Actual Navigation Performance
Actual Aircraft Position Lies Within the ANP Circle As installed
Copyright . The Boeing Company. See title page for details.
11.31.8 June 6, 2003
Flight Management, Navigation -Flight Management System Operation
737 Operations Manual
Required Navigation Performance (RNP)
The FMC supplies a default required navigation performance (RNP) value for oceanic, en route, terminal, and approach phases of flight. RNP can also be supplied by the Navigation Database or may be entered by the crew. Actual navigation performance (ANP) should not exceed RNP.
Environment Default RNP Time to Alert
Oceanic 12.0 NM 80 sec.
En route 2.0 NM 80 sec.
Terminal 1.0 NM 60 sec.
Approach 0.5 NM 10 sec.
If ANP exceeds a Navigation Database or crew entered RNP value, the message UNABLE REQD NAV PERF–RNP appears in the scratchpad after the designated time to alert has elapsed and in amber on the MAP display only when in the approach environment. If ANP exceeds a default RNP value for the current navigation environment, the IRS NAV ONLY message is displayed in the scratchpad after the designated time to alert has elapsed.
Lateral Navigation (LNAV)
LNAV provides steering commands to the next waypoint. If selected, LNAV engages when laterally within 3 nautical miles of the active route leg. If outside of 3 nautical miles of the active route leg, LNAV engages if on an intercept heading of 90 degrees or less and the intercept will occur before the active waypoint. FMC LNAV guidance normally provides great circle courses between waypoints. However, when an arrival or approach from the FMC database is entered into the active route, the FMC can supply commands to fly a constant heading, or track, as required by the procedure.
Waypoints
Waypoint (navigation fix) identifiers are displayed on the CDU and EHSI. The CDU message NOT IN DATA BASE is displayed if a manually entered waypoint identifier is not stored in the database. The waypoint can still be entered
as a latitude/longitude, place–bearing/distance, or place–bearing/place–bearing waypoint. FMC–generated waypoints contain a maximum of five characters assigned
according to the following rules.
Flight Management, Navigation -Flight Management System Operation 737 Operations Manual
Navaid Waypoint Names
VHF – waypoints located at VHF navaids (VOR/DME/LOC) are identified by the official one, two, three, or four character facility identifier. Examples:
.
Los Angeles VORTAC – LAX
.
Tyndall TACAN – PAM
.
Riga, Latvia – RIX.
NDB – waypoints located at NDBs are identified by use of the station identifier. Example:
. FORT NELSON, CAN – YE.
Fix Waypoint Names
Fixes with one–word names – waypoints located at fixes with names containing five or fewer characters are identified by the name. Examples:
.
DOT
.
ACRA
.
ALPHA.
Long Waypoint Names
Names with more than five characters are abbreviated using the following rules sequentially until five characters remain. Double letters are deleted. Examples:
.
KIMMEL becomes KIMEL
.
COTTON becomes COTON
.
RABBITT becomes RABIT.
Keep the first letter, first vowel and last letter. Delete other vowels starting from right to left. Examples:
.
ADOLPH becomes ADLPH
.
BAILEY becomes BAILY
.
BURWELL becomes BURWL. Keep the last letter, then delete consonants from right to left. Examples:
.
ANDREWS becomes ANDRS
.
BRIDGEPORT becomes BRIDT
.
HORSBA becomes HORSA. Fixes with multiword names use the first letter of the first word and abbreviate the
last word, using the above rules sequentially until a total of five characters remain. Examples:
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