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12/2/21 

AIM 

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: 

1. 

Aerodynamic surfaces, which impart some 

stability or control capability not found in the basic 
VFR configuration. 

2. 

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

way switch on the cyclic. This 

is a system that supports “hands on” flying of the 
helicopter by the pilot. 

3. 

Stability Augmentation Systems (SASs), 

which provide short

term rate damping control 

inputs to increase helicopter stability. Like trim 
systems, SAS supports “hands on” flying. 

4. 

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

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. 

5. 

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. 

6. 

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

pointer”) or “single cue” (commonly known 

as a “vee

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 limita-

tions associated with IFR flight. Typically, these 
limitations include, but are not limited to: 

1. 

Minimum equipment required for IFR flight 

(in some cases, for both single pilot and two pilot 
operations). 

2. 

Vmini (minimum speed 

 IFR). 

Helicopter IFR Operations 

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