Cat launch: aft stick halfway through stroke?

[Nealius]

I recall seeing a lot of pictures of tomcats launching with their stabilators with quite a lot of pitch-up deflection, and after digging around I found that in real life it was common to give some aft stick halfway through the cat stroke.

 

However, when I try this in DCS, the nose rates up way too severely. Even if I don't touch the stick, with 0 pitch trim (or the default 2-3 ticks you get after putting the wings in AUTO), the nose rates up at least 5 degrees above the horizon with no input from the pilot. Is this normal?

[sLYFa]

the nose rates up at least 5 degrees above the horizon with no input from the pilot. Is this normal?

It should be since the nose strut extends at the end of the cat shot, giving you some pitching moment. However, it does seem excessive.

I've also seen videos of F-14s taking off with full aft stick (e.g. Topgun intro). Maybe that has something to do with CG (nose heavy AC > use more aft stick). Also, I'm still not sure how DCS adjusts catapult endspeed for different weights. Maybe the catshot in DCS gives you way more endspeed than in RL, substantially increasing pitch rates at a given stick deflection.

[Spiceman]

The nose gear strut is designed to provide a hands-off launch. The strut bottoms out during the cat stroke, storing 4 inches worth of instant energy when the launch bar leaves the shuttle. That instant energy release provides a sufficient nose up pitching moment that you shouldn’t need any stick deflection during launch. After that instant release, the nose strut then extends normally (by this time you’re off the deck).

[uhntissbaby111]

The nose gear strut is designed to provide a hands-off launch. The strut bottoms out during the cat stroke, storing 4 inches worth of instant energy when the launch bar leaves the shuttle. That instant energy release provides a sufficient nose up pitching moment that you shouldn’t need any stick deflection during launch. After that instant release, the nose strut then extends normally (by this time you’re off the deck).

 

 

As the OP observed, I too observed during every F14 cat shot I’ve seen on YouTube that half way through the elevators deflect what looks like full nose up. The nose strut extension helping makes sense, however it seems like the pilots still deflected the stick aft during launch. If you deflect the stick aft in the HB F14 the nose will aggressively pitch up

[Spiceman]

Edited.... the NATOPS states that the pilot should maintain a loose grip on the stick and allow it to naturally move aft during the cat stroke. This is probably what you see happening.

Edited June 20, 2019 by Spiceman

[uhntissbaby111]

Edited.... the NATOPS states that the pilot should maintain a loose grip on the stick and allow it to naturally move aft during the cat stroke. This is probably what you see happening.

 

 

Very interesting. I wonder if it’s the increase in airspeed that moves the elevators nose up? Although I feel like airspeed wouldn’t be able to overcome hydraulically powered flight controls

[Spiceman]

Right, no, it wouldn’t be aerodynamics on the control surface. It’s probably just the G on the control stick itself.

[Eldur]

This should be modelled via FFB...

[Dino Might]

Regardless of the reason for stick/elevator movement, it seems that trying to make the aircraft control surfaces mimic position of real life launches causes very prompt pitch up and near stall conditions.

 

No way I know to accurately measure or test. Just looking at the external views relative to videos (e.g., Top Gun slow motion).

 

We have to remember, we currently have the B. I'm not sure how different (other than burners vs mil power) the catapult launches are for the A vs the B, especially in terms of control surface geometry.

[Nealius]

D model launches appear to have the same pitch-up deflection, so I would safely assume B models did as well.