Spit IIA Speed in game test

[5./JG27.Farber]

Me and my wingman often have 200m's defference staring from the same field on our altimeters.

[klem]

Originally Posted by 5./JG27.Farber

Me and my wingman often have 200m's defference staring from the same field on our altimeters.

??!!

Both have same baro setting?
Reading from the tooltip or the gauge needle?
Tooltips are to nearest 100 feet in RAF planes so one a/c at 90 feet and one at 105 feet will read 0 and 100 respectively.

Or the 109s are porked and next time I will run from a 109 at 25 feet and see what happens behind me

[5./JG27.Farber]

We both take off and he'll say 2000m's and Ill say what? we are are at 2200. Read from the needle.

[IvanK]

Easiest way to set accurate QNH is set the Altimeter to the field elevation. Field elevation can be found in FMB. Attached file has every airfield's elevation in the Sim all obtained from FMB.

A 1mb error should only result in 30ft/10m error.

I do believe the default maps have some diurnal variation in both Temperature and pressure. I too have seen 992mb as the setting on ATAG at some times and 995mb at other times.

[klem]

Originally Posted by 5./JG27.Farber

We both take off and he'll say 2000m's and Ill say what? we are are at 2200. Read from the needle.

Specsavers?

Seriously, that's weird. Even if he had set field elevation, typically 995mb, thats only about 150 feet/50m difference from the default 1000mb. 992 would be about 240ft/80m.

[Crumpp]

Seriously, that's weird.

YES and pretty much invalidates the ability to test any kind of performance without a stable atmospheric model.

[Crumpp]

Even if he had set field elevation, typically 995mb, thats only about 150 feet/50m difference from the default 1000mb. 992 would be about 240ft/80m.

It should be easy to confirm the atmospheric model.

1. Go to a known airport like London Biggen Hill. The field elevation at EGKB is 599 ft.

2. Set your altimeter to field elevation (599 ft) and your altimeter setting should read 992mb when converted. If it does not read the setting and record the temperature.

[klem]

Originally Posted by Crumpp

It should be easy to confirm the atmospheric model.

1. Go to a known airport like London Biggin Hill. The field elevation at EGKB is 599 ft.

2. Set your altimeter to field elevation (599 ft) and your altimeter setting should read 992mb when converted. If it does not read the setting and record the temperature.

Temperature is if course important. btw Biggin alt may vary according to spawn point. On my server its true height (pos.z) is 180.77m/593.1 feet at the runway intersections and at the central 'airfield' symbol position in FMB but is listed as 587 feet in the info IvanK posted from the FMB.

In the ATAG server I find 992Mb is almost correct on the safe side but I've never seen Biggin in use on the patched server.

In my Channel test map for my own server I get Tangmere scripted out as 45 feet and temperature 16.9 deg C. Atimeter setting of 996mb gives altimeter reading of 59.08 feet and 995mb gives 31.36 feet (altimeter figures actually captured by scripting but gauge reading is correct as far as the human eye can tell).

At Manston it is scripted out as 150.2 feet and 16.7 degrees C. Alt setting of 996 gives altimeter reading of 167.24 feet and 995mb gives 139.74.

So, on that mission map I would set 995 to give me a safety margin for very low flying.

Now between airfield, a 0.2 degree C change over 145.2 feet altitude change = 1.377 deg C per 1000 feet. Standard rate is ~1.98 degrees C / 1000 ft but my only usng 1 decimal place for temp and a non-standard day pressure could be the cause of that anomaly as, say, 16.949 (Tangmere 16.9) minus 16.551 (Manston 16.6) would take us to 2.74 degrees / 1000. The real figure is somewhere in between so very likely 1.98.

My point is that I'm guessing the atmosphere across the map is consistent and without weather pattern although why it would be different in my server (Multiplayer, Server, Create Server) and the ATAG server I can't say UNLESS ATAG's Mission Parameters aren't standard (does Flow affect this?). I did try different mission start times to see if there is a generic 'day' weather pattern operating changing temperature and pressure over time but the temperature and required baro settings didn't alter between 7 a.m., 12 noon and 9:00 pm.

OK, just some more spare time rambling to indicate we don't have a standard day and we don't know why it changes between servers. Or why Farber's wingman's altimeter reads different to his by 200m

[5./JG27.Farber]

Originally Posted by klem

Specsavers?

Seriously, that's weird. Even if he had set field elevation, typically 995mb, thats only about 150 feet/50m difference from the default 1000mb. 992 would be about 240ft/80m.

Im talking about the 109. Maybe its different.

[Crumpp]

Biggin alt may vary according to spawn point.

Of course, I got my elevation from an aeronautical information site.

Look under METAR and be advised it changes with conditions. It will vary from 597-600 depending on which site you check.

Here it is 600 today:

http://www.checkwx.com/wxmain/fullsite/EGKB