Boeing 717-200
The wing area of this airplane is 1000 ft2 (based on trapezoidal reference extended into centerline)
and has a sweep at the c/4 line of 24.5 degrees. The taper ratio is 0.20. The tail area is 275.5 ft2
with a taper ratio of 0.352 and a sweep of 31.6 deg at the c/4 line. The distance from the wing 25% MAC to the
tail 25% MAC location is 52.5 ft. The airplane weighs 100,000 lbs.
1. Estimate the location of the neutral stability point or aerodynamic center for the wing/tail combination shown
above at low speeds. Ignore the fuselage effects and the very important nacelle and pylon effects for the moment.
a. Use analytic formulas for lift curve slope including downwash on the tail and assume the a.c. of each surface
is located at 25% of its MAC.
b. Use the LinAir program in the notes and compare your answers. Why are these different?
2. Compute the tail lift required to trim at CL = .45 if the c.g. were located at 25% of the wing MAC
and the wing Cm_a.c. was -0.07 based on MAC. Express your answer in terms of Ltail / Lwing.
You may use analytic expressions or the LinAir program to compute this.
3. Estimate the airplane trim drag ignoring compressibility effects. The trim drag is the extra airplane drag associated
with the requirement for trim. Express your answer in terms of DCD_trim.
Note that the overall airplane CD is about 0.030 at this flight condition.