Development of Swept Wings ~PLANES OF INCREASING SPEED

CHEUNG YAN LONG 3035044897

Swept Wing Examples• Backward Swept

Messerschmitt Me 262 Schwalbe

• WWII German Fighter

Boeing 787 Dreamliner• Modern Commercial Plane

Outline•Aerodynamic knowledge•Basic Idea of Swept Wing - types - applications•Q & A

Dunne D.8

Aerodynamics Drag

•Drag -- acts on any moving solid body in the direction of the fluid freestream flow.

-wave drag component of the drag on an object moving at transonic and supersonic speeds, due to the presence of shock waves

Basic Idea of Swept Wing

Wave Drag 3. Mikoyan-Gurevich MiG-15

4. Boeing 7471. Wright

Flyer I

2. Mitsubishi A6M

Critical Mach no.

Airflow perpendicular to the leading edge

Spanwise flow along the wing

Theory of Swept Wing•a wing with infinite length

•velocity heading to wing contribute to wave drag

•Critical Mach number

Pythagoras' Theorem

Advantages•Increase aircraft high speed performance (>~0.8Mach no.) - max. speed & energy efficiency 1. faster 2. Longer Range 3. More cost efficient

As a modern plane, why don’t I use swept wing?

RQ 4 Global Hawk PLA Dong

Feng 4

Drawbacks•Low Aspect ratio - lower lift (~30%) •unfavorable slow speed handling characteristics

-spanwise flow• Much easier to stall•Structural design

DerivativesVariable Backward Swept

Forward Swept

Grumman F-14 Tomcat• 20° - 68 ° backward

Least swept

Fully swept Сухой Су-47 Беркут

• Sukhoi Su-47 Berkut• ~20° forward• Extremely high

Maneuverability

The next derivatives•Oblique wing

AD-1 NASA,1994

Summary•Swept Wings Theory•Advantages & Disadvantages•Examples

•Future development

Airbus A380

References•http://www.desktop.aero/appliedaero/potential3d/sweeptheory.html

•http://talkaviation.com/content/stalls-jet-676/ Авіалінії Антонова

Ан-225 "Мрія“

• The Largest plane• The lower one, of

course!!

Q&A

Extra I – Critical Mach number

• Definition

The free-stream Mach number at which a local Mach number of 1.0 is attained at any point on the body under consideration.

• (always <=1.0 Mach)

• Different between airfoils

factors -angle of swept

-thickness of wings

(In general a thicker wing will have a lower Critical Mach number, because a

thicker wing accelerates the airflow to a faster speed than a thinner one.)

Reference sites for Critical mach no.•http://www.akiti.ca/Mcrit.html•http://soliton.ae.gatech.edu/labs/windtunl/classes/hispd/hispd04/Critical_Mach_Number.html

•http://soliton.ae.gatech.edu/labs/windtunl/classes/hispd/hispd04/Critical_Mach_Number.html

Extra II – Delta wing• Advantages - a large enough angle of rearward sweep - gives the largest total wing area low wing loading, accepted maneuverability

- simplicity of manufacture, strength• Disadvantages - high induced drag <1.0 mach - supersonic maneuverability restricted (as elevons become less effective) - large swept disadvantages under low speed

Extra III – More on Forward swept• Advantages

- inward spanwise flow

- maintain airflow over their surfaces

at steeper climb angles ( great AoA)

- high transonic maneuverability

• Disadvantages

- very strong structure needed (wings easily twisted)

- Yaw instability (rear swept reduced along the direction)

(remark: negative stability fit the tech “relaxed stability”

Extra IV – Mach Number•Depends on air pressure and temperature

•At Standard Sea Level conditions ,15 degrees Celsius

•340.3 m/s (1225 km/h, or 761.2 mph, or 661.5 knots, or 1116 ft/s)

•speed of sound increases with Temperature

•E.g. 86% only at 36000ft•39 x (outside air temp. in K)^2