Excessive pitch-up on cat shots recently?

Has anyone noticed a tendency for the Hornet to pitch up violently on cat launches the last couple of weeks? About three to four weeks ago it was quite mild, but as I've been doing CASE I practice recently it feels like something's changed.

-GW 34,000 to 36,000lbs

-Centerline fuel tank, no other stores

-Flaps HALF

-T/O Trim set, trim increased to 16° NU per NATOPS

-MIL or AB shot doesn't make a difference

Observed behavior:

-HUD attitude symbol (w) shoots up to 15° NU

-AoA 13.9° measured during the pitch moment

-Overwing vapes observed

I can't climb and maintain 500' for CASE I without aggressively shoving the nose down. I don't recall this behavior a couple of weeks ago, but at that time I was launching much heavier jets with a warload....could I be launching too light? Is anyone else observing the same?

Try to use less Oitch trim for 33-34000lbs, something like 15.

Not sure what NATOPS says, but 16 for 34000lbs is to much.

I don't recall NATOPS having a pitch trim for 33-34000lbs. Lowest setting was 16 for "<44,000lbs," going off memory. I'll have to double check my manuals.

Checked. NATOPS launch trim says:

<44,000lbs = 16

45-48,000lbs = 17

>49,000lbs = 19

Is this happening on initial T/O or only after a previous landing? I've had a serious pitch up like your describing after a landing and taxi'ing back to relaunch.

After landing on the boat and relaunch, check flaps :)

It happens any time at the boat. Ramp hot start, T/O trim already set, flaps already set half. It also happens after I've trapped and I do another launch too. I've double and triple checked that my flaps are set half. I've double and triple checked that T/O trim is set, and trim on the FCS page is showing 16 NU. I'll grab a track next time it happens--maybe tomorrow.

Well, try as I may, I couldn't reproduce. Followed the same procedure (though a different mission), and everything was fine.

I still have the video footage and server/client track files of the pitching moments, but if it's a one-off bug I guess it doesn't really matter.

34,000 lbs sounds really low, are you sure its not 44,000 lbs? 34k is max trap weight which is like 4000 lbs of fuel.

Centerline tank, empty gun, 9,158lbs of fuel gives GW of 35,091lbs.

By the time I've done a CASE I departure, two circuits in Marshal, and arrived on Initial I have roughly 6,500lbs of fuel and ~32,400lbs GW. Perfect for three looks at the boat. Four if I'm feeling ballsy.

Taking off with more fuel than that and I'm wasting time dumping it all before I can practice my traps.

Is that weight according to the rearming window or what the aircraft thinks it weighs on the checklist page?

Mission Editor and rearm window. I've been ignoring the checklist page since the weight calculation bug was introduced. ME/Rearm menu seem to be the same as they always have been.

I would check that your looking at Legacy Hornets NATOPS and not the Rhino (Super Hornets) Natops.

A1-FA18AC-NFM-000. Page III-8-5 gives the launch trim:

<44,000 = 16

45,000-48,000 = 17

>49,000 = 19

Here's a recording of the server replay track. What's weird is that halfway through the cat shot the stabs suddenly increase in pitch. I wasn't moving the stick. That happened on all three launches. But again, since a system reboot I have not been able to reproduce.

vC5JHJRPoS0

Huh. Weird. Nice skin though!

My system seems to do all sorts of weird crap from time to time. One day one module does something funny, the next day a different module does something funny, the next day my VR headset goes to sleep and won't wake up without restarting Windows Explorer....it never ends.

Nealius,

the video you've posted looks like normal operation for the Hornet. This jet is "fly by wire" and it's designed to accomplish the entire catapult shot without pilot input. The process is designed to place the jet into a nose up climb attitude allowing for minimum (or no) sinking below the deck depending on aircraft weight. Once the aircraft is in stable flight with a climbing trend, then you should apply control inputs to maneuver the aircraft.

To re-iterate, the catapult stroke in the Hornet is completely hands off..

He knows that I think.

Yes I do know that, and what I posted in the video is not normal. In standard carrier launches max hands-off commanded AoA is 12, with 18NU trim. I launched with 16NU trim, which should correspond to about 10 AoA being commanded off the deck. This is all per NATOPS. My jet pulled 13.9....

At any rate, I think this is one of those random DCS bugs when you don't restart the sim between flights. I had the same crazy pitch-up moment in the Tomcat last night. With stab trim zero. The only variable that was the same between these two incidents was that I ran 2-3 flights without restarting the sim.

Almost looks like an unexpected CG issue the FCS is dealing with. Your gun drum wouldn't be empty by any chance, would it?

A1-FA18AC-NFM-000. Page III-8-5 gives the launch trim:

 

<44,000 = 16

45,000-48,000 = 17

>49,000 = 19

 

Here's a recording of the server replay track. What's weird is that halfway through the cat shot the stabs suddenly increase in pitch. I wasn't moving the stick. That happened on all three launches. But again, since a system reboot I have not been able to reproduce.

 

vC5JHJRPoS0

Awesome, looks like the FCS now pulls up during the launch. This wasn't in back when the Hornet released so they must be working on it.

This is realistic behavior, but I also want to dig into exactly how many degrees the FCS puts the elevator up at:

Santi,

The FCS logic is described in A1-F18AC-NFM-000, Part 3, Ch 8.2.8. "Catapult Launch".. it mentions AOA values as high as 13º while seeking the max AOA target of 12º.

Also interesting as I thought the elevator deflection at the end of the stroke was just a quirk of DCS, I didn't realize it was true to the aircraft... what neat detail!

Santi,

 

 

The FCS logic is described in A1-F18AC-NFM-000, Part 3, Ch 8.2.8. "Catapult Launch".. it mentions AOA values as high as 13º while seeking the max AOA target of 12º.

 

 

Also interesting as I thought the elevator deflection at the end of the stroke was just a quirk of DCS, I didn't realize it was true to the aircraft... what neat detail!

In that case it might not be detailed in the natops. You can see in pretty much all the hornet (and super hornet) cat shot videos, it goes far beyond 13 degrees.

You can see in pretty much all the hornet (and super hornet) cat shot videos, it goes far beyond 13 degrees.

Do you have a link for these videos? I haven't found a single one which shows an excessive AoA.

We're talking aircraft Angle of Attack Santi, not elevator deflection degrees...