- IMC (instrument meteorological conditions) is the time you spend in weather that precludes the ability to use visual references. This can only be experienced in an actual flying aircraft - you CANNOT experience IMC in a training device.
- Simulated Instrument is the time you spend where you must rely on your instruments for safe flight, other than when you are in actual IMC in an aircraft. This can be either in an actual flying aircraft - in which case you are using a view limiting device (like a hood) or it can be in a training device ("simulator") such as an ATD, FTD, or Full Flight Simulator when the training device is emulating IMC.
- Ground Simulator time is the time you spend in a training device, whether or not it is emulating IMC.
Visually, you can think about this as follows:
| Comment | IMC | Simulated Instrument | Ground Sim | Total Time |
| 1 hour of flight in a C-172, half of which was in the clouds | 0.5 | 0 | 0 | 1.0 |
| 1 hour of flight in a C-172, half of which was with a hood (and, presumably, a safety pilot or instructor) | 0 | 0.5 | 0 | 1.0 |
| 1 hour in a multi-engine FTD; half an hour spent practicing single-engine procedures and half an hour spent doing approaches with the screen emulating instrument conditions (i.e., pure white/gray) | 0 | 0.5 | 1.0 | 0 |
Note, by the way, that the "Total Time" field for the FTD flight above is 0. See my prior entry about logging time in training devices for some more tips here.
For purposes of progress towards ratings, such as 61.65 (Instrument Rating), the MyFlightbook will credit simulated instrument time in an ATD, FTD, or FFS towards the required minimum amount of "instrument" time that is required (e.g., 61.65(d)(2) for airplanes requires 40 hours), up to the limit of 20 hours for an FTD/FFS (per 61.65(h)) or 10 hours for an ATD (per 61.65(i)). Note that if you are training per part 142, 61.65(h) actually allows up to 30 hours in an FTD/FFS, but MyFlightbook uses the more conservative 20 hour limit.
