Aero 101 - ask your burning questions here

[Nose]

The F-14 does have a flight computer that controls all 3 sas actuators pitch, roll and yaw. It is a flyby wire type system. At speed the f-14 does def tend to start yawing back and forth, the human mind can't keep up with the corrections quick enough. so the flight computer puts in the required inputs to keep the plane flying straight

He meant "had"...

 

[HeyJoe]

He meant "had"...

Unless he's referring to those still flying in Iran

 

[phrogpilot73]

If you damp out the instability in a helo, doesn't the helo cease to exist?

Theoretically, I guess that would be true. Engineers could probably also mathematically prove it. They still can't mathematically prove that a helo can fly (there are two "theories"). So, I'm going to default to the idea that helos fly using PFM. Most of our stability stuff eliminates PIO or environmental effects on the controls. It actually works pretty good. I think the 60 is suspect since it has so little vibration...

USMC/USA tandem rotor, maybe, but then how the hell do you sideflare?

Ahh, the sideflare. I wish I knew what it felt like to fly. Since they're trying to eek every minute of flight time out of the mighty Battle Phrog, sideflares are prohibited for us.

I also went for the basic "we don't need them for anti-torque" statement, because trying to explain tilting the rotor disc up front one way, and tilting the aft one another way may make them even more afraid than they already are

 

[cosmania]

The F-14 does have a flight computer that controls all 3 sas actuators pitch, roll and yaw. It is a flyby wire type system. At speed the f-14 does def tend to start yawing back and forth, the human mind can't keep up with the corrections quick enough. so the flight computer puts in the required inputs to keep the plane flying straight

I can't react to quotes like these quick enough.:icon_smil

 

[Swanee]

It's completely wrong. "Adverse yaw" is produced by the ailerons. When you roll, one aileron goes up, the other goes down. The one going down produces "induced drag", which is drag caused by an increase in lift, and makes the aircraft yaw into the down aileron. Example: I roll left, but the jet initially yaws rights. This is prevalent in longer wing aircraft, especially when the ailerons go all the way to the tips.
In a jet like the T-38, the designers gave it "differential ailerons", so that the up aileron sticks up much further, giving extra drag, and thus cancelling out the induced drag of the down aileron. That's why you don't need to use rudders to get a coordinated turn in the T-38/F-5.
The rudder usage you mention is to cancel the adverse yaw and stay coordinated. If you too much or not enough rudder, you'll skid or slip, but that is different than the adverse yaw.
If this isn't making sense, p.m. me and we'll take it from there.

This is really apparent in sailplanes with those nice long wings. To get a coordinated turn in a sailplane its," Lots of rudder, little stick".

I know a guy who is at the E2/C2 Rag that says the Cod coming in on a carrier is a a lot like landing a sailplane. Not sure how much validity there is to that, perhaps some other guys can speak up who have that kind of experience.

 

[HuggyU2]

Ah, I get it. I amn't that bright.

Well, you taught me a new term: proverse roll. I'll have to go read up on that one now, as I've never heard of it.

 

[Schnugg]

F-14 in all variants (A/B/D) never had a true fly by wire flight control system.

Later versions (late 90s) had a DFCS (Digital Flight Control System) that helped the pilot with inputs. It did help correct the yaw that came with roll inputs on the ball, at high AOA and a reduced the aircraft's tendency to depart controlled flight at high AOA and IMN.

But never a true fly by wire system with you getting a vote and the computer getting 2.

 

[Catmando]

F-14 in all variants (A/B/D) never had a true fly by wire flight control system.

True. In fact the F-14A (and other models?) flight controls were hydraulically operated by systems of pushrods and bell cranks.

The only fight controls of the A model that were true fly-by-wire were the spoilers. And early on, they were a source of many problems with some occasional, spurious and un-commanded spoiler deflections and stuck spoilers. This early state-of-the-art fly-by-wire system put a few F-14's on the sea bottom. I once watched an un-commanded spoiler deployment put an F-14A into the drink on a bolter just off the angle. (crew ejected OK)

 

[Semper Jump Jet]

I thought the pedals were foot rests... At least they are for us in the tandem rotor world Sorry, couldn't resist...

In the Harrier they are footrests, at least above 250 knots, unless you like high speed departures.

I can remember flying with instructors in flight school who came from the Tomcat stomping all over the rudders (looking at you Cosmania).

I think most jets have a SAS system, the Harrier's adds rudder to coordinate the turns for you, to a degree. Kind of like how the Hornet's computer totally flies the jet for them.

 

[eddie]

This is really apparent in sailplanes with those nice long wings. To get a coordinated turn in a sailplane its," Lots of rudder, little stick".

A lot of crossed controls too.

 

[ftrooper]

"I think most jets have a SAS system, the Harrier's adds rudder to coordinate the turns for you, to a degree. Kind of like how the Hornet's computer totally flies the jet for them. "

It just makes the jet work harder, you know, the computer likes kicking you're ass, too. Our rudders work a little better, but then again, so does the rest of the airplane!

 

[Beans]

Huggy, you might have heard of proverse roll referred to as "rudder-aileron effect." Or maybe you were being sarcastic... regardless, how does the U-2 behave when you just use rudder?

Does anyone know if there are sailplanes w/o ailerons? I would think that in some cases they wouldn't even be necessary. I know that's true for R/C model sailplanes, but they don't have people inside...

 

[HuggyU2]

No, there was no sarcasm intended.
In the Deuce, pushing rudder gives you yaw,... only yaw. No roll. There is no stab-aug system either, as the flight controls are just like you'd find on a Piper Cub: cables and pushrods from the yoke to the surfaces, and no hydraulics.
If you push full ruddder in, and get the jet yawing, then when you get the full yaw, reverse the rudder, and repeat this, you can REALLY get the jet flying almost sideways... to the point where you will get scared and not do that again.
But, like manay have alluded to, when you start a turn in the U-2, you "lead with your fee". The ailerons run out to the wingtips of those 104' wings, and that means a lot of adverse yaw.

 

[CenterMass]

I Was reading a post by someone where they mentioned using trim in order to help with maneuverability during BFM/ACM. I thought it was by A4s in the Adversary Squadron thread, but I searched and could not find the post.

If a pilot is pulling full aft stick deflection will trimming provide more deflection?

I'm guessing this is different for every airframe, but If so is this because of trim-tabs or are the elevators designed with a "false-stop" except for trim.

 

[insanebikerboy]

If a pilot is pulling full aft stick deflection will trimming provide more deflection?

While I don't know about jets per se, the principles are the same. That said, if you pull full aft stick, trims tabs won't let you pull further, they'll just ease the amount of pressure you physically have to exert on the stick. Combine that with the rapid movements associated with BFM/ACM, I can see how trim would play a big factor in that.