Spitfire Mk.I strange behaviour

[Flanker35M]

S!

First of all this issue came up after had a talk with a friend. He had ran some tests on Spits and Bf109E's and noted something. I tested quickly on ATAG with Spitfire Mk.I and noted the same thing as my friend. Let me explain.

First I took off with a Spitfire Mk.I with 25% fuel and NO ammo, so the plane is light and should go fast. I flew level for some time at sea level to stabilize things and I got 250mph IAS with full throttle(6.25lbs) and pitch on coarse(pitch 2 in game).

Then I took same plane with guns loaded and 100% fuel. Again stabilized to level flight at sea level. What I got now was 265mph IAS! So the heavier Spitfire was faster than the empty one. In both cases plane was trimmed so everything was centered.

My friend said this applies to Spits at least, has not tested Hurricanes yet. He did a comparison with the Bf109E-4 and the difference was a mere 2-5km/h so there plane weight did not effect the slightest. I need to test and verify this too.

Comments? I smell a possible bug here which hampers performance for some reason.

I have to test it myself.

One thing I like to mention that should be considered when interpreting the results:

The weight in itself has no direct influence on the speed as such. The only impact on speed is due to induced drag as more angle of attack has to be applied for a higher weight which will increase the drag from which a reduced max speed results. This may be not extensive so only a little speed loss may be all right. The weight will overall be however very disadvantageous for acceleration.

However it shoulf of course not go faster with higher mass.

[trademe900]

well said. As with cars, increased weight does not effect top speed, only acceleration. With planes however the angle of attack comes into it.

[Osprey]

265mph in a loaded MkI seems a bit quick. Are you sure you were in a descent or just exited one?

[koko]

Hi,

agreed with Stormcrow

Originally Posted by 41Sqn_Stormcrow

This may be not extensive so only a little speed loss may be all right. The weight will overall be however very disadvantageous for acceleration.

However it shoulf of course not go faster with higher mass.

and Flankers question/point was...

Originally Posted by Flanker35M

So the heavier Spitfire was faster than the empty one.

I got same 265mph IAS at SL with guns loaded + 100% fuel. Takeoff weight 2756kg

and about 253-255mph IAS at SL without cartridges + 10% fuel Takeoff weight 2330kg.

I kept both speeds long enough to make sure that i'm not in a descent.



<S>koko

[41Sqn_Banks]

That's weird.

Also weird: The Spitfire Ia doesn't achieve +6 1/4 boost at 3000 RPM after take-off, only when RPM is dropped to 2600 the boost increases +5.x to +6 1/4.

[Flanker35M]

S!

Maybe a test server would be in place to gather more information before and after the patch? Could easily compile data to an easy to read form to be submitted to devs. Just an idea..

[gimpy117]

Aerodynamically that makes no sense...weight has an effect on drag from the wings. Heavier planes should be slightly slower

[Kurfürst]

Weight has very marginal effect on top speed. See for example this German graph for 109G speed decrease at various weights: http://www.kurfurst.org/Performance_...fect_speed.jpg

The story short: the graph says that if you increase the 109G weight from 3000 kg massively, to 4000 kg, speed will decrease by about 7 km/h at SL and by about 18 km/h at rated altitude.

As more practical or realistic weight changes, ie. 1-200 kg (plane carried 300 kg fuel), the speed difference is only 1-2 km/h...

[Flanker35M]

S!

But the thing is that on Bf109E the difference between empty and full is next to nothing, within 2-3km/h. On Spitfire the difference is over 10mph so a lot more. And the heavier beng faster. Strange behaviour in the game. Need more testing.