Aero 101 - ask your burning questions here

[Schnugg]

Lateral stick throw was restricted as a function of airspeed in the F-14. If you could command full deflection at a high IMN you could break up the jet. I watched an F-14D break up as a result of full deflection of a horizontal stab at 650+ knots.

Like the airliner that took off out of La Guardia or JFK shortly after 9/11 that crashed in Queens (?) minutes after takeoff. It hit some turbulence and the pilot commanded full rudder, causing it to lose it's rudder...contributing to the mishap.

Without yaw SAS in an F-14, the nose tends to swing left or right and wants to keep going in that direction. No YAW SAS is typically downing in a jet. You need it more than you'd think during any maneuvering flight or ACM. We really don't fair (sp?) to the relative wind like a dart or arrow as you would think.

 

[phrogpilot73]

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

 

[Catmando]

Without yaw SAS in an F-14, the nose tends to swing left or right and wants to keep going in that direction. No YAW SAS is typically downing in a jet.

It certainly was a downing gripe in the F-14.

You are right. And I had forgotten how unstable the F-14 was in yaw without SAS, despite its twin tails.

 

[Catmando]

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

For a very few weak VF-types, rudders were indeed their foot rests. We called them 'grapes' since they always got beat in ACM/BFM and could never figure out why.

Also, I did get my hand on a collective a few times. Never really knew what it did…. But when I got scared and pulled up on it, it seemed to help matters. (But that was single rotor; tandem rotors have too many moving parts to ever work well; yet with no great yaw it pretty much almost controls itself I think. Yes? )

 

[WheelsUpHeelsUp]

One item that hasn`t been discussed here is the fact that rudder throw is restricted at higher mach numbers, either by a bellows, computers or pfm.

Yup, bellows changed the fulcrum point and decreased mechanic advantage.....on the E2 anyway if I remember correctly.

 

[HuggyU2]

From my understanding adverse yaw comes from too much rudder usage or not enough rudder usage during a bank, if that's completely wrong please correct me.

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.

 

[cosmania]

Can we change the name of this thread to "Aero 101" with the subtitle "How flight controls work and how some sub par pilots don't know how to use them" ???

 

[Nose]

SAS- Stability Augmentation System. Can't speak to Fly By Wire, but in the 60 it helped damp out the instability of the helo, while being able to "fly thru" it.

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

 

[Nose]

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.

Huggy is correct, but I think he meant to say the one going "up" creates induced drage, because it is producing more lift.

Roll left/yaw right.

Is that right?

The opposite of Adverse Yaw is Proverse Roll.

In the E-2 and other aircraft with a lot of rudder, the rudder is the most powerful roll influence on the aircraft. When you turn a hummer, the turn begins with the feet. As an LSO, I could always tell when the "light came on" for an RP because they used the rudder behind the ship to coordinate lineup and power corrections.

I've always suspected that the pilot flying in the American A-300 crash discussed above came from some aircraft that used a lot of rudder and he was familiar with concept of proverse roll. When the Ailerons failed to level the wings, he tried rudder. Unfortunately, the Airbus has the structural strength of a GMC Pacer and folded up. But what do I know? I'm just a dumb-ass pilot.

 

[puck_11]

Huggy is correct, but I think he meant to say the one going "up" creates induced drage, because it is producing more lift.

Roll left/yaw right.

Is that right?

I've always suspected that the pilot flying in the American A-300 crash discussed above came from some aircraft that used a lot of rudder and he was familiar with concept of proverse roll. When the Ailerons failed to level the wings, he tried rudder. Unfortunately, the Airbus has the structural strength of a GMC Pacer and folded up. But what do I know? I'm just a dumb-ass pilot.

Huggy said it right, he said the down going aileron creates lift, which caused the wing to go up, and the creation of lift = induced drag...

Right after the accident, it was stated in the media that the pilot flew taildraggers on the weekend. After flying a taildragger, you tend to use the rudders a lot more to keep the ball centered, in addition to if he did any aerobatics in it.

 

[bert]

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

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

 

[HH-60H]

Huggy is correct, but I think he meant to say the one going "up" creates induced drage, because it is producing more lift.

Roll left/yaw right.

Is that right?

You are both right, but you misunderstood what he said. He said the aileron that goes down creates more induced drag. He means the aileron goes down and the wing goes up.

 

[rcastor426]

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

 

[HH-60H]

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

 

[Nose]

Huggy said it right, he said the down going aileron creates lift, which caused the wing to go up, and the creation of lift = induced drag...

Ah, I get it. I amn't that bright. Sorry Huggy. I don't do well with just words, I need pictures too!