747 Weird problem

[Schnyd]

I recently started flying the stock 747 and I've had a pretty big issue. When I get up to cruising altitude and turn on autopilot I get a lot of fluctuation in the speed. The plane will accelerate to a high speed and then it's like it hits a speed bump and slows way down. Also the plane gets a lot of side to side movement and rotation. If I leave it alone long enough it will eventually stall and spin out of control.

Evey other plane I've flown I don't have this issue. I've tried thing like turning on de-ice and even messed with the setting to limit turbulence but nothing seems to help.

The only add-on that I'm running that may play a part is HIFI Active Sky. But again I've had no issue on any other aircraft.

Any thoughts?

Thanks.

[jlab58]

maybe an expert will correct me, but i think turning on auto pilot is't enough on these big birds. prior to auto pilot you probably must select your altitude and speed, your heading would make some sens.good luck.

[SeanTK]

Before engaging the AP, be sure to set your desired altitude, heading/lnav function, and airspeed (in mach units, not knots.)

[hhomebrewer]

What I do in FS9 is get to altitude and heading, then set it all, including kicking in the auto-throttle. Never a problem. Probably works the same in FSX. Try it...

[topcatin]

You have to set the altitude,speed and rate of climb and heading. After setting these parameters then use "ctrl+z" to set the auto-pilot.

[westside]

Weight and Balance....... Have you tried setting up the aircraft before leaving the ground? FS seems to default to a fully loaded aircraft. If the aircraft is to heavy no autopilot system can keep it flying. A fully loaded 747 (fuel, passengers and cargo) is at the limit of the aircraft's capabilities. Try taking off some fuel and cargo and see if that helps. It is important to keep a good balance or the aircraft won't successfully get off the ground.

Mark

[Schnyd]

I'm not sure if load is the issue. I'm flying with about 50% fuel. But fully loaded otherwise. It's just strange that I never had this issue with the 737.