F-18 catapult take-offs

[PR19_Kit]

Here's a question triggered by some You Tube vids of F-18s being cat shot.

Before they fire the cat, the F-18s have both their rudders deflected INWARDS, opposite to each other.

Why? I'd have thought that would just increase the drag and require more cat steam pressure.

[perttime]

It adds some more up elevator authority.

I've seen video of an F/A-18 launching from the ground with the air brake raised.... Not sure if it was intentional.

[DogfighterZen]

The rudders are deflected inwards during takeoff of the F/A-18 to help in raising the nose of the aircraft as it leaves the ship. As the vertical fins are canted outwards, deflecting both the rudders inwards generates a downforce, which, due to its location aft of the center of gravity, creates a pitch-up moment.

Google answers...

P.S.;  More extensive explanation here: https://aviation.stackexchange.com/questions/19214/why-are-the-f-a-18-rudders-deflected-in-opposing-directions-during-takeoff

[PR19_Kit]

All very educational, thanks very much.   

[Dizzyfugu]

It adds some more up elevator authority.

That would be my thought, too, using all area to rotate the nose upwards once the aircraft leaves the deck.

[thundereagle1997]

Imagine an F-18 being launched from a truck via the ZELL launch system.