Altitude Control when following GPS Route?

Recently I have been creating scenic flight paths by entering GPS lat’ & long’ way points of towns & cities that I wish to fly over and saving the route in flight planner.

Typically flying a Cessna 172 or a Beechcraft Baron, I take off switch on auto pilot and the plane follows my GPS route. My question is can I automatically control the altitude at which the plane flies the route?

When entering the details for each waypoint into the flight planner there is a field for altitude. I may enter say - 2,000 or 3,000ft for each way point but it makes no difference, the planes height is just governed by the throttle.

If I go to the bottom of the radio stack and switch on ALT (right hand side of AP radio), no change. If on the Alt radio I set 2000 ft and 200 ft/min VS, nothing happens.

Am I missing a step or are these selected planes not capable?

I presume for this to work I would need some sort of auto throttle?

Any feedback would be much appreciated

 

Robert

The altitude in the flight plan mean atc will tell you to fly that altitude. No more.

 

The autopilot will hold that altitude, but you will need to switch the AP on first. (button on the left.)

 

In those planes you have no autothrottle, so make sure to push the throttle if you make the AP climb.

The altitude in the flight plan mean atc will tell you to fly that altitude. No more.

 

The autopilot will hold that altitude, but you will need to switch the AP on first. (button on the left.)

 

In those planes you have no autothrottle, so make sure to push the throttle if you make the AP climb.

 

Also watch your airspeed on descent for the same reason..

Following the altitude profile of a flightplan: generally speaking only (full) VNAV capable aircraft can do this. You will find this feature in airliners mostly, as it requires some sort of flight management computer. The aircraft cannot blindly follow the vertical path, as altitude changes require changes in power settings, so the AC needs some sort of engine management system too (like auto thrust). And the computer will make sure that following the profile does not exceed the aircrafts' capabilities and simply ignore the path otherwise.