Planning the next x-c, and suspicious RTFP data...

We're planning for a second x-c this Monday afternoon after Husband's BFR.

The route this time is JGG->LVL->PHF->JGG. The first leg is ~60 nm, and the second is ~66 nm. PHF is ~12 nm from JGG, but it's Class D so the aim is for me to be endorsed to fly there solo (and get more practice with a tower on my own time).

I intend to do the two long legs by DR since that's what I feel least comfortable with at this time and since it seems to me that it would be the most challenging nav method to "update" in-flight; during the last x-c, Chuck said to have my E6B in-hand on this upcoming flight and we'd do what-if scenarios for wind conditions that differ from what was expected.

Last night I sat down with the sectional and measured everything out and did all the calculations by hand for the no-wind situation. I then hopped on RTFP and compared to their results; again, it was similar* but RTFP's time was a little shorter (no landing at LVL, presumably). I then checked the weather along the route so I could do the wind corrections as though I was going to do that trip in the immediate future. ("similar*" means read the rest of this post...)

(There was a NOTAM for PHF saying: PHF 12/017 PHF 7/25 CLSD 0500-1100 DLY WEF 0612100500-0612171100. I'll have to figure that one out here shortly to see if it'll be a factor.)

I was dissatisfied again with RTFP on account of not being able to indicate different altitudes for different legs. I expect 4500 going to LVL and 3500 coming back to PHF. I decided to use 4000 for the exercise. The DUATS readout gave a bunch of information and I wasn't sure what to use; the winds-aloft/temperature table gave listings for ORF, RIC, RDU, etc but not for any place along the route. If I had to pick, I'd have chosen the RIC numbers since they're geographically the closest to LVL. Since I wasn't sure about this, I checked RTFP's nav log. The numbers it used for each leg didn't totally make sense to me. Here's what the table said:

FT	3000	6000	Interpolated for 4000	Dist to JGG	Dist to LVL	Dist to PHF
ORF	3222	3427	3323	32	77	20
RIC	3122	3426	3223	33	49	45
RDU	3320	3426	3321	129	72	134
HAT	3322	3426	3323	?	?	?
EMI	3029	3231	3129	?	?	?

I don't know what HAT is -- perhaps KHSE at 132 nm from JGG on the NC Outer Banks? No idea about EMI (other than a VOR in MD), either.

RTFP used 310@22 for JGG-->LVL, same as RIC for 3000'. Why not the 4000' interpolation numbers? It used 328@23 for LVL-->PHF. Huh? Maybe that comes from seeing that (1) LVL is closer to RDU than ORF (but closest overall to RIC) and (2) PHF is 20 nm from ORF, so there are two votes for 330 and one for 320 -- settle on 328? Why not 327? Does it take distance into consideration? (77*33 + 49*32 + 72*33)/(77+49+72) => 327.5. Maybe that's why? What about the PHF side of the trip? (20*33 + 45*32)/65 => 323. Ehrn?

There *must* be a more sophisticated model in it for how it decides what to use. But let's go back to the by-hand method: a pilot with a sectional, a nav log and a DUATS brief isn't going to use a sophisticated model. From that table, what would I use?

That confusion aside, the point of the exercise was to use some winds to practice the calculations and learn to use the wind calculator, so I took RTFP's numbers. This would at least allow me to compare my results to theirs. And it was pretty easy. That wheel is easy to use and pretty slick.

But I did get results that made me even less confident in the information that RTFP gives me, and Husband and I compared this with Seattle Avionics' Voyager (the free version) for the same trip. Voyager agreed with my calculations. The problem, I think, is that RTFP didn't correct the heading out of JGG for magnetic variance (which is 10W here) -- the heading was 10 degrees less than what I thought it should be.. I had kinda noticed in the previous x-c that the corrected heading coming back to JGG was 10 degrees different from what I had expected, but I figured since it was my first time doing the grunt work that I had mis-measured or been sloppy with the wheel or some similar error.

I'm still reserving judgment since it's such a "stable" software package that I assume is widely used. 50 million Elvis fans can't be wrong, right? In that case, I must be doing something wrong. But then that means that Voyager is doing something wrong, too.

Could they have JGG in the wrong place? The instrument approach to JGG is the HCM VOR 188 radial. In RTFP if you make a direct route from HCM to JGG it says the heading is 192 (no weather downloaded). All of my other heading calculations between points -- Aberdeen-->ECG, ECG-->CVI, CVI-->RZZ, RZZ->EMV, EMV-->AKQ, LVL-->PHF -- have matched very closely to the RTFP results; it just seems to be an error with JGG, so far in my trials. But this sample size is pretty small...

I just don't know what to make of that yet.