[Juha]

Christer
the beauty of graphs is that one sees at glance roughly how much faster than Spit F. V LF V was at certain level, up to what level it was faster and how must faster F. V was above that at any given altitude. To explain that in writing one need a table which is more difficult to gasp.

Usually there are at least a speed graph, time to altitude graph and rate of climb graph for a certain type/version of a/c in books.

Beauty of a speed graph is that at level flight max speed is attained when max. thrust possible to develop with the engine-propeller combination (plus exhaust stack jet thrust) is equal to the drag. From that one can deduce much, if the thrust is smaller a certain amount because for ex. engine wear, propeller pitch problem, propeller wear because of stone hits etc, the max speed is lower by certain amount which is possible to calculate. Same way if the a/c skin is carefully waxed the drag of the plane is a little bit smaller and the plane is a certain amount faster. All is pure physics, not simple physics but anyway calculable.

There are books which explain the basics on all this, certainly also in Swedish.

I agree that the performance graphs might be more important for understanding fighters than ground attack planes.

HTH
Juha

PS as Jukka wrote, one can presents many phenomes by graphs, they are like compressed info.