jbob Posted December 1, 2014 Share Posted December 1, 2014 Figured us Herc guys would be interested in how the counterrotating props appeared. Quote Link to comment Share on other sites More sharing options...
Spectre623 Posted December 1, 2014 Share Posted December 1, 2014 Looks like no prop brake I guess. Quote Link to comment Share on other sites More sharing options...
jbob Posted December 1, 2014 Author Share Posted December 1, 2014 Bill...I'd be interested to see how these props work. Free spool? With counter rotating props I'm not sure of the technology behind the operation. May not require a prop brake. Just feathering to produce minimal drag. Quote Link to comment Share on other sites More sharing options...
tinwhistle Posted December 2, 2014 Share Posted December 2, 2014 I have to plead complete ignorance. What purpose is there in these counter rotating props? Seems to me they would be self defeating, counter productive if you will. I certainly do not understand the engineering behind (what appears to be) very complicated technology..... Quote Link to comment Share on other sites More sharing options...
jbob Posted December 2, 2014 Author Share Posted December 2, 2014 The engine used is the Kuznetsov NK-12. After a little Google searching I found this. The biggest problems for the turboprop engines were being resolved quickly. The largest of these problems was to have a propeller capable of absorbing great power without having very large diameter and not be very wide blades. The diameter limits the propeller speed because the tips of the blades to spin at supersonic speed, they lose much of their efficiency. A string (wide) very large blade generates too much drag and wastes excessive power. The solution was found in the form of two counter-rotating propellers mass coaxial 4 blades each. Propellers counter-rotating coaxial were common in nautical use, especially in torpedoes, but were not very usual in aviation. It was a good solution, even having disadvantages such as increased mechanical complexity and weight powerplant assembly. and The specific consumption of the NK-12 engine, 0.360 lb / hp-hour, is well below the consumption of turboprop engines of the same generation as Americans Allison 501A, 4,100 HP and specific consumption of 0.490 lb / hp-hour, or even much more modern engines. Quote Link to comment Share on other sites More sharing options...
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