This shouldn't be right.

[Disso]

I've been wondering about this for ages, and finally decided it was time to ask.

 

When Hornets take off, Super Hornets included, they seem to deflect both rudders inwards. This has always baffled me as common sense tells you that would simply result in more drag, and nothing more. It's like opening your airbreak as you takeoff.

 

I've only seen the Hornet undertake this, and no other. Why do they do this, why only the Hornet, and is it pilot-inputed, or are they automatically deflected inwards when the aircraft goes max power by the FBW.

 

http://www.airliners.net/open.file?id=1015650

 

http://www.airliners.net/open.file?id=1022214

 

http://www.airliners.net/open.file?id=1098842

 

Thanks in Advance!

[Guest IguanaKing]

Deflecting both rudders inward gives the Hornet more elevator authority. BTW, the cat launch is completely hands-off for the Hornet pilot, the plane does it all. :smilewink:

[Disso]

hmm...more pitch authority. But why is this so? In what way would deflecting both inward have any effect on the horizontal stabilizers?

[britgliderpilot]

hmm...more pitch authority. But why is this so? In what way would deflecting both inward have any effect on the horizontal stabilizers?

 

It has no effect on the vertical stabilisers.

 

 

The Hornet's tailfins are canted outwards slightly - V-tail effects hence apply to them.

 

The lift vector generated by each tailfin with the rudder inwards is perpendicular to the fin, and hence angled just a little bit above the horizontal.

 

The horizontal component of the lift from each fin cancels out so no side thrust (although some drag and yes, some bending moment on the fin), but the vertical components add together and you effectively get a second set of elevators.

 

Not a huge effect, but it does have some effect. Any improvement could be useful in combat.

[Guest IguanaKing]

Its mostly because of their diagonal placement. A small correction to what I meant to say before, it gives the aircraft more elevator authority in the upward direction. As you correctly assumed, it does increase drag, and that drag gives the tail of the aircraft a little more push downward to rotate the aircraft and get the nose in the air. An old aircraft that does this using no actual seperate elevator is the Beech V35 Bonanza. The elevator and rudders are the same control surfaces, and both get deflected inward when pulling back on the yoke.

 

Sorry for the misundrestanding, I didn't mean to suggest that it actually affects the elevators. ;)

[Force_Feedback]

They are at an angle, and create an inward moment, compressing the air between the rudders, like putting a weight on the back of the plane, it too will push the back down, and the nose goes up.

[Gripes]

When the pilot trims the Hornet for T/O (hits the button) the rudders

are toed in. Hornets are nose heavy during the T/O roll due to the fact

that the outboard part of the wing is pointed down.

The wing is like this to give the Hornet more controll at high AOA.

The tradeoff... huge speedbrake.

[britgliderpilot]

When the pilot trims the Hornet for T/O (hits the button) the rudders

are toed in. Hornets are nose heavy during the T/O roll due to the fact

that the outboard part of the wing is pointed down.

The wing is like this to give the Hornet more controll at high AOA.

The tradeoff... huge speedbrake.

 

 

. . . . the Boeing Super Airbrake (aka the Super Compromise) makes a welcome return to draggy infamy on the Lockon forums!

[dynamocl]

Why does the swiss aircraft deflect outwards, while the other 2 inwards. Any reason for this?

[britgliderpilot]

Why does the swiss aircraft deflect outwards, while the other 2 inwards. Any reason for this?

 

. . . . . now THERE's a good question!

 

I lay the question at the feet of the mighty Fly By Wire Computers - I'm not actually sure.

 

 

Anyone suggest a reason for having the ruddervators in pitch-down position while the elevators are in pitch-up position?

 

Carefully balancing pitch at high alpha, perhaps?

[Disso]

Thanks for all the responses guy's, Defenitely cleared everything up over here!

 

It's nice being able to come on these boards and ask a question knowing you're going to get an abundance of detailed replies. Thanks fella's!

[Camoman]

Why does the swiss aircraft deflect outwards, while the other 2 inwards. Any reason for this?

 

From janes (I am lucky to have subscription access to all the aircraft bits through my uni):

"both rudders turned in at take-off and landing to provide extra nose-up trim effort"

So this is the correct answer given by many already.

 

As far as the Swiss aircraft goes my opinion is that it is a dirty config of controls which isn't very efficient and he is flying like this to allow quick recovery from such a high alpha. By turning them outwards he is generating a pitch down trim which will assist as soon as he needs to pitch down. He doesn't need lift as he would on take off by turning them in as there is a large amount of lift available from the AoA.

[Lt.Seahawk]

Deflecting both rudders inward gives the Hornet more elevator authority. BTW, the cat launch is completely hands-off for the Hornet pilot, the plane does it all. :smilewink:

 

Thats what ive heard aswell