimum altitude rule without an emergency condition to justify it. Make sure that you put your gear down and go through all the other motions when doing “practice go-arounds”, or it would be difficult to argue that you were planning on landing. If anyone was suspicious of my intentions, I can always just say that “it didn’t look good, and I didn’t think it was safe” (too high/hot or not on glideslope or whatever).
6) So what about “IFR practice approaches” (done under VFR) that terminate in a “low pass”? This is really the same situation, as if you dip below 1,000’ AGL (as most practice approaches will) before “going missed”, you have effectively violated 91.119 (minimum altitude rule) again, whether the controllers were okay with it or not. Honestly, I usually break with my previous advice on this one. I usually inform the controller (that usually asks) that my approach will terminate in a “low pass” rather than a “full stop”), simply because: a) I consider it to be more disruptive of the traffic flow to surprise the controller, b) violations start with complaints from controllers- if you “work with them”, they’re not likely to violate you; if you try to trick them, and it screws with their sequencing/separation, they ARE likely to look for a way to violate you, and c) if you continually “go missed” when you say you’re going to “full stop”, they might think you’re an imbecile and not let you keep messing around with their traffic/approach pattern, or get alarmed that you may be experiencing some other problem.
7) If you practice your VFR go-arounds at an untowered field, there’s no controller around to make trouble for you. Just be sure to make good use of the CTAF frequency for the benefit of all your other two-winged friends up there, fly considerately, and see-and-avoid.Remember- in the end, rules don't matter if you bend metal, so safety first!