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Elite 1K Joined: Jan 31, 2004 Posts: 1530 Status: Offline

Weasel_Keeper wrote:

Well, I'm hoping not to hear about the "sim ain't the jet" thing. I was just curious because the official sim is the only way I'll ever get a chance to "fly".

Same here.

My meaning was, every time I got into "discussions" with pilots or IPs about some aspect of flyin' the jet, I'd always qualify my point with "ya know..I tried this or that in the sim and here's what I saw". To which they'd invariably reply "Yeah..well..the sim ain't the jet". And I can see their point. You'll never get the sensations of the real deal in the sim and you'll never hear pilots in the O-club spin exciting yarns like "So there I was...35,000 feet, no motor, EPU fuel down to 10%, no divert field in range, crickets in the RWR...and then the host computer up and crashes".

Apparently it's close enough to the jet to qualify you to fly it, but beyond that we've got nothin' to talk about? OK..whatever.

And don't lose heart 'bout gettin' a ride. I'm sure you'll get it one day. And we'll expect a full report with lotsa pics! Thumb

We now return you to the topic at hand....rudder use was it?

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Sorry to jump in here late, but was getting new confuser online and checked the forums.

1) I don't get the impression that Cylon or anyone else here ever flew one of the older jets.

2) John-boy has it right WRT to the ARI implementation, and one on the wrenchbenders has the guns compensation right, best I know.

************

I can flat-a$$ guarantee that the older jets used ONLY RUDDER when maneuvering at high AoA. We're talking Double-Ugly, Hun, SLUF, Thud and more.

Honest, the Double-Ugly folks used to tell me that they locked their arms between their knees to keep from making any aileron inputs and used only rudder to roll. Although the SLUF had a decent control system and even spoilers to help with adverse yaw, it was about the same. Too much aileron and you departed. On an aggresive "break" I used full stick and full rudder rolling into the break turn.

Viper, OTOH, went where you pointed it. Good ol' FLCS control laws and ARI cranked in gobs of rudder to keep the pointy end forward. Used to demo this to student studly on first hop. Look over shoulder while banking hard at the limiter and note the rudder movement.

Only time I used the Viper's rudder in the air was in close (very close) formation chasing a gomer on his solo flight. Used the rudder to make small decreases in speed versus the speed brake.

Oh well,

Gums sends ....

IIRC commanded rudder input via pedals is washed out as airspeed increases. IOW above a certain speed stomping your feet will not mean you get max (or even much) rudder deflection. The rudder may still move, but only as much as the FLCC wants it to.

Habu2 has it right about washed out rudder angle as airspeed increases. The angle is limited, but due to increased airspeed, the load on the rudder and tail is maintained. In fact, that is the reason for the washout - to prevent overload on the tail. Rudder load is self limited by the hydraulic capacity of the actuator, which means the rudder strength is the same as the capacity of the actuator. Of course, the rudder, like all other structure, has a minimum 1.5 factor of safety built into it.

Max deflection is 30 deg, but that is almost never seen. A more common deflection at moderate speeds (400 - 500 kt) is 12 deg. for max pedal command. At 700 - 800 kt, only about 6 deg is available.

Gums, the YF-16 and FSD pilots mostly came from F-4 ranks, so initially had to really concentrate on keeping the feet on the floor, especially during lower airspeed rolls.

During the FLCS Programmable Gains check, there is a scenario during which rudder movement goes to practically zero regardless of pedal input. I wish I could remember the circumstances under which this happens, but in fourteen years of working Vipers, I only did two (yep, only TWO, thank God) of these checks. And, since I've been retired for several years now, the memory's fading. What sticks out more than anything else is the amount of preparation for that check. It's just as bad as the Alpha N check. Remember that one??

Enthusiast Joined: Apr 09, 2005 Posts: 23 Status: Offline

I don’t know if this applies for the newer blocks with the digital FLCS (DFLCS) but in our old block 10 and 15 the rudder is locked out gradually from 15 degrees AOA and until 25.5 degrees AOA where the rudder is completely locked out (Stores config. Switch in CAT 1).

We try that on handling flights by pitching op to 30 degrees and maintaining that attitude until the speed drops and the AOA builds up. Then at maximum AOA we press the pedals to maximum deflection and note that the rudder does not move (no yaw).

The only thing that will move the rudder in this situation (with maximum AOA) is the gun compensation and the ARI to counter adverse yaw if the aircraft is commanded to roll. Pilot rudder input will be ignored.

Correct, Guy, but there is another rudder driver. If a spin starts to develop, the yaw rate will feed into the FCC and it will command rudder and aileron anti-spin controls. But that would only occur at AOA well above the 25.5 degree limit.

Enthusiast Joined: Apr 10, 2007 Posts: 73 Status: Offline

If the slip-ball never moves, do you need a rudder?

Enthusiast Joined: Apr 09, 2005 Posts: 23 Status: Offline

F16JOAT

The rudder is what keeps the ball centered!

Enthusiast Joined: Apr 10, 2007 Posts: 73 Status: Offline

If the rudder keeps the ball centered, then why is it no rudder is required for B2?

Enthusiast Joined: Apr 09, 2005 Posts: 23 Status: Offline

The B2 does not have a conventional rudder since it does not have a tail, but I can assure you that it has rudder pedals in the cockpit.

The rudder is used to control yaw.

On a B2 the yawing effect of the rudder is probably achieved by the use of spoilers and differential aileron input.

Elite 1K Joined: Aug 19, 2004 Posts: 1090

F16JOAT wrote:

If the rudder keeps the ball centered, then why is it no rudder is required for B2?

The B-2 uses an advanced fly-by-wire flight control system which asymmetrically varies the position of the outer most control surfaces to provide directional stability (i.e. to keep the ball centered). On a conventional aircraft, these control surfaces would be used for roll control (ailerons), but on the B-2 they are used as rudders and/or speedbrakes. Without the fly-by-wire flight control system, the pilot would not be able to keep the aircraft from wanting to swap ends.

Enthusiast Joined: Apr 10, 2007 Posts: 73 Status: Offline

Ah, then it must be true that the F-16 can lock out the rudder and fly with coupled stabilators and flaprons.

Elite 1K Joined: Aug 19, 2004 Posts: 1090

F16JOAT wrote:

Ah, then it must be true that the F-16 can lock out the rudder and fly with coupled stabilators and flaprons.

No, because it was not designed to operate like this. You have to specifically design the aircraft and it's control system logic to operate without the use of a vertical tail/rudder.

Enthusiast Joined: Apr 09, 2005 Posts: 23 Status: Offline

Yes, the F-16 can fly with a locked rudder, but it is not something that the pilot can elect to do. It will only happen in a situation where the rudder ISA (integrated servo actuator) fails. The pilot will then arm the ISA and if the malfunction repeats itself the rudder ISA will center up the rudder surface and lock it.

The rest of the flight from then on will be straight home to the nearest suitable runway and the pilot will need to fly the jet very gently as abrupt manoeuvring might send the jet out of control.

By the way, in this situation the ball will move every time the aircraft is banked.

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Rudder use in an F-16