Greenville Downtown Airport - GMU
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Flight Instruments Sign
Primary Flight Instruments

What are the main gauges?
What do they tell you?

Airplane cockpits (flight decks) have instruments that help the pilot maintain control of the aircraft whether they are flying in the clouds or flying on bright sunny days. Most airplanes have six basic flight instruments: airspeed indicator, attitude indicator,
altimeter, turn coordinator, heading indicator, and vertical speed indicator.

When you first learn to fly you earn your Private Pilot 
Certificate. You will use a combination of looking outside the aircraft and looking at your flight instruments. This is called flying by Visual Flight Rules (VFR). By comparing the aircraft’s instrument panel against the horizon, a pilot is able to understand if the plane is flying straight and level. The pilot looks at the flight instruments to confirm the aircraft’s speed, altitude and attitude against the horizon.

Many pilots choose to add an Instrument Rating 
to their Private Pilot Certificate. This allows a pilot to fly by only looking at the flight instruments to determine the aircraft’s position in relation to the horizon. This is called flying by Instrument Flight Rules (IFR).

How fast is the plane going?
The Airspeed Indicator shows the pilot the difference between the outside air pressure and the speed at which a tube on the outside of the plane is collecting air. The difference is the air speed. The gadget that collects the air is called a Pitot Tube.  The reason a comparison is needed is air pressure changes as altitude changes. Air is denser closer to the surface of the earth and thinner as you fly higher.

The green arc represents Normal Operating Airspeed Range; most of the flight 
occurs here. The yellow arc represents Caution Range; planes should only fly at
this speed if the air is smooth. The red line represents the Never Exceed Speed; if entered, structural damage to aircraft may occur. The white arc represents Flap Operating Range. This is the speed at which you can lower your aircraft’s flaps, usually during approach to landing.

The Airspeed Indicator pictured shows that the aircraft is going 120 mph.

How fast?
A Cessna 310 can fly up to 220 miles per hour. The Lockheed SR-71 Blackbird has held the world record for the fastest manned aircraft since 1976 (2,193.2 miles
per hour).

At what rate is the aircraft climbing or descending?

The Vertical Speed Indicator displays the rate of climb and the rate of descent (how quickly the aircraft is changing its altitude). This is important when determining time
needed to reach a certain altitude, whether ascending or descending.

The Vertical Speed Indicator pictured shows that the aircraft is decreasing its altitude 
800 feet per minute.

How steep?
A Cessna 310 has a rate of climb of 1,700 feet per minute. A Learjet 60 has a rate of climb of 4,500 feet per minute.

In which direction is the plane flying?

The Heading Indicator informs a pilot which direction the plane is headed. The pilot 
sets the heading indicator using a compass when the plane is straight and level.

The Heading Indicator also helps pilots orient themselves to which runway they want to use. How? Runways are numbered at each end according to the magnetic heading they face. The numbers are rounded and a zero is added. For
Example: A pilot landing on runway 19 would be flying at a heading of around 190°.

What direction?
The Heading Indicator pictured shows the aircraft is heading North. The Cessna 310 on display in the park is currently heading 58 degrees NE.

Is the plane right side up or upside down?

The Attitude Indicator displays the aircraft’s position in relation to the horizon.  
It is also called the artificial horizon.

The instrument uses an internal spinning gyro which stays level with the horizon.  
Most people can visualize this by remembering playing with a spinning toy top as a child. Because the gyro stays oriented with the horizon, a pilot is shown
if the aircraft is pitching up or down or banking left or right. How? The center of the gauge has a small aircraft depicted as a red dot (nose of aircraft) and two red lines (wings of aircraft). The artificial horizon behind the small aircraft moves to reflect how the actual aircraft is positioned in relation to the horizon (blue represents the sky and brown represents the ground).

What position?
The Attitude Indicator pictured shows the aircraft is flying straight and level.

How high or low is the airplane flying?

The Altimeter displays the aircraft’s altitude above mean sea level (MSL). If a pilot wants to know how high they are above ground level (AGL), they must subtract the altitude displayed on their gauge from the ground’s elevation.
For example, an Altimeter indicating 3,000 feet would mean a pilot is actually 2,000 feet above the Greenville Downtown Airport because the airport is approximately 1,000 feet above mean sea level.

The Altimeter pictured shows the aircraft is flying at 5,320 feet above mean sea 

How high?
A Cessna 310 can fly up to 20,000 feet above mean sea level. The Concorde flew at 60,000 feet above mean sea level!

In which direction is the plane turning?

The Turn Coordinator provides two pieces of information. The top part of the 
gauge shows the direction the plane is turning (left or right) as well as the rate of turn (degrees it turns per second). The bottom is an inclinometer which consists
of a ball inside of a tube. The ball moves by centrifugal force. The pilot uses the rudder along with the ailerons to make sure the turn is coordinated. A coordinated turn is when the tail of the plane follows behind the nose. If the pilot uses too much left rudder while in a left turn, the tail of the plane slides outside of the turn and the aircraft is in a “skid.” If the pilot uses too little left rudder while in a left turn, the tail of the plane slides inside of the turn and the aircraft is in a “slip.”

What direction is the plane turning?
The Turn Coordinator pictured shows the aircraft is not turning and is coordinated.

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