Position Updating
Figure 005
Runway Takeoff Shift for Takeoff Position Updating
Figure 006
POSITION MONITOR Page Access
Figure 007
SELECTED NAVAID Page
Figure 008
-This page also displays, in 1L, the onside navaid used for display in the same manner as for navaids used for navigation. In addition to this, the tuning mode is displayed in green small font in columns 8-13. This tuning mode is either: AUTO MAN (for manual) RMP (The selection of the displayed navaid is explained in Para. B and C).
-Line 4L displays, by ident and frequency with its class and
selection mode, the ILS which is tuned (if any)
-Pressing a key 1L, 2L, 3L or 4L displays the NAVAID page describing the information concerning the chosen navaid. The SELECTED NAVAIDS page is returned through a RETURN prompt in NAVAID page in field 6R.
-The pilot may also deselect up to 6 navaids in fields 1R through 6R. Deselection results in that navaid not being tuned or used for navigation by the FMGC until the pilot allows again the use of that navaid (using CLR function). The fields are cleared upon transition to DONE or preflight phase or when the second data base is activated on the A/C STATUS page.
-A DESELECTED GPS prompt in 5L allows the pilot to manually deselect the GPS. GPIRS position use in FMGC position computation is then inhibited until the pilot reselect it (via the same prompt).
(8) Other navigation computations
-Ground speed and track The ground speed is computed by updating a mixed IRS velocity by the rate of variation of the GPIRS or radio position (used as a GPIRS or radio velocity). The mixed IRS velocity is either a simple average of the three IRS velocities if they are all available and valid, or a single IRS velocity. In this case, the IRS used to compute the IRS velocity is the same as the one used for position computation (Ref Para. (2)). The North and East components define the ground speed vector. Then the A/C track is derived from that Ground Speed.
-Wind Current wind (magnitude and direction) is computed by using the aircraft geometry defined by groundspeed and track (computed by FMS) and true airspeed and heading (provided by ADR). This wind value is displayed on the ND.
-Bearing/distance to a fix On pilot demand, the FMS computes and displays the bearing and distance from the A/C position to a dedicated fix.
This fix can be a waypoint, a navaid, a NDB, or an airport reference point runway and is selected on the PROG page. (Ref. Fig. 009)
B. Navigation Mode Selection and Class of Navigation
(1)
General The navigation mode with the least error is chosen based upon the best GPIRS or radio position available as defined in Para. B and C. The available modes of navigation include the following:
-GPS/INERTIAL
-DME/DME/INERTIAL
-DME/VOR/INERTIAL
-INERTIAL ONLY. The mode chosen will be as defined in Para. A.(1). If an IR position is available, one of the modes described in Para. 1. will be used. If not, no navigation computation is provided. As well as mode annunciation, navigation will supply data for class annunciation ; this annunciation will be dependent upon the navigation error and the navigation mode (Ref. Para. A.(2)).
(2)
Navigation mode selection
(Ref. Fig. 010)
(a) GPS/INERTIAL If a valid and reasonnable hybrid GPS/IRS position is available from one of the IRS's, the GPS/INERTIAL mode is choosen. The logic to determine the availability of the hybrid GPS/IRS position takes into account the hybrid factor of merit delivered by the IRS. As long as GPS/INERTIAL mode is active, no DME/DME or VOR/DME radio updating is allowed. However, LOC updating can apply on GPS/INERTIAL position. The FM only uses one input of GPIRS hybrid position for computing FM position. The FMGC position is a mix of the hybrid GPIRS position and the mixed IRS position and the navigation mode displayed on the POSITION MONITOR page is N IRS/GPS, with N being the number of IRS's used to compute mixed IRS position. The selected hybrid GPIRS position is displayed on the POSITION MONITOR page in place of radio position. The mixed IRS position and the IRS deviations displayed on the POSITION MONITOR page do not change and are still computed using pure IRS inputs. The GPS/INERTIAL mode is inhibited if pilot deselects GPS through the SELECTED NAVAIDS page. 中國航空網 m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：A320飛機維護手冊 AMM AUTO FLIGHT 自動飛行3(70)
