Originally Posted by ryane946
Does anyone know much about the TU-95 Bear? This bomber could go as fast as a B-52 and it used 4 turboprop engines. Was it just incredibly inefficient, or did they develope something to solve the problems that keep propeller aircraft slow?
Don't quote me on this but if i remember things correctly...
I believe the key to keeping propeller aircraft efficient at high speeds is to develop more power from slower turning props. They do this with more blades on each engine. This is allows the propeller itself to turn slower but because more airfoils are moving through the air more thrust is developed. By turning the propeller slower you reduce problems with shockwaves forming on the propeller blades as they approach supersonic speeds. Thats how the DO328, Saab 2000 and Q400 get their speed and efficiency. True they don't reach RJ speeds but they get pretty darn close. I remember flying from Fargo, ND to Denver on both RJs and DO328s when AWAC still had them and the difference in block times was only about 20 mins. Not bad for a 700nm leg!
As far as the Bear goes, it had 2 propellers on each engine turning in opposite directions (can you imagine the complexity of the gearing on that!) So effectively each engine had an 8 (maybe 12?) blade propeller on it. Why bother getting that complex? Why not just slap 36 blades on one propeller? It turns out that when you get more than about 6 blades on a propeller you run into problems with each blade causing interference and turbulence for the blade following it. I believe that is how they were able to get so much speed out of the Tu-95 but as far as range and reliability, I don't think it was as good as the B-52.