Maximum Climb Rating

Figure 10.43 shows the maximum climb SHP and fuel flow (sfc) in nondimensional form for the standard day up to a 30,000-ft altitude for four true air speeds from 50 to 200 kts. Intermediate values may be linearly interpolated. The break in SHP generation up to a 6,000-ft altitude is due to fuel control to keep the EGT low.

Equation 11.15 (see Chapter 11; the turboprop case is not worked out) requires a factor k2 (varies with speed and altitude) to be applied to the SHP. From Figure 10.43a, a value of 0.85 may be used to obtain the initial climb SHP. Initial climb is at an 800-ft altitude. In the example, the uninstalled initial climb power is then 0.85 x 1,075 = 914 SHP. The integrated propeller performance after deducting the installation losses gives the available thrust. Typically, the initial climb starts at a constant EAS of approximately 200 kts, which is approximately Mach 0.3. At a con­stant EAS climb, the Mach number increases with altitude; when it reaches 0.4, it

(a) Shaft Horsepower (b) Specific Fuel Consumption

Figure 10.43. Uninstalled maximum climb rating (turboprop)

is held constant. Fuel flow at the initial climb is obtained from Figure 10.43b. The example gives 0.522 x 914 = 477 lb/hr. With varying values of altitude, climb calcu­lations are performed in small increments of altitude, within which the variation is taken as the mean and is kept constant for the increment.

Maximum Cruise Rating

Figure 10.44 shows the maximum cruise SHP and fuel flow in nondimensional form for the standard day from a 5,000- to 30,000-ft altitude for true air speed from 50 to 300 kts. Intermediate values may be linearly interpolated. The graph takes into account the factor k1 (varies with speed and altitude) as indicated in Section 11.3.3, Equation 11.19.

In the example, the design initial maximum cruise speed is given as 300 kts at a 25,000-ft altitude. From Figure 10.44a, the uninstalled power available is 0.525 x 1,075 = 564 SHP. In Figure 10.44b, the corresponding fuel flow is 0.436 x 564 = 246 lb/hr. The integrated propeller performance after deducting the installation losses gives the available installed propeller performance.

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