The British ASI

[bolox]

some 'evidence'


taken from (fig
http://jsbsim.sourceforge.net/spit_flying.pdf

note it is for a Va but it is a fully instrumented test.
a quick try at replicating these conditions ingame ( SpitIIa 210 IAS trimmed level flight, 2650rpm estimated 2G pull) gives a drop in IAS to ~165mph and ~200 on release. To me that is a huge difference- infact the chart shows a very slight increase in IAS at pull

The graphs of timed 180 turn also fail to show any noticeable corellation between sideslip and IAS, certainly not the ~30mph difference experienced ingame.

Is this sufficient proof to put to Luthier? or are there any errors that anyone can spot that need to be addressed?

[IvanK]

Thanks for reopening the Bug on the tracker site Ataros

Good reference there BOLOX.

[Osprey]

Yes this is a big annoyance and one of the main reasons the 109 can just go vertical to live. Tactically, that aside, can someone please explain how to vote for a bug please? I see lots have done it but I must be dim because I can't work it out.

[41Sqn_Banks]

Originally Posted by Osprey

Yes this is a big annoyance and one of the main reasons the 109 can just go vertical to live. Tactically, that aside, can someone please explain how to vote for a bug please? I see lots have done it but I must be dim because I can't work it out.

As far as I understand it's only a instrument error and doesn't effect the actual air speed.

[IvanK]

Originally Posted by 41Sqn_Banks

As far as I understand it's only a instrument error and doesn't effect the actual air speed.

Agreed its an instrument display indication bug. Actual IAS is not changing So FM wise it has no impact.

[albx]

Originally Posted by Osprey

Yes this is a big annoyance and one of the main reasons the 109 can just go vertical to live. Tactically, that aside, can someone please explain how to vote for a bug please? I see lots have done it but I must be dim because I can't work it out.

go here http://www.il2bugtracker.com/issues/2 if you are logged in then click the green arrow next to Votes...

[Osprey]

Thanks mate, I hadn't registered, it was obvious really..........D'oh!

[bolox]

been doing some more digging on this, mainly trying to be a 'devil's advocate' to punch holes in my theory that the effect as currently modeled is incorrect.

http://naca.central.cranfield.ac.uk/...rc/rm/3365.pdf

is the only thing i've found, and while not conclusive it does show some tests between various types, including a German pitot (HNG). This would appear to show small variations between types but not the variations seen ingame, to me they appear to be of almost an order of magnitude out.

anyone an expert on fluid dynamics here care to look these over?

2 other slightly relevant things i've discovered- spitII had a modified pitot fitted- 'single' tube as compared to the earlier 'forked' type (separate pitot and static tubes mounted parallel )
http://spitfiresite.com/2010/04/supe...ed-line.html/3

also acceptable tolerance for alignment of pitot head in HurriII is +/-2 deg which seems to fit with errors given in first reference, showing less than 1% difference below ~15 deg of off axis alignment and gross errors only occurring above ~20 deg off axis

[ElAurens]

Is it possible that the mechanical parts of the cockpit instrument itself are being affected by G-loading? I know this was a problem with some Smiths tachometers fitted to various racing cars in the 60s. When they came to Daytona to run the 24 hour race the drivers were reporting visual RPM drops when the cars were on the high banking at speed. The G forces were actually pulling the needle down.

Just a thought.

[IvanK]

I don't think so. Firstly its designed to operate in a high G environment. Secondly the needle always reduces even when sitting at the 3 O Clock position and G is applied ... i.e against the force !

There is no Historical record that I know of the current behaviour.