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Aircraft not straight and level in cruise

PostPosted: Fri May 18, 2007 2:34 pm
by TheConfused
Hi all
I have installed SP1 hoping that this would solve this problem. When flying at say FL290 the aircraft always points nose upwards and the artificial horizon is not level. When I make it level the aircraft losses altitude. I have seen this problem before in this forum but unable to find that thread now. I was hoping SP1 would sort it but I cant believe they have not sorted out that issue. Really disappointed.

Thanks for any help

Mart

Re: Aircraft not straight and level in cruise

PostPosted: Fri May 18, 2007 9:55 pm
by richardd43
Does it do it if you engage the autopilot?

It sounds like the aircraft is flying to slow and is nose up trying to maintain altitude.

I have had my trim out of whack so bad I had to use autopilot to get it right again.

Re: Aircraft not straight and level in cruise

PostPosted: Fri May 18, 2007 10:00 pm
by Ashton Lawson
what aircraft are you flying, and what speed are you flying at?

the autopilot will try to maintain a certain altitude no matter how fast you're going, so the plane being pitched up is no surprise.  try flying at full throttle, just to see what the autopilot will do then.

Re: Aircraft not straight and level in cruise

PostPosted: Sat May 19, 2007 1:17 am
by ozzy72
Have you got the aircraft properly trimmed before activating the AP?

Re: Aircraft not straight and level in cruise

PostPosted: Sat May 19, 2007 4:01 am
by TheConfused
I was using autopilot (I think that automatically trims the aircraft?) and it always points nose up (using default 747). Speed was approx mach 0.77. When autopilot turned off and I force aircraft to straight and level attitude it loses hight at about 500fpm. This in turn increases the air speed so aircraft should start to level out unless I apply nose down pressure and retard the throttle (am I wrong on this??) So in other words, to make it fly straight and level I have to have the nose up, and to begin a decent I  level the aircraft (with the artificial horizon showing level flight).  
I have seen this problem on this forum and the fix involved a modification of a file within FSX, and as I did not want to mess with that I elected to wait for the service pack. But alas, just cant find the thread now.

thanks

Mart

Re: Aircraft not straight and level in cruise

PostPosted: Sat May 19, 2007 6:36 am
by vololiberista
To fly straight and level with a marked nose up attitude indicates two things. First and the most common is airspeed.  As your airspeed diminishes the AP will (assuming it is set to fly at a fixed altitude) compensate for the loss of airspeed by increasing the angle of attack (what you see as a nose up attitude) It will keep on doing this until the AOA is too high and thus the a/c enters the stall.

The second point would be CoG (Centre of Gravity). If in the a/c it is too far behind station zero the a/c will always fly in a nose up attitude.

Any other case would indicate that the a/c was built on a Friday afternoon or in your case there is a discrepancy in the values set up by the a/c cfg file.
Vololiberista

Re: Aircraft not straight and level in cruise

PostPosted: Sat May 19, 2007 7:42 am
by cdub420
here is your fix. third one down

http://www.simviation.com/fsxjets4.htm

Re: Aircraft not straight and level in cruise

PostPosted: Sat May 19, 2007 3:53 pm
by TheConfused
Thanks, that link sorted it, and also finally got the wing flex effect. Why Microsoft never sorted that I don't know.

Thanks to you all for you help

Mart