Hello everybody~I have a very small question that constantly ignored by me, but now I can't hold anymore to know the answer.No matter it is a PMDG747 or PMDGMD-11, FS9 or FSX, when the aircraft makes a turn by autopilot, especially at low speed, the altitude tends to drop a little (20~60feet), of course when the turn is completed, the autopilot climbs back to the designated altitude. It looks like the autopilot isn't fast enough to maintain certain altitude or certain vertical speed. I've been searching the forum for clues, but without proper answer. I'm not sure whether it's a FS limitation or not, but I really want to know the answer.Thank you very much!! I enjoy every flight as long as it is flown by a PMDG jet.Tom

You forgot the question, Tom.A manual slow flight turn involves a loss of airspeed and altitude unless you are ahead of the airplane, and is a favorite manuever given by flight instructors to check your airmanship.A loss of 20-ft during a turn would not give the strictest check pilot any cause for concern, but the 60-ft deviation could raise an eyebrow unless you were really on the slow side of the power curve.Don't expect the autopilot to fly the airplane like it is on rails in all corners of the flight envelope, but in general it should do much better than the human pilot in the normal flight envelope.

You forgot the question, Tom.A manual slow flight turn involves a loss of airspeed and altitude unless you are ahead of the airplane, and is a favorite manuever given by flight instructors to check your airmanship.A loss of 20-ft during a turn would not give the strictest check pilot any cause for concern, but the 60-ft deviation could raise an eyebrow unless you were really on the slow side of the power curve.Don't expect the autopilot to fly the airplane like it is on rails in all corners of the flight envelope, but in general it should do much better than the human pilot in the normal flight envelope.

Your exactly right. Its extremely hard to keep a plane exactly at an altitude during a turn.

You forgot the question, Tom.A manual slow flight turn involves a loss of airspeed and altitude unless you are ahead of the airplane, and is a favorite manuever given by flight instructors to check your airmanship.A loss of 20-ft during a turn would not give the strictest check pilot any cause for concern, but the 60-ft deviation could raise an eyebrow unless you were really on the slow side of the power curve.Don't expect the autopilot to fly the airplane like it is on rails in all corners of the flight envelope, but in general it should do much better than the human pilot in the normal flight envelope.

Thanks for your prompt reply!I'm actually not so worry about the drop of so small amount of altitude which commended by autopilot. Nevertheless, what really interests me is that the real aircraft seems capable of maintaining perfect altitude when turning, of course I mean in perfect weather condition. I've watched several cockpit DVDs, and those big jets do maintain their altitude precisely during a steep turn. I have a friend who is a FO of the Embraer ERJ 190, has also confirmed that his jet does maintain its altitude flawlessly no matter how it turns, in good weather condition.I therefore wondering why my jet always drops at least 20ft during a turn, but during cruising phase, it turns perfectly with drop of no altitude.