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pirep2222

Autopilot HDG Select Issue

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Has anyone had the problem where the autopilot maintains a heading of 5 degrees to the left of whatever you command it to fly

 

Ive tried uninstalling and then reinstalling both FSX and the NGX but it still does the same thing

 

Thanks

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First a quick sanity check before anyone engages in more detailed troubleshooting: you are aware of the difference between aircraft track and heading, right?

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Hi! Don't want to sound patronizing. Are you sure it's not the wind? What weather and weather addon did you have when you noticed the issue?

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I'v never seen the registry issue effect the NGX. I'v literally had the 747 and MD11 both effected, and without fixing it the NGX is fine.

In the below image, the heading "190" is selected. Due to the 16 knot crosswind, the track is 193° across the ground.

pfd_nd_nps.jpg

The nose of the plane is pointed exactly at 190° Magnetic heading.
The 193° is track across the ground due to crosswind.

When ATC gives vectors they will usually say "Turn *left/right* heading _ _ _"
Heading is the direction the nose of the plane is pointing. That means set HDG to (in this case) 190 on the MCP, and the 3° track error is left uncorrected. (by the pilot, The ATC can correct it if they want and give another vector later on).

Please note: During the situation of the image, the heading set in the MCP would be exactly 190.
The track is 193° due to the crosswind. The nose is still pointed at 190.

 

As you know, at higher flight levels, the wind speed can increase to over 100kts, leading to track/heading variances of significant degrees.

 

This is why when an aircraft is in cruise, headings are often given as "Track 20 degrees left" instead of an actual 3 digit figure. This is because ATC can't see the Heading information, and only have track. An aircraft tracking 193° might have a heading of 180° or anything if it is travelling through a jetstream with a 150kt wind. Telling the aircraft to turn Left heading 180 would be confusing. (turn left from 180 to 180 by turning 0° to the left).

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Here's another diagram I drummed up that might paint (ms paint? lol) a clearer picture.

 

5cuh.jpg

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