Just reread the report and cockpit recording. They were flying the approach at 180 knots, TORBY is at 3.8 miles which was within the 4.5 miles for a Cat E approach.
...
They were flying an instrument approach, Torby was within the protected area for the speeds they were flying and the instruction ATC made sense for this aircraft being flown the way it was being flown.
...
I thought was outside the protected area but now I know it was not for the speeds being flown. I should have read the reports again, I would have answered my own question.
I wasn't going to open this whole bag of worms, but since you brought it up... your first reading was exactly right. This is the other reason that I think the "circling" instructions given by the tower were bad. You are correct, that at 180 kts, that put the Lear into a Cat E circle. There is no Cat E minimums on the chart. The only obstacles that were looked at were the ones in the Cat D protected airspace. Nobody knows what obstacles were between 2.3 and 4.5.
We can kind of see that when they went from the "old" minima to the "new." When the Cat D protected airspace went from 2.3 (old) to 3.7 (new), the MDA went up 220', from 820 MSL to 1040 MSL. The circling airspace gives you 300' of protection above any obstacle in the protected airspace. So, when they looked at the expanded area, there must be an obstacle (somewhere) in that new area that's about 740' MSL. So conceivably, with a circle at TORBY, at 180 knots at 820' MSL, you could be flying around with only 80' of obstacle clearance.
Again, it's a bad instruction. I know the others on here will come and say that hundreds of pilots fly this approach every day and don't hit anything, and that's true. But I think it sets people up for a false sense of security, and they may then take that lax view of circling protected airspace and circling MDAs to another airfield where it DOES matter. They they hit a guy wire from a tower they didn't see, and we'd all wonder what they were doing maneuvering down low outside the circling protected airspace.
Dturri, I'm a newly minted instrument pilot, I like going through these things to learn stuff. I have a good instructor who told me that circling to land, at night, at mda, in instrument conditions, for the type of flying I do, recreational, is probably not a smart thing to be doing. I agree with him. I'd prefer a precision approach, or at least one aligned with the runway and conditions not at minimums. Some will say "what's the point of having the rating if you can't fly to minimums?" My answer to that is we can't all be Aces, if it works for you, have at it.
Your instructor is smart and you have the right attitude towards this. Don't let the naysayers tell you otherwise. Aviation is all about risk mitigation. There's absolutely nothing wrong with having personal minimums, in fact, as a newly-minted instrument pilot, I would highly encourage you to set personal minimums and use them. As you become more proficient and comfortable, you can lower them, or get rid of them altogether. The airlines do it and as does the Air Force, so don't worry, you'd be in good company.
A night, circling approach at MDA in marginal weather is an extremely high risk item. For me, that would require significant planning and forethought before I would do it, especially at an unfamiliar field, if I would do it at all.