Pt. 121, App. G

14 CFR Ch. I (1-1-19 Edition)

3. Equipment and equipment installation - Inertial Navigation Systems (INS). (a) If an applicant elects to use an Inertial Navigation
System it must be at least a dual system (including navigational computers and reference units). At least two systems must be
operational at takeoff. The dual system may
consist of either two INS units, or one INS
unit and one Doppler Radar unit.
(b) Each Inertial Navigation System must
incorporate the following:
(1) Valid ground alignment capability at
all latitudes appropriate for intended use of
the installation.
(2) A display of alignment status or a ready
to navigate light showing completed alignment to the flight crew.
(3) The present position of the airplane in
suitable coordinates.
(4) Information relative to destinations or
waypoint positions:
(i) The information needed to gain and
maintain a desired track and to determine
deviations from the desired track.
(ii) The information needed to determine
distance and time to go to the next waypoint
or destination.
(c) For INS installations that do not have
memory or other inflight alignment means,
a separate electrical power source (independent of the main propulsion system) must
be provided which can supply, for at least 5
minutes, enough power (as shown by analysis
or as demonstrated in the airplane) to maintain the INS in such condition that its full
capability is restored upon the reactivation
of the normal electrical supply.
(d) The equipment must provide such visual, mechanical, or electrical output signals
as may be required to permit the flight crew
to detect probable failures or malfunctions
in the system.
4. Equipment and equipment installation - 
Doppler Radar Systems. (a) If an applicant
elects to use a Doppler Radar System it
must be at least a dual system (including
dual antennas or a combined antenna designed for multiple operation), except that:
(1) A single operating transmitter with a
standby capable of operation may be used in
lieu of two operating transmitters.
(2) Single heading source information to
all installations may be utilized, provided a
compass comparator system is installed and
operational procedures call for frequent
cross-checks of all compass heading indicators by crewmembers.
The dual system may consist of either two
Doppler Radar units or one Doppler Radar
unit and one INS unit.
(b) At least two systems must be operational at takeoff.
(c) As determined by the Administrator
and specified in the certificate holder-s operations specifications, other navigational aids
may be required to update the Doppler Radar
for a particular operation. These may in-

clude DME, VOR, ADF, ground-based radar,
and airborne weather radar. When these aids
are required, the cockpit arrangement must
be such that all controls are accessible to
each pilot seated at his duty station.
5. Training programs. The initial training
program for Doppler Radar and Inertial
Navigation Systems must include the following:
(a) Duties and responsibilities of flight
crewmembers, dispatchers, and maintenance
personnel.
(b) For pilots, instruction in the following:
(1) Theory and procedures, limitations, detection of malfunctions, preflight and
inflight testing, and cross-checking methods.
(2) The use of computers, an explanation of
all systems, compass limitations at high
latitudes, a review of navigation, flight planning, and applicable meteorology.
(3) The methods for updating by means of
reliable fixes.
(4) The actual plotting of fixes.
(c) Abnormal and emergency procedures.
6. Equipment accuracy and reliability. (a)
Each Inertial Navigation System must meet
the following accuracy requirements, as appropriate:
(1) For flights up to 10 hours- duration, no
greater than 2 nautical miles per hour of circular error on 95 percent of system flights
completed is permitted.
(2) For flights over 10 hours- duration, a
tolerance of Section20 miles cross-track and Section25
miles along-track on 95 percent of system
flights completed is permitted.
(b) Compass heading information to the
Doppler Radar must be maintained to an accuracy of Section1Section and total system deviations
must not exceed 2Section. When free gyro techniques are used, procedures shall be utilized
to ensure that an equivalent level of heading
accuracy and total system deviation is attained.
(c) Each Doppler Radar System must meet
accuracy requirements of Section20 miles crosstrack and Section25 miles along-track for 95 percent of the system flights completed. Updating is permitted.
A system that does not meet the requirements of this section will be considered a
failed system.
7. Evaluation program. (a) Approval by evaluation must be requested as a part of the application for operational approval of a Doppler Radar or Inertial Navigation System.
(b) The applicant must provide sufficient
flights which show to the satisfaction of the
Administrator the applicant-s ability to use
cockpit navigation in his operation.
(c) The Administrator bases his evaluation
on the following:
(1) Adequacy of operational procedures.
(2) Operational accuracy and reliability of
equipment and feasibility of the system with
regard to proposed operations.

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