you can search for the data, but we all know that a lot of FS aircraft don't stay close to real numbers through the whole spectrum (like fuel consumption).
Since I like to fly a variety of aircraft, I've found that a combination of AFSD and FSDat
http://pagesperso-orange.fr/hsors/afsd.html
with a simple test flight gets most of what you need... Full fuel, take off, climb, level and accelerate while monitoring the various numbers in AFSD, scribble notes and then put them in a simple spreadsheet (or just a notebook). Then you can plug the numbers into FSNav and be good to go. 10-15 minutes for each type ( while enjoying the scenery) and you end up with a pretty good FS9/FSX database and more 'realistic' than a lot of the historical data.
Rob
...since AFSD monitors the sim data it's pretty reliable ( even the fuel/range #s). For example I did a range test on a new a/c last month... once in cruise it said I had a range of 780 miles... I found an airport about 770 miles away, flew to it, landed (conserving fuel on the way down), landed and checked... 6 gal. remaining.