Flight control lecture 1

Question 1

Aircraft Flight Control Introduction

Answer 1

A pilot uses flight control systems to control the forces of flight and the
aircraft’s direction and attitude. It should be noted that flight control
systems and characteristics can vary greatly depending on the type of
aircraft flown. The most basic flight control system designs are mechanical
and date back to early aircraft. Flight control systems are subdivided into
what are referred to as primary and secondary flight controls.

Question 2

For steady flight, the aircraft must be in a _________(zero moments around the
axes) and the controls enable this to be achieved for all possible configurations and
CG (Center of Gravity) positions.

Answer 2

a state of balance

Question 3

The moment around an axis is produced by changing the aerodynamic force on the
appropriate aerofoil and this may be done by:

Answer 3

• changing the camber of the airofoil
• changing the angle of attack (incidence) of the aerofoil
• decreasing the aerodynamics force by “spoiling” the airflow

Question 4

the basic rotation controls around 3 axis:

Answer 4

longitudinal axis, lateral axis and vertical axis

Question 5

rolling

Answer 5

longitudinal axis

Question 6

is controlled by the ailerons, or for
some aircraft, spoilers, or by a
combination of the two.

Answer 6

longitudinal axis

Question 7

turning the control wheel (____) left or right causes the aircraft to bank.

Answer 7

yoke, aileron

Question 8

pitching

Answer 8

lateral axis

Question 9

is controlled
by elevators or by a moving tail
plane.

Answer 9

lateral axis

Question 10

pushing the control wheel forward or pulling it back causes the noise of the airplane to pitch down or up.

Answer 10

elevators

Question 11

yawing

Answer 11

rudder

Question 12

is controlled by the rudder

Answer 12

vertical axis

Question 13

pressing on its pedal causes the noise of an airplane to move left or right.

Answer 13

rudder

Question 14

Helicopters utilize a \_\_\_\_ to
tilt the rotor in the desired
direction along with a
\_\_\_\_\_\_\_\_\_\_ to manipulate
rotor pitch and \_\_\_\_\_\_\_\_ to control yaw.

Answer 14

cyclic, collective lever, anti-torque pedals

Question 15

AircraƏt Flight Control System Design

Answer 15

mechanically, hydraulically, electrically

Question 16

The control surfaces are connected directly to the cockpit controls by
a system of cables, rods, levers, and chains.

Answer 16

mechanically

Question 17

Movement of the cockpit control sends an electrical signal to the
control surface. The movement of the control may be achieved hydraulically.

Answer 17

electrically

Question 18

The control surfaces are moved by hydraulic power. The control
valve may still be operated mechanically

Answer 18

hydraulically

Question 19

The most basic flight control systems are ________ and, although they date back to the earliest aircraft types, they are in use in the majority of light, general aviation aircraft.

Answer 19

mechanical

Question 20

In this design, a collection of mechanical
components such as ____, ___, ____, and _____ transmit the movement of the flight deck controls to the appropriate control surfaces

Answer 20

cables,pulley, rods and chains

Question 21

HYDRO-MECHANICAL
The complexity and weight of mechanical
flight control systems increase considerably
with the \_\_\_\_ and \_\_\_\_\_\_\_ of the
aircraft.

Answer 21

size, performance

Question 22

The complexity and weight of mechanical
flight control systems increase considerably
with the size and performance of the
aircraft. _______ powered control
surfaces help to overcome these limitations.

Answer 22

Hydraulically

Question 23

With ______ flight control systems, the
aircraft’s size and performance are limited
by economics rather than a pilot’s muscular
strength

Answer 23

hydraulic

Question 24

A hydro-mechanical flight control system has two

parts:

Answer 24

mechanical circuit and hydraulic circuit

Question 25

links the cockpit controls with the hydraulic circuits. Like the mechanical flight control system, it consists of rods, cables and pulleys.

Answer 25

The mechanical circuit

Question 26

has hydraulic pumps, reservoirs, filters, pipes, valves and actuators. The actuators are powered by the hydraulic pressure generated by the pumps.

Answer 26

The hydraulic circuit,

Question 27

The actuators convert hydraulic pressure into | control surface movements. The _______ servo valves control the movement of the actuators.

Answer 27

electro-hydraulic

Question 28

is the generally accepted term for those flight control systems which use computers to process the flight control inputs made by the pilot or autopilot, and send corresponding electrical signals to the flight control surface actuators.

Answer 28

fly-by-wire

Question 29

FBW

Answer 29

FLY-BY-WIRE

Question 30

This arrangement replaces mechanical linkage and means that the pilot inputs do not directly move the control surfaces. Instead, inputs are read by a computer that in turn determines how to move the control surfaces to best achieve what the pilot wants.

Answer 30

FLY-BY-WIRE

Question 31

It is used to ensure that the FBW aircraft stays within its certificated flight envelope.

Answer 31

Feedback control of airspeed, Mach Number, attitude and angle of attack

Question 32

Two strategies are being used to achieve fly by wire

Answer 32

Airbus strategy, Boeing strategy

Question 33

the _______ of` ‘hard limits’ in which the control laws have absolute authority control unless the pilot selects Direct Law

Answer 33

Airbus strategy

Question 34

The ________ of ‘soft limits’ in which the pilot can override Flight Envelope Protection and so retains ultimate control over the operation of the aircraft.

Answer 34

Boeing strategy

Question 35

An aircraft must have sufficient ___ to maintain a uniform | flightpath and recover from the various upsetting forces.

Answer 35

stability

Question 36

is the characteristic of an aircraft that tends to cause | it to fly (hands off) in a straight-and-level flightpath.

Answer 36

stability

Question 37

is the ability of an aircraft to correct for conditions that act on it, like turbulence or flight control inputs.

Answer 37

Stability

Question 38

two general types of stability

Answer 38

static and dynamic

Question 39

is the characteristic of an aircraft to be directed along a desired flightpath and to withstand the stresses imposed.

Answer 39

Maneuverability

Question 40

is the quality of the response of an aircraft to | the pilot’s commands while maneuvering the aircraft.

Answer 40

Controllability

Question 41

is the initial tendency of an aircraft to return to its original position when it's disturbed.

Answer 41

Static stability

Question 42

here are three kinds of static stability:

Answer 42

positive, neutral, negative

Question 43

exists when the disturbed object tends to return to equilibrium

Answer 43

Positive static stability

Question 44

For example: The ball return to starting position when disturbed

Answer 44

positive static stability

Question 45

An aircraft that has ______ static stability tends to return to its original attitude when it's disturbed. Let's say you're flying an aircraft, you hit some turbulence, and the nose pitches up. Immediately after that happens, the nose lowers and returns to its original attitude.It's something you'd see flying an airplane like a Cessna 172.

Answer 45

positive

Question 46

exists when the disturbed object has neither tendency, but remains in equilibrium in the direction of disturbance.

Answer 46

Neutral static stability

Question 47

For Example: Ball remains in new position when disturbed

Answer 47

neutral static stability

Question 48

An aircraft that has _____ static stability tends to stay in its new attitude when it's disturbed.

Answer 48

neutral

Question 49

``` For example, if you hit turbulence and your nose pitches up 5 degrees, and then immediately after that it stays at 5 degrees nose up, your airplane has ______ static stability ```

Answer 49

neutral

Question 50

or static instability, exists when the disturbed object tends to continue in the direction of disturbance

Answer 50

Negative static stability

Question 51

For Example: Ball moves away from starting position when disturbed

Answer 51

negative static stability

Question 52

An aircraft that has _____ static stability tends to continue moving away from its original attitude when it's disturbed.

Answer 52

negative

Question 53

``` For example, if you hit turbulence and your nose pitches up, and then immediately continues pitching up, you're airplane has a _______ static stability. For most aircraft, this is a very undesirable thing ```

Answer 53

negative

Question 54

Stability which is how an airplane responds over time to a | disturbance.

Answer 54

dynamic

Question 55

There are three kinds of dynamic stability:

Answer 55

positive, neutral, negative

Question 56

Oscillations decrease in amplitude with time

Answer 56

Positive Dynamic Stability

Question 57

Aircraft with a ______ dynamic stability have | oscillations that dampen out over time

Answer 57

positive

Question 58

The Cessna 172 is a great example. If your 172 is trimmed for level flight, and you pull back on the yoke and then let go, the nose will immediately start pitching down. Depending on how much you pitched up initially, the nose will pitch down slightly nose low, and then, over time, pitch nose up again, but less than your initial control input. Over time, the pitching will stop, and your 172 will be back to its original attitude.

Answer 58

Positive Dynamic Stability

Question 58

The Cessna 172 is a great example. If your 172 is trimmed for level flight, and you pull back on the yoke and then let go, the nose will immediately start pitching down. Depending on how much you pitched up initially, the nose will pitch down slightly nose low, and then, over time, pitch nose up again, but less than your initial control input. Over time, the pitching will stop, and your 172 will be back to its original attitude.

Answer 58

Positive Dynamic Stability

Question 59

Oscillations are constant in amplitude with time

Answer 59

Neutral Dynamic Stability

Question 60

Aircraft with _______ dynamic stability have oscillations that never dampen out.

Answer 60

neutral

Question 61

``` if you pitch up a trimmed, neutrally dynamic stable aircraft, it will pitch nose low, then nose high again, and the oscillations will continue, in theory, forever. ```

Answer 61

Neutral Dynamic Stability

Question 62

Oscillations increase in amplitude with time

Answer 62

Negative Dynamic Stability

Question 63

Over time, the pitch oscillations get more and | more amplified.

Answer 63

Negative Dynamic Stability

Question 64

Aircraft with ______ dynamic stability have oscillations that get worse over time.

Answer 64

negative