f4 j/s elevator authority
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f4 j/s elevator authority
Hello,
just updated to the j/s adv version, trying to get a handle on the changes, one issue:
when lightly loaded (half fuel, sidewinders only), takeoff requires some amount of nose up trim or else it will not leave the ground with stick full aft going over 180kts. seems the elevator authority is lacking from what i'm experiencing.
of course i can give it some nose up trim prior to takeoff roll but once airborne and clean up, it just goes vertical without frantic nose down trim to counter this action.
what's going on?
just updated to the j/s adv version, trying to get a handle on the changes, one issue:
when lightly loaded (half fuel, sidewinders only), takeoff requires some amount of nose up trim or else it will not leave the ground with stick full aft going over 180kts. seems the elevator authority is lacking from what i'm experiencing.
of course i can give it some nose up trim prior to takeoff roll but once airborne and clean up, it just goes vertical without frantic nose down trim to counter this action.
what's going on?
- doodlebug
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Re: f4 j/s elevator authority
I think that's the nature of the beast in the real world - you also need to switch on your Stability Augmentation System (SAS- Pitch/Roll/Yaw)
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Re: f4 j/s elevator authority
yup, sas is switched on, but that comes into play once airborne.
the fact that it needs large nose up trim just to lift off, then it goes ballistic once gear up (mil thrust) seems a little off...
the fact that it needs large nose up trim just to lift off, then it goes ballistic once gear up (mil thrust) seems a little off...
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Re: f4 j/s elevator authority
What flaps are you using?. Only HALF flaps are allowed in this aircraft for airfield takeoff. In FULL flaps the hstabs authority is very reduced and hence, rotation and liftoff speeds will exceed the allowable limits. Full flaps are only used for carrier takeoff (only if a/c configuration recommends so - see NATOPS - ) and landing.kdfw wrote: ↑Wed Jan 16, 2019 2:09 amHello,
just updated to the j/s adv version, trying to get a handle on the changes, one issue:
when lightly loaded (half fuel, sidewinders only), takeoff requires some amount of nose up trim or else it will not leave the ground with stick full aft going over 180kts. seems the elevator authority is lacking from what i'm experiencing.
of course i can give it some nose up trim prior to takeoff roll but once airborne and clean up, it just goes vertical without frantic nose down trim to counter this action.
what's going on?
Also, you NEVER ever should trim UP a Phantom for take off, only trim down (1 to 3 units). The reason for this is to counter the progressive pitch up with increasing speed caused by its singular pitch flight control system (bellows).
In any case, please, check the NATOPS (F4J/S flight manual) and the ADV User Manual.
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Re: f4 j/s elevator authority
Yes, this is with half flap setting.
Recap:
Half fuel
Sidewinders
Half flap
Mil thrust
Neutral trim
Stick full aft ac does not lift off > 180kts
And yes, nose up trim allows lift off but severe nose up pitch after cleanup.
Recap:
Half fuel
Sidewinders
Half flap
Mil thrust
Neutral trim
Stick full aft ac does not lift off > 180kts
And yes, nose up trim allows lift off but severe nose up pitch after cleanup.
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Re: f4 j/s elevator authority
Does it happen in J and S versions?
What sim version?
What sim version?
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Re: f4 j/s elevator authority
This is p3dv44 on both j and s models. Thanks.
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Re: f4 j/s elevator authority
Does anything change if you try a no flaps takeoff?
Also, if you enable "instructor mode" in the ADV menu, what weight and CG does it show when you change your configuration?
Also, if you enable "instructor mode" in the ADV menu, what weight and CG does it show when you change your configuration?
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Re: f4 j/s elevator authority
One other check, if you slew to altitude instead of taking off, do you have any control at all once at speed?
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Re: f4 j/s elevator authority
ok, let me check these things.
in the mean time, watched related video which explains the behavior of the f4.
https://youtu.be/Y6RcTtGfG3E
in the mean time, watched related video which explains the behavior of the f4.
https://youtu.be/Y6RcTtGfG3E
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Re: f4 j/s elevator authority
Oh and please verify you are not running EZDock.
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Re: f4 j/s elevator authority
Also, make sure the aircraft.cfg files are NOT edited / overwritten after the ADV pack installation.
Basic F4 aircraft.cfg files CANNOT be used in the ADV version. Just in case...
Basic F4 aircraft.cfg files CANNOT be used in the ADV version. Just in case...
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Re: f4 j/s elevator authority
no flaps seems to make climb event after clean up a little easier, it's the half flap retraction that causes the ac to baloon, which i need to quickly counter by nosedown trim.
no ezdock or viewer used.
i had the classic f4j/s already installed then upgraded to the adv pack (to make f4j/s work in p3dv4.4), it looks like installing the adv pack overwrote many files like the panel folder, so i'm assuming it overwrote the aircraft.cfg as well.
reading the natops and watching the yt vids on the real f4, takeoff speeds are quite high even at light loads. so maybe elevator effectiveness kicking in at higher speeds (>180kts) is reasonable?
another thing that's puzzling is the ballooning with half flap retraction climbing at around 250kts. this can be reduced with some nosedown trim at takeoff but that prevents nose from lifting off at full aft stick. i guess i'll need to play around with the trim values a bit more.
thanks.
p.s. i'm not finding a way to load a fs flight plan and having it followed, hsi modes for tacan tuning i get, but is there a way to load a flight plan and have it followed or at least cdi point to the waypoint?
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Re: f4 j/s elevator authority
This aircraft isn't a F-16 or F-15. It has a very high wing loading which translates to a rather high takeoff speed. Loaded with bombs and at MTOW, you aren't likely to be able to rotate and get off the ground below 200 kts. And normally 2 units of nose down trim is required on takeoff to prevent the ballooning, because as you accelerate the trim position will move back to neutral and eventually nose up. It isn't a fixed position.
As for FS flight plans, you can load them, then select the active waypoint from the F-4 menu in the Addons menu. In order to get steering data from the navigation computer, set the nav source switch and knob for the HSI/ADI to NAV COMP, and set the navigation computer mode to BASE instead of TGT. TGT uses the lat/lon entered on the target position indicators, while BASE will use a internally stored lat/lon which in this case will be the selected flight plan point.
As for FS flight plans, you can load them, then select the active waypoint from the F-4 menu in the Addons menu. In order to get steering data from the navigation computer, set the nav source switch and knob for the HSI/ADI to NAV COMP, and set the navigation computer mode to BASE instead of TGT. TGT uses the lat/lon entered on the target position indicators, while BASE will use a internally stored lat/lon which in this case will be the selected flight plan point.
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Re: f4 j/s elevator authority
thanks for this, i couldn't find the nav settings in the manual or in this forum.JonathanBleeker wrote: ↑Sun Jan 20, 2019 7:13 am
As for FS flight plans, you can load them, then select the active waypoint from the F-4 menu in the Addons menu. In order to get steering data from the navigation computer, set the nav source switch and knob for the HSI/ADI to NAV COMP, and set the navigation computer mode to BASE instead of TGT. TGT uses the lat/lon entered on the target position indicators, while BASE will use a internally stored lat/lon which in this case will be the selected flight plan point.
one final question, is the pullup light (gpws) supposed to work?