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Chapter 10.  Helicopter Operations

Section 1.  Helicopter IFR Operations

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1.  Helicopter Flight Control Systems

a.

The certification requirements for helicopters to operate under
Instrument Flight Rules (IFR) are contained

in 14 CFR Part 27, Airworthiness Standards: Normal Category Rotorcraft,
and 14 CFR Part 29, Airworthiness

Standards: Transport Category Rotorcraft. To meet these requirements,
helicopter manufacturers usually utilize

a set of stabilization and/or Automatic Flight Control Systems
(AFCSs).

b.

Typically, these systems fall into the following categories:

Aerodynamic surfaces, which impart some stability or control capability
not found in the basic VFR

configuration.

Trim systems, which provide a cyclic centering effect. These systems
typically involve a magnetic

brake/spring device, and may also be controlled by a four

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way switch on the cyclic. This is a system that supports

"hands on" flying of the helicopter by the pilot.

Stability Augmentation Systems (SASs), which provide short

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term rate damping control inputs to

increase helicopter stability. Like trim systems, SAS supports "hands
on" flying.

Attitude Retention Systems (ATTs), which return the helicopter to a
selected attitude after a disturbance.

Changes in desired attitude can be accomplished usually through a four

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way "beep" switch, or by actuating a

"force trim" switch on the cyclic, setting the attitude manually, and
releasing. Attitude retention may be a SAS

function, or may be the basic "hands off" autopilot function.

Autopilot Systems (APs), which provide for "hands off" flight along
specified lateral and vertical paths,

including heading, altitude, vertical speed, navigation tracking, and
approach. These systems typically have a

control panel for mode selection, and system for indication of mode
status. Autopilots may or may not be installed

with an associated Flight Director System (FD). Autopilots typically
control the helicopter about the roll and

pitch axes (cyclic control) but may also include yaw axis (pedal
control) and collective control servos.

FDs, which provide visual guidance to the pilot to fly specific
selected lateral and vertical modes of

operation. The visual guidance is typically provided as either a "dual
cue" (commonly known as a

"cross

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pointer") or "single cue" (commonly known as a "vee

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bar") presentation superimposed over the attitude

indicator. Some FDs also include a collective cue. The pilot
manipulates the helicopter's controls to satisfy these

commands, yielding the desired flight path, or may couple the flight
director to the autopilot to perform automatic

flight along the desired flight path. Typically, flight director mode
control and indication is shared with the

autopilot.

c.

In order to be certificated for IFR operation, a specific helicopter
may require the use of one or more of these

systems, in any combination.

d.

In many cases, helicopters are certificated for IFR operations with
either one or two pilots. Certain

equipment is required to be installed and functional for two pilot
operations, and typically, additional equipment

is required for single pilot operation. These requirements are usually
described in the limitations section of the

Rotorcraft Flight Manual (RFM).

e.

In addition, the RFM also typically defines systems and functions that
are required to be in operation or

engaged for IFR flight in either the single or two pilot configuration.
Often, particularly in two pilot operation,

this level of augmentation is less than the full capability of the
installed systems. Likewise, single pilot operation

may require a higher level of augmentation.

f.

The RFM also identifies other specific limitations associated with IFR
flight. Typically, these limitations

include, but are not limited to:

Helicopter IFR Operations

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