Exercise 3 Aircraft Performance Given Aircraft Conditions Gr

Exercise 3: Aircraft Performance Given Aircraft Conditions: Gross Weight for Cruise = 300,000 lbs Wing Area = 3050 ft2 Wing Span = 156 ft Wing Efficiency = .75 CDp = 0.0119 Twin turbofan engine Aircraft Temp-Standard Figure 2.1 Atmospheric Conditions Figures 4.3 and 4.5

1. Find Stall Speed ?Stick Shaker? (KEAS) and Body AOA for Flaps 0 and Flaps 30 Configurations (Figure 4.3). Assume Wing area increases are adjusted in reported CL values.

2. Find L/D max. Flaps 0 and ignore the effects of compressibility with respect to CL and CD (Figure 4.5).

3. Find Best Endurance Airspeed (KEAS) and Mach number at FL350. Flaps 0 and ignore compressibility effects on CL and CD.

4. Find Body Angle of Attack associated with Best Endurance Airspeed. (Ignore effects of compressibility with respect to CL and CD).

5. Find Best Glide ratio and Distance Traveled (nm) at Best Glide AOA/Airspeed if the aircraft lost both engines at 35,000 ft (no wind). A. What is the glide path angle (deg)? B. What is the Pitch attitude (deg) using AOA from Question 4.

6. Using Equation 5.2, find Thrust Required (Drag) to maintain FL350 at best endurance speed (Flaps-0) and given Cruise Weight. (Ignore Compressibility Effects on Drag and see Figure 4.5.)

7. Using Equations 5.7/5.10/5.11, find Total Drag, Parasite Drag, and Induced Drag at FL350 (35,000 Pressure Altitude) at Max Endurance Speed and then compare to Problem 6.

8. Using Equation 5.14, find Power Required (hp) at FL350 Max Endurance Airspeed.

Solution

Given data

Gross weight for cruise = 3000000lbs

Wing Area = 3050ft²

Wing Span = 156ft

Wing efficiency = 0.75

CDp = 0.0119

Twin turbofan engine aircraft temp-standard

Figures 4.5

1) Stall speed = ?

      Stall speed stick shaker (KEAS) and body AOA for flaps 0 and flaps reported CL values

at flas O, CL (max) = 0.9 at 8.5 deg AOA

at flaps 30(CL(max) = 1.7 at 9.9 deg AOA

Vso = 180KEAS

Vs30 = 131KEAS

2) ( L / D)max = ?

   Flaps 0 and ignoring the effects of compressiblity with respect to CL and CD( From figure 4.5)

Slope of the tangent line from the origin intersects the drag polar in figure 4.5 at CL / CD = L / D = 0.48 / o.024 =20

3) Best endurance airspeed (KEAS) and mach number at FL350.Flaps 0 and ignore compressibility effects on CL and CD.

     VBE = 246KEAS

     350 = 0.235

       M = 0.766