Hello, everyone.
It¡¯s really good to see you again.
Have you ever thought how could the pilots know
where the aircraft is,
where the aircraft is going to,
how fast it is flying and how high it is flying?
The flight instruments will tell the answers.
In 1937,
the Royal Air Force selected six critical instruments
to be installed in nearly all of its aircraft.
Adopted by both commercial
and general aviation aircraft manufacturers
for decades thereafter,
the arrangement became known as the ¡±six pack¡±.
What are the six basic aircraft instruments?
For this part,
you will be able to acquire the general concept
of the basic six instruments,
to explain the working principles
of pitot-static instruments
and to illustrate the characteristics
of gyroscopic instruments.
A quick scan of the six pack provides the pilot
with current information on aircraft speed,
altitude,
climb/descent,
attitude,
heading and turning/banking.
Individually,
the six pack instruments are airspeed indicator,
altimeter,
vertical speed indicator,
attitude indicator,
heading indicator and turn coordinator.
The following video will give us a more detailed
explanation of the basic ¡°six pack¡±.
According to the working principle
of the flight instruments,
the six pack instruments
can be divided into two categories,
that is,
pitot-static instruments and gyroscopic instruments.
The source of the pressure
for operating the airspeed indicator,
the vertical speed indicator and the altimeter
is the pitot-static system
while the gyroscopic instruments
include the heading indicator,
attitude indicator and turn coordinator.
The pitot-static system includes a few components:
a pitot tube,
one or more static ports and the associated lines
that run from the pitot tube
and the static ports to the airspeed indicator,
vertical speed indicator and altimeter.
The pitot tube is usually mounted
on the wing of the airplane
so that it faces into the relative wind.
A small hole in the tube allows impact air pressure,
also known as ram air pressure,
to enter.
The static ports are attached to the airplane¡¯s fuselage
and they read static air pressure.
The pitot-static system of instruments
uses the principle of air pressure gradient.
It works by measuring pressures
or pressure differences and using
these values to assess the speed and altitude.
The static pressure is used in all measurements,
while the pitot pressure is used only
to determine airspeed.
The airspeed indicator compares
both types of air pressure to provide a readout
for the pilot.
The airspeed indicator is the only instrument
in the pitot-static system
that uses both types of air pressure.
The altimeter,
which displays altitude in feet,
uses static pressure to sense pressure changes.
The vertical speed indicator measures
static pressure differential to display rate of climb
or descent in feet per minute.
During pre-flight inspection,
the pilots need to check the pitot tube
and static ports to ensure there¡¯s no blockage,
because the presence of debris
or insects could prevent the pitot tube
and ports from doing their job¡ª
which is to sample air pressure
that in turn is measured by the airspeed indicator,
vertical speed indicator and altimeter.
A clog in the front of the pitot tube
will cause the airspeed indicator to read zero,
as it will not sense a difference
between static and ram air pressure.
A clogged pitot tube affects only the airspeed indicator.
One or more clogged static ports
will affect the airspeed indicator,
the vertical speed indicator and the altimeter.
The airspeed indicator will continue to operate,
but it won¡¯t be accurate.
Meanwhile,
the vertical speed indicator
will show a constant zero indication
and the altimeter will freeze at the altitude
at which the blockage occurred.
At this time,
the pilots should consult
the Pilot's Operating Handbook/
Airplane Flight Manual
to determine the amount of error.
When it is not being flown,
the aircraft may wear a little sleeve
called a pitot cover on its pitot tube.
The cover protects the pitot tube
from insects or dirt entering either of its ports¡ª
the one in the front that reads air pressure,
and the one in the back
that is a drainage hole
in the event you fly in precipitation.
The most common instruments containing gyroscopes
are the turn coordinator,
heading indicator,
and the attitude indicator.
Each contains a gyro rotor driven by air or electricity
and each makes use of the gyroscopic principles
to display the attitude of the aircraft.
There are two fundamental properties
of gyroscopic action:
rigidity in space and precession.
Rigidity in space refers to the principle
that a gyroscope remains in a fixed position in the plane
in which it is spinning.
Regardless of the position of its base,
a gyro tends to remain rigid in space,
with its axis of rotation pointed
in a constant direction.
Precession is the tilting
or turning of a gyro in response to a deflective force.
This principle allows the gyro
to determine a rate of turn
by sensing the amount of pressure
created by a change in direction.
The rate at which the gyro precesses
is inversely proportional to the speed of the rotor
and proportional to the deflective force.
Well, that¡¯s all for today.
Thanks for your attention.