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Instrument Flying Handbook
Flight Instruments
Required Navigation Instrument System Inspection

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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

resolution advisory
Figure 3-58. An example of a resolution advisory being provided
the pilot, in this case, the pilot is requested to climb, with 1,750
feet being the appropriate rate of ascent to avoid traffic conflict.
This visual indication plus the aural warning provide the pilot
with excellent traffic awareness that augments see and avoid

Terrain Alerting Systems

Ground Proximity Warning System (GPWS)

An early application of technology to reduce CFIT was the
UPWS. in airline use since the early 1970s, GPWS uses the
radio altimeter, speed, and barometric altitude to determine the
aircraft's position relative to the ground. The system uses this
information in determining aircraft clearance above the Earth
and provides limited predictability about aircraft position
relative to rising terrain. It does this based upon algorithms
within the system and developed by the manufacturer for
different airplanes or helicopters. However, in mountainous
areas the system is unable to provide predictive information
due to the unusual slope encountered.

This inability to provide predictive information was evidenced
in 1999 when a DH-7 crashed in South America. The crew
had a GPWS onboard, but the sudden rise of the terrain
rendered it ineffective. The crew continued unintentionally
into a mountain with steep terrain. Another incident involved
Secretary of Commerce Brown who, along with all on board,
was lost when the crew flew over rapidly rising terrain where
the GPWS capability is offset by terrain gradient. However,
the GPWS is tied into and considers landing gear status, flap
position, and ILS glide slope deviation to detect unsafe aircraft
operation with respect to terrain, excessive descent rate,
excessive closure rate to terrain, unsafe terrain clearance while
not in a landing configuration, excessive deviation below an
ILS glide slope. It also provides advisory callouts.

Generally, the GPWS is tied into the hot bus bar of the electrical
system to prevent inadvertent switch off. This was demonstrated
in an accident involving a large four-engine turboprop airplane.

While on final for landing with the landing gear inadvertently
up, the crew failed to heed the GPWS warning as the aircraft
crossed a large berm close to the threshold. In fact, the crew
attempted without success to shut the system down and attributed
the signal to a malfunction. Only after the mishap did the crew
realize the importance of the GPWS warning.

Terrain Awareness and Warning System (TAWS)

A TAWS uses GPS positioning and a database of terrain and
obstructions to provide true predictability of the upcoming
terrain and obstacles. The warnings it provides pilots are
both aural and visual, instructing the pilot to take specific
action. Because TAWS relies on GPS and a database of
terrain/obstacle information, predictability is based upon
aircraft location and projected location. The system is time
based and therefore compensates for the performance of the
aircraft and its speed. (Figure 3-59)

Head-Up Display (HUD)
The HUD is a display system that provides a projection of
navigation and air data (airspeed in relation to approach
reference speed, altitude, left/right and up/down glide slope)
on a transparent screen between the pilot and the windshield.
The concept of a HUD is to diminish the shift between
looking at the instrument panel and outside. Virtually any
information desired can be displayed on the HUD if it is
available in the aircraft's flight computer. The display for
the HUD can be projected on a separate panel near the
windscreen or as shown in Figure 3-60 on an eye piece. Other
information may he displayed, including a runway target in
relation to the nose of the aircraft, which allows the pilot to
see the information necessary to make the approach while
also being able to see out the windshield.

Required Navigation Instrument System

Systems Preflight Procedures
Inspecting the instrument system requires a relatively small
part of the total time required for preflight activities, but its
importance cannot be overemphasized. Before any flight
involving aircraft control by instrument reference, the pilot
should check all instruments and their sources of power
for proper operation. NOTE: The following procedures are
appropriate for conventional aircraft instrument systems.
Aircraft equipped with electronic instrument systems utilize
different procedures.