SPRINGBOK From United Kingdom, joined Jun 2001, 192 posts, RR: 1 Posted (13 years 11 months 3 weeks 4 days ago) and read 3396 times:
Still in deep shock, but i have a question "How do the LNAV and VNAV operate with the Autopilot and when are they operated?after purchasing PSS747-400
Any views much appreciated!
P.S RIP to all affected by the attack
AJ From Australia, joined Nov 1999, 2403 posts, RR: 24
Reply 1, posted (13 years 11 months 3 weeks 3 days 14 hours ago) and read 3352 times:
LNAV (lateral natigation) and VNAV (vertical navigation) operate using data from the flight management computer.
On a normal B747-400 operation with a SID programmed for departure LNAV and VNAV can be armed for departure.
At 50' TOGA will change to LNAV in the roll mode and the flight director will follow instructions from the FMC to fly the SID. When the autopilot is engaged it will follow these commands. LNAV can remained engaged, follow a programmed STAR right to the destination. Normally it is only disconnected for radar vectors (HDG SEL), weather diversions (HDG SEL) or Localiser intercept (LOC).
At 400' TOGA will change to VNAV in the pitch mode and the flight director will follow instructions from the FMC VNAV page. The first speed commanded is V2+10kts to +25kts depending on current speed. VNAV will then command acceleration for flap retraction at the appropriate altitude and programmed climb speed (VNAV SPD). VNAV will not climb through or leave an MCP entered altitude (VNAV ALT). If cruise altitude on the MCP matches the altitude on the VNAV CRZ page in the FMC you will hav VNAV PTH (path) displayed on the PFD. Approaching TOD calculated by the FMC you will get the message 'Reset MCP altitude'. If the MCP altitude is below the cruise altitude the thrust will reduce to idle and descent will commence in VNAV PTH. VNAV will maintain the path up to 15kts away from the programmed speed. Outside of this VNAV SPD will be displayed and the descent profile will be left. This will normally require speedbrake to resume path with the message 'Drag Required'. VNAV will follow the speed transitions entered in the VNAV DESCENT page, such as 240kts below 10000'. It will also attempt to comply with STAR altitude restrictions. If an intermediate altitude is captured on climb or descent VNAV ALT will be displayed. Once the MCP altitude is reset the selector button must be pushed to resume the climb or descent. VNAV can remain engaged until glideslope (GS/APP) intercept.
I don't want to make this too complicated, I hope this info helps!
Concorde1518 From United States of America, joined May 2001, 746 posts, RR: 0
Reply 2, posted (13 years 11 months 3 weeks 2 days 18 hours ago) and read 3343 times:
Basically, the flight planner on MSFS is like programming the FMC, and using the NAV button is like hitting the LNAV. (With a few differences) On real aircraft, the closest thing to the NAV button is the VOR/LOC button which will fly to the airport LOC, or a VOR. Either way, the VOR or LOC frequency must be inputed in the radios.