- •Textbook Series
- •Contents
- •1 Overview and Definitions
- •Overview
- •General Definitions
- •Glossary
- •List of Symbols
- •Greek Symbols
- •Others
- •Self-assessment Questions
- •Answers
- •2 The Atmosphere
- •Introduction
- •The Physical Properties of Air
- •Static Pressure
- •Temperature
- •Air Density
- •International Standard Atmosphere (ISA)
- •Dynamic Pressure
- •Key Facts
- •Measuring Dynamic Pressure
- •Relationships between Airspeeds
- •Airspeed
- •Errors and Corrections
- •V Speeds
- •Summary
- •Questions
- •Answers
- •3 Basic Aerodynamic Theory
- •The Principle of Continuity
- •Bernoulli’s Theorem
- •Streamlines and the Streamtube
- •Summary
- •Questions
- •Answers
- •4 Subsonic Airflow
- •Aerofoil Terminology
- •Basics about Airflow
- •Two Dimensional Airflow
- •Summary
- •Questions
- •Answers
- •5 Lift
- •Aerodynamic Force Coefficient
- •The Basic Lift Equation
- •Review:
- •The Lift Curve
- •Interpretation of the Lift Curve
- •Density Altitude
- •Aerofoil Section Lift Characteristics
- •Introduction to Drag Characteristics
- •Lift/Drag Ratio
- •Effect of Aircraft Weight on Minimum Flight Speed
- •Condition of the Surface
- •Flight at High Lift Conditions
- •Three Dimensional Airflow
- •Wing Terminology
- •Wing Tip Vortices
- •Wake Turbulence: (Ref: AIC P 072/2010)
- •Ground Effect
- •Conclusion
- •Summary
- •Answers from page 77
- •Answers from page 78
- •Questions
- •Answers
- •6 Drag
- •Introduction
- •Parasite Drag
- •Induced Drag
- •Methods of Reducing Induced Drag
- •Effect of Lift on Parasite Drag
- •Aeroplane Total Drag
- •The Effect of Aircraft Gross Weight on Total Drag
- •The Effect of Altitude on Total Drag
- •The Effect of Configuration on Total Drag
- •Speed Stability
- •Power Required (Introduction)
- •Summary
- •Questions
- •Annex C
- •Answers
- •7 Stalling
- •Introduction
- •Cause of the Stall
- •The Lift Curve
- •Stall Recovery
- •Aircraft Behaviour Close to the Stall
- •Use of Flight Controls Close to the Stall
- •Stall Recognition
- •Stall Speed
- •Stall Warning
- •Artificial Stall Warning Devices
- •Basic Stall Requirements (EASA and FAR)
- •Wing Design Characteristics
- •The Effect of Aerofoil Section
- •The Effect of Wing Planform
- •Key Facts 1
- •Super Stall (Deep Stall)
- •Factors that Affect Stall Speed
- •1g Stall Speed
- •Effect of Weight Change on Stall Speed
- •Composition and Resolution of Forces
- •Using Trigonometry to Resolve Forces
- •Lift Increase in a Level Turn
- •Effect of Load Factor on Stall Speed
- •Effect of High Lift Devices on Stall Speed
- •Effect of CG Position on Stall Speed
- •Effect of Landing Gear on the Stall Speed
- •Effect of Engine Power on Stall Speed
- •Effect of Mach Number (Compressibility) on Stall Speed
- •Effect of Wing Contamination on Stall Speed
- •Warning to the Pilot of Icing-induced Stalls
- •Stabilizer Stall Due to Ice
- •Effect of Heavy Rain on Stall Speed
- •Stall and Recovery Characteristics of Canards
- •Spinning
- •Primary Causes of a Spin
- •Phases of a Spin
- •The Effect of Mass and Balance on Spins
- •Spin Recovery
- •Special Phenomena of Stall
- •High Speed Buffet (Shock Stall)
- •Answers to Questions on Page 173
- •Key Facts 2
- •Questions
- •Key Facts 1 (Completed)
- •Key Facts 2 (Completed)
- •Answers
- •8 High Lift Devices
- •Purpose of High Lift Devices
- •Take-off and Landing Speeds
- •Augmentation
- •Flaps
- •Trailing Edge Flaps
- •Plain Flap
- •Split Flap
- •Slotted and Multiple Slotted Flaps
- •The Fowler Flap
- •Comparison of Trailing Edge Flaps
- •and Stalling Angle
- •Drag
- •Lift / Drag Ratio
- •Pitching Moment
- •Centre of Pressure Movement
- •Change of Downwash
- •Overall Pitch Change
- •Aircraft Attitude with Flaps Lowered
- •Leading Edge High Lift Devices
- •Leading Edge Flaps
- •Effect of Leading Edge Flaps on Lift
- •Leading Edge Slots
- •Leading Edge Slat
- •Automatic Slots
- •Disadvantages of the Slot
- •Drag and Pitching Moment of Leading Edge Devices
- •Trailing Edge Plus Leading Edge Devices
- •Sequence of Operation
- •Asymmetry of High Lift Devices
- •Flap Load Relief System
- •Choice of Flap Setting for Take-off, Climb and Landing
- •Management of High Lift Devices
- •Flap Extension Prior to Landing
- •Questions
- •Annexes
- •Answers
- •9 Airframe Contamination
- •Introduction
- •Types of Contamination
- •Effect of Frost and Ice on the Aircraft
- •Effect on Instruments
- •Effect on Controls
- •Water Contamination
- •Airframe Aging
- •Questions
- •Answers
- •10 Stability and Control
- •Introduction
- •Static Stability
- •Aeroplane Reference Axes
- •Static Longitudinal Stability
- •Neutral Point
- •Static Margin
- •Trim and Controllability
- •Key Facts 1
- •Graphic Presentation of Static Longitudinal Stability
- •Contribution of the Component Surfaces
- •Power-off Stability
- •Effect of CG Position
- •Power Effects
- •High Lift Devices
- •Control Force Stability
- •Manoeuvre Stability
- •Stick Force Per ‘g’
- •Tailoring Control Forces
- •Longitudinal Control
- •Manoeuvring Control Requirement
- •Take-off Control Requirement
- •Landing Control Requirement
- •Dynamic Stability
- •Longitudinal Dynamic Stability
- •Long Period Oscillation (Phugoid)
- •Short Period Oscillation
- •Directional Stability and Control
- •Sideslip Angle
- •Static Directional Stability
- •Contribution of the Aeroplane Components.
- •Lateral Stability and Control
- •Static Lateral Stability
- •Contribution of the Aeroplane Components
- •Lateral Dynamic Effects
- •Spiral Divergence
- •Dutch Roll
- •Pilot Induced Oscillation (PIO)
- •High Mach Numbers
- •Mach Trim
- •Key Facts 2
- •Summary
- •Questions
- •Key Facts 1 (Completed)
- •Key Facts 2 (Completed)
- •Answers
- •11 Controls
- •Introduction
- •Hinge Moments
- •Control Balancing
- •Mass Balance
- •Longitudinal Control
- •Lateral Control
- •Speed Brakes
- •Directional Control
- •Secondary Effects of Controls
- •Trimming
- •Questions
- •Answers
- •12 Flight Mechanics
- •Introduction
- •Straight Horizontal Steady Flight
- •Tailplane and Elevator
- •Balance of Forces
- •Straight Steady Climb
- •Climb Angle
- •Effect of Weight, Altitude and Temperature.
- •Power-on Descent
- •Emergency Descent
- •Glide
- •Rate of Descent in the Glide
- •Turning
- •Flight with Asymmetric Thrust
- •Summary of Minimum Control Speeds
- •Questions
- •Answers
- •13 High Speed Flight
- •Introduction
- •Speed of Sound
- •Mach Number
- •Effect on Mach Number of Climbing at a Constant IAS
- •Variation of TAS with Altitude at a Constant Mach Number
- •Influence of Temperature on Mach Number at a Constant Flight Level and IAS
- •Subdivisions of Aerodynamic Flow
- •Propagation of Pressure Waves
- •Normal Shock Waves
- •Critical Mach Number
- •Pressure Distribution at Transonic Mach Numbers
- •Properties of a Normal Shock Wave
- •Oblique Shock Waves
- •Effects of Shock Wave Formation
- •Buffet
- •Factors Which Affect the Buffet Boundaries
- •The Buffet Margin
- •Use of the Buffet Onset Chart
- •Delaying or Reducing the Effects of Compressibility
- •Aerodynamic Heating
- •Mach Angle
- •Mach Cone
- •Area (Zone) of Influence
- •Bow Wave
- •Expansion Waves
- •Sonic Bang
- •Methods of Improving Control at Transonic Speeds
- •Questions
- •Answers
- •14 Limitations
- •Operating Limit Speeds
- •Loads and Safety Factors
- •Loads on the Structure
- •Load Factor
- •Boundary
- •Design Manoeuvring Speed, V
- •Effect of Altitude on V
- •Effect of Aircraft Weight on V
- •Design Cruising Speed V
- •Design Dive Speed V
- •Negative Load Factors
- •The Negative Stall
- •Manoeuvre Boundaries
- •Operational Speed Limits
- •Gust Loads
- •Effect of a Vertical Gust on the Load Factor
- •Effect of the Gust on Stalling
- •Operational Rough-air Speed (V
- •Landing Gear Speed Limitations
- •Flap Speed Limit
- •Aeroelasticity (Aeroelastic Coupling)
- •Flutter
- •Control Surface Flutter
- •Aileron Reversal
- •Questions
- •Answers
- •15 Windshear
- •Introduction (Ref: AIC 84/2008)
- •Microburst
- •Windshear Encounter during Approach
- •Effects of Windshear
- •“Typical” Recovery from Windshear
- •Windshear Reporting
- •Visual Clues
- •Conclusions
- •Questions
- •Answers
- •16 Propellers
- •Introduction
- •Definitions
- •Aerodynamic Forces on the Propeller
- •Thrust
- •Centrifugal Twisting Moment (CTM)
- •Propeller Efficiency
- •Variable Pitch Propellers
- •Power Absorption
- •Moments and Forces Generated by a Propeller
- •Effect of Atmospheric Conditions
- •Questions
- •Answers
- •17 Revision Questions
- •Questions
- •Answers
- •Explanations to Specimen Questions
- •Specimen Examination Paper
- •Answers to Specimen Exam Paper
- •Explanations to Specimen Exam Paper
- •18 Index
Stability and Control 10
Summary
Self Study
Stability is the inherent quality of an aircraft to correct for conditions that may disturb its equilibrium and to return to, or continue on its original flight path. An aircraft can have two basic types of stability: static and dynamic, and three condition of each type: positive, neutral, and negative.
Static stability describes the initial reaction of an aircraft after it has been disturbed from equilibrium about one or more of its three axes.
Positive static stability is the condition of stability in which restorative forces are set-up that will tend to return an aircraft to its original condition anytime it’s disturbed from a condition of equilibrium. If an aircraft has an initial tendency to return to its original attitude of equilibrium, it has positive static stability. (statically stable).
An aircraft with neutral static stability produces forces that neither tend to return it to its original condition, nor cause it to depart further from this condition. If an aircraft tends to remain in its new, disturbed state, it has neutral static stability. (statically neutral).
If an aircraft has negative static stability, anytime it is disturbed from a condition of equilibrium, forces are set up that will tend to cause it to depart further from its original condition. Negative static stability is a highly undesirable characteristic as it can cause loss of control. When an aircraft continues to diverge, it exhibits negative static stability. (statically unstable).
Most aeroplanes have positive static stability in pitch and yaw, and are close to being neutrally statically stable in roll.
When an aircraft exhibits positive static stability about any of its three axes, the term “dynamic stability” describes the long term tendency of the aircraft.
When an aircraft is disturbed from equilibrium and then tries to return, it will invariably overshoot the original ATTITUDE (due to its momentum) and then start to return again. This results in a series of oscillations.
Positive dynamic stability is a condition in which the forces of static stability decrease with time. Positive dynamic stability is desirable. If oscillations become smaller with time, an aircraft has positive dynamic stability. (dynamically stable).
Neutral dynamic stability causes an aircraft to hunt back and forth around a condition of equilibrium, with the corrections getting neither larger or smaller. (dynamically neutral). Neutral dynamic stability is undesirable.
If an aircraft diverges further away from its original attitude with each oscillation, it has negative dynamic stability. Negative dynamic stability causes the forces of static stability to increase with time. (dynamically unstable). Negative dynamic stability is extremely undesirable.
The overall design of an aircraft contributes to its stability (or lack of it) about each of its three axes of motion.
Stability and Control 10
315
10 Stability and Control
Control and Stability 10
The vertical stabilizer (fin) is the primary source of directional stability (yaw).
The horizontal stabilizer (tailplane) is the primary source of longitudinal stability (pitch).
The wing is the primary source of lateral stability (roll).
CG location also affects stability.
If the CG is close to its aft limit, an aircraft will be less stable in both pitch and yaw. As the CG is moves forward, stability increases.
Even though an aeroplane will be less stable with an aft CG, it will have some desirable aerodynamic characteristics due to reduced aerodynamic loading of the horizontal tail surface. This type of an aeroplane will have a slightly lower stall speed and will cruise faster for a given power setting.
Manoeuvrability is the quality of an aircraft that permits it to be manoeuvred easily and to withstand the stresses imposed by those manoeuvres.
Controllability is the capability of an aircraft to respond to the pilot’s control, especially with regard to flight path and attitude.
An aircraft is longitudinally stable if it returns to a condition of level flight after a disturbance in pitch, caused by either a gust or displacement of the elevator by the pilot. The location of the CG and the effectiveness of the tailplane determines the longitudinal stability, and thus the controllability of an aircraft.
Increasing stability about any axis:
•decreases manoeuvrability and controllability, and
•increases stick (or pedal) forces.
Phugoid oscillation is a long-period oscillation in which the pitch attitude, airspeed and altitude vary, but the angle of attack remains relatively constant. It is a gradual interchange of potential and kinetic energy about some equilibrium airspeed and altitude. An aircraft experiencing longitudinal phugoid oscillation is demonstrating positive static stability, and it is easily controlled by the pilot.
An aircraft will return towards wing level after a wing drop if it has static lateral stability.
The wing of most aircraft has a positive geometric dihedral angle (dihedral). This is the angle produced by the wing tips being higher than the wing root. If the left wing drops in flight, an aircraft will momentarily begin to slip to the left, and the effective angle of attack of the left wing will increase and the effective angle of attack of the right wing will decrease. The change in angle of attack of both wings will cause the wing to return back towards a level attitude.
Sweepback also has a “dihedral effect”. This is a by-product. A wing is swept-back to give an
aircraft a higher MCRIT. An aircraft with a swept-back wing will not require as much geometrical dihedral as a straight wing.
Some aircraft have the wing mounted on top of the fuselage for various reasons. Also as a by-product, a high mounted wing will give a “dihedral effect” due to the direction of airflow around the fuselage and wing during a sideslip. An aircraft with a high mounted wing does not require as much geometric dihedral.
316
Stability and Control 10
An aircraft which has a high mounted, swept-back wing will have so much lateral stability that the wing is usually given anhedral (negative dihedral).
Too much static lateral stability could result in dynamic instability - Dutch roll.
Static directional stability is the tendency of the nose of an aircraft to yaw towards the relative airflow. It is achieved by the keel surface behind the CG being larger than that in front of the CG.
A swept-back wing also provides a measure of static directional stability.
Too much static directional stability could result in dynamic instability - Spiral Instability.
Interaction between static lateral stability and static directional stability. If a wing drops and the aircraft begins to slip to the side, directional stability will cause the nose to yaw into the relative airflow.
“Dihedral effect” tends to roll an aircraft when a wing drops, and directional stability causes the nose to yaw into the direction of the low wing.
These two forces interact (coupled motion):
•An aircraft with strong static directional stability and weak “dihedral effect” will have a tendency towards spiral instability.
•When a wing drops, the nose will yaw toward the low wing and the aeroplane will begin to turn. The increased speed of the wing on the outside of the turn will increase the angle of bank, and the reduction in the vertical component of lift will force the nose to a low pitch angle. This will cause the aircraft to enter a descending spiral.
•An aircraft with strong “dihedral effect” and weak directional stability will have a tendency towards dutch roll instability.
A Mach trim system maintains the required stick force gradient at high Mach numbers by adjusting the longitudinal trim. The Mach trim system only operates at high Mach numbers.
Stability and Control 10
317
10 Questions
Questions
|
1. |
An aeroplane which is inherently stable will: |
||
|
|
a. |
require less effort to control. |
|
|
|
b. |
be difficult to stall. |
|
|
|
c. |
not spin. |
|
|
|
d. |
have a built-in tendency to return to its original state following the removal of |
|
|
|
|
any disturbing force. |
|
|
2. |
After a disturbance in pitch an aircraft oscillates in pitch with increasing amplitude. |
||
|
|
It is: |
|
|
|
|
a. |
statically and dynamically unstable. |
|
|
|
b. |
statically stable but dynamically unstable. |
|
|
|
c. |
statically unstable but dynamically stable. |
|
|
|
d. |
statically and dynamically stable. |
|
10 |
3. |
Longitudinal stability is given by: |
||
Questions |
||||
|
b. |
the wing dihedral. |
||
|
|
a. |
the fin. |
|
|
|
c. |
the horizontal tailplane. |
|
|
|
d. |
the ailerons. |
|
|
4. |
An aircraft is constructed with dihedral to provide: |
||
|
|
a. |
lateral stability about the longitudinal axis. |
|
|
|
b. |
longitudinal stability about the lateral axis. |
|
|
|
c. |
lateral stability about the normal axis. |
|
|
|
d. |
directional stability about the normal axis. |
|
|
5. |
Lateral stability is reduced by increasing: |
||
|
|
a. |
anhedral. |
|
|
|
b. |
dihedral. |
|
|
|
c. |
sweepback. |
|
|
|
d. |
fuselage and fin area. |
|
|
6. |
If the wing AC is forward of the CG: |
||
|
|
a. |
changes in lift produce a wing pitching moment which acts to reduce the |
|
|
|
|
change of lift. |
|
|
|
b. |
changes in lift produce a wing pitching moment which acts to increase the |
|
|
|
|
change of lift. |
|
|
|
c. |
changes in lift give no change in wing pitching moment. |
|
|
|
d. |
when the aircraft sideslips the CG causes the nose to turn into the sideslip thus |
|
|
|
|
applying a restoring moment. |
|
|
7. |
The longitudinal static stability of an aircraft: |
||
|
|
a. |
is reduced by the effects of wing downwash. |
|
|
|
b. |
is increased by the effects of wing downwash. |
|
|
|
c. |
is not affected by wing downwash. |
|
|
|
d. |
is reduced for nose-up displacements, but increased for nose-down |
|
|
|
|
displacements by the effects of wing downwash. |
318
|
|
Questions |
|
10 |
|
|
8. |
To ensure some degree of longitudinal stability in flight, the position of the CG: |
|||||
|
|
|
||||
|
a. |
must always coincide with the AC. |
|
|
|
|
|
b. |
must be forward of the Neutral Point. |
|
|
|
|
|
c. |
must be aft of the Neutral Point. |
|
|
|
|
|
d. |
must not be forward of the aft CG limit. |
|
|
|
|
9. |
When the CG is close to the forward limit: |
|
|
|
||
|
a. |
very small forces are required on the control column to produce pitch. |
|
|
|
|
|
b. |
longitudinal stability is reduced. |
|
|
|
|
|
c. |
very high stick forces are required to pitch because the aircraft is very stable. |
|
|
|
|
|
d. |
stick forces are the same as for an aft CG. |
|
|
|
|
10. |
The static margin is equal to the distance between: |
|
|
|
||
|
a. |
the CG and the AC. |
|
|
|
|
|
b. |
the AC and the neutral point. |
10 |
|||
|
c. |
the CG and the neutral point. |
||||
|
|
|
|
|||
|
d. |
the CG and the CG datum point. |
|
Questions |
||
11. |
If a disturbing force causes the aircraft to roll: |
|
||||
|
|
|
||||
|
a. |
wing dihedral will cause a rolling moment which reduces the sideslip. |
|
|
|
|
|
b. |
the fin will cause a rolling moment which reduces the sideslip. |
|
|
|
|
|
c. |
dihedral will cause a yawing moment which reduces the sideslip. |
|
|
|
|
|
d. |
dihedral will cause a nose-up pitching moment. |
|
|
|
|
12. |
With flaps lowered, lateral stability: |
|
|
|
||
|
a. |
will be increased because of the effective increase of dihedral. |
|
|
|
|
|
b. |
will be increased because of increased lift. |
|
|
|
|
|
c. |
will be reduced because the centre of lift of each semi-span is closer to the |
|
|
|
|
|
|
wing root. |
|
|
|
|
|
d. |
will not be affected. |
|
|
|
|
13. |
Dihedral gives a stabilizing rolling moment by causing an increase in lift: |
|
|
|
||
|
a. |
on the up-going wing when the aircraft rolls. |
|
|
|
|
|
b. |
on the down-going wing when the aircraft rolls. |
|
|
|
|
|
c. |
on the lower wing if the aircraft is sideslipping. |
|
|
|
|
|
d. |
on the lower wing whenever the aircraft is in a banked attitude. |
|
|
|
|
14. |
A high wing configuration with no dihedral, compared to a low wing configuration |
|
|
|
||
|
with no dihedral, will provide: |
|
|
|
||
|
a. |
greater longitudinal stability. |
|
|
|
|
|
b. |
the same degree of longitudinal stability as any other configuration because |
|
|
|
|
|
|
dihedral gives longitudinal stability. |
|
|
|
|
|
c. |
less lateral stability than a low wing configuration. |
|
|
|
|
|
d. |
greater lateral stability due to the airflow pattern around the fuselage when |
|
|
|
|
|
|
the aircraft is sideslipping increasing the effective angle of attack of the lower |
|
|
|
|
|
|
wing. |
|
|
|
319
10 Questions
15. |
At a constant IAS, what effect will increasing altitude have on damping in roll? |
||
|
a. |
It remains the same. |
|
|
b. |
It increases because the TAS increases. |
|
|
c. |
It decreases because the ailerons are less effective. |
|
|
d. |
It decreases because the density decreases. |
|
16. |
Sweepback of the wings will: |
||
|
a. |
not affect lateral stability. |
|
|
b. |
decrease lateral stability. |
|
|
c. |
increases lateral stability at high speeds only. |
|
|
d. |
increases lateral stability at all speeds. |
|
17. |
At low forward speed: |
||
|
a. |
increased downwash from the wing will cause the elevators to be more |
|
10 |
|
responsive. |
|
b. |
due to the increased angle of attack of the wing the air will flow faster over |
||
|
|||
Questions |
|
the wing giving improved aileron control. |
|
c. |
a large sideslip angle could cause the fin to stall. |
||
|
|||
|
d. |
a swept-back wing will give an increased degree of longitudinal stability. |
|
18. |
Following a lateral disturbance, an aircraft with Dutch roll instability will: |
||
|
a. |
go into a spiral dive. |
|
|
b. |
develop simultaneous oscillations in roll and yaw. |
|
|
c. |
develop oscillations in pitch. |
|
|
d. |
develop an unchecked roll. |
|
19. |
To correct Dutch roll on an aircraft with no automatic protection system: |
||
|
a. |
use roll inputs. |
|
|
b. |
use yaw inputs. |
|
|
c. |
move the CG. |
|
|
d. |
reduce speed below MMO. |
|
20. |
A yaw damper: |
||
|
a. |
increases rudder effectiveness. |
|
|
b. |
must be disengaged before making a turn. |
|
|
c. |
augments stability. |
|
|
d. |
increases the rate of yaw. |
|
21. |
A wing which is inclined downwards from root to tip is said to have: |
||
|
a. |
wash out. |
|
|
b. |
taper. |
|
|
c. |
sweep. |
|
|
d. |
anhedral. |
320
Questions 10
22.The lateral axis of an aircraft is a line which:
a.passes through the wing tips.
b.passes through the centre of pressure, at right angles to the direction of the airflow.
c.passes through the quarter chord point of the wing root, at right angles to the longitudinal axis.
d.passes through the centre of gravity, parallel to a line through the wing tips.
23.Loading an aircraft so that the CG exceeds the aft limits could result in:
a.loss of longitudinal stability, and the nose to pitch up at slow speeds.
b.excessive upward force on the tail, and the nose to pitch down.
c.excessive load factor in turns.
d.high stick forces.
24 |
The tendency of an aircraft to suffer from Dutch roll instability can be reduced: |
|
|
|
a. |
by sweeping the wings. |
10 |
|
|
||
|
b. |
by giving the wings anhedral. |
Questions |
|
c. |
by reducing the size of the fin. |
|
|
|
||
|
d. |
by longitudinal dihedral. |
|
25.What determines the longitudinal static stability of an aeroplane?
a.The relationship of thrust and lift to weight and drag.
b.The effectiveness of the horizontal stabilizer, rudder, and rudder trim tab.
c.The location of the CG with respect to the AC.
d.the size of the pitching moment which can be generated by the elevator.
26.Dihedral angle is:
a.the angle between the main plane and the longitudinal axis.
b.the angle measured between the main plane and the normal axis.
c.the angle between the quarter chord line and the horizontal datum.
d.the upward and outward inclination of the main planes to the horizontal datum.
27.Stability around the normal axis:
a.is increased if the keel surface behind the CG is increased.
b.is given by the lateral dihedral.
c.depends on the longitudinal dihedral.
d.is greater if the wing has no sweepback.
28.If the Centre of Gravity of an aircraft is found to be within limits for take-off:
a.the C of G will be within limits for landing.
b.the C of G for landing must be checked, allowing for fuel consumed.
c.the C of G will not change during the flight.
d.the flight crew can adjust the CG during flight to keep it within acceptable limits for landing.
321
10 Questions
|
29. |
The ailerons are deployed and returned to neutral when the aircraft has attained |
|
|
|
a small angle of bank. If the aircraft then returns to a wings-level attitude without |
|
|
|
further control movement it is: |
|
|
|
a. |
neutrally stable. |
|
|
b. |
statically and dynamically stable. |
|
|
c. |
statically stable, dynamically neutral. |
|
|
d. |
statically stable. |
|
30. |
The property which tends to decreases rate of displacement about any axis, but |
|
|
|
only while displacement is taking place, is known as: |
|
|
|
a. |
stability. |
|
|
b. |
controllability. |
|
|
c. |
aerodynamic damping. |
|
|
d. |
manoeuvrability. |
10 |
31. |
If an aircraft is loaded such that the stick force required to change the speed is zero: |
|
|
|
|
|
Questions |
|
a. |
the CG is on the neutral point. |
|
b. |
the CG is behind the neutral point. |
|
|
|
||
|
|
c. |
the CG is on the manoeuvre point. |
|
|
d. |
the CG is on the forward CG limit. |
322