Turbofan Engine: Civil Aircraft

All thrusts discussed in this section are uninstalled thrust. There is loss of power when an engine is installed in an aircraft, as discussed in Section 10.10, from 7 to 10% at the takeoff rating depending on how the ECS is managed. At cruise, the loss discreases to 3 to 5%. For simplicity, both military and civil aircraft installation losses are kept at a similar percentage, although the off-take demands are signifi­cantly different.

Figures 10.45 through 10.51 show the turbofan power at the three ratings in a nondimensional form for civil aircraft engines with low and high BPRs. Civil – aircraft turbofan performance is also divided into two categories: one for a lower BPR on the order of 4 and the other at 5 and above. The most recent engines (i. e., engines for the newer Boeing787, Airbus350, and Bombardier Cseries) have

reached a BPR of 8 to 12; however, the author could not obtain realistic data for this class of turbofans.

The higher the BPR, the less is the specific thrust (TSLS/ma, lb/lb/s). There is a similar trend for the specific dry-engine weight (TSLS/dry-engine weight, nondimen­sional). Table 10.7 may be used for the computations.

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