The A2A Simulations Community

Scott or SD (hell, and anyone else who could explain what is probably remedial aerodynamics to a layman... )

Maybe you could shed a little light on this, but the A6M5's trim characteristics as modelled has me a little perplexed. Now it says on the checklist that "above speeds of about 220 KIAS, the trim is not sufficient to counter this pitching-up tendency and someforward stick will need to be added to full nose-down trim to keep the playing flying level." Now, I'm no engineer (which is probably why I need the explanation, ) but as I understand it, the trim tabs are tiny airfoils attached to the trailing edge of the control surface, and when they are deflected INto the slipstream, they force the control surface in the opposite direction. So (again, with no engineering degree so bare with me) I'm assuming the trim tab should be able to move the control surface to the stop if necessary, and that if pilots came back from long missions and complained about having to hold forward pressure, the engineers could correct this. Maybe make the trim tab larger? or longer?

Just curious about why this was and why it wasn't corrected...seems like a strange characteristic to persist in a plane that was otherwise brilliantly designed...

AU

The zero has some interesting flight characteristics for sure. I wish there was some more zero pilot accounts to read, there are just too few. I'm sure there must have been a Army Air Corps or Navy/Marine flight test done on a captured zero? Does anyone know of a website link or book? S/F Mud

Mudmarine I have a PDF from a captured A6M2 zero. This tes was conducted at San Diego (the San Diego A6M2 Report). It is interesting to note they claim the A6M2 cuts out under negative G manouvers but it turned out they had the carbeurator installed incorrectly. They also claimed the F4F was faster than the A6M2 at low level. A claim which was rebuked as "flat wrong" by USN aviators.

As I say it is an intersting read but also shows how far off the mark some tests on captured fighters are. I can e-mail it to you if you are interested.

Here are a few links you might be interested in reading

http://www.warbirdforum.com/zerodunn.htm

http://www.j-aircraft.com/

alias_unknown_2004 wrote:Scott or SD (hell, and anyone else who could explain what is probably remedial aerodynamics to a layman... )

Maybe you could shed a little light on this, but the A6M5's trim characteristics as modelled has me a little perplexed. Now it says on the checklist that "above speeds of about 220 KIAS, the trim is not sufficient to counter this pitching-up tendency and someforward stick will need to be added to full nose-down trim to keep the playing flying level." Now, I'm no engineer (which is probably why I need the explanation, ) but as I understand it, the trim tabs are tiny airfoils attached to the trailing edge of the control surface, and when they are deflected INto the slipstream, they force the control surface in the opposite direction. So (again, with no engineering degree so bare with me) I'm assuming the trim tab should be able to move the control surface to the stop if necessary, and that if pilots came back from long missions and complained about having to hold forward pressure, the engineers could correct this. Maybe make the trim tab larger? or longer?

Just curious about why this was and why it wasn't corrected...seems like a strange characteristic to persist in a plane that was otherwise brilliantly designed...

AU

No, the trim tab is by no means powerful enough to deflect the control surface to the stop, nor should it be. However not all trim is set up that way, some aircraft simply use a variable incidence elevator, wherein the entire tailplane incidence is changed to vary trim.

This characteristic was confirmed by a pilot who is currently flying the only remaining A6M5 with a Sakae engine. Considering the poor performance of the Zero in a dive, this explains a lot.

"No, the trim tab is by no means powerful enough to deflect the control surface to the stop, nor should it be." yeah i figure under ordinary circumstances, it certainly shouldn't be necessary, but it seems odd that this nose-up tendency wouldn't have been addressed in at least the later model Zekes, either through the addition of larger, more effective trim tabs, or through maybe a permanent adjustment to tailplane incidence, as you suggest. Or maybe even modifying the tailplane airfoil itself. Of course, I'm sure if they coulda, they woulda...

I remember Pappy Boyington writing about securing the control stick in his Corsair with rubberbands so he could sleep off his hangover during long missions (believing that the younger members of his squadron had better eyes and would certainly alert him if there were any bandits). He said he could tell by the sound if the Corsair began to climb or descend and he'd make a slight adjustment to the rubberbands. I wonder if maybe Zeke pilots came up with their own contraptions to compensate for lack of elevator trim...

ICDP--Thanks for the links and I'd love a copy of that too, if you don't mind sending it around.

AU

If you would like to change the elevator trim issue, go into the Aircrafts CFG notepad, and edit the following section...

[airplane_geometry]
wing_area = 229.270
wing_span = 36.094
wing_root_chord = 8.460
wing_dihedral = 5.000
.............(scroll down..)
rudder_limit = 28.000
elevator_trim_limit = 8.000 <CHANGE 8.000 TO 15.000
spoiler_limit = 0.000
..............
------END

Instead of the 8.000, make it 15.000 like i did.

Even though this may not be realistic, it solves the autopilot issues of holding altitude. Enjoy,
Joe

Cherokeepilot19 wrote: Even though this may not be realistic, it solves the autopilot issues of holding altitude.

You're worried about A6M Zero autopilot fixes being realistic? *big big grin* Actually, I'd be very surprised if any pilots complained about trim. Remember the culture and the times (we're talking a culture that thought making pilot trainees jump out of 20+ ft towers would make them better pilots! *grin*)

Posted: Fri Jul 21, 2006 5:04 pm Post subject:

--------------------------------------------------------------------------------

If you would like to change the elevator trim issue, go into the Aircrafts CFG notepad, and edit the following section...

[airplane_geometry]
wing_area = 229.270
wing_span = 36.094
wing_root_chord = 8.460
wing_dihedral = 5.000
.............(scroll down..)
rudder_limit = 28.000
elevator_trim_limit = 8.000 <CHANGE 8.000 TO 15.000
spoiler_limit = 0.000
..............
------END

Instead of the 8.000, make it 15.000 like i did.

Even though this may not be realistic, it solves the autopilot issues of holding altitude. Enjoy,
Joe

well no, if that is the way the zero flew, I'd rather leave it as is. and i've never used auto pilot except once in real life when i was moving up from the 1979 C-172 to the Millenium Edition and in love with the gadgetry (but then i'm only vfr so...)


AU

Actually, I'd be very surprised if any pilots complained about trim. Remember the culture and the times (we're talking a culture that thought making pilot trainees jump out of 20+ ft towers would make them better pilots! *grin*)

actually, i remember reading once, either in the "Tech Series" or the "warbird History" series that fighter pilots in pre-war China had a LOT of influence in the development of the Zero. I can't imagine seasoned combat pilots who felt they were being instrumental in the design of the ultimate figher NOT complaining or being concerned about trim effectiveness...

-E wrote:

Cherokeepilot19 wrote: Even though this may not be realistic, it solves the autopilot issues of holding altitude.

You're worried about A6M Zero autopilot fixes being realistic? *big big grin* Actually, I'd be very surprised if any pilots complained about trim. Remember the culture and the times (we're talking a culture that thought making pilot trainees jump out of 20+ ft towers would make them better pilots! *grin*)

Heh heh, we could have just left the autopilot out of all these planes and really been realistic! But indeed, changing this would affect the "manual" flight characteristics. Normally you would never fly at over 200 KIAS during cruise anyway so it should be a moot point for the autopilot.

I looked at the Aircraft.Cfg for the Zero and it's missing a entire section called:

[Flight Tuning]
cruise_lift_scalar=
pitch_stability=
roll_stability=
yaw_stability=
parasite_drag_scalar=
induced_drag_scalar=
elevator_effectiveness=
aileron_effectiveness=
rudder_effectiveness=
elevator_trim_effectiveness=
aileron_trim_effectiveness=
rudder_trim_effectiveness=
p_factor_on_yaw =
torque_on_roll =
gyro_precession_on_yaw =
gyro_precession_on_pitch =


Jack

Wow, by autopilot, i mean altitude hold, or a simple way of being able to trim to level flight, not have the autopilot do EVERYTHING.

This quick fix is for the people who want to beable to crusie at higher speed and not hve to hold the stick down. It is a simple fix for making the pilot trim the a/c correctly.

Joe

I see that this was never addressed/answered. Even after the update, the Zero has no [Flight Tuning] section in its aircraft.cfg. Do the settings within just revert to a default value if it's not present? What is that value? I'd think it'd be "1.0" but I see some of the other planes DO have this section with all of the values listed as "1.0" which makes me think that maybe that's NOT the default value. If it were, why bother to put the section in there if all the values are just default?

Jack wrote:I looked at the Aircraft.Cfg for the Zero and it's missing a entire section called:

[Flight Tuning]
cruise_lift_scalar=
pitch_stability=
roll_stability=
yaw_stability=
parasite_drag_scalar=
induced_drag_scalar=
elevator_effectiveness=
aileron_effectiveness=
rudder_effectiveness=
elevator_trim_effectiveness=
aileron_trim_effectiveness=
rudder_trim_effectiveness=
p_factor_on_yaw =
torque_on_roll =
gyro_precession_on_yaw =
gyro_precession_on_pitch =


Jack

Digging around on the Zero threads and found a few gems, glad to see an interest in this plane. Jack, this section is not needed in the aircraft.cfg file if the flight model is properly designed. It's intended for quick and dirty changes only. In some aircraft containers all the values are set to "1" which is the same as deleting the entire section.

BTW the other post was accurate, the Zero did not have enough elevator trim range to compensate above a certain airspeed.

As far as the autopilot, well, it's a convenience and works well for those long dreary flights.

DougHillman wrote:I see that this was never addressed/answered. Even after the update, the Zero has no [Flight Tuning] section in its aircraft.cfg. Do the settings within just revert to a default value if it's not present? What is that value? I'd think it'd be "1.0" but I see some of the other planes DO have this section with all of the values listed as "1.0" which makes me think that maybe that's NOT the default value. If it were, why bother to put the section in there if all the values are just default?

Smart fellow.