Lemmy
Topic Author
Posts: 243
Joined: Fri Dec 10, 2004 8:40 am

Does F-18 Take Off With Speedbrake Extended?

Fri Dec 16, 2005 5:08 am

I understand that, instead of a traditional speedbrake, the F-18 uses a combination of rudder and elevator deflection to create drag.

This picture seems to show an F-18 rumbling down the catapult with the speedbrake at least partially deployed:


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Photo © Chad Thomas - Jetwash Images



If this is really the case, why? I can understand using the speedbrake on approach, since it enables the pilot to keep the engines spooled up in case of a bolter. But why do it on takeoff?
I am a patient boy ...
 
flyf15
Posts: 6633
Joined: Tue May 18, 1999 11:10 am

RE: Does F-18 Take Off With Speedbrake Extended?

Fri Dec 16, 2005 5:33 am

All those control surfaces are deflected to help get that nose pointed up the second it leaves the ship... a very important thing to have happen. As the vertical stabs are angled outwards, deflecting both rudders inwards also gives a downward component of lift, which assists the elevators.
 
Contact_tower
Posts: 534
Joined: Mon Sep 17, 2001 4:05 am

RE: Does F-18 Take Off With Speedbrake Extended?

Fri Dec 16, 2005 5:38 am

The F-18 is on "autopilot" until it leaves the deck correct??? Hands off until you have positive rate of climb or something?
 
ftrguy
Posts: 347
Joined: Fri Aug 29, 2003 8:17 am

RE: Does F-18 Take Off With Speedbrake Extended?

Fri Dec 16, 2005 5:51 am

Quoting Flyf15 (Reply 1):
All those control surfaces are deflected to help get that nose pointed up the second it leaves the ship... a very important thing to have happen. As the vertical stabs are angled outwards, deflecting both rudders inwards also gives a downward component of lift, which assists the elevators.

You are correct. The towing in of the rudders helps to lift the nose. You will also notice that as soon as the plane is airborne, the rudders go back to their normal position.

Quoting Contact_tower (Reply 2):
The F-18 is on "autopilot" until it leaves the deck correct??? Hands off until you have positive rate of climb or something?

Sort of but not really. There is no "autopilot" button you push prior to the cat shot. You simply set the trim to a specific angle and the fly-by-wire system maintains that angle off the ship. You better believe that my hands are on that stick as soon as I feel the end of the cat stroke though.
 
ftrguy
Posts: 347
Joined: Fri Aug 29, 2003 8:17 am

RE: Does F-18 Take Off With Speedbrake Extended?

Fri Dec 16, 2005 5:56 am

Forgot to mention that the Hornet in the picture is a C model. A through D models actually have a rather large speedbrake between the tails that works quite well. It is not up in the picture.

The Super Hornets use a combination of control surface movements and two small spoilers on the leading edge extensions to slow it down. I've heard that it doesn't work that well.
 
Lemmy
Topic Author
Posts: 243
Joined: Fri Dec 10, 2004 8:40 am

RE: Does F-18 Take Off With Speedbrake Extended?

Fri Dec 16, 2005 8:44 am

Quoting Flyf15 (Reply 1):
All those control surfaces are deflected to help get that nose pointed up the second it leaves the ship

Oh, gotcha. So if the control surfaces were really acting as a speedbrake in the photo, the elevators would be pointing in the other direction to cancel out the tail-down force from the rudders?
I am a patient boy ...

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