Speed graphs for Spitfire and Hurricane

[ramstein]

Originally Posted by Insuber

It is interesting to see the wide tolerance of the contractual performance of the Bf-109. The error of +/-5% on the top speed of 500 km/h translates into 10% or 50 km/h of allowed error in absolute figures. Add to that the wear of operations and you can easily have poor performers.
It would be equally interesting to know the tolerance of the British types, I would not be surprised to see higher tolerance values for the Spitfire, given the poor status of the Supermarine rigs and tools at the beginning of production (see the Leo McKinstry book on the Spitfire to have an idea about the mess of the Supermarine works in 1938-39).

PS: how nice if this variability is modeled ... it shouldn't be that difficult ...

speaking tolerances..., in piston engines, I learned while attending a college in auto mechanics.. and engine rebuilding, that the tolerance for engine pistons in cylinders was purposely set a bit loose like .004 of an inch for faster break ins for engines that needed less break in times from the factory... , though you could set the tolerance down to .003 inch clearance of the pistons and cylinder for a much tighter fit, but slower break in times..

I would bore the cylinder and put a .003 inch clearance in the cylinder of v8 engines.
I also cut valves, rods, etc, on machining equipment.

Taking into account this was a long time ago in engines from the 1960's. the engine parts from the 1930's and 40's were still much older and had much different metal properties that the engines I worked on... and now they are completely different metal properties and break in periods..

the differences are the metals, and cast and forged engine components.. and the rings are totally different too... The oils were absolutely different back then, they were non detergent oils...

I was thinking the tolerances must have been much looser, as they really didn't have time to run long break ins to get performance.

The altitude difference and the condensation from going up and coming down in altitude is considerable and must have introduced a lot more water into the engines and oil, from more open breathing designs of engines...

The condensation buildup or moisture in aircraft (of any age) is significant from the changes in altitude and humidity, inside and outside of aircraft, and even more so when pressurized. Those engines must have been through hell to go into war when new, and no time to break in parts..

I could see how there could be large differences in the performance of the same type aircraft... as the first few hours of engine running made a lot of difference in the life of the aircraft parts.. so a 50-100 kmh difference makes sense..