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Gh3003

VNAV programming issue

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Greetings fellow members -

 

On the act rte 1 legs page, i enter the waypoints followed by speed/altitude. I arm vnav, and find the plane ignoring the data i entered on the mentioned page.

 

I set the speed initially in the mcp to f. ex. 270, and arm vnav when in cruise. When i enter a waypoint, like:

 

BAVAD 220/3400

 

- The plane ignores this and continue in the same altitude and speed i entered in the mcp (or by hand-flying).

 

What am i missing here?

 

Greetings from Gunnar

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So, you're not arming VNAV until the cruise?  VNAV in the 744 is normally armed on the ground.  If you're not arming VNAV until the cruise, then yes it will ignore your entry in the FMC. It sounds like you're climbing out in FLCH mode. If so, that will over ride speed/Altitude entries in the FMC.  You'll see the FMA's on the PFD change to indicate that.

 

Edit:  Just had another read of you question.  Is the entry you're making in the cruise?

 

Buzz

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Greetings fellow members -

 

On the act rte 1 legs page, i enter the waypoints followed by speed/altitude. I arm vnav, and find the plane ignoring the data i entered on the mentioned page.

 

I set the speed initially in the mcp to f. ex. 270, and arm vnav when in cruise. When i enter a waypoint, like:

 

BAVAD 220/3400

 

- The plane ignores this and continue in the same altitude and speed i entered in the mcp (or by hand-flying).

 

What am i missing here?

 

Greetings from Gunnar

 

Hi, Gunnar,

 

I don't own the 747 but the 777 and NGX are similar, so I will try to answer.

 

First, about entering a waypoint while in cruise: just entering a waypoint on the FMC LEGS page won't cause the aircraft to descend to the new altitude.  You need to set the MCP altitude to 3400 (in your example) or to a lower intermediate altitude.  You may have to click on the MCP altitude knob as well.  Also, the FMC should calculate a TOD including the new waypoint info.  If you haven't reached the TOD yet, it won't start to descend.

 

Second, you need to give more information for the first part of your post.  Are you on the ground?  Are you arming LNAV and VNAV before takeoff?  Is your first waypoint pretty much in line with the runway heading?  What, in detail, is the procedure you are following?

 

Mike

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Martybuzz and Mike: now i tried to arm it on the ground before take-off, but i can not arm the main autopilot switch. LNAV wont arm (i dont see the light appear on the switch itself, nor in the PFD. I was able to arm VNAV.

 

My waypoint was not in line with the airport, but after reading your answer i added a waypoint. I was still not able to arm LNAV. I could not arm the main autopilot switch either.

 

When i tried flying now i saw on the VNAV page that the waypoint was mentioned at the E/D (dont know what that is), but the plane did not descend at at all -

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You cannot "arm" the main A/P switch on the ground. There is no "arm" for A/P it is either on or off. Above 400 feet you can turn it on.

 

I suggest a good read of the manual and try the tutorial flight.

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Yep, what Peter says, have a bit of a study.  If LNAV won't arm on the ground, then your first waypoint is not within the LNAV limits as you said.  The easy way around that is to fly "Heading Select" and then perform a "Direct to" in the legs page of the FMC.  My bible when flying is the "FMC User's Guide" written by Bill Bulfer.  I'm not so sure whether it's still available.

 

The aircraft will not descend until you either select a lower altitude whilst in VNAV mode or you push the knob under the Altitude window.  The "Speed" window will open and you'll descend in FLCH mode.

 

You'll get there, we all started at the begining.  Also get to know your FMA's as they will always let you know what mode is controlling the aircraft.  A few pilots have come unstuck not observing their FMA's. 

 

Buzz

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As

 

Martybuzz and Mike: now i tried to arm it on the ground before take-off, but i can not arm the main autopilot switch. LNAV wont arm (i dont see the light appear on the switch itself, nor in the PFD. I was able to arm VNAV.

My waypoint was not in line with the airport, but after reading your answer i added a waypoint. I was still not able to arm LNAV. I could not arm the main autopilot switch either.

When i tried flying now i saw on the VNAV page that the waypoint was mentioned at the E/D (dont know what that is), but the plane did not descend at at all -

 Hi, Gunnar,

 

As Peter and Buzz said, you need to go through the tutorials that came with the 747.  If you somehow managed to turn on (not "arm") the autopilot on the ground it would likely cause elevator trim to go to maximum up, causing the aircraft to pitch up sharply on takeoff or even take off before you are ready.

 

It is impossible to learn this type of aircraft by posting one question at a time.  From what you are saying, any number of things could be wrong.   This aircraft doesn't fly like a default FSX aircraft at all -- it is much more complex and realistic.  That's the fun of it!

 

If you are still having problems after doing the tutorials, post back here with screen shots of your MCP, PFD and CDU screen.

 

Mike

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