Horizontal Lift

[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...