= Fixed-wing aircraft
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A <fixed-wing aircraft> obtains most of its aerodynamic support from <aircraft wings> that do not continuously rotate around a shaft to generate <lift>. The word fixed distinguishes the lifting arrangement; it does not require every surface to be immovable or perfectly rigid. Both powered airplanes and an unpowered <glider (aircraft)> can use fixed wings.
<Thrust> and aerodynamic support are distinct. Relative motion through air produces <lift> and <drag>; an engine can supply the <thrust> needed to balance drag in steady level flight. The components must be resolved as <vectors>, since their directions change with the motion and attitude.<Four Forces on an Airplane by NASA Glenn Research Center>[Lift, Drag, Thrust and Weight]{ref}
For an original ideal turning model, suppose a point-mass <aircraft> maintains horizontal circular flight at constant <airspeed> $V$, with negligible vertical thrust and no net vertical acceleration. If its lift vector is inclined through a <bank angle> $\phi$, then
$$
L\cos\phi=W,\qquad L\sin\phi=\frac{mV^2}{R},\qquad W=mg.
$$
The horizontal component supplies <centripetal acceleration>. Eliminating $L$ gives $L/W=1/\cos\phi$ and $R=V^2/(g\tan\phi)$. With $V=40\,\mathrm{m/s}$, $\phi=30\,{}^{\circ}$ and $g=9.81\,\mathrm{m/s^2}$, the radius is about $282.5\,\mathrm m$ and the required lift is about $1.1547W$. The wing remains fixed to the body while its force direction changes in space.
This is a Newtonian force model, not a prediction that an arbitrary airplane can produce the required <lift>. The attainable <lift coefficient>, <wing loading>, propulsion and aerodynamic moments determine whether a particular steady condition can exist. In a steady unpowered descent, the balances instead lead to the <glide angle> relation.
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