Chapter 7
Introduction
This chapter presents information on IFR helicopter
operations in the National Airspace System. Advances in
avionics technology installed in helicopters such as Global
Positioning System (GPS) and Wide Area Augmentation
System (WAAS) are bringing approach procedures to
heliports around the country.
The ability to operate helicopters under IFR increases
their utility and safety. Helicopter IFR operators have
an excellent safety record due to the investment in
IFR-equipped helicopters, development of instrument
approach procedures (IAPs), and IFR-trained flight crews.
The safety record of IFR operations in the Gulf of Mexico is
equivalent to the safety record of the best-rated airlines.
Manufacturers are working to increase IFR all-weather
capabilities of helicopters by providing slower minimum
instrument airspeeds (V MINI), faster cruising speeds, and
better autopilots and flight management systems (FMS).
As a result, in October 2005, the first civil helicopter in
the United States was certified for flight into known icing
conditions. [Figure 7-1]
Helicopter Instrument
Procedures
Figure 7-1. Icing tests. To safely provide an all-weather capability
and flight into known icing conditions that would otherwise delay
or cancel winter flight operations, the digital control of the S-92
Rotor Ice Protection System (RIPS) determines the temperature and
moisture content of the air and removes any ice buildup by heating the
main and tail rotor blades. The system is shown here during testing.
Helicopter Instrument Flight Rule (IFR)
Certification
It is very important that pilots be familiar with the IFR
requirements for their particular helicopter. Within the
same make, model, and series of helicopter, variations in
the installed avionics may change the required equipment
or the level of augmentation for a particular operation. The
Automatic Flight Control System/Autopilot/Flight Director
(AFCS/AP/FD) equipment installed in IFR helicopters can
be very complex. For some helicopters, the AFCS/AP/
FD complexity requires formal training in order for the
pilot(s) to obtain and maintain a high level of knowledge
of system operation, limitations, failure indications, and
reversionary modes. For a helicopter to be certified
to conduct operations in instrument meteorological
conditions (IMC), it must meet the design and installation
requirements of Title 14 Code of Federal Regulations (14
CFR) Part 27, Appendix B (Normal Category) and Part 29,
Appendix B (Transport Category), which is in addition to
the visual flight rule (VFR) requirements.
These requirements are broken down into the
following categories: flight and navigation equipment,
miscellaneous requirements, stability, helicopter flight
manual limitations, operations specifications, and
minimum equipment list (MEL).
Flight and Navigation Equipment
The basic installed flight and navigation equipment for
helicopter IFR operations is listed under 14 CFR Part 29, §
29.1303, with amendments and additions in Appendix B of
14 CFR Parts 27 and 29 under which they are certified. The
list includes:
• Clock
• Airspeed indicator
• Sensitive altimeter (A “sensitive” altimeter relates to
the instrument’s displayed change in altitude over
its range. For “Copter” Category (CAT) II operations,
the scale must be in 20-foot intervals.) adjustable
for barometric pressure.
• Magnetic direction indicator
• Free-air temperature indicator
• Rate-of-climb (vertical speed) indicator
• Magnetic gyroscopic direction indicator
• Stand-by bank and pitch (attitude) indicator
• Non-tumbling gyroscopic bank and pitch (attitude)
indicator
• Speed warning device (if required by 14 CFR Part 29)
Miscellaneous Requirements
• Overvoltage disconnect
• Instrument power source indicator
• Adequate ice protection of IFR systems
• Alternate static source (single-pilot configuration)
• Thunderstorm lights (transport category helicopters)
Stabilization and Automatic Flight Control
System (AFCS)
Helicopter manufacturers normally use a combination
of a stabilization and/or AFCS in order to meet the IFR
stability requirements of 14 CFR Parts 27 and 29. These
systems include:
• Aerodynamic surfaces, which impart some stability
or control capability that generally is not found in
the basic VFR configuration.
• Trim systems provide a cyclic centering effect. These
systems typically involve a magnetic brake/spring
device and may be controlled by a four-way switch
on the cyclic. This system requires “hands on” flying
of the helicopter.
• Stability Augmentation Systems (SAS) provide
short-term rate damping control inputs to increase
helicopter stability. Like trim systems, SAS requires
“hands-on” flying.
• Attitude Retention Systems (ATT) return the
helicopter to a selected attitude after a disturbance.
Changes in attitude can be accomplished usually
through a four- way “beep” switch or by actuating a
“force trim” switch on the cyclic, which sets the desired
attitude manually. Attitude retention may be a SAS
function or may be the basic “hands off” autopilot
function.
• Autopilot Systems (APs) provide for “hands off”
flight along specified lateral and vertical paths. The
functional modes may include heading, altitude,
vertical speed, navigation tracking, and approach.
APs typically have a control panel for mode selection
and indication of mode status. APs may or may not be
installed with an associated FD. APs typically control
the helicopter about the roll and pitch axes (cyclic
control) but may also include yaw axis (pedal control)
and collective control servos.
• Flight Directors (FDs) provide visual guidance to
the pilot to fly selected lateral and vertical modes of
operation. The visual guidance is typically provided
by a “single cue, ” commonly known as a “vee bar, ”
which provides the indicated attitude to fly and
is superimposed on the attitude indicator. Other
FDs may use a “two cue” presentation known as a
“cross pointer system. ” These two presentations
only provide attitude information. A third system,
known as a “three cue” system, provides information
to position the collective as well as attitude (roll
and pitch) cues. The collective control cue system
identifies and cues the pilot what collective control
inputs to use when path errors are produced or when
airspeed errors exceed preset values. The three-cue
system pitch command provides the required cues
to control airspeed when flying an approach with
vertical guidance at speeds slower than the best-
rate-of-climb (BROC) speed. The pilot manipulates
the helicopter’s controls to satisfy these commands,
yielding the desired flightpath or may couple the
autopilot to the FD to fly along the desired flightpath.
Typically, FD mode control and indication are shared
with the autopilot. Pilots must be aware of the mode
of operation of the augmentation systems and the
control logic and functions in use. For example, on an
instrument landing system (ILS) approach and using
the three-cue mode (lateral, vertical, and collective
cues), the FD collective cue responds to glideslope
deviation, while the horizontal bar cue of the “cross
pointer” responds to airspeed deviations. However,
the same system when operated in the two-cue
mode on an ILS, the FD horizontal bar cue responds
to glideslope deviations. The need to be aware of the
FD mode of operation is particularly significant when
operating using two pilots.
Pilots should have an established set of procedures and
responsibilities for the control of FD/AP modes for the
various phases of flight. Not only does a full understanding
of the system modes provide for a higher degree of
accuracy in control of the helicopter, it is the basis for crew
identification of a faulty system.
Helicopter Flight Manual Limitations
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
additional equipment is required for single-pilot operation.
In addition, the Helicopter Flight Manual (HFM) defines
systems and functions that are required to be in operation
or engaged for IFR flight in either the single or two-pilot
configurations. Often, in a two-pilot operation, this level of
augmentation is less than the full capability of the installed
systems. Likewise, a single-pilot operation may require a
higher level of augmentation.
The HFM also identifies other specific limitations associated
with IFR flight. Typically, these limitations include, but are
not limited to:
• Minimum equipment required for IFR flight (in some
cases, for both single-pilot and two-pilot operations)
• VMINI (minimum speed—IFR) [Figure 7-2]
• VNEI (never exceed speed—IFR)
• Maximum approach angle
• Weight and center of gravity (CG) limits
• Helicopter configuration limitations (such as door
positions and external loads)
• Helicopter system limitations (generators, inverters,
etc.)
• System testing requirements (many avionics and AFCS,
AP , and FD systems incorporate a self-test feature)
• Pilot action requirements (for example, the pilot must
have hands and feet on the controls during certain
operations, such as an instrument approach below
certain altitudes)
Final approach angles/descent gradient for public
approach procedures can be as high as 7.5 degrees/795
ft/NM. At 70 knots indicated airspeed (KIAS) (no wind),
this equates to a descent rate of 925 fpm. With a 10-knot
tailwind, the descent rate increases to 1,056 fpm. “Copter”
Point-in-space (PinS) approach procedures are restricted
to helicopters with a maximum V MINI of 70 KIAS and an
IFR approach angle that enables them to meet the final
approach angle/descent gradient. Pilots of helicopters with
Augusta
A-109C
Bell
BH 212
BH 214ST
BH 222
BH 222B
BH 412
BH 430
Eurocopter
AS-355
AS-365
BK-117
EC-135
EC-155
Sikorsky
S-76A
S-76A
S-76B
S-76C
SK-76C++
9.0
5.0
4.0
4.5
4.5
6.0
4.6
4.0
3.5
7.5
7.5
6.5
NOTE: The VMINI, MAX IFR Approach Angle and G/A Mode Speed for a specific helicopter may vary with avionics/autopilot installation.
Pilots are, therefore, cautioned to refer only to the Rotorcraft Flight Manual limitations for their specific helicopter. The maximum rate of
descent for many autopilots is 1,000 FPM.
LEGEND
In some helicopters with the autopilot engaged, the VMINI may increase to a speed greater than 70 KIAS, or in the “go around”
mode requires a speed faster than 70 KIAS.
SAMPLE NOT FOR ACTUAL USE
VMINI Limitations MAX IFR Approach Angle G/A Mode Speed Manufacturer
75 KIAS
75 KIAS
75 KIAS
60 (80 coupled)
50 (65 coupled)
45 (70 coupled)
60 (AFCS Phase II)
50 (AFCS Phase III)
50 (60 coupled)
Figure 7-2. VMINI limitations, maximum IFR approach angles and G/A mode speeds for selected IFR certified helicopters.
a VMINI of 70 KIAS may have inadequate control margins
to fly an approach that is designed with the maximum
allowable angle/descent gradient or minimum allowable
deceleration distance from the missed approach point
(MAP) to the heliport. The “Copter” PinS final approach
segment is limited to 70 KIAS since turn containment and
the deceleration distance from the MAP to the heliport may
not be adequate at faster speeds. For some helicopters,
engaging the autopilot may increase the VMINI to a speed
greater than 70 KIAS, or in the “go around” (G/A) mode,
require a speed faster than 70 KIAS. [Figure 7-2] It may be
possible for these helicopters to be flown manually on the
approach or on the missed approach in a mode other than
the G/A mode.
Since slower IFR approach speeds enable the helicopter
to fly steeper approaches and reduces the distance from
the heliport that is required to decelerate the helicopter,
you may want to operate your helicopter at speeds slower
than its established V MINI. The provision to apply for a
determination of equivalent safety for instrument flight
below V MINI and the minimum helicopter requirements
are specified in Advisory Circulars (AC) 27-1, Certification
of Normal Category Rotorcraft and AC 29-2, Certification
of Transport Category Rotorcraft. Application guidance is
available from the Rotorcraft Directorate Standards Staff,
ASW-110, 2601 Meacham Blvd., Fort Worth, Texas, 76137
4298, (817) 222-5111.
Performance data may not be available in the HFM for
speeds other than the best rate of climb speed. To meet
missed approach climb gradients, pilots may use observed
performance for similar weight, altitude, temperature, and
speed conditions to determine equivalent performance.
When missed approaches utilizing a climbing turn are
flown with an autopilot, set the heading bug on the
missed approach heading, and then at the MAP , engage
the indicated airspeed mode, followed immediately by
applying climb power and selecting the heading mode.
This is important since the autopilot roll rate and maximum
bank angle in the Heading Select mode are significantly
more robust than in the NAV mode. Figure 7-3 represents
the bank angle and roll limits of the S76 used by the FAA for
flight testing. It has a roll rate in the Heading Select mode
of 5 degrees per second with only 1 degree per second in
the NAV mode. The bank angle in the Heading Select mode
is 20 degrees, with only 17 degrees in the NAV Change
Over mode. Furthermore, if the Airspeed Hold mode is
not selected on some autopilots when commencing the
missed approach, the helicopter accelerates in level flight
until the best rate of climb is attained, and only then will
a climb begin.
Figure 7-3. Autopilot bank angle and roll rate limits for the S-76
used by the William J. Hughes Technical Center for Flight Tests.
Heading hold
VOR/RNAV
(Capture)
VOR/RNAV
(On Course)
Heading Select
VOR/RNAV
(Course Change
Over Station/Fix)
<6
+/–22
+/–13
+/–20
+/–17
None specified
5 VOR/RNAV Approach
Bank Angle Limit
(Degrees)
Roll Rate Limit
(Degrees/Sec)
Autopilot
Mode
SAMPLE NOT FOR ACTUAL USE
WAAS localizer performance (LP) lateral-only PinS testing
conducted in 2005 by the FAA at the William J. Hughes
Technical Center in New Jersey for helicopter PinS also
captured the flight tracks for turning missed approaches.
[Figure 7-4] The large flight tracks that resulted during
the turning missed approach were attributed in part to
operating the autopilot in the NAV mode and exceeding
the 70 KIAS limit.
Operations Specifications
A flight operated under 14 CFR Part 135 has minimums and
procedures more restrictive than a flight operated under
14 CFR Part 91. These Part 135 requirements are detailed
in their operations specifications (OpSpecs). Helicopter Air
Ambulance (HAA) operators have even more restrictive
OpSpecs. Shown in Figure 7-5 is an excerpt from an
OpSpecs detailing the minimums for precision approaches.
The inlay in Figure 7-5 shows the minimums for the ILS
Runway 3R approach at Detroit Metro Airport. With all
lighting operative, the minimums for helicopter Part 91
operations are a 200-foot ceiling, and 1,200-feet runway
visual range (RVR) - one-half airplane Category A visibility
but no less than 1⁄4 SM/1,200 RVR. However, as shown in
Figure 7-4. Flight tests at the William J. Hughes Technical Center
point out the importance of airspeed control and using the correct
technique to make a turning missed approach.
MAP 1000 ft. 2000 ft. 3000 ft. 4000 ft. 5000 ft. 6000 ft. 7000 ft. 8000 ft.
Distance from MAP
×
×
×
×××
×
×
×
×
×
×
Bin Mean
Bin Maximum
Approach Tracks
Legend
×
the OpSpecs, the minimum visibility this Part 135 operator
must adhere to is 1,600 RVR. Pilots operating under 14 CFR
Part 91 are encouraged to develop their own personal
OpSpecs based on their own equipment, training, and
experience.
Minimum Equipment List (MEL)
A helicopter operating under 14 CFR Part 135 with
certain installed equipment inoperative is prohibited
from taking off unless the operation is authorized in the
approved MEL. The MEL provides for some equipment to
be inoperative if certain conditions are met. [Figure 7-6]
In many cases, a helicopter configured for single-pilot
IFR may depart IFR with certain equipment inoperative
provided a crew of two pilots is used. Under 14 CFR Part
91, a pilot may defer certain items without an MEL if
those items are not required by the type certificate, CFRs,
or airworthiness directives (ADs), and the flight can be
performed safely without them. If the item is disabled,
removed, or marked inoperative, a logbook entry is made.
Pilot Proficiency
Helicopters of the same make and model may have
variations in installed avionics that change the required
equipment or the level of augmentation for a particular
operation. The complexity of modern AFCS, AP , and FD
systems requires a high degree of understanding to safely
SAMPLE NOT FOR ACTUAL USE
U.S. Department
of Transportation
Federal Aviation Operations Specifications
Administration
Print Date: 4/16/2008 H117-1
H117. Straight-in Category I Precision Instrument Approach HQ Control: 11/22/00
Procedures - All Airports HQ Revision: 000
a. Except as provided in this paragraph, the certificate holder shall not use any Category I IFR landing
minimum lower than that prescribed by any applicable published instrument approach procedure. The
IFR landing minimums prescribed in this paragraph are the lowest authorized (other than Airborne
Radar approaches) for use at any airport. Provided that the fastest approach speed used in the final
approach segment is less than 91 knots, the certificate holder is authorized to conduct straight-in
precision instrument approach procedures using the following:
(1) The published Category A minimum descent altitude (MDA) or decision height (DH), as
appropriate.
(2) One-half of the published Category A visibility/RVR minimum or the visibility/RVR minimums
prescribed by this paragraph, whichever is higher.
b. Straight-In Category I Precision Approach Procedures . The certificate holder shall not use an IFR
landing minimum for straight-in precision approach procedures lower than that specified in the
following table. Touchdown zone RVR reports, when available for a particular runway, are controlling
for all approaches to and landings on that runway. (See NOTE 2.)
Precision Approaches Full ILS (See NOTE 1), MLS, or PAR
Approach Light
Configuration
HAT Helicopters Operated at
Speeds of 90 Knots or Less
Helicopters Operated at
Speeds More Than 90 Knots
Visibility In
SM.
TDZ RVR
In Feet
Visibility In
SM.
TDZ RVR In
Feet
No Lights or ODALS or
MALS or SSALS
200 3/4 3500 3/4 4000
MALSR or SSALR or
ALSF-1 or ALSF-2
200 1/4 1600 1/2 2400
MALSR with TDZ and
CL or SSALR with TDZ
and CL or ALSF-1/ALSF-
2 with TDZ and CL
200 1/4 1600 1/2 1800
NOTE 1: A full ILS requires an operative LOC, GS, and OM or FAF. A precision or surveillance radar
fix, an NDB, VOR, DME fix, or a published minimum GSIA fix may be used in lieu of an outer marker.
NOTE 2: The Mid RVR and Rollout RVR reports (if available) provide advisory information to pilots.
The Mid RVR report may be substituted for the TDZ RVR report if the TDZ RVR report is not available.
c. Special Limitations and Provisions for Instrument Approach Procedures at Foreign Airports . If the
certificate holder is authorized operations at foreign airports, the following criteria apply.
(1) Foreign approach lighting systems equivalent to U.S. standards are authorized for both precision
and nonprecision approaches. Sequenced flashing lights are not required when determining the
equivalence of a foreign lighting system to U.S. standards.
(2) For straight-in landing minimums at foreign airports where an MDA or DH is not specified, the
lowest authorized MDA or DH shall be obtained as follows:
SAMPLE NOT FOR ACTUAL USE
SAMPLE NOT FOR ACTUAL USE
Figure 7-5. Operations Specifications.