Forces/Aerofoil

What are the forces acting on an aircraft in flight? Drag, thrust, lift, and weight. When thrust and drag are in equilibrium, an aircraft will maintain a steady speed. For an aircraft to accelerate, thrust must exceed the value of drag. When lift and weight are in equilibrium, an aircraft will maintain a steady, level attitude. For an aircraft to climb, lift must exceed the weight of the aircraft. In a banked turn, weight is a constant, but lift is lost due to the effective reduction in wing span. Therefore, to maintain altitude in a banked turn, the lift value needs to be restored by increasing speed and/or the angle of attack.

 

What produces the maximum glide range?

A maximum lift-drag ratio, obtained by the aircraft being flown at its optimal angle of attack and corresponding minimum drag speed (VIMD), produces an aircraft’s maximum glide range.

What is the effect of weight on the glide range?

The glide range does not vary with weight, provided that the aircraft is flown at its optimal angle of attack and speed for that weight, because the glide range is proportional to the lift-drag ratio, which does not vary with weight. Therefore, if a heavy aircraft were flown at the correct angle of attack and speed, it would glide the same distance as a lighter aircraft. However, the heavier aircraft would have a higher airspeed than the lighter aircraft, and therefore, although it would glide the same distance, it would take less time to do so.

What is rate of climb/descent?

Rate of climb/descent is the vertical component of the velocity of an aircraft and determines the time it will take to either climb or descend from a given height. It is normally expressed in terms of feet per minute.

What is the effect of weight on rate of descent?

The heavier the aircraft, the greater its rate of descent. This is so because a heavy aircraft will fly at a higher airspeed for a given angle of attack, and so its rate of descent will be increased.

What is an aerofoil?

An aerofoil is a body that gives a large lift force compared with its drag when set at a small angle to a moving airstream, e.g., aircraft wings, tailplanes, rudders, and propellers.

What is an aerofoil chord line?

The chord line is a straight line from the leading edge to the trailing edge of an aerofoil.

What is the mean chord line?

The mean chord line is the wing area divided by the wing span (sometimes referred to as the standard mean chord).

What is the mean chamberline?

The mean chamberline is a line from the leading edge to the trailing edge of equidistance on the upper and lower surfaces of an aerofoil.

What is the angle of incidence?

The angle of incidence is the angle between the aerofoil’s chord line and the aircraft’s longitudinal datum. It is a fixed angle for a wing but may be variable for a tailplane. (It is sometimes called rigging incidence.)

What is angle of attack?

Angle of attack is the angle between the chord line of an aerofoil and the relative airflow.

What is washout on a wing?

Washout is a decrease in the angle of incidence from the wing root to the tip. This compensates for the early stall due to the higher levels of loading experienced at the wing tips.

What is dihedral?

Dihedral is the upward inclination of a wing from the root to the tip.

What is anhedral?

Anhedral is the downward inclination of a wing from the root to the tip.

 

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