Sometimes (like 50%of the time) when I engage the autopilot shortly after takeoff it goes into a dive. This will also happen when flaps/slats are up and the aircraft is properly trimmed. Does anybody else have this behaviour ?
Is there a way to mitigate this ?
Thanks

BrzI wrote on Dec 20^th, 2014 at 9:32am:

Sometimes (like 50%of the time) when I engage the autopilot shortly after takeoff it goes into a dive. This will also happen when flaps/slats are up and the aircraft is properly trimmed. Does anybody else have this behaviour ? Is there a way to mitigate this ? Thanks

Turning on your Flight Director after engaging the autopilot should stop this from happening.

Tried it. It did not work....

Sorry, but I have to ask .... Have you trimmed the 727 to maintain a climb before you turn the Autopilot ON?

NOTE. The trim for the 727 is very sensitive. I tap the trim up/trim down buttons on my joystick or the changes are too great.

I always trim to as close to what to V-One gauge specifies. Yes, it is VERY sensitive. Even with tapping I can never get it quite right...usually within 0.10 degree margin of error.

Are you using Acceleration? I've read other have had issues with the 727 autopilot if it's not installed.

Yes, using Acceleration....

Why is it that when I set a pitch of 10 degrees up on flight director that upon takeoff it keeps that same distance ie. I cannot meet the FD crosshairs by pitching up ?

My 737-100 does not do this . . .

A fresh install of the 727-100 does not seem to help.

Well....I have figured out what works for me. Not sure if this is how it should work for everybody else so please keep that in mind.

727-100/200 loadout
75% passengers
60% cargo (positions 1,3 and 5 in front/rear bays)
Takeoff fuel:
30/30/30 to 70/30/70 (this is where I am at usually)
Start flight.
Reload aircraft (to get sounds). Do not want to use the 707 fix.
Set altitude
Initialize V-One gauges (no other mods)
Set flaps to 5 or 15 degrees

The odd part : I do not touch the flight director.

Release brakes, apply full throttle.
Rotate per schedule.
After rotation use the trim controls to maintain a pitch of 15 degrees maximum. Once the pitch is stable (ie. requires no more input) I engage A/P.
Bingo  . . . no more diving on A/P engagement.

My conclusion :

either:
I am doing something wrong
or
the flight director itself or it's connection to the A/P is buggy.

This will work for me. YMMV.

Curious to hear what other people are seeing.

Once again the 737-100 F/D and A/P work just fine.

Thanks

I have experienced the nosedive problem in the past, and I also determined that my use of the F/D was causing it.  I stopped using the F/D and everything works properly.

fsxpaul wrote on Dec 26^th, 2014 at 2:44pm:

Turning on your Flight Director after engaging the autopilot should stop this from happening.

BrzI wrote on Dec 31^st, 2014 at 9:13pm:

Tried it. It did not work....

I believe that's exactly what I stated in my post.
The flight director will not affect the AP after it has been engaged.

I've have found a method for the FD to work properly when engaging the AP.

I'm using Acceleration so I don't know if this will work for those who do not have it installed.

1. Turn on the FD to GA (Go Around) then adjust the pitch control knob as shown in these images:

http://i823.photobucket.com/albums/zz155/fsxpaul/FSX/FD_727_1_zps6ea70c8b.jpg

2. Adjust while observing the thin gray pitch line:

http://i823.photobucket.com/albums/zz155/fsxpaul/FSX/FD_727_2_zps370496b6.jpg

3. Click PITCH COMMAND on pedestal:

http://i823.photobucket.com/albums/zz155/fsxpaul/FSX/FD_727_3_zps6ee6aa0d.jpg

4. The pitch bars will re-center:

http://i823.photobucket.com/albums/zz155/fsxpaul/FSX/FD_727_4_zpsadb574c9.jpg

You're ready to go!
When engaging the AP the aircraft will hold approximately 9.3° to 9.6° and will not dive.

Hmm.... you are adjusting the Flight Director bars with autopilot controls...

That does not make sense...but I will definitely try it....

Yep, I am using acceleration.

It is at times like these that I am happy I only buy from CS when they have a sale - never know if they have a finished product or not. You would think that with v2.4 the sound issue would have been ironed out. But no, still need to reload and edit sound.ini to get sounds in cockpit.

I still remember the five years it took them to finish off the FS9 757.

To give them credit - their FS2002/4 727 was excellent - and finished off in an acceptable time frame.

Well, two for two....looks pretty good actually. What I like about this method is that it creates a smooth climb experience.

Now the question is : is this how it should be in the real world ? Or is this a chance discovery ?

I looked at the manuals. No mention of the thin grey line. . .

Thanks for the tip. Will keep using it.

BrzI wrote on Jan 4^th, 2015 at 9:45pm:

No mention of the thin grey line. . .

The thin grey line was my reference indicator for ease of explanation.

The 'mustache' bar in the second image is approximately 4° which does not correlate to the 9° pitch attitude on take-off.

Appears to be a 5° discrepancy.

Just my point - unfinished product.

Anyways, as long as I can predict the behaviour I am happy.

Thanks for all your help Paul. Happy new year.

PS.. got the AZI HD repaints. Posted some screenies on the AVSIM screenshot forum in case anybody is interested.