@ San Francisco, CA

October 2012

This Canadian CF-18 does a nice flyby during the San Francisco Fleet Week airshow

Wing shape is called ‘wing planform’ and it’s viewed from above. There’re varios planform shapes:

• Rectangular: most desirable stall characteristics (from wing root to wing tip). Ineffective from structural, weight and drag point of view.
• Elliptical: most efficient regarding structure, weight and drag. Disadvantages are stall characteristic (from midpoint along the trailing edge) and as the AoA increases, the stall spreads both inwards and outwards.
• Tapered: Mix between rectangular and elliptical on characteristics depending on the taper.
• Swept-back and Delta: very efficient on high-speed. Stall begins near the tip, causing poor lateral control.

Wing Placement

There’re:

• Low wings
• Mid Wings
• High Wings

All designed to ensure that the fore and aft CG of the airplane remain close to the lateral centre line of the wing structure throughout the whole flight envelope.

General Wing Construction Principles

Flutter. It’s a resonance vibration which can cause serious damage to the structure and eventually failure. If flutter is encountered, the speed should be immediately be reduced. Some planes, the management of fuel consumption is designed to reduce flutter, using the wing tanks to balance the wings, until the end of flight.

Spars. It corresponds to the longhorns of the fuselage. Loads imposed on wing structure are applied on the skin, and then transmitted to the spars through the skin and the ribs. This makes the spars the major load supporting members in the wing structure.

Wing Rib Lightnening Holes. Most important on design & construction is strength/weight ratio. To achieve this, it is used to make holes with flanged edges in the ribs.

Different Wing Construction Principles

Though the stressed skin structure is the most widespread construction principle, there are other methods of wing construction:

• Wing of Wooden Construction: apart from strength, a problem with water. It must be coated perfectly and provided with adequate draining holes to eliminate any moisture.
• Wing Consisting of Composite Material (Sandwich Construction): a wing made of laminated structure in which thin sheets of metal are bonded to a core of fibre glass, paper or metal honeycomb material.
• Honeycomb Core: major advantage is longitudinal strength and lightness.

Maximum Zero Fuel Mass: maximum permissible mass of an aircraft including useful load but with no usable fuel. It’s a limit set for structural reasons to prevent excessive bending stresses in the wing root.

October 2009