First OfficerI've found that using the autopilot to take off is the only way the airplane can keep itself trimmed during flight. This is the only way I've found to keep the nose from shooting way up or down upon disengaging the autopilot in flight.
Here's my procedure:
1. Before takeoff, set speed, heading, target altitude, and vertical speed in the autopilot. None of the activation buttons should be pressed except for the A/P master (CMD) at this time.
2. Perform all activities on checklist before takeoff.
3. When cleared for takeoff, release brakes and press the IAS button on the autopilot console. This will fire up the engines and get you moving down the runway.
4. At takeoff speed, press the ALT button on the autopilot console. This lifts the plane off the runway on its way to the target altitude at the set vertical speed.
5. Now whenever you disengage the autopilot for whatever reason, the plane maintains its trim (since it set its own trim to begin with). At this point, the plane would flare sharply up or down according to the manual trim if you had taken off manually.
If you take off manually, you MUST level the plane MANUALLY to zero the trim before engaging the autopilot. Otherwise, the trim would not be level, and the autopilot would retrim the plane based on the trim settings FROM THAT POINT. The plane assumes a level trim when autopilot is not engaged.
Example: You're flying the 747 manually at 15,000 feet on your way to a cruise altitude of 30,000. You've manually trimmed the plane to maintain a 1,500 ft/min climb (I'll come back to this later). Now say you want to turn on the autopilot and let it finish the climb and level out for you. You hit the appropriate buttons on the autopilot console, and the plane climbs and eventually levels out at 30,000 feet. So far, so good. You fly your route using the autopilot, taking your instructions from the ATC. Now let's say it's time to land. You've descended to 1,500 feet using the autopilot. You've reduced speed, added appropriate flaps, and you're smooth on the glideslope. You're getting ready to cross the threshold, so it's time to disengage the autopilot. You press the CMD button and OH MY GOD!! The nose of the plane has shot up to 25 degrees! I stall out and crash on the runway!! Why? Because you did not manually level out the trim before you engaged the autopilot after takeoff. Remember, the plane assumes a level trim at the time you engage the autopilot. So when the autopilot is DISengaged, the plane will automatically return to whatever trim was set when autopilot was turned on, assuming it was level flight (even if it wasn't level).
So what's the point of this post? To show you that if you let the autopilot maintain the trim ALL THE TIME (from takeoff clearance to landing clearance), you will never experience any unexpected flares up or down.
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Captain
Chief Captain
Wouldn't it be more appropriate to properly trim the plane? Even on those models that do not have a good indicator for trim, It is pretty easy to bring it down the same number of "notches" you brought it up originally.
