61.65 and Sims/Training Devices

Ever since I implemented support for instrument ratings progress for Instrument ratings (61.65(d)), there were two pesky problems regarding the use of simulators/training devices toward 61.65(d)(2)'s forty-hour requirement.  Namely, 

• 61.65(h) allows 30 hours (rather than 20) of FTD/FFS (Flight Training Device/Full Flight Simulator) time if your training is conducted under part 142, and 
• 61.65(i) distinguishes BATD (Basic Aviation Training Device) time from AATD (Advanced Aviation Training Device) time, allowing 10 hours for BATD and 20 hours for AATD.

I don't have a reliable way to tell if a given training session was performed under part 142, and I don't distinguish AATDs and BATDs anywhere else in the code (no real reason to do so), so I did the conservative thing and allowed up to 20 hours of FTD time or 10 hours of ATD time (limited to 20 hours total, per 61.65(j)).

Simple, and safe (won't overstate your time), but possibly cheats you out of some experience. So today I've taken out a change that addresses both of these changes.  

The part 142 one is easy: there are three new instrument rating progress items for 61.65 (d)-(f) where you simply declare that you want to see your progress assuming part 142.  If you choose that rather than the plain 61.65 ratings progress, then I will apply the 30 hour FTD/FFS limit rather than the 20 hour limit.  (Note that the 30 hour limit does not apply to ATD time!)

The ATD one is a bit more of a hack.  If the flight "aircraft" is identified in MyFlightbook as being an ATD (not enough to simply name it that - you have to add it and specify that it's an ATD), then I look at the model's name and the flight's comments.  If either of these contain the word "AATD", then I assume it is an AATD; if not, it is a BATD.

There's an interesting problem here, though - and I'd love if folks could weigh in.  61.65(i) allows up to 10 hours of BATD time OR 20 hours of AATD time.  The word "OR" there is interesting - it means there is a choice.  Other places where the FAA uses the word, they mean it as an exclusive "on or the other, but not both" option (e.g., see the "Grannis" interpretation referenced here).  FAA also usually uses words like "and" or "combination" when they mean you can mix and match.  

I have not seen an official interpretation on this, but I'm still going to be conservative and assume that "or" means "or".  So if you have, say, 9 hours of AATD time and 9 hours of BATD time, you can only count 9 hours of ATD time towards the 20 hour limit imposed by 61.65(j).  I don't know if that was the FAA's intent, but it's how I read the words.

Anyhow, here's some details on the math

• I compute your Aircraft time as the sum of your instrument time in real aircraft.
• Per 61.65(h), I compute FTD/FFS time as
     MIN(20, FTD/FFS instrument time)
• I also compute FTD/FFS-142 time as
     0 or MIN(30, FTD/FFS instrument time)
  depending on whether you are using the part-142 Training variant.
• Per 61.65(i) I compute ATD time as
     MAX(MIN(10, BATD instrument time), MIN(20, AATD instrument time))
  So for now, at least, if you have 9 hours of BATD time and 9 hours of AATD time, that’s just 9 hours, due to the “OR” in the reg.  Easy to change if I get an authority to say they can be combined.
• Per 61.65(j), I then compute your Non-142 Sim time as
     MIN(20, FTD/FFS time + ATD time)
• Finally, I compute your total experience as:
      Aircraft time + MAX(FTD/FFS-142 time, Non-142 Sim time)

Let me know if you have any reference on mixing/matching BATD and AATD time here.