Don't make performances secret this time

[Rama]

Originally Posted by PE_Tihi

Can a plane have a wingspan of 10, 11, and 12,5 m at the same time? Can it have a max. speed of 480, 530, and 565 km/h at the same time?

Wingspan isn't FM data, it's structural data.
About max speed, for each plane type you can find different sources giving you different numbers, and even different reference altitude for max speed.
... and that's including different real flight test data.

Originally Posted by PE_Tihi

Try here, you wont have to calculate anything:

Ahah.... and do you think your link gives the only valuable and universal source??? you must be kidding...
Have you tried, just for ONE type of plane to gather all different performance sources and to compare them... you should try, it will help you to understand the problem...