Section 4 – Normal procedures
ADDITIONAL GUIDANCE FOR RNAV GPS
AFMS N°D07 FOR GARMIN GFC700 AUTOPILOT AND VARIABLE PITCH PROPELLER EQUIPPED
AEROPLANES
9 ADDITIONAL GUIDANCE FOR RNAV GPS
Experience of RNAV systems, and Flight FMS in general, has identified the pitfalls of
waypoint entry error at the receiver as well as inaccuracies and errors in the database it-
self.
Research and experience have both shown that human error, often the result of a lack of
familiarity with the airborne equipment, represents the major hazard in operations using
RNAV systems. Therefore, it is imperative that pilots understand their system thoroughly
and are able to determine whether it is safe to proceed.
This requires robust procedures, which check for possible errors in the computer database,
monitor continued performance of the RNAV systems and enable pilots to identify and
avoid not only their own mistakes but also errors in the information presented to them.
Flight planning on RNAV routes should include the following recommendation.
- During the pre-flight planning phase, given a GPS constellation of 23 satellites or less
(22 or less for GPS stand-alone equipment that incorporate pressure altitude aiding),
the availability of GPS integrity (RAIM) should be confirmed for the intended flight
(route and time). This should be obtained from a prediction program either ground-
based, or provided as an equipment function, or from an alternative method acceptable to
the Authority;
- Where a navigation data base is installed, the data base validity (current AIRAC cycle)
should be checked before flight;
- Traditional navigation equipment (e.g. VOR, DME and ADF) should be selected to
available aids so as to allow immediate cross-checking or reversion in the event of loss
of GPS navigation capability.
1) Pre-flight Planning
During the pre-flight planning phase, the availability of the navigation infrastructure, re-
quired for the intended operation, including any non-RNAV contingencies, must be con-
firmed for the period of intended operation. Availability of the onboard navigation equip-
ment necessary for the route to be flown must be confirmed. The onboard navigation da-
tabase must be appropriate for the region of intended operation and must include the navi-
gation aids, waypoints, and coded terminal airspace procedures for the departure, arrival and
alternate airfields.
Where the responsible airspace authority has specified in the AIP that dual PRNAV sys-
tems are required for specific terminal P-RNAV procedure, the availability of dual P-
RNAV systems must be confirmed. This typically will apply where procedures are ef-
fective below the applicable minimum obstacle clearance altitude or where radar coverage
is inadequate for the purposes of supporting P-RNAV. This will also take into account the
particular hazards of a terminal area and the feasibility of contingency procedures follow-
ing loss of P-RNAV capability.
RAIM availability must be confirmed with account taken of the latest information
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