Stability Flashcards
The distance between the CG and neutral point is called the ___ __ and is expressed as a percentage MAC
static margin
The forward limit of the static margin is usually determined by ___
- A fast enough pitching rate
- A control force that is not too high
The aft limit of the static margin is usually determined by ___
- Not exceeding a certain pitching rate
- A control force that is not too low
Lowering flaps will move the CP ___wards
rearwards
Extension of the landing gear will cause a nose ___ pitching moment, __creasing the tail down force
down, increasing
Damping __creases with altitude
decreases
Swept finds stall at a ___ angle of attack
higher
Explain the purpose of dorsal and ventral fins
They increase the direction stability during extreme sideslip conditions
The ventral fin has its greatest effect when flying at ___ pitch angles
high
The purpose of vortex strakes is to ___
Reduce yawing disturbance caused by the crossflow generated by aircraft with long noses at high AoA
The dihedral is the angle between ___
the 0.25 chord line of the wing and lateral axis
A ___ wingspan has a greater lateral stability
larger
Spiral instability occurs when __ stability is too great compared to ___ stability
directional, lateral
Dutch roll occurs when ___ stability is too great
lateral
Sweepback and dihedral increase the ___ stability only
lateral
With increasing altitude at constant IAS, the static lateral stability will ___ and the dynamic directional stability will ___
increase, decrease
With increasing altitude at constant Mach number, the static lateral stability will ___ and the aerodynamic damping is ___ meaning the dynamic directional-lateral stability will ___
not change, reduced, reduce
Static stick force stability can be recognised by having to ___ the control column to maintain a speed above the trim
push
The effect of wing downwash on static longitudinal sability is ___
negative
A swept/straight wing and a high/low aspect ratio are the least affected by turbulence
swept, low
Stick force stability means ___
with higher airspeed, you’re required to push further forward on the control column to keep the aircraft in straight and level flight.
Negative stick force stability can be found during ___ flight as more ___ is required to keep the nose from dropping at high speeds
transonic, stick pulling, rather than pushing
An inset hinge provides ___
aerodynamic balance
A positive camber has ___ effect on longitudinal stability
no
The pitching moment about the aerodynamic centre is always ___, regardless of angle of attack.
negative
Phugoid damping is normally ___
weak
Short period damping is normally ___
significant
Speed and altitude vary ___ during the short period oscillation
slightly
Speed and altitude vary ___ during the phugoid
significant
Dorsal and ventral fins have a ___ effect on longitudinal stability, a ___ effect on lateral stability, and a ___ effect on directional stability
neutral, negative, positive
The wing sweep angle is the angle between the ___ and the ___
quarter chord and the wing lateral axis
Stick force stability depends on ___ stability
longitudinal
Stick force stability is determined by the distance from ___ to the ___
neutral point CG
A CG which is further forward means a ___ stick force stability
higher
Manoeuvre stability will ___ with the static margin
increase
The static margin is the distance from the ___ to the ___
manoeuvre point, CG
Positive stick position stability means ___
that you pull back on the stick if the speed decreases, and push forward if it increases
Fully hydraulic flight controls (don’t) require mass balancing
they do
With increasing altitude and constant IAS, an aircraft with swept back wings will see ___ static lateral stability and ___ dynamic lateral-directional stability
increasing, decreasing
With increasing altitude and constant Mach number, an aircraft with swept back wings will see ___ static lateral stability and ___ dynamic lateral-directional stability
no change in, decreasing
