Forum: F-16 Procedures

Do Vipers have a separate tiller for taxiing?

I don't see anything like that on pictures of the cockpits...

If they don't, what do pilots use to steer? Rudder pedals?

P.S.:What about A/Cs like F-14, F-15, F-18, F-22?

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Rudder pedals.

The rudder pedals only steer the nosewheel with NWS engaged by depressing the NWS switch on the outboard side of the stick.

Hi Habu,

I thought NWS was automatically engaged bij the WOW (Weight on wheels) sensor, and with a speed, slower than, 50 (?) knots?

Guest, according to the -1 it is manually engaged but automatically disengaged when the nose strut reaches full extension (weight *off* wheels?) - this is from memory so I could be wrong.

If NWS is engaged, the pilot uses the rudder pedals (which would otherwise control the rudder) to steer the nosewheel. The idea of nose wheel steering is similar to the tricycles we all used to ride before we moved on to bikes, just that instead of turning the handle to steer you gotta push the pedals. This idea (of pushing pedals) is also used on some boats. Dunno what they're called (no they're not power boats), but they're low, open and loads fun to ride in.

With NWS off the front wheel "casters" or self aligns with no input from the rudder pedals. Imagine the situation where an F-16 is landing in a heavy crosswind. The pilot is standing on one rudder pedal to crab (sideslip) the airplane into the relative wind yet still be aligned with the runway. If the nose wheel followed the rudder at this point it might not be aligned with the runway (or more precisely the velocity vector) and could damage, even collapse, the nose strut upon touchdown. So the nose wheel is free to align itself due to the caster of the suspension design. Once all three wheels are on the ground (WOW) the pilot can engage NWS to steer on the ground with the rudder pedals. Hope all that made sense.

GregD

Yup that is how it works Habu the NLG strut has a NWS actuator attached that takes commands from the NWS command poteniometer which gets its inputs from the rudder pedals this tells the actuator which way to turn, the caster you referred to is actually called a centering cam and functions as you stated .

Rigo

habu2 wrote:

With NWS off the front wheel "casters" or self aligns with no input from the rudder pedals. Imagine the situation where an F-16 is landing in a heavy crosswind. The pilot is standing on one rudder pedal to crab (sideslip) the airplane into the relative wind yet still be aligned with the runway. If the nose wheel followed the rudder at this point it might not be aligned with the runway (or more precisely the velocity vector) and could damage, even collapse, the nose strut upon touchdown. So the nose wheel is free to align itself due to the caster of the suspension design. Once all three wheels are on the ground (WOW) the pilot can engage NWS to steer on the ground with the rudder pedals. Hope all that made sense.

GregD

Umm....not to say that you're wrong, but why would that even be an issue? Every crosswind landing I've ever done, I've kicked out any crab before landing (when I did use the crab method), so as not to have any side loading on the main gear.

When using the cross-controlled method, the nose is pointed forward, although the aircraft is banked into the wind, and thus the upwind main tounches down first. I use the latter method more often than not, because it's easier to keep the gear lined up with the runway. It's also a more precise method.

But in either case, the point is to land with as little sideloading as possible. And why would it matter what way the nosewheel is turned before touchdown? Even if you landed with sideloading, you'd touch mains first, then nose, unless yout three-pointed it. Which would probably not be a good thing on a '16. So you'd touch mains first, then nose, and hopefully be pointed down the runway, because otherwise, it wouldn't be good either Wink

The Viper as far as I know cannot crab on landing due to the FLCCs every landing I have seen even in strong crosswinds has been straight on ( this I saw from numerous sessions at EOR at diiferent bases) I was told by the specs the FLCCs wont allow a crab landing when I was watching the jets land at EOR one day. The centering cam keeps the nosewheel locked in centered position for the reason Greg stated.

Rigo

Alright, no crab, but what about cross-controlled? Or will the Viper not do that?

I've never flown, much less landed, a real F-16 but I have done it countless times in the F-16 UTD and WST simulators. You do crab in during a crosswind landing, and you do use the rudder during rollout, especially before the nosewheel touches down.

From the TO -1:

The recommended technique for landing in a crosswind is to use a wing level crab throughout touchdown. At touchdown, the ARI (Aileron Rudder Interconnect) will switch out.
.....
After touchdown, perform two-point aerodynamic braking using the rudder to maintain aircraft track down the runway and flaperon to prevent wing rise. In crosswinds , the aircraft may drift downwind due to side loads imposed by the crosswinds or travel upwind due to insufficient directional control inputs/availability. As the airspeed decreases, increasing amounts of rudder are required to maintain track. Maintain two-point aerodynamic braking until approximately 80 knots or until roll or directional control becomes a problem. As the pitch attitude decreases, the nose tends to align itself with the ground track.
.....
Use rudder and differential braking to control ground track, especially on wet or icy runways. Engage NWS if required to maintain directional control and to prevent departure from the runway.

(end of TO -1 quotes)

That's their story and I'm stickin' to it. Very Happy

So you don't kick out the crab?

And this sounds a little unnerving:
"In crosswinds , the aircraft may drift downwind due to side loads imposed by the crosswinds or travel upwind due to insufficient directional control inputs/availability."

They want you to ride the wind? Yikes!
I've done that before, it's not fun! But I guess it's got a lot more wing loading and isn't predisposed to weathervaning.

I don't know about the Viper, but I know I wouldn't want to be cross controlled at touchdown speed in a T-38...with gusty winds, etc, could get ugly quick. That's why we crab to landing.

To expand a little. At high AOA (like you'll experience in the flare) the rudder is far more effective. In a crabbed landing we're actually flying coordinated flight (no rudder input necessary) so a rudder roll is not a factor. But if we went wing low (uncoordinated) we'd have to be very careful not to overcontrol with the rudder and cause a dangerous rolling situation.

Again, all I have is 38 time so far....wondering how the viper handles in the flare...(I guess this could be a new subject)

thanks all...

Forum: F-16 Procedures

How do Vipers taxi?