I'm not disagreeing with anything your wrote. It is barely possible that flying inverted, level flight might be reported as a negative AoA, but normally it would be slightly positive, just as it is in normal flight.Even a "dive" while inverted will display a negative AoA... ;)Without taking the time to look it up, my guess would be no...

Correct.And as was stated previously, the data is in polar format. However, FS will never read values that exceed +/- 90 degrees.

There can be no objection to your post. However, it doesn't address the specific point about negative angle of attack in inverted flight.The figure shows and aircraft in upright flight on the left and in inverted flight on the right in earth axes, i.e. relative to the earth. http://forums.avsim.net/user_files/194512.jpgIn inverted flight the lift force still has to be upwards to counter gravity and therefore airflow is also upwards, relative to earth. However, in inverted flight the lift force acts downwards and the airflow also is downwards relative to the aircraft. This is made clearer in the second figure in which the aircraft have been re-orientated into earth axes with the aircrafts' datum being horizontal. In inverted flight, the lift is negative and the angle of attack is negative. http://forums.avsim.net/user_files/194511.jpgRemember that lift is a vector and defined by its direction as well as its magnitude. If the aircraft is completely symmetrical aerodynamically in pitch and was flying at say +5 deg angle of attack in upright steady level flight at a given EAS then it would fly at -5deg angle of attack in steady level inverted flight at the same EAS because the magnitude of the lift force must be the same and equal to the weight. If the aircraft weren't symmetrical then it would fly inverted at the negative angle of attack that gave a negative lift coefficient with the same magnitude as for upright flight. To illustrate the point Lift Coefficient can be approximated by:Cl = Cl0 +ClAlpha * AlphaWhere Cl0 is the lift coefficient at zero Angle of Attack (Alpha) and can be about 0.2 for a cambered wing ClAlpha is the variation of Cl with Alpha, which has a typical value of about 0.1/degree away from the stall. In this case the variation of Alpha with Cl is:Alpha = (Cl-0.2)/0.1If the aircraft is in erect flight at a Cl of +0.7 then Alpha is (0.7 - 0.2)/0.1 or +5 deg. If it's in inverted flight at the same EAS and same magnitude of Cl to give the same magnitude of lift force, then Alpha becomes (-0.7 - 0.2)/0.1 or -9 deg.

I will agree with your post.However, you have to agree that in inverted flight a higher angle of attack is physically impossible.The primary reason is because with regard to lift, the 'reference line' is straight through the center of the wing, between the upper and lower surface, not with relation to the aircraft's overall body. In inverted flight, the surfaces are inverted and thus the airfoil's curvature is also inverted and not producing as much airflow acceleration across the upper surface because of the airfoil's shape.Thus, back to your original question regarding the data curve in the table... in flight you can never exceed +/-90* and are going to see a faster drop in Cl during inverted flight.Given that, the table in FS makes perfect sense.

"However, you have to agree that in inverted flight a higher angle of attack is physically impossible.The primary reason is because with regard to lift, the 'reference line' is straight through the center of the wing, between the upper and lower surface, not with relation to the aircraft's overall body. In inverted flight, the surfaces are inverted and thus the airfoil's curvature is also inverted and not producing as much airflow acceleration across the upper surface because of the airfoil's shape."I'm not sure what your point is. I showed that if the wing is cambered then a higher magnitude of angle of attack is needed for inverted flight than for upright flight. If the wing is symmetrical then the magnitudes will be the same. The reference line can be anything you want. For a wing it is normally taken as the chord line - the line connecting the leading and trailing edges - but for a complete aircraft it can be the fuselage horizontal datum. The choice will affect the value of Cl0The angle can exceed +90 deg. I've seen the so-called tail slide where an aircaft with a thrust/weight ratio of less than is put into a vertical climb. The speed diminishes until the aircraft stops climbing and then slides down backwards until the pilot takes control again. The angle of attack is close to 180 deg when the aircraft begins to slide backwards. I supect there can also be higher angles of attack in the spin also.Do you now agree that angle of attack is negative in inverted flight?

"Do you now agree that angle of attack is negative in inverted flight?"If you have to ask that question, you clearly didn't actually read all of my post.As for exceeding 90*. Nope. When the aircraft is 'sliding' tail first, the nose of the aircraft is no longer traveling forward and thus the wing is quite literally moving through the air in a rearward direction, thus transforming the 'leading edge' to the rear of the wing.How FS handles this is perhaps a question better suited for ACES.Going back to your original post... you said the table makes no sense. I've proven it makes sense. Now... if you want to argue things... at this point you're on your own. :)

I did read your post and still don't know what you mean by "However, you have to agree that in inverted flight a higher angle of attack is physically impossible."Higher than what?

Than what is possible during normal flight.The design if the wing would prevent it. If you think I'm incorrect... go take a 747 in FS and fly it inverted. See how well you do. ;)

"Than what is possible during normal flight."But i just showed that with an asymmetric, cambered wing the magnitude of the angle of attack in inverted flight is greater than in upright flight."The design if the wing would prevent it. If you think I'm incorrect... go take a 747 in FS and fly it inverted. See how well you do. ;)"I do think you are incorrect. Go take a Pitts Special in FS and fly it inverted.

A few definitions:Relative wind - The airflow that is exactly opposite to the direction of flight, i.e. is exactly opposite to velocity.Angle of attack - The angle between the chord and the relative wind, expressed in degrees. It is negative if the chord line is below the relative wind.Angle of attack is commonly confused with pitch attitude. They are not one and the same.

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>?There might be a reason I posted those, indeed. ;)

On the other hand there may not be a reason. May I suggest that if you have any points to make you make them clearly and logically or else...?

1) Angle of attack for an inverted wing will not typically be symmetrical because the aircraft's wing surface is not symmetrical. Very few aircraft made have a symmetrical surface. Thus the Cl will not be as high for inverted flight, this is even true for the aircraft you tossed into the discussion. The more assymetrical the wing, the less efficient the wing will be when inverted.2) An aircraft falling tail-first will have a relative wind from the trailing edge of the wing... thus the angle of attack will be in reference to the trailing edge, not the leading edge. Once again, the angle will not exceed +/-90*.3) While you showed that the same pitch for an aircraft in inverted flight may result in a higher angle of attack, you didn't actually show that it would not stall at that angle. You made the assumption that simply because you can get a wing into a higher angle of attack, it's valid. My statement regarding inverted angle of attack deals with actually producing lift without stall. If an aircraft has a maximum angle of attack of +12*... flying it inverted will typically result in a lower angle of attack at stall onset.4) Angle of attack is referenced to the wing's chord. Period. No exceptions. There is no 'aircraft reference datum' for angle of attack. Thus all measurements of angle of attack is based on the relative wind. As I stated, relative wind is exactly opposite the velocity vector.At no point is it physically possible to exceed a 90* angle of attack because if the aircraft is changing altitude at the same time the relative wind (which is always opposite direction of flight) is changing as well. A 90* angle of attack would place the wing's surface perpendicular to the relative wind.

"1) Angle of attack for an inverted wing will not typically be symmetrical because the aircraft's wing surface is not symmetrical. Very few aircraft made have a symmetrical surface. Thus the Cl will not be as high for inverted flight, this is even true for the aircraft you tossed into the discussion. The more assymetrical the wing, the less efficient the wing will be when inverted."If the aircraft is in steady level flight then the Lift must equal the Weight regardless of the aircraft's orientation. So the Lift is the same in steady level upright or inverted flight at the same EAS. Lift is given by 0.5 * rho * V * s * Cl so that Cl is the same. However,The Angle of Attack will be the same if the aircraft is symmetric and different if it isn't. "2) An aircraft falling tail-first will have a relative wind from the trailing edge of the wing... thus the angle of attack will be in reference to the trailing edge, not the leading edge. Once again, the angle will not exceed +/-90*."The following diagram shows how the Angle of Attack varies from 0 to +180 deg with the leading edge of the wing to the left.http://forums.avsim.net/user_files/194571.jpgIf the aircraft is falling tail first the the Angle of attack is 180 deg. What Angle of Attack do you say it is? It can't be 0 deg because that occurs when the relative wind is towards the actual leading edge of the wing. In the tail slide it is towards the actual trailing edge. Suppose it isn't exactly towards the trailing edge but is, say, 10 deg off. It can't actually be +10 deg or -10deg because those refer to the case when the relative wind is almost towards the leading edge. Because the wing isn't symmetric in a fore-and-aft direction the airflow around it is obviously different depending on whether the relative airflow is towards the leading or trailing edge. "3) While you showed that the same pitch for an aircraft in inverted flight may result in a higher angle of attack, you didn't actually show that it would not stall at that angle. You made the assumption that simply because you can get a wing into a higher angle of attack, it's valid. My statement regarding inverted angle of attack deals with actually producing lift without stall. If an aircraft has a maximum angle of attack of +12*... flying it inverted will typically result in a lower angle of attack at stall onset."I don't have to show the wing wouldn't stall. If an aircraft is actually flying in steady level inverted flight (as seen at any aerobatic display) then it obviously isn't stalled so what matters is the actual, unstalled, Angle of Attack under those conditions and your the Angle of Attack at the Stall is irrelevant to this case."4) Angle of attack is referenced to the wing's chord. Period. No exceptions. There is no 'aircraft reference datum' for angle of attack. Thus all measurements of angle of attack is based on the relative wind. As I stated, relative wind is exactly opposite the velocity vector."In fact, Angle of Attack can be referenced to anything. In the case of a complete aircraft is is often referenced to an aircraft datum. If it bothers you, simply replace the words Aircraft Datum with Chord in my diagrams when yopu'll see that my argument is totally unchanged."At no point is it physically possible to exceed a 90* angle of attack because if the aircraft is changing altitude at the same time the relative wind (which is always opposite direction of flight) is changing as well. A 90* angle of attack would place the wing's surface perpendicular to the relative wind."This is just a repetition of your Point 2 and my diagram still applies. If an aircraft is changing altitude in a vertical climb the relative wind isn't changing, so your statement isn't true. Consider a tail-wheeled aircraft at rest on the ground with a chord line at 10 deg relative to the ground. A headwind will have an Angle of Attack of +10 deg: a tailwind will have an Angle of Attack of -170 deg.