Stability

Question 1

The distance between the CG and neutral point is called the ___ __ and is expressed as a percentage MAC

Answer 1

static margin

Question 2

The forward limit of the static margin is usually determined by ___

Answer 2

• A fast enough pitching rate

- A control force that is not too high

Question 3

The aft limit of the static margin is usually determined by ___

Answer 3

• Not exceeding a certain pitching rate

- A control force that is not too low

Question 4

Lowering flaps will move the CP ___wards

Answer 4

rearwards

Question 5

Extension of the landing gear will cause a nose ___ pitching moment, __creasing the tail down force

Answer 5

down, increasing

Question 6

Damping __creases with altitude

Answer 6

decreases

Question 7

Swept finds stall at a ___ angle of attack

Answer 7

higher

Question 8

Explain the purpose of dorsal and ventral fins

Answer 8

They increase the direction stability during extreme sideslip conditions

Question 9

The ventral fin has its greatest effect when flying at ___ pitch angles

Answer 9

high

Question 10

The purpose of vortex strakes is to ___

Answer 10

Reduce yawing disturbance caused by the crossflow generated by aircraft with long noses at high AoA

Question 11

The dihedral is the angle between ___

Answer 11

the 0.25 chord line of the wing and lateral axis

Question 12

A ___ wingspan has a greater lateral stability

Answer 12

larger

Question 13

Spiral instability occurs when __ stability is too great compared to ___ stability

Answer 13

directional, lateral

Question 14

Dutch roll occurs when ___ stability is too great

Answer 14

lateral

Question 15

Sweepback and dihedral increase the ___ stability only

Answer 15

lateral

Question 16

With increasing altitude at constant IAS, the static lateral stability will ___ and the dynamic directional stability will ___

Answer 16

increase, decrease

Question 17

With increasing altitude at constant Mach number, the static lateral stability will ___ and the aerodynamic damping is ___ meaning the dynamic directional-lateral stability will ___

Answer 17

not change, reduced, reduce

Question 18

Static stick force stability can be recognised by having to ___ the control column to maintain a speed above the trim

Answer 18

push

Question 19

The effect of wing downwash on static longitudinal sability is ___

Answer 19

negative

Question 20

A swept/straight wing and a high/low aspect ratio are the least affected by turbulence

Answer 20

swept, low

Question 21

Stick force stability means ___

Answer 21

with higher airspeed, you’re required to push further forward on the control column to keep the aircraft in straight and level flight.

Question 22

Negative stick force stability can be found during ___ flight as more ___ is required to keep the nose from dropping at high speeds

Answer 22

transonic, stick pulling, rather than pushing

Question 23

An inset hinge provides ___

Answer 23

aerodynamic balance

Question 24

A positive camber has ___ effect on longitudinal stability

Answer 24

no

Question 25

The pitching moment about the aerodynamic centre is always ___, regardless of angle of attack.

Answer 25

negative

Question 26

Phugoid damping is normally ___

Answer 26

weak

Question 27

Short period damping is normally ___

Answer 27

significant

Question 28

Speed and altitude vary ___ during the short period oscillation

Answer 28

slightly

Question 29

Speed and altitude vary ___ during the phugoid

Answer 29

significant

Question 30

Dorsal and ventral fins have a ___ effect on longitudinal stability, a ___ effect on lateral stability, and a ___ effect on directional stability

Answer 30

neutral, negative, positive

Question 31

The wing sweep angle is the angle between the ___ and the ___

Answer 31

quarter chord and the wing lateral axis

Question 32

Stick force stability depends on ___ stability

Answer 32

longitudinal

Question 33

Stick force stability is determined by the distance from ___ to the ___

Answer 33

neutral point CG

Question 34

A CG which is further forward means a ___ stick force stability

Answer 34

higher

Question 35

Manoeuvre stability will ___ with the static margin

Answer 35

increase

Question 36

The static margin is the distance from the ___ to the ___

Answer 36

manoeuvre point, CG

Question 37

Positive stick position stability means ___

Answer 37

that you pull back on the stick if the speed decreases, and push forward if it increases

Question 38

Fully hydraulic flight controls (don't) require mass balancing

Answer 38

they do

Question 39

With increasing altitude and constant IAS, an aircraft with swept back wings will see ___ static lateral stability and ___ dynamic lateral-directional stability

Answer 39

increasing, decreasing

Question 40

With increasing altitude and constant Mach number, an aircraft with swept back wings will see ___ static lateral stability and ___ dynamic lateral-directional stability

Answer 40

no change in, decreasing