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If Wikipedia is correct the 60 years old NK-12 is more fuel efficient than the Europrop TP400, the engine for the Airbus A400M transport aircraft.

For the NK-12MV a specific fuel consumption of 0.219 kg/kW-hr is given.

The TP400 has a specific fuel consumption of 0.238 kg/kW-hr according to Wikipedia.

Am I interpreting these specifications wrongly?

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  • $\begingroup$ Can you provide some figures? $\endgroup$ – mins May 14 '15 at 9:00
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The source of the Specific Fuel Consumption in Wikipedia is unclear. I have found a paper (PDF) that discusses the efficiency of shaft power off-take (that is using engine power to drive systems such a electric and hydraulic generators instead of delivering propulsion).

It mentions the TP400-D6 (which is installed on the Airbus A400M) has a SFC of 0.167 kg/(kW.h) for shaft power off-take and a SFC of 0.213 kg/(kW.h) for delivering propulsive power. This means that the TP400 is more efficient than the Wikipedia article presents and more efficient than the SFC of the NK-12 presented by Wikipedia.

It also shows that the TP400-D6 is more efficient in delivering shaft power than in delivering propulsive power.

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Age of design

It is likely that the design of a newly manufactured NK-12 differs significantly from the original designs produced 60-years ago. So we are not really comparing the TSFC of an original 1950's NK-12.

Speed

Wikipedia's source for the NK-12 quotes a "TO" figure - presumably TSFC at take-off power.

Wikipedia doesn't identify a source for it's (T)SFC figure for the TP400. The makers of the TP400 don't publish SFC figures.

TSFC increases with speed. Many published TSFC figures are for cruise speeds.

Props

I imagine efficiency depends somewhat on application, and this must include propeller design.

It might be that there are factors other than fuel-efficiency that affect propeller design. For example, noise may not be a factor for most military applications but it would affect civil applications.

Both these engines were designed for military applications but there may have been some difference in prioritisation of these and other factors.

Conclusion

I don't think it has been clearly shown that the NK-12 is more efficient than the TP400 (though it may well be).

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    $\begingroup$ Knowing the speed at which the SFC figure is measured is key. BTW, I think the question is not about one particular engine which is 60 years old, but about the design per se, considering that materials and processes back then allowed lower compression ratios and turbine entry temperatures than today. $\endgroup$ – Peter Kämpf May 14 '15 at 10:07

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