I was fortunate enough to find the time yesterday, and last night to be able to do a real time flight from San Francisco to Honolulu. From SFO to HNL is 2081
miles on a great circle. Remember that number, please.
I planned to have a 150 mile descent, something in the vicinity of 7-900 fpm. Naturally, when the Navigator reported that we had flown 1930 miles, I started to pull the throttles back and begin my descent. I was tracking inbound on the Honolulu VOR. It was night.
Things were looking good until just a few minutes after initiating descent, my VOR needle spun around. I was over the VOR!!!???
Yes, indeed I was. At this moment of passing over the VOR, here is what the navigator's scratchpad said:
Flt Time: 7 hours 22 min
Distance: 1963 nm
Ground Speed: 291 kts
Ave Ground Speed: 266 kts
To Sea Level: 120 nm 25 min
Do you see the problem? Since at that very moment I was over the Honululu VOR, my distance from SFO travelled in the air was at least
2081 miles. Based on the time and distance, that means my average ground speed was ~ 280 knts. The Virtual Navigator used the incorrect 266 knots figure to calculate my total distance travelled, and therefore made an error of at least 120 miles. Needless to say my perfectly timed descent, was not so perfectly timed.
Before anybody tells me that he is not supposed to be accurate, or that I shouldn't rely on the virtual navigator and instead fly the plane with a slide rule, 120 miles is a big fricken error for the Navigator to be making, especially since his knowledge of instantaneous
ground speed, and wind seems to be 100% accurate. Sorry to be the bringer of bad news, but thats gotta be a bug.
My total flight time, after overshooting Hawaii, experiencing some engine trouble, and then landing was 7 hours and 56 minutes. At the end of my flight the Gnd Dist / Air Dist figure was 2259 / 2418 nm. The non-great Circle Ground distance between SFO and HNL might
be 2259 nm; But even though I overshot my Top of Descent, there is no way I flew 2418 miles in 7 hours, 56 minutes. My average ground speed was fast, but no way did I cover that much ground. Meanwhile the Navigator scratchpad, at the end of the flight didn't match, and I already explained that I thought that was wrong too...I don't understand these figures, or how they are calculated either.
(In part 2, I will describe how I stupidly froze my engines in order to make up for lost time..