An engineer compares two wings of identical area, span, and airfoil section: Wing A has a pure elliptical planform, and Wing B has a rectangular planform incorporating washout. Regarding stall progression across the span, which statement is correct?
- AWing planform and washout have no measurable effect on the spanwise stall pattern
- BWing A tends to stall nearly uniformly across the entire span with little stall warning, while Wing B stalls at the root first, preserving aileron control and giving buffet warning
- CWing A stalls at the tips first, giving strong aileron buffet warning, while Wing B stalls uniformly with no warning
- DBoth wings stall at the tips first regardless of planform or twist
Show answer & explanationAnswer & explanation
Correct answer: B. Wing A tends to stall nearly uniformly across the entire span with little stall warning, while Wing B stalls at the root first, preserving aileron control and giving buffet warning
An elliptical wing produces uniform lift distribution and therefore reaches critical AOA nearly simultaneously across the span, giving little pre-stall warning and abrupt aileron loss (as on the WWII Spitfire). A rectangular wing with washout has a lower AOA at the tips, so the root stalls first, keeping the ailerons effective longer and providing buffet as warning.
Why the other options are wrong
- A. Planform and washout are specifically designed to control stall progression.
- C. Reverses the actual stall behavior of the two planforms.
- D. Ignores the effect of washout, which deliberately delays tip stall.
Wing Planform and Stall Progression
Wing shape and twist (washout) determine where along the span the wing first reaches critical AOA and stalls.
- Elliptical wing stalls uniformly across span (least warning)
- Rectangular/tapered wing with washout stalls root first
- Root-first stall preserves aileron effectiveness and gives buffet warning
Memory trick: Elliptical = 'all at once' stall; washout wing = 'roots go first, tips stay flying.'