This topic has been touched upon many times, i believe, but always as a side issue, and i’ve never seen it really explained properly. So i’d like to ask:
How can the d-30f6 engine be so economical? I am aware that there is always a game of give and take and I’m sure there were lots of compromises to achieve the low fuel consumption at very high speeds (mach 2.5 and higher).
The engine is usually qouted with a bypass ratio figure of 0.56, which is quite a lot for a machine intented to propel its aircraft to speeds of even mach 3. Sea level thrust at 0 speed is quoted to be some 155 kn. Bypass part of that thrust should not be negligable, but what happens once we’re supersonic? We lost the bypass air part of thrust, we lost the thrust from thinner air (10 km altitude being 40% of density than at 0 altitude), yet the available thrust is enough to push mig31 to mach 3. How?
People are mentioning ram recovery, which is fine, but why does it work so well on mig31, as opposed to other planes? What techniques enabled mig31’s intakes and engines to be so good and what are their bad sides? Am i correct in assuming the bad sides are bad enough for most of the mission profiles that few other fighter planes or interceptor planes bothered to use similar solutions?
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December 14, 2009 at 8:25 pm