Why don´t these figures match up?
 

Hi folks,

I´ve been doing some tests for navigation. Basically I wanted to figure out the time I have to fly for a certain distance.

So I did this test in QMB (no wind, 100 meters hight):

Time: 3 minutes (0.05h)
Speed: 250 Km/h IAS (with this low alt and speed TAS/IAS shouldn´t make a big difference I guess)

So after the math is done (250km/h x 0.05h) the flown distance should be exactely 12.5 Km

I did the test several times with several planes and everytime the actual flown distance is 14,5 Km (that indicates a speed of somewhere around 285 Km/h).

Does anyone know where I did the mistake or is just some of the tools in the game broken (Speed gauge or distance meassure on the map)?

Thanks for help!

I would repeat the flight for a longer time, mate, so the distance is bigger and a potential position error would be minimized.

Which aircraft did you use?
The reason I ask is because in a test made in another thread (http://forum.1cpublishing.eu/showthread.php?t=34115) the results shows that the Spitfire in COD is roughly 14% slower than real life.

Since your figures show a 14% speed gauge error, it's tempting to suspect it's accually the speed gauge in the spit thats porked, not necessarily the FM ;)

But it might just be a coincidence

/m

Fair point.

We ran some tests last January (ancient history, now! LOL) over at the ATAG Server: http://theairtacticalassaultgroup.co...ull=1#post7326

In a nutshell, we established that the Channel map we use is 1:1 and the airspeed gauge on the Hurricane Rotol ran very true at sea level (where IAS was very close to TAS). Here's the text from the link above:

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OK, here's what I got:

I changed the route slightly to give me better landmarks to aim at: the tip of the "English point" (near Dungeness) to the tip of the "French point" (near Wissant). The in-game map tools shows it to be exactly 26 miles point-to-point, which is in agreement, IMHO, with the 25 mile distance you provided for the slightly different start/stop points you selected via google maps.

Holding 200 mph at approx 500 feet altitude, my time was 7:25, my calculator says it should've been 7:48. Pretty darn close considering the slight course corrections, plus trim and boost corrections. For those interested, I took a Rotol with 100% fuel (can't be too stingy on gas here), boost was mainly 0 lbs, rpms set to 2500, radiator half closed.

Other than a little bit of flak near Wissant, no one bothered me in this otherwise "hot" combat zone with 13 109's and a 110 swanning about. LOL

I think I can tell Ribbs the map is 1:1 as far as our travel time based on cockpit instruments is concerned.
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Yes I probably will. I think though the longer the time, the bigger the error as far as I understand it. :rolleyes:




I used only axis planes ;) The Me110, the 109 and the G.50.

Thanks for the post. The thing is though that it sounds not quite precise the way it´s done there.
Its much easier to do it offline and with autopilot and map markings.
So for example I made a waypoint just over Calais Marck airport and after 3 minutes I hit pause and checked my position on the map (which is very precisely because one sees your own plane as a miniature on the map).

That means the distance is very precisely and so is the time. Only the speed could make some trouble. But since you can mouse over the speed gauge (and I made the same speed on every waypoint in the FMB, 250kmh) I don´t see that as possible mistake either :confused:

But it´s interesting that in your test the plane also tend to be rather "too fast" which can´t be a coincidence I suppose.

For a very short visible aided test, you could use 2 balloons very precisely set using the FMB...or ie. 50 balloons for a greater distance

Nifty procedure -- much more precise than mine. Mousing over the airspeed indicator in the RAF fighters may introduce error; the readout rounds off to the closest +/- 10 mph. I don't know if that's the case with LW fighters (although the rounding off to the closest 10 kmh would introduce less error, I expect.)

Trying your procedure over a longer distance would be interesting to see if any error decreases, or, as you suspect, may stay the same % anyway.

If weather and cloud cover is ever introduced, your findings will be instrumental in calculating how to meet the waypoints towards the target......or missing them outright.

Good post. My head hurts. LOL

I did a little test in FMB, where I let 2 AI planes fly next to each other for some miles. One was a 109E-4 and the other a Spit 1.
I measured the time it took for them to travel 20 km and I checked their speed gaugets (AI on).

Observation 1: The 109E-4 outran the Spit on every try :-P No idea why they did not match speed since I used exactly the same settings on them.

Observation 2:
The airspeed gauge on the 109 red 310 kph, but the calculation gave me 325 kph=a difference ofabout 5%

The spits gauge showd 170 mph=273 kph, but the calculations gave me 316 kph=a difference of about 15%

I'm aware that I'm comparing IAS and ground speed here, but the difference at 500 meters should not be this big, right?

Comparing theese results with the table in post: http://forum.1cpublishing.eu/showthread.php?t=34115

Coincidence? :grin::confused:

/m

IAS will be equal to TAS at sea level only at certain air pressure and temperature. If present conditions are different (like you are flying on hotter/colder day), TAS and IAS will be different even if you are almost "surfing" the waves in your plane.