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Instrument Flying Handbook
Flight Instruments
Pitot Static System

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Instrument Flying


Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Using an Electronic Flight

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight

Chapter 6. Helicopter
Attitude Instrument Flying

Chapter 7. Navigation Systems
Chapter 8. The National
Airspace System

Chapter 9. The Air Traffic
Control System

Chapter 10. IFR Flight
Chapter 11. Emergency

Aircraft that are flown in instrument meteorological conditions
(IMC) are equipped with instruments that provide attitude
and direction reference, as well as navigation instruments that
allow precision flight from takeoff to landing with limited or
no outside visual reference.

The instruments discussed in this chapter are those required
by Title 14 of the Code of Federal Regulations (14 CFR)
part 91, and are organized into three groups: pitot-static
instruments, compass systems, and gyroscopic instruments,
The chapter concludes with a discussion of how to preflight
these systems for IFR flight. This chapter addresses additional
avionics systems such as Electronic Flight Information
Systems (EFIS), Ground Proximity Warning System
(GPWS), Terrain Awareness and Warning System (TAWS),
Traffic Alert and Collision Avoidance System (TCAS),
Head Up Display (HUD), etc., that are increasingly being
incorporated into general aviation aircraft,

Pitot Static Systems

Pitot pressure, or impact air pressure, is sensed through an
open-end tube pointed directly into the relative wind flowing
around the aircraft. The pitot tube connects to pressure
operated flight instruments such as the ASI.

Static Pressure
Other instruments depend upon accurate sampling of the
ambient still air atmospheric pressure to determine the

height and speed of movement of the aircraft through the
air, both horizontally and vertically. This pressure, called
static pressure, is sampled at one or more locations outside
the aircraft. The pressure of the static air is sensed at a flush
port where the air is not disturbed. On some aircraft, air is
sampled by static ports on the side of the electrically heated
pitot-static head. [Figure 3-1] Other aircraft pickup the static
pressure through flush ports on the side of the fuselage or
the vertical fin. These ports are in locations proven by flight
tests to he in undisturbed air, and they are nominally paired,
one on either side of the aircraft. This dual location prevents
lateral movement of the aircraft from giving erroneous static
pressure indications. The areas around the static ports may be
heated with electric heater elements to prevent ice forming
over the port and blocking the entry of the static air.

Three basic pressure-operated instruments are found in most
aircraft instrument panels. These are the sensitive altimeters,
ASI, and vertical speed indicator (VSI). All three receive
pressures sensed by the aircraft pitot-static system. The static
ports supply pressure to the ASI, altimeter, and VSI.

Blockage Considerations
The pitot tube is particularly sensitive to blockage especially
by icing. Even light icing can block the entry hole of the pitot
tube where ram air enters the system. This affects the ASI
and is the reason most airplanes are equipped with a pitot
heating system.

A Typical Electrically Heated Pitot Static Head.
Figure 3-1. A Typical Electrically Heated Pitot Static Head.