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straight line, fixed terminated
transition proceeds the start of
the final.
10-11-12-13 September 2002-Morocco ARAB INSTRUMENT PROCEDURE DESIGN SEMINAR
Navigation database related issues
Compatibility...
Navigation data production process
Procedure design
by Civil Aviation Authorities
Data Supplier
FMS Database Processing
FMS
AIP
ARINC 424 “master” file
Packed Data
operator
responsibility
Some top level issues
 Navigation database process is *not* certified
 Transcription of procedures in “computer” language
(ARINC 424) requires interpretation
 Procedure designer intent is currently only published under
“pilot language” format
 Each FMS implementation & logic is different
May results in different flight paths and SOP
 Charts and aircraft navigation displays differ
 Increased risk of Human error
 Training costs
Reminder - flight plan construction
 Charted procedure are translated into a sequence of
ARINC 424 legs in the Navigation Database
 Flight plans are entered into the FMS by calling
procedures from the navigation database
 Procedure segments are chained together (or melded) to
form the FMS flight plan
Example : F-PLN procedure melding
 Procedures are chained together to form the FMS flight
plan. Example :
Arrival chart
Airways chart
Approach chart
Enroute
(airways)
STAR-enroute
transition
STAR Approach
STAR-approach
transition (VIA)
Example : procedure compatibility ?
 Possible procedure misconnects between en-route,
arrival, and approach charts
 Possible discontinuities between or inside procedures
 Incompatible or conflicting altitude requirements
between arrival and approach charts
10-11-12-13 September 2002-Morocco ARAB INSTRUMENT PROCEDURE DESIGN SEMINAR
Navigation database recommendations
Waypoint naming issues
 Different approach procedure types (ILS/LOC/RNAV…)
use different trajectories and/or waypoint names without
reason
 Unnamed waypoints on charts are assigned default names
 Same waypoint names used at different locations
 Chart wording leading to usage of leg types which cause
the FMS to create its own waypoints, with names which do
not match chart
 Coding constraints lead to creation of waypoints not on the
chart
Procedure trajectory issues
 Chart wording and/or coding rules lead to coding of
magnetic course leg types such as CF legs
 Chart wording and/or coding rules lead to bad coding of
vertical descent angles, which are critical to a correct
vertical path
 IFR minimum altitudes often coded as “AT” constraints
 Overfly waypoints trajectories are not repeatable
 Barometric temperature limitations should be indicated
on charts
 Overfly waypoints : depending on wind, aircraft speed,
bank angle limitation etc… the FMS trajectory will be
different
Why not use overfly waypoints ?
trajectory
not repeatable
overfly wpt
 Fly-by waypoints : better trajectory control is achieved
as the FMS will track a pre-computed curve
Why use fly-by waypoints ?
controlled
trajectory
fly-by wpt
 CF leg magnetic course angles may mismatch :
excessive roll
maneuvering
Why not use CF legs ?
N N
 TF legs always fit, independently of magnetic variation :
Why use TF legs ?
IDLE segment
Why code FPA constraint on each
FINAL leg ?
FPA smaller than
altitude constraint
FPA greater than
altitude constraint
No FPA
FPA matches altitude
constraint
Why not use AT altitude constraints ?
 Using AT constraints may cause undesired vertical path :
navigation database vertical angle
navigation database vertical angle
MAP
approach profile
MDA
Why use AT_OR_ABOVE altitude
constraints ?
 Using AT_OR_ABOVE constraints and FPA constraint
on each leg ensures seamless path
MDA
navigation database vertical angle
navigation database vertical angle
MAP
approach profile
Medium term - recommendations
 Implementation of DO201A by civil aviation authorities for
procedure publication
 Implementation of DO200A by data providers
 Implementation of RTCA DO236 / EUROCAE ED-75
 
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