Changing VOR radials when on autopilot

[NClark]

Hi Guys,
Suppose you have a flight plan that takes you in towards a VOR on one radial (let's say 007) then as you overfly the VOR station the flight plan changes your course to fly outward (on, say, the 111 radial).

Can you do this while the autopilot is tuned to the VOR as NAV1?

I find that the autopilot can't track the VOR radials close to the VOR station, so I have to turn off the autopilot, or use the Heading hold rather than NAV1 as the autopilot input.

Is this what real world pilots do too?

Appreciate any thoughts...

Cheers,

N.

[ladamson]

>Is this what real world pilots do too?
>
In real life, these days....

You can pre-load the complete flight into the GPS. The auto-pilot will then fly the complete GPS route from waypoint to waypoint. Waypoints can be VORs, airports, a scenic destination, or where ever you want. Instead of zig-zagging from VOR to VOR, you can easily define a straight path with the GPS, but keep in mind restricted airspace etc. I find this useful when flying a real life cross-country heading that's close to 180 degrees. If I used strictly VOR to VOR, I'd be crossing back and forth across 180 degrees, which also requires even & odd altitude changes.

Some auto-pilots will also begin a gentle turn before the waypoint, for a smooth transition to the next track, without over flying the waypoint & then making a sharper turn to get back on the next heading.

In so many words, I use the GPS/Auto-pilot combo to track to VORs if desired. The GPS will track straight to it, while compensating for wind on a "track", instead of the airplanes actual heading. All this equipment is also available for small GA planes or experimental catagory.

There are lots of innovations these days. Some auto-pilot's can even be programmed to track a mile or so, off to the side of a busy VOR to VOR airway, just to avoid traffic.

Ladamson

[wray]

What your doing is right the nav wont find the radial when theres a big difference , so you help it with heading mode to intercept

[lnuss]

The VOR signal in the real world when very close appears just as unstable as in the sim. The needle (which the AP follows) wobbles badly until a few moments after station passage. So heading hold until past the VOR (and turn to new heading with manual AP) is needed RW and sim.

As mentioned above, the GPS is a better bet in this situation (and many others), but you've got the right idea when tied to the VOR.

[NClark]

Thanks guys! I really appreciate the explanations.

Cheers,

N.

[burnside]

>Hi Guys,
> Suppose you have a flight plan that takes you in
>towards a VOR on one radial (let's say 007) then as you
>overfly the VOR station the flight plan changes your course to
>fly outward (on, say, the 111 radial).
>
>Can you do this while the autopilot is tuned to the VOR as
>NAV1?
>
>I find that the autopilot can't track the VOR radials close to
>the VOR station, so I have to turn off the autopilot, or use
>the Heading hold rather than NAV1 as the autopilot input.
>
>Is this what real world pilots do too?
>
>Appreciate any thoughts...
>
>Cheers,
>
>N.
Yep, in the "old days", before GPS, pilots would disconnect the NAV setting and go to the heading mode before the signal became unstable. Keep in mind that if you are flying at 24000 ft, you will be over the station at approximately a 4 mile indication on the DME. This means you would start your turn at about 6 or 7 miles. If you have FSNAV, you can try this and then check the moving map to see how you did. Winds aloft can make this even tougher to figure. (That's why I almost always flew with a navigator!)

Dale

[old_doggie]

The autopilot system in fs "As Is" cannot track into and out of a VOR station without a lot of oscillation or "overshoots". Back in FS98 I made a few adventures that incorporated such a feature, changing radials or as in your question, tracking inbd on one radial and out bound on another, by simply programming the modes that would normally be switched by the autopilot.

As I was accustomed to the autopilot on the aircraft that I flew being able to do just that and knowing how this was accomplished.

This was way before GPS(I believe this, similar to GPS, was available in the early stages to mariners and seem to remember the system as satnav) anyways, there are many different autopilot systems and functions but in the 707 the autopilot in VOR/LOC mode would track the selected radial and when crossing the VOR automatically switched from the VOR signal to the heading reference based on the Capt's selected course for approximately 120 - 140 seconds, it then reverts to normal VOR tracking and in so doing prevents nuisance corrections while in the cone of confusion. Once the heading mode is engaged by the autopilot the course changed or new radial can be dialed in without the aircraft chasing the change.

Some autopilots, includind FS, my not support this feature and therefore requires the pilot to manually switch to HDG or heading mode until station passage with a good To/From indication and from your question thats is exactly what your are doing..

>>I find that the autopilot can't track the VOR radials close to the VOR station, so I have to turn off the autopilot, or use the Heading hold rather than NAV1 as the autopilot input.<<


Maybe in the next version they will incorporate this or maybe they will remain true to form and keep the fs community hungry with drips and drabs.

Douglas