Horizontal Lift

[Mmmmmm Burritos]

I found the new book online. $30 ouch, that's twice as much as the old one. $50 from the GPO. You'd think it'd be more prevalent out there having been published in Dec 2003. I bet they're just trying to sell off the old books before they sell the new.

Anyway we both have valid points and you present good arguments. I'm just trying to argue against a common misconception. I think we answered the original question.

The problem arises in that there's no way, in a coordinated banked turn, to have any significant "inertia" unless you are banking steeply. Then you feel it through the bottom of the seat as load factor. That force of course is very real. It can break wings off.

In a shallow or medium bank turn, the only way to feel the effects of a force acting out the side of the aircraft (away from the bank) are to yaw the aircraft with the rudder. But what that does is again to create two components of total lift, one from the wing and one perpendicular to that c oming from the rudder, which will result in a new total lift vector NOT perpendicular to the wing or the rudder. This new vector would be coming out of the plane diagonally. Then you definitely feel side force, which again is a result of the load factor being equal and opposite to the total lift.

And don't question my certification again. That was poor taste, especially since you only list four trainer aircraft and from my guess would be no higher than an instrument rating (unless you count 172RG/PA28R as 172/PA28)

Anyway, back to the airport...good day sir

 

[dmspilot00]

I'm just trying to argue against a common misconception.

Which one?

The problem arises in that there's no way, in a coordinated banked turn, to have any significant "inertia" unless you are banking steeply. Then you feel it through the bottom of the seat as load factor. That force of course is very real. It can break wings off.

The fact that you cannot feel it does not mean it does not exist. The inertia is equal to the horizontal component of lift in any coordinated turn. When the rate of turn is slow, you may not be able to feel it, but you've been saying all along it simply does not exist.

In a shallow or medium bank turn, the only way to feel the effects of a force acting out the side of the aircraft (away from the bank) are to yaw the aircraft with the rudder.

Not sure what the relevence of this is, as the whole point of this thread was to discuss coordinated turns. The reason you don't feel it in a shallow turn is because the horizontal component of lift is small in a shallow turn, but high in a steep turn.

 

[bigD]

As much as I cringe everytime I read yet another one of dmspilot's sardonic posts, he's right about the physics.

And Ralgha is just starting trouble for the hell of it, I guess.

 

[Ralgha]

Starting trouble? I'm just maintaining that it is not a force and shouldn't be referred to as such. So it was named wrong, doesn't mean you have to use that name.

Call it "centrifugal inertia" or something. Just don't call it a force. It makes things much more clear because it doesn't result in the whole "centrifugal force balances centripital" bit.

 

[Mmmmmm Burritos]

Anyone see Kill Bill vol. 1? I think they started a discussion about centrifugal force in that big fight scene in the Japanese club.

Can we all agree on this? Centrifugal force is not an observable force, but it magically causes a deflection in the force you actually feel (load factor).

I was never advocating that it does not ever exist, I was just saying that it doesnt exist as a force. That is probably why you feel I was contradicting myself. You just don't feel it the same in an airplane that you do in a car. This is the common misconception I speak of. Most books say centrifugal force is equal and opposite to centripetal force. But if it actaully was, then the aircraft wouldnt turn. Just like when lift and weight are equal in straight and level flight. The aircraft doesnt just climb, it maintains altitude.

You can draw a line that is "equal and opposite" to centripetal force, but it's just that, a line. It's easier to just say the load factor is equal and opposite to the total lift in a coordinated turn while maintaining altitude.

And yes it should be called something like "centrifugal confusing concept of misconception".

 

[bigD]

Ralgha - the problem is that the use of "centrifugal force" is so commonplace that when getting into any discussion related to this sort of thing, you're gonna have people that use the term. And most of the people that use it *know* it's not a force, but it's so ingrained in people's minds that it doesn't matter.

Does this justify using the term? Perhaps not, but calling people on it is kinda like correcting someone that says, "ATM Machine" or "go Xerox a copy for me", when the copy machine is not manufactured by Xerox. Technically you're right for correcting them, but it's pretty inane. At least to me. That's why I thought you were starting trouble.

 

[Mmmmmm Burritos]

Yeah. This is nothing more than an argument over semantics.

 

[bigD]

Heh! That tends to happen a lot on this board, doesn't it!?

 

[dmspilot00]

I agree with both BigD and Ralgha. It's hard not to use the term, but yet "centrifugal inertia" sounds like a better term to use.

That is probably why you feel I was contradicting myself. You just don't feel it the same in an airplane that you do in a car. This is the common misconception I speak of.

I agree centrifugal force is not a force, but the contradiction I speak of is in your comparison of a car and an airplane. From the start you have been saying that (to use a better term) centrifugal inertia in a car is completely different than centrifugal inertia in an airplane. They're not different. Case closed

 

[Mr. Cole]

Ok, glad we could all agree that centrifugal force is a ficticious force since a rotating frame is non-inertial and this "force" arises from our attempts to cast it in physics that only apply in an inertial frame. But the one issue that we shouldn't forget is that for circular motion the force must be central in that it points towards a center of motion. Horizontal lift alone doesn't cause a turn if it's not constrained to pass through the center of the circle. If we don't do this then the plane simply slips laterally to the side with no change in heading. Depending on the amount of bank, the rudder or elevator is what keeps the horizontal lift passing through the same point, allowing a coordinated turn.

Dave

 

[Ralgha]

And most of the people that use it *know* it's not a force, but it's so ingrained in people's minds that it doesn't matter.

Not intending to be argumentative or anything, but my experience has been exactly the opposite. Most people don't know it's not really a force.

 

[dmspilot00]

But the one issue that we shouldn't forget is that for circular motion the force must be central in that it points towards a center of motion. Horizontal lift alone doesn't cause a turn if it's not constrained to pass through the center of the circle. If we don't do this then the plane simply slips laterally to the side with no change in heading. Depending on the amount of bank, the rudder or elevator is what keeps the horizontal lift passing through the same point, allowing a coordinated turn.

My understanding and experience is almost the opposite: that you do not need rudder in an established coordinated turn. You do need rudder in order to cause an airplane to slip. However, I do recall that the book Aviators for Naval Aerodynamics or whatever , said that the elevator is what actually allows the airplane to turn, and I think the reasoning was that the elevator is what constrains the horizontal lift to pass through the same point, like you said. So, I'm not really sure I agree, but I don't disagree completely either. Maybe explaining more, or giving a reference would help.

 

[Mmmmmm Burritos]

Correct, the elevator/rudder is what actually makes the airplane start and continue in the circular path. You are using the elevator (and the rudder to an extent, especially at higher bank turns: think 70-80 degrees of bank) to maintain altitude. This causes rotation about the lateral axis which is pretty much aligned with the horizontal component of lift. The nose will lift into the turn. If you just bank the aircraft and let go of the controls, the airplane will slip down into the bank, and wont really turn.

I was trying to think how I can explain this one using eights on pylons but it's just too early in the morning to think clearly...