snippercr

Exactly, I wasn't trying to tell my students that the LIFT created is the same. I was just trying to demonstrate that angle of attack is the relation to chord/relative wind. In a vertical climb, the relative wind is still straight at the aircraft so the angle of attack is still very low - like in a cruise flight.

What I try to weed out with that question is the students who are not connecting flight path relation to the ground. So in the F16 example, if they say the AoA of a straight climb is "90 degrees" then I have to work with them more.

shdw

Emphasis added to quote.

The angle of attack isn't like in cruise flight. The angle of attack is at a specific setting to give the pilot zero lift, known as Absolute Angle of Attack.

In a vertical climb the aircrafts weight is being supported by engine thrust. In this case all forces are mathematically balanced when:

Thrust = Drag + Weight

Lift, as was defined in an earlier post, isn't present in a vertical climb like it is at cruise flight. If it were it would knock the aircraft off of its vertical path and require lift in the other direction to get back. An aircraft climbing vertically is similar to balancing a pencil on its tip. Any lifting force will blow the pencil over, so lift is kept at zero using absolute AOA.

Ralph Furley

This is not correct at all! I don't know who you fly for in Nigeria. My guess is that if you are in Africa you busted training somewhere in the USA(or more than one here). The fact is that if the aircraft is trimmed correctly and you have enough runway almost any plane will fly with no control input. I know for a fact that a crj-200 will rotate on its own and fly away on a runway as short as 7500 feet. I have done this before.

The Juice

My boy, Ralph, is tough

Ralph Furley

I speak only the truth. Thank you Sir. I also think you did not do it.!

bcrosier

What planet are you from? I have several friends and former colleagues who are flying in Africa currently, and it has NOTHING to do with their having busted training. It has quite a bit to do with losing in the "Will my airline stay in business" lottery.

I've never flown the CRJ so maybe there's something I'm missing here, but you're invalidating your takeoff data by not rotating the aircraft on schedule and at the proper rate. I'm sort of wondering why you would do that.

Further, in larger jets at heavy weights and/or flex power, there isn't a runway long enough to do that - so no they won't just fly off (that and you'd exceed max tire speed if you tried).

shdw

My knowledge here is purely academic, so forgive me if this is inaccurate. Anyways, we were taught that the majority of jets have the wings angle of incidence purposely set at absolute AOA (zero lift line). Granted the addition of flaps would add some lift and any back pressure, trim or pilot input, would increase AOA and thus increase lift.

We were told the purpose is to minimize drag during the takeoff roll to maximize takeoff performance. Is this inaccurate? Do we have any designers on these boards that can speak to the wing mounting of some of the jumbo jets or other jet aircraft? Thank you in advance.

crj700

No Bucks, no Buck Rogers!

plane4

The problem here is simple. We all know wings have a specific angle of attack where the lifting force becomes zero.


This statement is only true with:
1)a symmetric wing where the chord line is parallel to the horizontal line of the fuselage
2)a wing with a positive camber and the angle of incidence is negative
3)a wing with a negative camber and the angle of incidence is positive

Otherwise the plane cannot be perfectly vertical and fly perfectly vertical.

It' just theory!

Fly Boy Knight

It was said in a previous post that by not rotating on schedule, you would throw off your takeoff data but the airplane would still EVENTUALLY get off the ground. I agree with this idea because it is true. The Faster an airplane goes, more lift the wings make and eventually given enough runway to do so (yes that could mean 15 miles or so, this is strictly hypothetical and not practical what-so-ever), any airplane, if trimmed and configured properly will eventually develop enough life to get off the ground with no pilot input (assuming the wheels can take it up to said speed without falling off)

As for the F-16 in pure vertical flight, the wings are producing ZERO AERODYNAMIC FORCE except for drag, see the above post because he is correct. Regardless of the camber of a wing, you still have the capability to STOP it from creating any force Perpendicular to the Rel Wind by simply selecting an AOA that will yield zero aerodynamic force. Much like in a normal descent when a pilot reduces the AOA, thereby reducing lift to initiate a descent, in the case of pure vertical flight of a + cambered wing, the pilot simply holds the nose a few degrees nose down from directly vertical in order to reduce the AOA to the point where zero force is made (again, except for drag which is 100% countered by thrust). If the pilot did not do this, the airplane would actually travel horizontally across the ground (directly upward out of the canopy as seen by the pilot) while climbing vertically because the "lift" that is being created by the wings would pull the airplane in that direction.