The A2A Simulations Community

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.. )

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

Hmm - that is quite a gross navigational error.

After 3000 nm I was 30 nm off track but dead on time (all that distance was ocean, no beacons).

Best regards,
Robin.

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A2A/AccuSim. 'nuff said!

I probably should have put this in the technical section because I think we are looking at a program error of some sort. Maybe the administrator can move it there.
It also occurred to me that his 'clock' could have been off. FSX log gave me credit for 8.8 hours, and the Navigators total at touchdown was 7 hours and 56 minutes....That discrepancy could be the time spent taxiing and preflighting and then looking at the numbers after I was parked at the gate..but I'm not sure If we are dealing with a program 'feature' in which a built in error accumulates over time, then that would be good to know too. I would like to think that the Navigator is back there with his Xtant taking periodic fixes so that errors don't become cumulative to this extent....

The planned charter flight from Hawaii to Aerosoft Tahiti is on indefinite hold...

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

The FSX logbook records the time from when you enter "Fly" to the time you exit back to the selection screen, not just
hours in the air.

Paul

Thanks for clearing that up---So the great circle flight time to Hon really was 7 hours and 22 minutes (not accounting for the overshoot and circle back with two sick engines), and we are back to the Virtual Nav's poor accounting of Average Ground speed. The total flight time of 7 hr 56 min and then .8 hours spent on the ground pre-flighting, taxiing, and sitting at the arrival gate going over the flight sounds right to me. My opinion is that the Navigators distance Algorithim either needs to be fixed so that his Downrange error is within a 'reasonable' distance, or else it be eliminated altogether. If his error was 20 or so NM that would be understandable. (In real life, of course he would have gotten a cross bearing on the Honolulu VOR plus something on the Main Island, and there wouldn't have been an error at all). I might point out that there wasn't a charting error, just the number given for downrange distance which severely screwed up the entire flight. (Yes, I know Stratocruiser Captain's aren't supposed to rely on Distance Calculations, but instead only Time calculations, but that is a different story...I was making use of the information available to me from the Navigator, and the crux of this thread is understanding what can be relied upon and/or if there is program bug)

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

I should have put this thread in the technical section. Can any of the developers or beta testers explain to me what is going on, and why the Navigator fell so far short? I assumed that the distance travelled information was suppossed to be accurate...falling short by upwards of 100 nm seems very very steep for a straight-thru flight conducted in the 1950s. If his Average Ground Speed calculation and the distance travelled are suppossed to be wild estimates, with massive errors built in as a feature, than that is going to change the way I fly this airplane, so I need to know.

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

Maybe you slewed the aircraft or moved it to another airfield buy the drop down menu

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Ron
B-17 AIRFRAME 710 HRS PLUS AND CLIMBING




GIGABYTE X58A-UD5 MB, INTEL I7 950, 12GB DOMINATOR-GT DDR3 RAM, WIN7 64, GIGABYTE SUPER OVER CLOCK GTX 560 TI 1GB GGDDR5 1000Mz, CORSAIR 850W PS, NOCTUA NH-D14,
TRACKIR 5 & TrackClipPro

Not a chance. I already know not to move the aircraft via the dropdown menu, and there are no commands mapped to 'slew' in my configuration (it isn't possible to slew). In fact, there weren't even any major turns...it was a case of take off from RW 28R at SFO, turn ~50 degrees to a course of 235, and then make minor adjustments to follow the great circle route. Crosstrack error was negligible.

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

Well then you shouldn't make the same comment to other peoples threads when you don't know the facts or how their configuration is

So you are saying that the default commands on your keyboard has been removed

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Ron
B-17 AIRFRAME 710 HRS PLUS AND CLIMBING




GIGABYTE X58A-UD5 MB, INTEL I7 950, 12GB DOMINATOR-GT DDR3 RAM, WIN7 64, GIGABYTE SUPER OVER CLOCK GTX 560 TI 1GB GGDDR5 1000Mz, CORSAIR 850W PS, NOCTUA NH-D14,
TRACKIR 5 & TrackClipPro

Sorry, but the logs you originally posted in the show-off thread were suffering from some kind of distance problem...in that case I was able to induce that problem by using the Go To Airport function. That isn't what happened here, but I didn't mean to blow off your suggestion.

It is not lost on me that the GND DIST reported at the end of the flight between SFO and HNL was 2259 NM even though I know it is only 2081 NM via a Great Circle, and only 2090 NM Rhumb Line dist. So maybe there are additional problems going on here in the calculations.



Yes, I went in and specifically eliminated any keyboard or controller mappings for things like slew, which I never used, so slew isn't possible.

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

Ditto same here

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Ron
B-17 AIRFRAME 710 HRS PLUS AND CLIMBING




GIGABYTE X58A-UD5 MB, INTEL I7 950, 12GB DOMINATOR-GT DDR3 RAM, WIN7 64, GIGABYTE SUPER OVER CLOCK GTX 560 TI 1GB GGDDR5 1000Mz, CORSAIR 850W PS, NOCTUA NH-D14,
TRACKIR 5 & TrackClipPro

Apologies to Mr. Jigsaw for taking his Captain's Log from the other thread, without permission, I just needed a ready made example of ground distance discrepancy, so I hope he doesn't mind. But take a look at this:



That flight was from Newport Oregon to San Francisco. The real Ground Distance between those two points is: 425 NM. At first I thought it was because there was a conversion going on for Statute miles (which isn't obvious at first). That would be 488 Statute miles (notice the Air Distance is 488). So what is the Ground Distance, as listed??? These numbers just don't make sense to me.

Now my Captain's Log from the flight from SFO to HNL reported GND / AIR distance as 2259 / 2418 miles. Assuming those are Statute miles, when we convert them back to Nautical I get 1961 NM / 2099 NM). The first number, Ground distance looks suspiciously like the incorrect Navigator's AIR Distance Travelled number (which I reported earlier was 1963 NM as I passed over the Honolulu VOR). And nowhere do I see the correct Ground Distance of 2081 or 2091 Nautical Miles (2396 Statute or 2407 Rhumb Line ). As far as the AIR distance reported in my Captain's Log, 2418 miles, I can't account because I overshot my TOD and had at least a hundred mile detour, so I just don't know what is correct there (but it certainly wasn't 2099 NM or 2418 Statute Miles). In fact I don't even know if there is a NM to Statute conversion going on. GRRRRRRRRRRRRRRR this make me mad

So clearly, All these numbers are hopelessly mixed up. I hope the Developers are reading this thread Hopefully this is a case of me just be confused because of all the numbers, but I don't think it is.

Is this a completely separate issue from the demonstrably incorrect In-Flight Distance Travelled reported by the Navigator, when flying straight thru from point A to point B with no deviation? I don't know, I'm a bit confused myself, but there is definitely something funky going on with both.

Am I stupid for assuming that in the Captain's Log that the Ground Distance should be the distance on the Ground between two points on the globe, and that the Air Distance should be the distance above and beyond that spent in deviations from the flight path, patterns, procedure, and whatnot? That seem like the obvious interpretation, but if so, none of these numbers make a great deal of sense.

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

I know nobody is going to be able to make sense of what I wrote above, so suffice it to say, the numbers don't make sense to me either, and somebody from the Dev side should probably take a look at them, or tell me what it is I'm not interpreting correctly. I realize I might be totally full of it, and if so, then that is okay too. (Wise Stratocruiser Captain leave pride at Door, Good Stratocruiser Captain humble, Grasshopper)

Sorry to be the negative person that only reports problems, I really do love the Stratocruiser.

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli

I don't mind, but using data as an example without knowing how it was generated doesn't necessarily help finding the problem. I didn't go Direct to KSFO but used VOR navigation which took me quite a bit off the direct course, which certainly changes the amount of miles travelled. Also having to turn around after a taking off into the wind into the opposite direction and flying a wide traffic pattern to line up with the runway isn't part of the point to point distance.

I believe the difference between ground and air distance is not the difference between the direct line between points and the distance travelled by deviations etc. but simply the differene between the actual distance travelled over ground and the distance travelled through the air, because of tail- or headwinds based on the time in the air in relation to the airspeed. While the ground distance doesn't change, the duration of the flight will change through wind conditions and thus the engine milage can be changed considerably. So in my case the difference between 461 and 488 miles would mean that I had a headwind most of the time (which is true) which made me fly the equivalent of 488 miles through the air mass while I effectively only covered 461 miles over ground.

This may also account for the discrepancy in your results. Maybe the Distance Travelled miles in the report window are based on time vs airspeed and thus showing air distance and not ground distance? Wind crabbing etc on such a long flight could easily create a 125nm difference between the actual ground distance and the distance travelled in the moving air mass. It would be strange if that was the case, though, because that information wouldn't be very useful for things like TOD planning. Weird indeed.

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Happy Landings
- Patrick

yeah Jigsaw, I see what you are saying, and it -sort- of makes sense I hope you are correct that it is just an error of my interpretation. My understanding of Ground distance, while I think it is intuitive and the way that a normal person would interpret it, might be overly simplistic.

As far as the in-flight Distance Travelled report, I noticed that Virtual Navigator's calculations seem to be based on Time in Flight (a known) and an erroneous Average Ground Speed. He reported 266 kts, while my Actual Average Ground speed MUST have been in excess of 282 knots...(I flew at least 282 knots average in order to cover a minimum of 2080 nm in 7 hours and 22 minutes, and it might have been even faster when considering any extra distance caused by any minor deviations I made from the flight path enroute)

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1)i7 980x 4.35 ghz, gtx 470s SLI, Matrox th2go, Creative x-fi
2)i7 2600k, Gigabyte z68x, gtx 285s sli