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qid 12205 · engineering
Question: The wings of anaeroplanehave a total plan area of 320 ft^2 The plane weighs 18,000lbf, and the normal speed in level flightis 230 ft/sec when the atmospheric density is 0.076lbm/ft^3. (a) If thetailplanecontributes 5 percent of thetotal liftforce, whatmust be the lift coefficient of the wings at this operating condition ? (b) If, at the same flight condition, the drag coefficient of the wingsis 0.055, and the total drag is 1.75 times that caused bythe wings alone, what forward thrust is required? Ignore interferencebetween the wings and the fuselage.
- 0.85, 1937lbf
- 0.80, 1987lbf
- 0.95, 1837lbf
- 0.70, 2087lbf
- 0.78, 2032lbf
- 1.00, 1787lbf
- 0.90, 1887lbf
- 0.75, 2037lbf
- 0.60, 2187lbf
- 0.65, 2137lbf
Our answer: A. 0.85, 1937lbf Source quote machine-checked (exact quote)
How it was answered
Multi-step solver (maze), replayed by code
Current source
NASA Glenn Research Center, Beginner's Guide to Aeronautics, "The Lift Equation"
https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/lift-equation/
Source quote machine-checked (exact quote)
Earlier version (superseded)
No public source has been found for this card yet (3 places checked internally).