How the PITOT - STATIC system works (Private Pilot Ground Lesson 31)
Summary
TLDRThis pilot training video delves into the workings of pedostatic instruments, crucial for flight navigation. It explains the function of the airspeed indicator, altimeter, and vertical speed indicator, which rely on air pressure from the pitot tube and static port. The video clarifies the concepts of static, dynamic, and total air pressure, and how these instruments can be affected by blockages or errors in the system. It also offers solutions for dealing with clogged ports, ensuring accurate flight data for safer flying.
Takeaways
- 🌀 The lesson discusses pedostatic instruments, which are the airspeed indicator, altimeter, and vertical speed indicator, using air pressure for flight information.
- 📡 These instruments receive air pressure data from the pitot tube and static port, which are crucial for accurate flight data.
- 🌪️ Air pressure types involved are static air pressure (ambient), dynamic air pressure (impact from air molecules on a moving object), and total air pressure (combination of static and dynamic).
- 📍 Static air pressure is measured in inches of mercury, with an average of 29.92 inches at sea level, decreasing by one inch per thousand feet above sea level.
- 🛫 The altimeter uses static pressure to provide altitude readings, with static ports usually placed on the side of the aircraft to avoid wind influence.
- 🔄 The vertical speed indicator senses pressure differences during climb or descent, providing readings in feet per minute.
- 🚀 The airspeed indicator measures the ram air through the pitot tube and offsets it with static air from the static port to determine airspeed accurately.
- ⚠️ The angle of the pitot tube can affect the airspeed indicator's accuracy, and manufacturers provide correction charts in the Pilot Operating Handbook (POH).
- 💧 The pitot tube has a 'weeping hole' to prevent water from clogging it, and heating elements can melt ice to avoid blockages.
- 🚨 If the pitot tube or static port is clogged, it can cause inaccurate readings in the airspeed indicator, altimeter, and vertical speed indicator.
- 🔄 In case of a clogged static port, newer training aircrafts may have an alternate static source to provide less accurate but usable data.
- 🔮 As a last resort, breaking the glass on a static instrument, preferably the vertical speed indicator, can provide some data in an emergency situation.
Q & A
What are the three primary flight instruments discussed in the script that use air pressure?
-The three primary flight instruments discussed are the airspeed indicator, the altimeter, and the vertical speed indicator.
What are the three types of air pressure mentioned in the script?
-The three types of air pressure mentioned are static air pressure, dynamic air pressure, and total air pressure.
What is static air pressure, and how is it measured?
-Static air pressure, also known as ambient air pressure, is the pressure caused by the atmosphere. It is always present, whether the airplane is stopped or moving, and is measured in inches of mercury.
How does the static air pressure change with altitude?
-The static air pressure decreases with increasing altitude, reducing by one inch of mercury for every thousand feet above sea level.
What is dynamic air pressure, and how does it relate to the aircraft's speed?
-Dynamic air pressure is the pressure created on an object, like an airplane, as it moves through the air. It is directly related to the speed at which the aircraft is flying.
What is total air pressure, and why is it important for the pedostatic system?
-Total air pressure is a combination of dynamic and static air pressure. It is important for the pedostatic system because it helps in accurately measuring the airspeed of the aircraft.
How does the altimeter use static pressure to provide altitude readings?
-The altimeter uses a static port to sense the static pressure outside the aircraft. Since the static pressure changes with altitude, the altimeter can provide an altitude reading based on these changes.
What is the function of the vertical speed indicator, and how does it work?
-The vertical speed indicator measures the rate of climb or descent of the aircraft. It allows air to escape or come in through a small hole vented through the static port, sensing pressure differences as the aircraft climbs or descends, and provides a reading in feet per minute.
How does the airspeed indicator measure airspeed, and what role does the pitot tube play?
-The airspeed indicator measures the ram air that comes from the relative wind through the pitot tube. It also takes static air from the static port to offset any static air that might come in through the pitot tube, ensuring an accurate airspeed measurement.
What could potentially cause errors in the pedostatic instruments, and how can they be mitigated?
-Errors in the pedostatic instruments could be caused by the pitot tube or static port getting clogged with bugs, mud, ice, or if water freezes in the pitot tube. These can be mitigated by using a heating element to melt ice or by using an alternate static source if available.
What is the 'weeping hole' on the pitot tube, and why is it important?
-The 'weeping hole' is a small drain hole on the back of the pitot tube. It is important because it allows water that enters the front of the pitot tube to drain out, preventing clogging.
What should a pilot do if the static port gets clogged during flight?
-If the static port gets clogged, the pilot can use an alternate static source if available, or as a last resort, break the glass on one of the static instruments, preferably the vertical speed indicator, to allow some form of pressure sensing.
Outlines
🛫 Understanding Aerodynamic Instruments
This paragraph introduces the topic of pedostatic instruments used in aviation, focusing on airspeed indicators, altimeters, and vertical speed indicators. It explains how these instruments rely on air pressure from the pitot tube and static port to provide crucial flight information. The paragraph delves into the three types of air pressure: static, dynamic, and total air pressure, detailing their impact on flight instruments. It also highlights the importance of the pitot tube and static port placement for accurate readings and the potential issues that can arise if these components become clogged, such as inaccurate airspeed readings or frozen altitude indications.
🚨 Pitfalls of Clogged Aerodynamic Instrument Ports
The second paragraph discusses the consequences of clogged pitot tubes and static ports on the functionality of aerodynamic instruments. It outlines three scenarios that could affect the airspeed indicator if the pitot tube becomes clogged: airspeed dropping to zero, the airspeed indicator freezing at the last reading, or displaying incorrect higher airspeeds. The paragraph also covers the effects on the altimeter and vertical speed indicator if the static port is obstructed, which could result in a frozen altitude reading or a zero indication on the vertical speed indicator, respectively. It provides solutions such as using an alternate static source or, as a last resort, breaking the glass on the least critical instrument to regain some functionality. The paragraph concludes with a reminder of the importance of maintaining instrument accuracy for flight safety.
Mindmap
Keywords
💡Pedostatic Instruments
💡Airspeed Indicator
💡Altimeter
💡Vertical Speed Indicator
💡Static Air Pressure
💡Dynamic Air Pressure
💡Total Air Pressure
💡Pitot Tube
💡Static Port
💡Calibrated Air Speed
💡Pitot-Static System Blockage
Highlights
Lesson discusses pedostatic instruments and their function in flight.
Gyroscopic instruments were discussed in previous lessons, focusing now on primary flight instruments using air pressure.
Primary flight instruments include the airspeed indicator, altimeter, and vertical speed indicator.
Instruments receive air pressure from the pitot tube and static port to provide flight information.
Three types of air pressure are explained: static, dynamic, and total air pressure.
Static air pressure is ambient pressure, varying with altitude and sensed by static ports.
Static air pressure is measured in inches of mercury, with standard air pressure at 29.92 inches.
Dynamic air pressure is created by an object moving through air and is related to aircraft speed.
Total air pressure is a combination of dynamic and static air pressures.
Altimeter uses static pressure to give altitude readings, affected by changes in elevation.
Vertical speed indicator senses pressure differences during climb or descent, providing readings in feet per minute.
Airspeed indicator measures ram air from the pitot tube and offsets it with static air from the static port.
Pitot tube and static port placement on the aircraft is crucial for accurate readings.
Angle of attack and aircraft configurations can affect the accuracy of the airspeed indicator.
Clogged pitot tube or static port can cause errors in flight instruments.
Heating elements in the pitot tube prevent ice formation and maintain instrument accuracy.
If the pitot tube is clogged, the airspeed indicator may show zero or freeze at the last reading.
Clogged static port affects the altimeter and vertical speed indicator, potentially freezing or showing zero.
Newer training airplanes may have an alternate static source to maintain instrument functionality.
In an emergency, breaking the glass on a static instrument can provide a less accurate but usable backup.
Transcripts
in this lesson from free pilot training
we'll be discussing the pedostatic
instruments and we'll explain how those
work
in the last few lessons we've been
discussing the gyroscopic instruments
but today we're going to talk about
three of those primary flight
instruments that use air pressure to
give us information these are the air
speed indicator the altimeter and the
vertical speed indicator these
instruments are provided air pressure
from the pitot tube and the static port
and they turn it into information that's
really important for pilots in flight
there are three types of air pressure
that come into play when we talk about
these instruments static air pressure
dynamic air pressure and total air
pressure
static pressure which is also called
ambient air pressure is pressure that's
caused by our atmosphere
this is always present whether the
airplane is stopped or moving
and although it might seem unnoticeable
to you these air molecules push on
everything in our atmosphere
the closer you are to the center of the
earth the more tightly these air
molecules are packed and because they're
packed so tightly at lower elevations
the lower your altitude the higher your
static air pressure is and our airplanes
use static ports to sense this type of
air pressure these are usually placed on
the side so they're not affected by
relative wind static air pressure is
measured in inches of mercury on a
normal standard day at sea level the
average air pressure is 29.92 inches of
mercury now the air pressure isn't
always 29.92 inches of mercury there but
this is about the average so this is
what we call standard air pressure
then every thousand feet above sea level
the pressure reduces by one inch of
mercury in the next lesson we're going
to go into a lot more detail about this
and how the altimeter works so if you
haven't already subscribed please
consider doing so
now anytime an object like an airplane
moves through the air it's impacted by
the air molecules that is traveling
through and this creates a certain
amount of pressure on the object that's
equal and opposite to the airplane's
direction of travel and this is called
dynamic air pressure and in order to
understand how the pedostatic system
works you have to understand that this
pressure is directly related to the
speed at which the aircraft is flying
next we have the total air pressure
and this is a combination of dynamic and
static air pressure and while this may
seem obvious at first you'll see why we
talk about this here in just a minute
now the altimeter uses a static port to
sense the static pressure outside the
aircraft and because the static pressure
changes one inch of mercury every
thousand feet the altimeter is able to
give us an altitude reading because it
senses that pressure now as i mentioned
before static ports are placed on the
side of aircraft
and this keeps the instruments from
being affected by dynamic air pressure
and this keeps the readings as accurate
as possible
the other instrument that uses a static
port is the vertical speed indicator
this instrument allows air to escape or
come in through a small hole which is
vented through the static port
by allowing air to come in or go out
this instrument senses the pressure
differences as we climb or descend then
it gives us a reading in feet per minute
the airspeed indicator is a little bit
different animal it also receives air
from the static pore but not for reasons
you might think
the airspeed indicator measures the ram
air that comes from relative wind
through the pitot tube but this doesn't
give us an accurate measurement because
static air actually makes its way into
the pitot tube as well and this is that
total air pressure we were talking about
earlier
and by taking static air from the static
port the air speed indicator is able to
offset any static air that might come in
through the pitot tube
to keep the air speed indicator as
accurate as possible the people who
designed your airplane usually put the
pitot tube in a spot where it won't be
affected by the prop wash but there is
something that can affect your airspeed
indicator and that's the angle of the
pitot tube in relation to the relative
wind
high angles of attack and different
airplane configurations can affect the
accuracy of your airspeed indicator
and that's because weird angles can make
it difficult for the ram air to enter
the pitot tube
every airplane is different but every
airplane has some kind of error caused
by this and the manufacturers account
for this by putting a chart in the poh
this is what we call calibrated air
speed once you make these corrections
using these charts
something else you could run into that
would cause these instruments to get
errors is if the pitot tube or the
static port got clogged up and there's a
lot of different things that could clog
up these things anything from bugs mud
ice and that's just to name a few one
thing that shouldn't clog up your pitot
tube though is water that's because of
this little drain hole here on the back
i call this the weeping hole this is
there so if water enters the front of
your pitot tube it'll just slide right
out the back here
but if the water freezes in or on the
pitot tube then it can start clogging it
up again but that's what these little
heating elements are for you just turn
the pedo heat on in your cockpit and it
should heat these up enough to melt that
ice
so what happens if these things get
clogged well if the pedo2 gets clogged
the only instrument that's going to be
affected is your airspeed indicator and
if you remember that's because this is
the only instrument that uses dynamic
air pressure to give us a reading for
the airspeed indicator three possible
problems could happen the first would be
if the hole in the front of the pitot
tube for the ram air got clogged
as long as your drain hole doesn't get
clogged what will happen is your air
speed will drop to zero and that's
because the pitot tube is no longer
taking in ram air but the static port
and the drain hole are still both taking
in static air which allow them to offset
each other the second possibility is if
the front of the pitot tube and the
drain hole gets clogged
if this happens any air pressure in the
pitot system will be trapped and your
air speed indicator is frozen at the
last indication it was giving you
from here if the static port is also
plugged you won't see any change but if
the static port is clear then the
airspeed indicator will make minor
changes with altitude i like to tell
students that your airspeed indicator
just turned into an altimeter at this
point the third thing that could
possibly happen is only the static port
gets clogged if this happens the pitot
tube is still taking in the dynamic and
the static pressure from the front of
the pitot tube but the static port is
unable to offset that static air that's
also coming in the front and this means
that your airspeed indicator is going to
give you faster air speeds than what
you're actually going
now because the altimeter and the
vertical speed indicator both use a
static board to get their information if
this gets clogged it's going to affect
both of those too for the altimeter if
the static port gets clogged it's going
to freeze at the last altitude that it
was indicating but the vertical speed
indicator will only display 0 because it
can no longer sense a climb or a descent
if you're lucky enough to have a clogged
static port i do have some good news for
you though on most newer training
airplanes they have something called an
alternate static source
typically this is an alternate static
port that's on the inside of your
cockpit and you can select this
alternate static port by flipping a
switch labeled alternate static on most
airplanes just keep in mind when you use
this alternate static source it's not
quite as accurate as the one on the
outside of the airplane and that's
because the pressure difference on the
inside of the cab is slightly different
than outside now if you don't have an
alternate static source one thing you
can do is you can break the glass on any
of the static instruments
if you do this i recommend breaking the
glass on the vertical speed indicator
and that's because it's by far the least
important of the instruments
and once again if you do this this is
nowhere nearly as accurate as a static
port on the outside of the airplane but
something is better than nothing and in
an emergency this could save your life i
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