Technical English 2

Semana 8
Bernaulli’s Equation

• This is Bernoulli’s equation for an incompressible fluid, i.e. a fluid that

cannot be compressed or expanded, and for which the density is
invariable.
 Ejes verticales
timón -
Estabilidad
movimiento de
direccional
guiñada

Ascensor –
movimiento de
tono alerón –
movimiento de
balanceo

eje lateral eje longitudinal

estabilidad estabilidad
Longitudinal Lateral
Pitch •Rotation around the side-to-side axis is called pitch.
 Primary Flight Controls

• Aileron
• Elevator
• T-tail
• Rudder
• V-tail
Roll
•Rotation around the front-to-back axis is called roll.
Yaw
•Rotation around the vertical axis is called yaw.
Secondary Flight
Controls
• Flaps
• Leading Edge Devices
• Spoilers
• Trim Devices
 Flaps
A flap is a high-lift device used to reduce the stalling
speed of an aircraft wing at a given weight. Flaps are
usually mounted on the wing trailing edges of a fixed-wing
aircraft. Flaps are used to reduce the take-off distance and
the landing distance. Flaps also cause an increase
in drag so they are retracted when not needed.
The flaps installed on most aircraft are partial-span flaps;
spanwise from near the wing root to the inboard end of
the ailerons. When partial-span flaps are extended they
alter the spanwise lift distribution on the wing by causing
the inboard half of the wing to supply an increased
proportion of the lift, and the outboard half to supply a
reduced proportion of the lift. Reducing the proportion of
the lift supplied by the outboard half of the wing is
accompanied by a reduction in the angle of attack on the
outboard half. This is beneficial because it increases the
margin above the stall of the outboard half, maintaining
aileron effectiveness and reducing the likelihood of
asymmetric stall, and spinning.
Extending the wing flaps increases the camber or
curvature of the wing, raising the maximum lift coefficient
 or the upper limit to the lift a wing can generate. This
allows the aircraft to generate the required lift at a lower
speed, reducing the minimum speed (known as stall
speed) at which the aircraft will safely maintain flight. The
increase in camber also increases the wing drag, which
can be beneficial during approach and landing, because it
allows the aircraft to descend at a steeper angle. For most
aircraft configurations, a useful side effect of flap
deployment is a decrease in aircraft pitch angle which
lowers the nose thereby improving the pilot's view of the
runway over the nose of the aircraft during landing.
Another side effect however, depending on the type of
flap, location on the wing and deployment speed during
their extension, is that the flaps will cause the indicated (or
relative to the unchanged airfoil) angle of attack to lower
within a short time due to an increase in nose-down
pitching moment which is characteristic to all trailing-edge
flaps, as well as leading-edge flaps, then followed by a
nose rise (pitch-up) due to the increase in lift, thus
obscuring the pilot's view of the runway if no action is
taken over the pitch inputs.
Leading Edge Devices
Leading edge devices are located at the leading
edge of the wing and can be deployed during
different flight phases (take off, landing and
cruise) in order to improve the aerodynamic
performances of the the aircraft. More generally
they are used during take off and landing to
increase the lift and so be able to reduce the
landing speed, or increase lift for take off. Also
leading edge devices will create drag but the
overall Lift to drag ratio is still an advantage.
Following on this, the leading edge devices are
retracted for cruise to decrease the drag and so
have clean airfoil profile which is more efficient
for cruise condition.
The leading edge devices were used on early
aircraft to improve the performance of the
aircraft. One of the pioneer of the leading edge
device was Handley Page who first tried this on
his aircraft. First of all he used a fixed leading
edge slat which provided him with high lift
coefficient but the associated drag was
detrimental to maximum speed. Handley page
then tried to have an automatic deployment of
the leading edge slat using the aerodynamic
forces at the leading edge (suction). As the
aircraft take off and land the speed
Spoilers
A spoiler is an element of a
disseminated summary or
description of any piece of fiction
 that reveals any plot elements.
Typically, the details of the
conclusion of the plot, including the
climax and ending, are especially
regarded as spoiler material. It can
also be used to refer to any piece
of information regarding any part of
a given media that a potential
consumer was not intended to
know beforehand.
 Trim Systems
Trim Systems are considered to be a "secondary" 
flight control system.
By definition, to "trim" an aircraft is to adjust the
aerodynamic forces on the control surfaces so that the
aircraft maintains the set attitude without any control input.
While all axes of rotation are affected by aerodynamic
forces, not all aircraft types are capable of being trimmed in
all three axes. Virtually all aircraft designs incorporate some
form of pitch axis trim and most have provisions of some
description for trimming in the yaw axis. Roll axis trim
exists on many aircraft but it is the least frequently
encountered installation of the three. There are several
different types of trim systems in use and more than one type
may be found on a given aircraft.
The most commonly used trim system is the trim tab which
can be installed in both fixed or flight adjustable
configurations. Adjustable springs, anti-servo tabs on a 
stabilator equipped aircraft and a 
trimmable horizontal stabiliser are other types of trim
systems.
Trim Systems

• Trim Tabs
• Balance Tabs
• Anti-servo Tabs
• Ground Adjustable Tabs
• Adjustable Stabilizer
Trim Tabs
Trim tabs are small, secondary flight control surfaces that are attached to the
trailing edge of a larger, primary control surface such as an elevator or 
rudder. The trim tab is used to "trim", or counteract the aerodynamic force
on, the control surface and thus stabilise the aircraft in the axis of rotation
 associated with the primary control. Trim tabs can be either flight adjustable
or fixed.
By adjusting the angle of the trim tab relative to the larger control surface,
the neutral position of the control surface is changed. This occurs because
the distance from the control surface hinge at which the trim tab is mounted
provides sufficient moment or force to move the larger surface.
Fixed trim tabs are most often encountered on the rudder or aileron of a
light, single engine aircraft. A fixed tab is ground adjusted (bent) to the
desired position to overcome any unwanted roll or yaw tendencies of the
aircraft. Adjustable trim is virtually always installed to adjust control loading
associated with the pitch axis and may also be used to trim for yaw or roll.
The position of an adjustable trim tab can be changed in flight, using cockpit
controls, to counter any variation in control loading resulting from changes
in airspeed, centre of gravity, aircraft configuration or due to an engine
failure. Trim tabs can be manually or electrically controlled (or both),
depending upon the aircraft installation.
Anti-servo Tabs
A servo tab is a small hinged device installed on
an aircraft control surface to assist the
movement of the control surfaces. Introduced by
the German firm Flettner, servo tabs were
formerly known as Flettner tabs. Servo tabs are
not true servomechanisms, as they do not
employ negative feedback to keep the control
surfaces in a desired position; they only provide
a mechanical advantage to the pilot.
 Ground Adjustable Tabs

Many small aircraft have a nonmovable metal trim

tab on the rudder. This tab is bent in one direction
or the other while on the ground to apply a trim
force to the rudder. The correct displacement is
determined by trial and error. Usually,
small adjustments are necessary until the aircraft
no longer skids left or right during normal cruising
flight.
 Adjustable
Stabilizer
Rather than using a movable tab on the trailing edge of
the elevator, some aircraft have an adjustable stabilizer.
With this arrangement, linkages pivot the horizontal
stabilizer about its rear spar. This is accomplished by
the use of a jackscrew mounted on the leading edge of
the stabilator. On small aircraft, the jackscrew is cable
operated with a trim wheel or crank. On larger aircraft,
it is motor driven. The trimming effect and flight deck
indications for an adjustable stabilizer are similar to
those of a trim tab.