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Posted (edited)

When I take off sometimes with plane that is loaded ready to go on ramp, the T/O trim I set jumps at about 120KIAS. On the takeoff run if I watch the FCS page I will have it set to 15+ for weight etc. At about 120+ Kias the Stab Trim will jump to like 20 or 22 and you can see the stab jump up. I am not pulling to rotate I am neutral on stick and it jumps.

 

This happens sometimes on cold A/C I start aswell.

 

Here's a track of it.

Trim Jump 2.trk

Edited by HawkDCS

Rig: 5960X @ 4.5GHZ 32GB 3000Mhz DDR4 Titan XP Dell 3415W 21:9 Thrustmaster Warthog

Posted

Think you're only supposed to be using 12° NU trim on land. The plane probably thinks you're on the catapult and is doing it's thing for the end of the cat stroke.

Posted

I was under the impression that you needed to set Stab Trim to A/C weight per manual. Can you confirm you just set 12 Trim on ground?

Rig: 5960X @ 4.5GHZ 32GB 3000Mhz DDR4 Titan XP Dell 3415W 21:9 Thrustmaster Warthog

Posted
I was under the impression that you needed to set Stab Trim to A/C weight per manual. Can you confirm you just set 12 Trim on ground?

 

That is what the T/O trim button on top of the rudder trim knob does and it is correct and realistic for land takeoffs.

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Posted
I was under the impression that you needed to set Stab Trim to A/C weight per manual. Can you confirm you just set 12 Trim on ground?

 

 

 

Yes. On land you press the t/o trim button and confirm you have 12 NU. Done. On the boat you hold t/o trim until you get the advisory and then add extra trim depending on weight.

Posted

Even if I just set it to 12 with T/O Trim it will jump on T/O roll to 16 something is up...

Rig: 5960X @ 4.5GHZ 32GB 3000Mhz DDR4 Titan XP Dell 3415W 21:9 Thrustmaster Warthog

Posted (edited)
Don't see anything unusual, you're pulling back on the stick a fair amount.

 

Squirrel the stick is neutral when the jump occurs. :music_whistling:

 

I am pulling hard to rotate because the plane is 45,500LBS with 12 Stab Trim.

 

Here's another track of the issue and you can see the stick position. I am not even touching my stick and it goes from 12 to 16 degrees on T/O Roll.

Trim Jump 4.trk

Edited by HawkDCS

Rig: 5960X @ 4.5GHZ 32GB 3000Mhz DDR4 Titan XP Dell 3415W 21:9 Thrustmaster Warthog

Posted

I know the NATOPS says use 12 NU for land take offs, but I find following the carrier take off trim procedures/weight seems to work better. I hope it's just an early release thing that is causing this, meaning that 12 NU doesn't work well for a loaded down F18 taking off from a runway.

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Posted
The FCS is going from a ground state to a flight state and adjusting accordingly. On your takeoff roll let the aircraft rotate and come off the ground without applying any stick. The aircraft will fly away on its own, you don't want to yank it off the ground.

 

No. This is happening prior to getting airborne.

 

There's nothing in NATOPS that describes automatic pitchup for a field takeoff; indeed it says early back pressure doesn't work, so it makes no sense for the aircraft to automatically command nose up.

 

The only time it does this is for a carrier takeoff, so IMO the most logical explanation is a bug. I think it's got confused and thinks it's taking off from the carrier.

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