Overrotation/Tail strike

[Wrench 9,801]

I've got a small issue I can't seem to solve. No matter what statement I use (take off rotation), the aircraft over rotates, strikes and drags it's ass for a bit. I've tried moving the CG forward, but can't really (now that I found the point where it doesn't slowly rear up like a cat begging for treats), as then in flight, it starts the slight nose down drift.

this is the AI takeoff statement:

[AIData]
TakeOffRotationAngle=0.0

dosen't do anything (at least for the player-flown bird)

you can see the images, especially the last one (4) it's just before the strike. even removing the hit boxes/collision points for the tail and fin meshes, don't help. I still get that "crashing metal" noise.

You all know i'm not that knowledgeable on MAX, but does the world center of the object have anything to do with this? Meaning, if the WC is too far aft, would correcting the CG even effect it? Or is the CG simply for aerodynamic forces, not effecting "on the ground". Cat shots off the boat do NOT have the tail strike problem.

So, what can be done?

[+guuruu 5,909]

Try with flaps.

More CLiftdc, less DeltaStallAlpha.

Edited March 30, 2021 by guuruu

[+Cliff7600 1,148]

Here's what I would try :

First, in the 3D model, check that the "x=0,y=0,z=0" point is where the 3 axis should join.
- X in the middle of the aircraft
- Y just ahead of the main landing gear, between the nose and main wheels, but close to the center of the plane (around where it is actually on the aircraft)
- Z in the axis of the engines, just because it is simpler for the FM  (it may not be not realistic compared to the actual plane)

Then, check all the "MassFraction" values in the data.ini file.
Best is to have all components with a "MassFraction" value (even the fake components) and leave the Fuselage without the entry, and the fuselage component will take all the rest of the weight.
MassFraction value are 0.xx of the total weight.
Check the estimated weight of the fuselage.
If necessary create some component (like tail, aft section of the fuselage...)
Often there's no engine nacelles : create components for the nacelle to have drag and weight where it should be -> MinMaxPosition values should be checked too

I do that all the time.
Hope it'll help

Edited March 30, 2021 by Cliff7600

[+guuruu 5,909]

1 hour ago, Wrench said:

would correcting the CG even effect it?

Yes, but more important are forces from steering surfaces and plane inertia.

[Wrench 9,801]

I've passed some requests to the modler, and we'll see what he does. I did notice the piviot point is off on the flaps, they should also go back and down, but that'll be fixed. The fins may be too low, compared to some photos and drawings

I used the Hawkeye's FM, including adding fake components (why does TK insist on using "**_mid_wing", when there isn't one???) It flys just like the E-2 (no surprise), except for bouncing it's butt!!

But I've asked Veltro to recheck everything.

thanks guys!

[+allenjb42 4,232]

I think there's a C-2 in the SF2:OTC campaign pack. It's set to use the DAT model's LODs, but there's .ini files that may be useful.

[amariani 4,840]

What's your rotation speed for takeoff?

[+Cliff7600 1,148]

The C-2 seems to have that tail-strike tendency, but it has a tail skid 

Edited March 31, 2021 by Cliff7600

[+daddyairplanes 10,148]

it might irk v2k, but that skid Cliff7600 points out could be a solution.

if the Greyhound has a RL tendency to tailstrikes, put a skid on the model as another (wheel less and short ) landing gear

[Wrench 9,801]

wonder if it could be done 'virtually'? and how the statements would look?? something to explore...

[+Nyghtfall 2,154]

Why not just add an invisible skid? Just add this under the landinggear section of the planes data.ini and adjust the ContactPoint-values and it should work.

luk1978 posted this as a solution for belly landings a while ago and it works very well.

[Skid]
SystemType=LANDING_GEAR
Retractable=FALSE
IsSkid=TRUE
NoContactOnGround=true
HideGearNode=true
ModelNodeName=
ShockStroke=0.05
SpringFactor=0.2
DampingFactor=2.1
ContactPoint=-0.64,-2.5,-0.85
RollingCoefficient=1.0
MaxLoadFactor=25.0

 

[+Cliff7600 1,148]

That's what I had in mind.

Look at Logan's MiG-Ye8 for example, it has that tail-bumper :

[TailSkid]
SystemType=LANDING_GEAR
Retractable=FALSE
DragArea=0.0
IsSkid=TRUE
NoContactOnGround=TRUE
ContactPoint=0.0,-5.34,-0.7
MaxLoadFactor=0.5

As long as there's a mesh in the 3D model, or at least a shape of it, there's no problem to add it to any aircraft, like the Canberra / B-57.

For the C-2, as it is an animated device, the shock/spring/damp entries should be used like Nyghtfall's example.

The important thing not to forget is "NoContactOnGround=TRUE", or the wingmen will pile up on the runway after landing.