B727 Horizontal Stabilizer Trim. Fine tuning?

[domzalskiavn1]

When trying to trim the "Flying Tail" Horizontal Stabilizer, the trim is done in very big increments as degrees wise. I see the trim gauge on the instrument panel and it looks like it is jumping about 2 degrees at a time (very hard to keep acft in a steady pitch attitude in flight). Is there a way to adjust the Stabilizer Trim to smaller adjustments or increments so I'm not Porpoising about the skies? Or do I do that with the Elevator trim for the fine tuning?

I have the Richard Probst and George Carty style B727-200 panel.


Thanks, Jim D

[aerofoto - HJG Admin]

Would I be correct to assume that you have your TRIM assigned to your joystick/yoke device ?

"IF SO" .... then this might like account for any excessive Trim sensitivity which you're experiencing .... and which has come up on the C135's too.

I can assure you/everyone that very careful adjustments to Trim response were applied by myself and Mike .... to reduce excessive Elevator Trim sensitivity.

I, personally, recommend the use of both "HOME and "END" keyboard commands in order to set Elevator Trim up/down during manual comtrolled flight .... and which will/should then result in perfectly smooth Elevator Trim response/sensitivity.

During AP comtrolled flight you should be adjusting/setting Trim per the Thumb Wheel on the AP .... using your Mouse .... and which will/should also result in perfectly smooth Elevator Trim response too.

Again .... from what I/we've been able to determine, to date, excessive Trim sensitivity seems to result only when using joystick/Yoke Trim assignments.

Mark C
AKL/NZ

[domzalskiavn1]

I do not have my trim assigned to joystick. I have it assigned to keyboard as follows:

7 stabilator pitch up
1 stabilator pitch down

8 elevator pitch up
2 elevator pitch down

(7 & 1 adjust the pitch trim on the "flying tail", the whole "T-tail" , of the 727, you can watch it move up and down in the outside view and does not release when putting flight control inputs for pitch up and down)

(8 & 2 on the other hand adjust the elevator pitch up and pitch down and when you make control inputs it releases the elevator trim that you put in.)

I also worked on the Boeing 727 for 1 1/2 years......got to know the girl pretty well.

On the Horizontal Stabilator of the 727 the Horizontal stabilator is adjusted by a large jackscrew located in the vertical stabilator. This process was done with "smooth" adjustments. Just wondering if the adjustments can be fine tuned or smoothed out in the NON-AP mode. (Everyrthing works great in the AP mode)

I hope you are unsderstanding what I'm asking.

[aerofoto - HJG Admin]

I hope you are understanding what I'm asking.

YEAH .... I'm aware of what you're saying .... I believe .... and I'm also aware of those other technical details associated with the B727 tail which you mention too !

How FS interprets and responds to inputs associated with Trim with can vary .... and be dependent on a number of things.

Incidentally .... the only reason I first raised the possibility of Joystick/Control device assignments applying, in you case, is simply because we are aware .... that depending on some FS sensitivities which may be set/customized in respect of these devices .... we have seen evidence, in some cases only, of overly sensitive Trim response .... but .... which shouldn't happen of course if these settings are sensibly adjusted !

During pre-release flight testing (more than 1 year ago now) we adjusted Trim sensitivity (within the CFG data), for all of the B727's to a value, which we determined, provided the best response (and which is a major improvement over that of the original data) during both manual and AP controlled flight. Since the release of the B727, here at HJG, we have not had any reason to adjust the Trim value we selected.

If your Trim response is working well during AP controlled flight .... then it should also be working equally well when set manually too.

"IF" .... you're getting overly sensitive Trim response during manual setting .... then that "may" be the result of depressing those numbers keyboard commands either too aggressively .... or .... for too long a duration maybe .... or .... possibly these assignments may currently be sent to values (within FS) which are still far too sensitive.

It's hard to say !

Personally .... I won't assign Trim to any of these numbers pad keyboard commands .... but .... that's just my own preference.

On the basis of my own, personal, experience, I'll only use the "HOME" and "END" keyboard commands to set and adjust Trim manually .... requiring only light finger taps/inputs .... and which, admittedly, adjusts the axis of the entire flying tail rather than the trailing edge tabs, but which, provides, for me, very acceptable/smooth response to manual input.

Mark C
AKL/NZ

[gus]

Hello,

I can suggest you a experiment ....

Aircraft.cfg

[flight_tuning]
cruise_lift_scalar=1.000
pitch_stability=1.000
roll_stability=1.000
yaw_stability=1.000
parasite_drag_scalar=1.000
induced_drag_scalar=1.000
elevator_effectiveness=1.000
aileron_effectiveness=1.000
rudder_effectiveness=1.000
elevator_trim_effectiveness=0.450
aileron_trim_effectiveness=1.000
rudder_trim_effectiveness=1.000

You can try some differents numbers (low number = low sensitivity)

Regards.

[Mike Monce - HJG]

Another place to try is in the MSFS settings menu. Once the yoke you are using is set, scroll down until you find the yoke button assingments for the elevator trim. In the last column should be a sliding bar for "repeat"> It seems to have only 3 settings: on, off, midway. If it's set to ON, try resetting to mid way and see if that helps also.

Mike

[domzalskiavn1]

OK !!! Got It! WHEW!!!
Thanks for your help Mark, Mike, and Gus.......very helpful. One thing the key requiring only light finger taps/inputs helped VERY much, Thank you Mark. I was for one, "Hitting the key tooooo long !!!!"

I did the experiment for changing the elevator effectiveness but no change.......or too little to notice a change, but Thanks a million for the help . The AP is good and now the manual trim is good...... Thanks for the advice and help guys!!

Jim D