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Loran
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F/A-18 Rudders: Question

Sun May 21, 2006 12:27 am


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Please take a close look at the two rudders on the vertical fins, they are both deflected inwards. What is the reason for this configuration? I have seen videos from carrier takeoffs, where they seem to go back into normal position shortly after leaving the deck of the ship. I haven't seen this on the F-14s, neither on any other fighter.

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Loran
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LMP737
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RE: F/A-18 Rudders: Question

Sun May 21, 2006 12:47 am

When the F-18 was being developed it was discovered it's approach speed was a bit to high. One of the fixes was to program the rudders inboard. On the F-14 with it's long wing span and full span flaps this was not needed.
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usnseallt82
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RE: F/A-18 Rudders: Question

Sun May 21, 2006 12:59 am

Quoting LMP737 (Reply 1):
When the F-18 was being developed it was discovered it's approach speed was a bit to high.

I was going to say the same thing. From what I understand, the aerodynamics of the aircraft are so good that it doesn't induce the normal amount of drag that most others do. This is good for enroute portions of flight, but you need the drag on approach. Therefore, the stabs come inward to provide a vertical-flap type of system.

The only concern I have with this picture is that its at full power, with the burners lit. I can't see why the rudders would come inward at this power setting, unless the rudders are programmed to come in during regular flap settings, as you can see those are still deployed. If that's the case, then it makes sense because he would still have his flaps deployed from the previous approach. Looks like this guy just missed the wire or did a touch and go.

Hope this helps.
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brendows
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RE: F/A-18 Rudders: Question

Sun May 21, 2006 1:03 am

Quoting Loran (Thread starter):
Please take a close look at the two rudders on the vertical fins, they are both deflected inwards. What is the reason for this configuration?

The question has come up here before. IIRC, some answered that the rudders are put in this position to help the elevators with pushing the nose up on takeoff.
 
ftrguy
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RE: F/A-18 Rudders: Question

Sun May 21, 2006 5:04 am

Quoting Brendows (Reply 3):
the rudders are put in this position to help the elevators with pushing the nose up on takeoff.

Brendows is correct. They create a lifting moment on the nose for takeoff. It you were to see the hornet in the picture above a split second later, you would have noticed that the rudders went back to their normal position. They only toe-in when you are on the ground and have the flaps down (1/2 or Full).

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