Vertical Stabilizer Characteristics of the Example Helicopter

Just as was done for the horizontal stabilizer, the aerodynamic characteristics of the vertical stabilizer of the example helicopter can be estimated from its physical parameters (Table 8.3).

Source: Von Mises, Theory of Flight, McGraw-Hill, 1944.

Fuselage

Conditions at the fuselage are shown in Figure 8.23. The various fuselage effects enter into the equations of equilibrium as:

X, = —Dp cos[0 – yc- e„f] + Lp sin[0 – Ус – гт]

YF = S. F.p cos p — DF sin p

ZF = —Lf cos[0 – yc – г„р] – Dp sin[0 – yc – £Mp]

MF = q{№/q)F, Nf = tf{N/q)F, RF =

Z

Rear View

FIGURE 8.23 Aerodynamic Conditions at the Fuselage

Lift, Drag, and Pitching Moments

Methods for estimating fuselage drag were outlined in Chapter 4. Methods for estimating fuselage lift and pitching moment prior to wind tunnel tests can be done either with the airplane methods of reference 8.1 or by direct comparison with wind tunnel results of previous helicopter fuselages. Figure 8.24 shows a compilation of the lift and pitching moment data as a function of angle of attack for several rather typical single-rotor helicopter fuselages in full-scale wind tunnel tests reported in references 8.18 and 8.19. The data has been nondimensionalized by dividing by the product of maximum fuselage width and length for lift data and the product of maximum fuselage width and fuselage length squared for moment data.

Another set of data reduced to coefficient form is given on Figure 8.25 for several fuselages of Bell helicopters. This data was taken from reference 8.2 and uses a different riondimensionalizing scheme than Figure 8.24.

The angle of attack of the fuselage is where

_ Vy TM

мр Vx 4qAM

The angle for zero lift can be assumed to be the same as for zero moment which in lieu of wind tunnel tests may be taken as the angle the aerodynamic cbrdline of the fuselage makes with the body axis.