autopilot mode

HI, I recently intalled a skyview and I am wondering what is the difference between TRACK and NAV mode for horizontal axis.
Can somebody explain?

Nav mode follows your nav input, say from your GPS or other nav source.

Track follows a given track over the ground, taking crab angle into account.

Heading simply follows a magnetic heading.

Hi Bill, in my case I have a skyview that is driven by a garmin 695. In this case, whats the difference between track and nav. I have hdg nailked, lol!

Track follows the ground track, based on how the heading bug is set. It has nothing to do with having a direct-to set in the GPS. You don't even need the GPS to have any direct to to use track. It just flies in a straight line all day. Exactly the same as the heading mode, except it holds your heading over the ground, not just the nose of the plane.

NAV follows the HSI on the EFIS. So if you have a flight plan in your GPS, it will turn when it gets to the next waypoint.

I am feeling stupid.... I really have not figured yet how track works, I got Nav follows HSI and needs an external source. I am using that. Figured HDG too as it maintain stablished airplane heading. Now as for track, how it differs from hdg? Does it take wind into consideration? It was mentioned it takes crab into consideration. How does it know the plane is in a crab if is not using gps info? Sorry to insist!!

Hi Sebastiao...

..I think there is a small misunderstanding. In 'track' mode, the airplane will fly straight and not crab....no crab angle.

In "Nav' mode, with a go-to waypoint being sent from a GPS, the airplane will automatically fly to the destination AND possibly have a 'crab' angle if there is a crosswind aloft.

Best,

Maybe this will help:

AUTOPILOT MODES

HDG - Heading Mode
The autopilot keeps the nose of the airplane pointed at the magnetic heading bug. If there is a crosswind, the aircraft's ground track will "drift" with the crosswind. For instance, if you wish to go to an airport that is 270 degrees from your location, but there is a wind from 180 degrees, you will end up north of your target because the crosswind pushed you north. This mode is generally only used when ATC tells you to fly a direction, since they assume you will use a compass not a GPS to fly this vector.

TRK - Track Mode
The autopilot uses GPS information to keep the ground track of the airplane on a straight line toward the heading bug. If there is a crosswind, the nose of the aircraft (heading) will not point the same as the heading bug since the autopilot will adjust the heading to maintain a straight line over the ground. This is generally used any time the pilot wants to “hold” the direction of the aircraft without actually flying a specific GPS course or VOR radial. If the pilot hand flies the airplane off the track, the autopilot will correct back to the track, but this will not be the exact same line over the ground, since this is not a course line, but a ground track hold.

NAV - Navigation Mode
The autopilot keeps the CDI needle that is displayed on the HSI centered. This CDI source may be a VOR, localizer, or GPS. Generally, this means the autopilot is flying you straight down a radial or direct to your GPS waypoint. This will fly you onto the GPS course or radial if you are off it when you engage the mode. If needed, the aircraft will maintain the correct heading to compensate for any crosswind. If you reach a GPS waypoint or change your desired radial, the autopilot will turn to intercept this new course.

In reality, you want to use TRK mode any time you want to hold the airplane's direction across the ground. You will want to use HDG mode when ATC tells you to fly a direction, since they assume you will use a compass and not a GPS to fly this vector.

Great, now is making much more sense. In a previous post was stated that track would work regardless of the GPS and that threw me off!

Discussing a little further, why should I use TRACK instead of NAV? Let?s consider I will always be using a GPS with a direct to navigation selected, would still track be a better option over track? Wouldn?t the distance travelled in either mode be the same and wouldn?t the plane arrive at the destination using the same amount of time in either mode (NAV or TRACK)? Or not?
Thank you guys once again

Moura

OK, here's a situation where you might prefer to use TRK instead of NAV: Let's say you're flying in NAV along a route to your destination and right in the way is a MOA or a thunderstorm on your XM/GPS display. You can use TRK to make sure the airplane misses this 'obstruction' without worrying about changing enroute winds altering your ground track. If you used HDG instead, you may not miss it because the winds aloft can change, altering your course. In my airplane, TRK works far better than HDG because my magnetic heading constantly moves back and forth - and so does the airplane when in HDG mode. In TRK, it flies as straight as an arrow across the ground and doesn't constantly wander back and forth. I'm not the only one experiencing this 'phenomenon'. TRK is better for navigating than heading. HDG is what to use when ATC says maintain a certain heading, although if ATC told me to hold a heading and I wanted to use the autopilot, I'd use TRK because it works better in my plane. If I'm off a little, they'll tell me to turn a few degrees - no big deal.

In simple words........

HDG mode. This will hold a compass heading it uses the compass as the reference source, say 075 deg. But with winds you may drift along a track or 068 deg.

If you have a GPS connected, like your trusty G696, and you want to fly from point A to B which is 075deg. if you set your bug to 075 and hit TRK your plane will follow a ground track of 075 degrees exactly fed from GPS data not your compass, which in theory could say any number at all....even if you can fly backwards

NAV mode follows the flight plan or Magenta line if you use GOTO or a plan in your GPS.

Does that help.

Go try it on a day with a big cross wind component.

DB