First, some definitions...
As a legally critical point of semantics, let's not forget the definitions of VMC, IMC, simulated instrument conditions (which for brevity I'll call SIC here), and actual instrument conditions (AIC).
VMC is flight conditions in which VFR flight is permitted under 14 CFR 91.155. These conditions change depending on altitude and airspace.
IMC is flight conditions in which VFR flight is
not permitted under 14 CFR 91.155.
From the 1984 Carr letter of interpretation:
"Simulated" instrument conditions occur when the pilot's vision outside of the aircraft is intentionally restricted, such as by a hood or goggles.
"Actual" instrument flight conditions occur when some outside conditions make it necessary for the pilot to use the aircraft instruments in order to maintain adequate control over the aircraft. Typically, these conditions involve adverse weather conditions.
Note in particular the "typically," as oppose to "always" in the AIC definition.
Thus, you can be in AIC in VMC -- say, between layers at night with several thousand feet between the layers and miles of visibility, but no visible ground or horizon references for navigation or control. Likewise, you can be in IMC without being in AIC, say, when you're 1500 feet laterally from the only cloud in a clear blue sky.
This may seem silly, but it's an important point to remember when discussing these rules, particularly since there are times you can be legally logging approaches for currency in VMC, and there are also times you cannot legally log them for currency when in IMC.
Now, the Chief Counsel gave a legal interpretation in 1992 on how much of the approach must be flown and how low it must be taken. See the Slater interpretation, #92-5, quoted below:
Second, you questioned how low a pilot must descend (i.e., minimum descent altitude or decision height or full-stop landing) on the six instrument approaches he must log to meet the recent IFR experience requirements specified in FAR Section 61.57(e)(1)(i) (14 CFR Section 61.57(e)(1)(i)). You also asked if an instrument approach "counts" if only part of the approach is conducted in actual IFR conditions. Section 61.57(e)(1)(i) states that: No pilot may act as pilot in command under IFR, nor in weather conditions less than the minimums prescribed for VFR, unless he has, within the past 6 calendar months - (i) In the case of an aircraft other than a glider, logged at least 6 hours of instrument time under actual or simulated IFR conditions, at least 3 of which were in flight in the category of aircraft involved, including at least six instrument approaches, or passed an instrument competency check in the category of Ò aircraft involved. For currency purposes, an instrument approach under Section 61.57(e)(1)(i) may be flown in either actual or simulated IFR conditions. Further, unless the instrument approach procedure must be abandoned for safety reasons, we believe the pilot must follow the instrument approach procedure to minimum descent altitude or decision height.
However, they have
never said how much of the approach must be flown in actual instrument conditions. I would note that it is probably a good thing that nobody has pressed the issue on how much of the approach must be flown in instrument conditions, as we probably could not stand the answer, which might be "all of it," in which case you'd not be able to count any approach you successfully completed, since if you were still in instrument conditions as DH/MDA, you wouldn't be able to land, so if you successfully landed, you wouldn't be able to count it. Best to let this sleeping dog continue to doze.
Now, to your specific questions...
Does an instrument approach constitute an approach under an IFR clearance if it's in full VMC?
No.
Does it mean anything below VFR? Meaning, I can break out at 2999ft and it counts?
No. The categorical weather descriptions of VFR/MVFR/IFR/LIFR are irrelevant to this issue.
Does it mean anything below MVFR, meaning I can break out at 999ft and it counts?
No, for the same reason.
Does it mean you have to have been in IMC at some point during your approach?
No, but you must have been in
actual instrument conditions at some point, and as discussed above, that's not the same as being in IMC.
Does it mean you have to have had IMC after that FAF?
No, for the same reason, not to mention that the FAA doesn't specifically require that you have been in actual instrument conditions on the final segment (although personally, I don't log it if I wasn't).
Does it mean you have to have gone through some IMC before DA?
No, but you will have had to have gone through some actual instrument conditions somewhere between the IAF and the runway or missed approach point.
Does it mean it has to be IMC until minimums?
First, it
never has to be in IMC. Second, as stated above, the FAA has said you must fly the approach all the way to MDA/DH without specifying exactly how much must have been in actual instrument conditions.
