Slips in the Hornet...

[McGarnagle]

Hello, this is my first post and I'm relatively new to DCS (been using it about a year and it is my current obsession). I have a question regarding forward/side slips in the Hornet. I have watched quite a few tutorials on how this maneuver is performed and understand the concept and fundamentals on what is happening well. However, whenever I try to implement the technique in the Hornet it doesn't seem to respond the way I would assume it would. Specifically, it doesn't seem to respond to it at all. Even with full rudder in either direction and compensating with opposing bank and pitch it just doesn't seem to respond to the inputs. Just curious, does this have to do with the fly-by-wire sytem of the aircraft? Granted this could be ENTIRELY user error (which is 99.999% likely), but I'm just curious what experience others have or what tips they might be able to give. Are others able to slip the aircraft successfully? Thank you very much for any help or advice you can give!

[Stearmandriver]

I've noticed rudder is extremely ineffective in the Hornet until you're extremely slow / high alpha, and trying for some nose pointing yaw in a dog fight. At normal cruise speeds, full rudder input is hardly noticeable. Having never flown a Hornet I can't say if this is correct or not, but I suspect it's not, for an airframe designed to be maneuverable. I'm curious though; why are you trying to slip it anyway?

[Rick50]

I think some airliners have a speed rating for their rudders: at a certain speed and above, the amount of maximum allowable rudder is much less, than slow during landing. AFAIK, too much rudder deflection with turbulent air and higher speeds contributed to an A300 losing it's tail and crashing.

https://en.wikipedia.org/wiki/American_Airlines_Flight_587

[maxTRX]

I've noticed rudder is extremely ineffective in the Hornet until you're extremely slow / high alpha, and trying for some nose pointing yaw in a dog fight. At normal cruise speeds, full rudder input is hardly noticeable. Having never flown a Hornet I can't say if this is correct or not, but I suspect it's not, for an airframe designed to be maneuverable. I'm curious though; why are you trying to slip it anyway?

 

In my opinion rudder is extremely effective in BFM in the Hornet.

 

Here's a final part of my recent gunfight with AI JF17 (equipped with anti-matter propulsion:D)

It shows couple of rudder turns. Notice how fast the heading tape is moving on the HUD especially with the nose pointing down. The a/s is bleeding slow but the angle gain is incredible.

 

I screw up on this one and got stuck in lag for a long time and almost ran out of gas but rudder saved my butt.

 

[McGarnagle]

I've noticed rudder is extremely ineffective in the Hornet until you're extremely slow / high alpha, and trying for some nose pointing yaw in a dog fight. At normal cruise speeds, full rudder input is hardly noticeable. Having never flown a Hornet I can't say if this is correct or not, but I suspect it's not, for an airframe designed to be maneuverable. I'm curious though; why are you trying to slip it anyway?

Oh more just general learning more than anything, trying to learn and absorb as much information as I can and this flight concept recently came up, so I figured I'd give it a try. It's seeming like it isn't really applicable for the Hornet and is used in much smaller planes.

[Stearmandriver]

Oh more just general learning more than anything, trying to learn and absorb as much information as I can and this flight concept recently came up, so I figured I'd give it a try. It's seeming like it isn't really applicable for the Hornet and is used in much smaller planes.

 

True; as a general rule we don't slip swept wing aircraft. Slipping is a primary maneuver in light aircraft like my namesake; I wouldn't even consider turning someone loose in a taildragger unless they were proficient at slips over obstacles to landing. I think, though, that you aren't going to find much use for it in a tactical jet. Might try it in the P-51, but even that might be highly wing-loaded enough that slipping isn't too useful.

 

Just ruddering the nose around is a different story, and I have found it effective in high alpha, low energy states in the Hornet sim, but at normal cruise speeds I've been surprised at the ineffectiveness of the rudder. Perhaps it is really limited by the FCS that way. It's true that many airliners limit rudder usage at higher speeds; it's acomplished via computer in fly- by- wire jets, but even conventional hydraulically boosted flight control systems like on the 737 accomplish it by partially removing hydraulic pressure to the rudder at higher speeds.

[Bunny Clark]

I think this mostly has to do with the FCS. Remember, the Hornet is an entirely FBW aircraft, when you stomp on the rudder pedal there's no link to the actual rudder, you're just telling the FCS what you want the aircraft to do and it adjusts any number of control surfaces to execute that. Since side slips are generally undesirable in anything other than a light GA aircraft, my guess is the FCS is programmed not to allow them to happen.

 

Same is true with rudder deflection at high speed. Excessive yaw input at high speed can be quite dangerous and there's really no reason to want sudden strong yaw when cruising straight and level at high speed, it's not surprising at all that the FCS would dampen that out.

 

I'm pretty sure the FCS gains override and manual reversion work to some degree in the Hornet right now, it might be interesting to see if you can get it to slip with part of the FCS bypassed.

[Stearmandriver]

It would be interesting to try to get it to slip in the bypass mode.

 

I'm just surprised at the FCS allowing strong yaw in a high alpha state if it's intentionally limiting it in cruise; and what it allows is skidding, not slipping. An uncoordinated skidding condition at high alpha is the worst case scenario, if you're talking about a threat of departure. And that's the thing it allows.

 

Of course, there's also use for that, in slow-speed nose pointing during a dogfight. You're right, I can't think of why you'd want to do it in cruise, minus jammed or damaged roll control (ailerons, stabs, flaps). But maybe at that point the FCS limits no longer apply? Don't know, but it's an interesting question.

[kengou]

I believe this is the FCS. At normal flight (not high AoA situations) the FCS tries to keep the aircraft stable and this means it minimizes sideslip. Stomping on the rudders won't make the aircraft slip like crazy because there's just no real reason for a pilot to ever do that and it could lead to departing the aircraft, so the FCS stops it from happening. (again, in normal flight. combat is a different story and the FCS will give lots of rudder authority in that situation)

[maxTRX]

I believe this is the FCS. At normal flight (not high AoA situations) the FCS tries to keep the aircraft stable and this means it minimizes sideslip. Stomping on the rudders won't make the aircraft slip like crazy because there's just no real reason for a pilot to ever do that and it could lead to departing the aircraft, so the FCS stops it from happening. (again, in normal flight. combat is a different story and the FCS will give lots of rudder authority in that situation)

 

By saying 'rudder' authority I'm sure you mean authority given to FCS to move every part of the control system to produce yaw when you kick the rudder pedals, a/s permitting.

By kicking the rudders and moving the stick in the same direction within certain a/s limits will invoke pirouette logic or a loaded roll if you're too fast.

Now, I can't see the reason for cross control 'slip' in jets. (doesn't mean it there is none:joystick:)

 

In GA props... sure. Works better then DLC in Tomcats;) The airbrake on the Hornet is pretty effective with a slight nose down in case you have to get rid of some altitude on approach... heck, the entire airframe is a huge airbrake in PA mode.:)

[Bunny Clark]

I'm just surprised at the FCS allowing strong yaw in a high alpha state if it's intentionally limiting it in cruise; and what it allows is skidding, not slipping. An uncoordinated skidding condition at high alpha is the worst case scenario, if you're talking about a threat of departure. And that's the thing it allows.

 

Of course, there's also use for that, in slow-speed nose pointing during a dogfight. You're right, I can't think of why you'd want to do it in cruise, minus jammed or damaged roll control (ailerons, stabs, flaps). But maybe at that point the FCS limits no longer apply? Don't know, but it's an interesting question.

 

Part of it is that high rudder deflection at cruise speeds is less a threat of departure and more of a threat of structural damage to the aircraft. There have been multiple incidents of rudder deflection causing the vertical stabilizer to rip off of airliners, and my guess is that is the primary concern for dampening rudder authority at cruise speeds. Coupled with the fact that there's really no reason to want to do it.

 

As you correctly point out, having high yaw authority at high AoA is extremely valuable in a fight, and one of the key benefits of the Hornet's FCS is allowing the pilot to comfortably fly the aircraft right up to the edge of controlled flight without needing to worry about a departure.

[Stearmandriver]

Part of it is that high rudder deflection at cruise speeds is less a threat of departure and more of a threat of structural damage to the aircraft. There have been multiple incidents of rudder deflection causing the vertical stabilizer to rip off of airliners, and my guess is that is the primary concern for dampening rudder authority at cruise speeds. Coupled with the fact that there's really no reason to want to do it.

 

As you correctly point out, having high yaw authority at high AoA is extremely valuable in a fight, and one of the key benefits of the Hornet's FCS is allowing the pilot to comfortably fly the aircraft right up to the edge of controlled flight without needing to worry about a departure.

 

True, but what's weird to me is that you can hardly yaw the plane at cruise speeds. It makes sense that control deflection is limited at these speeds, but not control authority. In a moderate or high airspeed scenario, it just takes less control surface deflection to create the same effect. In the airliners you're talking about, rudder deflection is limited but you can most assuredly get the same amount of yaw out of the jet at about any speed (I've been flying airliners for over 20 years, was sitting in a captain upgrade class when that Airbus went in in New York because the FO stomped in stop-to-stop travel... but that's an Airbus, they're not to be trusted ;). )

[Ahmed]

Same perception here. The rudder seems to have very little effect aside from at very low speeds / high aoa.

 

It also especially exhibits very little roll coupling (with no visible FCS counter action in the FCS page).

 

Airliners do indeed have a rudder limiter to avoid overstress. However a tiny bit of rudder does develop a significant yaw and roll rate on them at any speed, as Stearmandriver says.

Edited July 25, 2020 by Ahmed

[Ahmed]

Search youtube for "f-16 rudder test" for an example HUD video of how an F-16 reacts to rudder deflection (didn't embed the video due to some footage of another sim at the end of it)

[maxTRX]

Same perception here. The rudder seems to have very little effect aside from at very low speeds / high aoa.

 

It also especially exhibits very little roll coupling (with no visible FCS counter action in the FCS page).

 

Airliners do indeed have a rudder limiter to avoid overstress. However a tiny bit of rudder does develop a significant yaw and roll rate on them at any speed, as Stearmandriver says.

 

In the Hornet I think it's right on the money. I checked it in a level flight anywhere between 300 to 500 knots.

There was a substantial yaw and the mild roll followed shortly after. The FCS page showed only rudder movement and I think that's the way it's supposed to work under these flight conditions.

 

I'll try to get some more info on this. This part shouldn't be too sensitive :shifty:

[Scaley]

As to the original question - my understanding of the RL Hornet docs is that you shouldn't be able to sideslip by cross-controlling the aircraft since the FCS logic will override either the stick or pedal input. It's interpreting the control inputs as a pilot commanded roll and yaw in opposite directions. The larger magnitude input should essentially "win" and you just get one effect, either the roll (stick) or roll+yaw (pedal)