Swept Wing Flashcards
What is a swept back wing?
A swept back wing is an aerofoil with a design where the leading edge and trailing edges of the wing are not perpendicular to the relative airflow, but rather fall back from the leading inboard section to the trailing outboard section of the aerofoil. Most jetliners and fighter jets have swept back wings due to its improved performance characteristics at high speeds.
What are the advantages of wing sweep back?
- Higher Mcrit, due to the delayed sonic disturbances
- Increased stability in turbulences, due to lack of lift production capability in up-drafts compared to a straight wing with the same surface area.
What are the disadvantages of wing sweep back?
- Increased difficulty in design
- Poorer lift qualities compared to straight wing with same surface area
- Higher stall speeds due to the increased lifting requirements
- Speed instability at slow speeds
- Increased wing-tip stalling tendency
Where does a swept wing stall first?
If uncorrected by wing fences, vortex generators, washout or other aerodynamic features the wing tip of a swept wing will stall first due to greater aerodynamic loading of the outer wing due to the wing sweep. This in turn causes a greater angle of incidence and an earlier stall. Span-wise flow increases this tendency.
What happens to the CoG when a swept back wing stall?
As the wing tip of a swept back wing will stall first this will cause the CoP t move forward and cause the nose to pitch up. This aggravates the stall condition.
How can a wing tip stall be reduced?
- Wash out
- Increased camber of the outer wing section
How does a swept back wing change the critical Mach number (Mcrit) and why?
Wing sweep increases Mcrit by breaking the vectors of the relative airflow into two components (airflow perpendicular to leading edge and span wise flow). This reduces the effective airflow which is perpendicular to the leading edge. As this airflow is the determining factor for Mcrit (this airflow is subject to sonic disturbances) the aircraft can fly faster before reaching the critical speed.
