Module 1 Lateral Stability Flashcards
Lateral Stability relate too?
When an unexpected force produces a rolling moment about the longitudinal axis, the aircraft will be in a. lateral disturbance.
When would an aircraft be laterally stable?
If the aircraft is able to produce a restoring rolling moment to return to its equilibrium position. “keel effect”
How is the sideslip created?
When aircraft is in a roll disturbance Lift and weight don’t act through the same place, so the sum of these two forces directs it to one side, this movement is the sideslip.
When is the sideslip angle positive in lateral stability?
When the relative airflow is comes from right of heading, otherwise it is negative sideslip angle.
When is rolling moment positive and negative in a left roll disturbance?
Rolling moment is positive when it rolls to the right and negative when it rolls to the left.
Which factors effect Lateral Stability?
Lateral Dihedral, Shielding, Wing position (vertical), Fin area, Sweep back wings
How does lateral Dihedral effect lateral stability?
give an example?
Dihedral wing can produce a restoring moment when the aircraft is in rolling disturbance.
Aircraft with dihedral wing is in a disturbance of left roll, and the wing sideslips to the left. Which means the RAF comes from left of the heading, (negative sideslip angle). The RAF forms a greater aoa on the down going wing then the up going wing which produce more lift and produce a right roll restoring moment.
What does Anhedral wings do to lateral stability?
AOA of lower wing to the RA is less than the upper wing so encourages the disturbance?
Benefit of Anhedral wings?
Prevent unstable dynamic oscillations like dutch roll.
How does shielding effect lateral stability?
The fuselage acts a shield of the upper wing from the RAF so the lower wing will produce more lift and greater rolling moment to raise the Lower wing.
How does high wing aircraft effect lateral stability?
High wing position, makes the wings above the centre of gravity and the fuselage acts as a shield of the RAF. So the lower wing will produce more left than the upper wing to create a restoring moment.
Stable feature of lateral stability.
How does low wing aircraft effect lateral stability?
It is an unstable effect.
How does fin area effect lateral stability?
Produces drag to the sideslip, fin area located above the longitudinal axis, so it is a positive restoring moment.
How do sweep back wings effect lateral stability?
Sweep back wings create a higher effect wingspan and higher aspect ratio of its lower wing to the relative airflow when is roll disturbance. So the lower wing will produce higher lift due to its greater lift than the upper wing.
