Unbalanced Load + Trim + CAT III Landings

[snipy]

To start, I'm a terrible pilot, been playing DCS less than a year, and have fewer than 24 hours in any flight simulator, and 20 of it are in the F-16.

 

Doing the AIM-120 training yesterday, for about the 10th time, I set up the jet as CAT III, as it has external fuel, and then was playing around with switching between missiles when doing the two targets at once.  Anyway, I ended up, after all four targets were down, with 120s on 9 and 8, and nothing on the left side.  I put some pretty heavy LWD trim, and decided to fly around to run the external tanks out.   Nothing really felt too out of the normal, though, until I was on the downwind and put the gear down.  And then the plane got complete squirrely.  All the trim was now no longer needed, or needed much much more, and I had to fight the stick the whole way down. 

 

I finally felt like speed and everything was alright after 4 waive off, but the second the wheels came down, the plane jerked and was tough to keep on the runway.  I ended up not being able to, rolled and died.

 

So I've been practicing this yesterday and today. 

 

Is it normal to have the trim reset when the wheels touch down?  Because I've noticed that it does, and thought maybe that would have something to do with why the plane jerks when touching down. 

 

Also, is it normal for the jet to need a change in trim when the gear is down in CAT III?  It seems like an in opportune time to start having to correct when also about to make the break. 

 

Lastly, should all VFR landings just be in CAT I, where I feel like I have more control, even if carrying a CAT III load?  CAT III landings just seem harder.

 

 

Edited March 4, 2021 by snipy

[Florence201]

So not sure how you’ve ended up with both weapons on 1 side of the jet, but in that instance yes you’ll need to trim. 
 

once the gear is down, you’re now into a different DCS engineered drag scenario that means different trim is required. Same for on the runway, DCS drag will affect you harshly with an asymmetric loadout. Rudder during 13deg AOA aero braking helps and then independent wheel braking until below 60kts, then NWS

[snipy]

1 hour ago, Florence201 said:

So not sure how you’ve ended up with both weapons on 1 side of the jet, but in that instance yes you’ll need to trim. 
 

once the gear is down, you’re now into a different DCS engineered drag scenario that means different trim is required. Same for on the runway, DCS drag will affect you harshly with an asymmetric loadout. Rudder during 13deg AOA aero braking helps and then independent wheel braking until below 60kts, then NWS

 

In this training mission, the first missile off was one off the left wing in a 1 on 1 head on engagement.  The second is 2 on 1, which sends one on the right and one on the left.  So now I'm two off the left wing and one off the right wing.  The third engagement is a mad dog 120, off the tip, so holding the side button with a long name (NWS AAR Discon MSL Step) switches to the 120Cs, then bore, and release.  If somewhere along the way, I quick hit the MSL step, which I did, then I'm now three off the left wing and only one off the right wing.  It's not terribly difficult to do, for me.  But, I can then either just jetison everything, which seems wasteful.  Or try to figure out how to fly this plane unbalanced, which seems like a better plan. 

 

The difference, at least the little bit I've played with it, is that all of that doesn't seem as noticeable with that Cat I switch on.

 

I'll keep playing around with it, but it seems a lot easier in Cat I, than Cat III, even with everything else the same. 

 

Why does the trim get taken off the plane when the wheels touch the runway?  If I have to accelerate to take off, because I'm not going to stop before the end, I end up fighting it up, since all the trim corrections are no longer applied to the jet. 

[Florence201]

If you're landing on sped you should have adequate runway to stop the aircraft, unless you're landing on a very short runway. The "grip and drag" FM on landing is such that asymmetric loadout will seriously affect how the aircraft responds on the runway. 

 

As for why the asymmetric, I would you suggest that you did MSL Step inadvertently, hence why you ended up with the loadout you did.

[snipy]

1 hour ago, Florence201 said:

If you're landing on sped you should have adequate runway to stop the aircraft, unless you're landing on a very short runway. The "grip and drag" FM on landing is such that asymmetric loadout will seriously affect how the aircraft responds on the runway. 

 

As for why the asymmetric, I would you suggest that you did MSL Step inadvertently, hence why you ended up with the loadout you did.

 

CAT III on a clean jet seems to lands different, to me, as well.  I can also land an asymmetrical jet easier on CAT I. 

 

It doesn't seem like it is just asymmetry, if setting the symmetry the same, and just flipping the CAT I and CAT III switch makes a difference.

 

 

Edited March 4, 2021 by snipy

[Florence201]

CAT III limits AOA, roll rate etc, but shouldn't affect the FM

[snipy]

11 minutes ago, Florence201 said:

CAT III limits AOA, roll rate etc, but shouldn't affect the FM

 

Yea, that is why it seems odd.  It should be the same AOA to land, but it feels different. 

 

I'm going to keep practicing, and if I can't get it, just add "switch to CAT I" on downwind.  That way, if it's mental, I'll be good to go.

[ruddy122]

As a former military pilot just because you dropped the gear doesn’t mean trim is the same you got to retrim the aircraft for the new configuration cause the gear is out

in real life when I dropped the gear in the 10 I had to retrim or I’m fighting the gear all the way down

Trim is your friend not the enemy


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[snipy]

32 minutes ago, ruddy122 said:

As a former military pilot just because you dropped the gear doesn’t mean trim is the same you got to retrim the aircraft for the new configuration cause the gear is out

in real life when I dropped the gear in the 10 I had to retrim or I’m fighting the gear all the way down

Trim is your friend not the enemy


Sent from my iPhone using Tapatalk

 

And if I was in the F-5, I wouldn't have noticed it, because trim is part of the package.  But it seems like the F-16... trim is meant to be an odd thing, done in certain instances.

 

I'm kind of surprised the flight control system can auto trim the aircraft, but loses its shit the second the gear come down.  Maybe manually adjusting the trim turns the auto trimming off complete, no idea. 

 

Just seemed odd to me. 

[ruddy122]

The F-16 should auto trim to 1 G

Trimming is for aircraft that can’t auto trim like the KC-10

But your right the plane should recognize it and trim appropriately

I know the FM is not the greatest but the real F-16 can do that


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[TobiasA]

The F-16 trims for 1G. That's it. It doesn't trim roll or yaw when carrying asymmetric loadouts.