Flight control lecture 1 Flashcards
Aircraft Flight Control Introduction
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.
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.
a state of balance
The moment around an axis is produced by changing the aerodynamic force on the
appropriate aerofoil and this may be done by:
- changing the camber of the airofoil
- changing the angle of attack (incidence) of the aerofoil
- decreasing the aerodynamics force by “spoiling” the airflow
the basic rotation controls around 3 axis:
longitudinal axis, lateral axis and vertical axis
rolling
longitudinal axis
is controlled by the ailerons, or for
some aircraft, spoilers, or by a
combination of the two.
longitudinal axis
turning the control wheel (____) left or right causes the aircraft to bank.
yoke, aileron
pitching
lateral axis
is controlled
by elevators or by a moving tail
plane.
lateral axis
pushing the control wheel forward or pulling it back causes the noise of the airplane to pitch down or up.
elevators
yawing
rudder
is controlled by the rudder
vertical axis
pressing on its pedal causes the noise of an airplane to move left or right.
rudder
Helicopters utilize a \_\_\_\_ to tilt the rotor in the desired direction along with a \_\_\_\_\_\_\_\_\_\_ to manipulate rotor pitch and \_\_\_\_\_\_\_\_ to control yaw.
cyclic, collective lever, anti-torque pedals
AircraƏt Flight Control System Design
mechanically, hydraulically, electrically
The control surfaces are connected directly to the cockpit controls by
a system of cables, rods, levers, and chains.
mechanically
Movement of the cockpit control sends an electrical signal to the
control surface. The movement of the control may be achieved hydraulically.
electrically
The control surfaces are moved by hydraulic power. The control
valve may still be operated mechanically
hydraulically
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.
mechanical
In this design, a collection of mechanical
components such as ____, ___, ____, and _____ transmit the movement of the flight deck controls to the appropriate control surfaces
cables,pulley, rods and chains
HYDRO-MECHANICAL The complexity and weight of mechanical flight control systems increase considerably with the \_\_\_\_ and \_\_\_\_\_\_\_ of the aircraft.
size, performance
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.
Hydraulically
With ______ flight control systems, the
aircraft’s size and performance are limited
by economics rather than a pilot’s muscular
strength
hydraulic
A hydro-mechanical flight control system has two
parts:
mechanical circuit and hydraulic circuit
links the cockpit controls with the hydraulic circuits. Like the mechanical flight control system, it consists of rods, cables and pulleys.
The mechanical circuit
has hydraulic pumps, reservoirs, filters, pipes, valves and actuators. The
actuators are powered by the hydraulic pressure
generated by the pumps.
The hydraulic circuit,
The actuators convert hydraulic pressure into
control surface movements. The _______ servo valves control the movement of the actuators.
electro-hydraulic
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.
fly-by-wire
FBW
FLY-BY-WIRE
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.
FLY-BY-WIRE
It is used to ensure that
the FBW aircraft stays within its certificated flight
envelope.
Feedback control of airspeed, Mach Number, attitude and angle of attack
Two strategies are being used to achieve fly by wire
Airbus strategy, Boeing strategy
the _______ of` ‘hard limits’ in which the
control laws have absolute authority control unless the
pilot selects Direct Law
Airbus strategy
The ________ of ‘soft limits’ in which the pilot can
override Flight Envelope Protection and so retains
ultimate control over the operation of the aircraft.
Boeing strategy
An aircraft must have sufficient ___ to maintain a uniform
flightpath and recover from the various upsetting forces.
stability
is the characteristic of an aircraft that tends to cause
it to fly (hands off) in a straight-and-level flightpath.
stability
is the ability of an aircraft to correct for conditions that act on
it, like turbulence or flight control inputs.
Stability
two general types of stability
static and dynamic
is the characteristic of an aircraft to be
directed along a desired flightpath and to withstand the
stresses imposed.
Maneuverability
is the quality of the response of an aircraft to
the pilot’s commands while maneuvering the aircraft.
Controllability
is the initial tendency of an aircraft to return to its original position when it’s disturbed.
Static stability
here are three kinds of static stability:
positive, neutral, negative
exists when the disturbed object tends to return to equilibrium
Positive static stability
For example: The ball return to starting position when disturbed
positive static stability
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.
positive
exists when the disturbed object has neither tendency, but remains in equilibrium in the direction of disturbance.
Neutral static stability
For Example: Ball remains in new position when disturbed
neutral static stability
An aircraft that has _____ static stability tends to stay in its new attitude when it’s disturbed.
neutral
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
neutral
or static instability, exists when the disturbed object tends to continue in the direction of disturbance
Negative static stability
For Example: Ball moves away from starting position when disturbed
negative static stability
An aircraft that has _____ static
stability tends to continue moving away
from its original attitude when it’s
disturbed.
negative
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
negative
Stability which is how an airplane responds over time to a
disturbance.
dynamic
There are three kinds of dynamic stability:
positive, neutral, negative
Oscillations decrease in amplitude with time
Positive Dynamic Stability
Aircraft with a ______ dynamic stability have
oscillations that dampen out over time
positive
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.
Positive Dynamic Stability
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.
Positive Dynamic Stability
Oscillations are constant in amplitude with time
Neutral Dynamic Stability
Aircraft with _______ dynamic
stability have oscillations that never
dampen out.
neutral
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.
Neutral Dynamic Stability
Oscillations increase in amplitude with time
Negative Dynamic Stability
Over time, the pitch oscillations get more and
more amplified.
Negative Dynamic Stability
Aircraft with ______ dynamic
stability have oscillations that get
worse over time.
negative
