2: The IF is part of the next leg. No transition exists.
3: NAV is disengaged in discontinuity. No transition exists.
4: Both legs must have the same radius. No transition exists.
(3) Use-display To define a path the active, next and third legs are checked to determine the required transitions. Based on the path definition, the FMGC produces the leg geometry and the active leg path geometry. The ACT LEG PATH GEOMETRY is used to control the aircraft and consists of the active leg, the next leg and the transition between them. The LEG GEOMETRY is used in generating the EIS F-PLN display. In all cases, it consists of the active leg, next leg and transition between them. However, if the transition between the next leg and the third leg is a type III or type V, it is also displayed with the third leg.
Teardrop Entry
Figure 023
Parallel Entry
Figure 024
Type III Transition CF - VA
Figure 025
Type IV and Type V Transitions
Figure 026
Leg Transition Types
Figure 027
F. Displayed Parameters - Path Errors
(1)
General The FMGC computes for display on the EIS or on the MCDU, lateral references, lateral path errors, also used in the lateral control laws and leg sequencing logic, and destination distance for performance.
(2)
Lateral references
(a) Definition
(Ref. Fig. 028, 029)
The position reference parameters are as follows:
-Bearing to go : bearing to go from the current aircraft position to the leg termination point.
-Distance to go : direct distance to go from the current aircraft position to the leg termination point.
-Time to go : time to go from the current aircraft position to the leg termination point. Time to go is always the distance to go divided by the current ground speed.
-Desired track : current tangent for the active leg.
NOTE : If the current leg termination is not a fixed waypoint,
____ distance to go, time to go and bearing to go are referred to the predicted termination (altitude, VOR radial, distance to a navaid).
NOTE : If the current leg is a manual termination leg, only the
____
desired track is computed.
(b) Display of positions reference parameters (Ref. Fig. 030) Bearing to go and distance are displayed on both EIS and MCDU. Time to go and desired track are only displayed on EIS.
(3) Lateral path errors
(a) Definition The FMGC computes a crosstrack error and a track angle error for control of the aircraft along the lateral path also for determination of lateral path capture and leg sequencing.
-
The TRACK ANGLE ERROR is always the difference between the DESIRED TRACK and the TRUE TRACK.
-
The CROSSTRACK ERROR to a course leg is the perpendicular distance to the leg. (Ref. Fig. 031)
Reference Parameters for a CF Leg
Figure 028
PF Leg (Procedure Turn)
Figure 029
Reference Parameters Display
Figure 030
Lateral Path Error on Straight or Great Circle Path
Figure 031
-The CROSSTRACK ERROR to a circular arc is the difference between the distance from the A/C position to the turn center and the turn radius of the arc. (Ref. Fig. 032) This definition applies for all circular arcs in holding patterns (HX legs) or AF legs.
(b) Display Only the CROSS TRACK ERROR is displayed on the EIS (nav display). (Ref. Fig. 030)
(4)
Destination distances
(a)
Definition The FMGC computes the distance to destination (DIST TO DEST) and direct distance to destination (DIRECT DIST TO DEST). It also computes the ALONG TRACK DIST TO GO used for performance computations.
-
The DIRECT DIST TO DEST is the distance along a great circle path connecting the A/C position to the LOC capture point or runway axis intercept point and then to destination runway (Ref. 22-73).
-
The ALONG TRACK DIST TO GO is the distance along the active leg from the point where CROSSTRACK ERROR is computed to the leg termination point. (Ref. Fig. 033)
-
The DIST TO DEST is a sum of the lateral leg distances in the flight plan beginning with the active leg termination and the ALONG TRACK DIST TO GO as defined above. (Ref. Fig. 033)
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