Flight Model SDK

[WarpD 824]

You're incorrect. However, it's abundantly clear that there is zero chance of getting you to understand where you're making your mistakes.I'll simply state changing the rules and formula regarding aerodynamics isn't a valid approach to proving a point.Further discussion is moot.

[mgh 89]

Then tell me where I am incorrect and what rules and formulae I've changed. That's the valid aproach to proving a point. Running away isn't.

[WarpD 824]

>Then tell me where I am incorrect and what rules and formulae>I've changed. That's the valid aproach to proving a point.>Running away isn't.You cannot change the definition of angle of attack, for one. Nor can you change the definition of relative wind. I provided the actual definitions and your conclusions don't fit with them. As a result, you chose to redefine to make them fit.

[mgh 89]

I defined Angle of Attack as "The Angle of Attack is the angle between a fixed datum line in the aircraft/wing and the relative airflow" in Post #10. What's your definiition, remembering that the chord line is a fixed datum line? Where did I change the definition of Relative Wind? My diagrams in Post #17 show the Lift at right angles to the Relative Wind. By implication the Drag (which is at right angles to the Lift) is parallel to the relative Wind. What's wrong with that and what's your definition?If you still belrive I am wriong why don't you offer similar diagrams to mine?

[WarpD 824]

The actual definition of angle of attack when discussing lift is relative to the wing's chord. There is no other definition.It's such a simple statement, no diagram should be necessary. Not to mention, you can draw anything you want... but that doesn't make it accurate.Relative wind is opposite velocity... read that again... opposite velocity. Lift and velocity are not assured to be at right angles.While the flight equation is all vector math, thare are rather specific rules that are rigid and unbendable. Once you are willing to bypass/ignore those rules, your calculations/conclusions are invalidated.

[mgh 89]

"The actual definition of angle of attack when discussing lift is relative to the wing's chord. There is no other definition.It's such a simple statement, no diagram should be necessary. Not to mention, you can draw anything you want... but that doesn't make it accurate."The chord is an arbitary reference datum and any other datrum can be used and the Angle of Attack measured relative to that. there is nothing magic about the chord line. It is a purely arbitary datum that has absolutely no physical significance. Any reference datum will do for determining lift. In the real world, aircraft designers will use a datum aligned to the fuselage centre-line and reference everything to that - wing, tailpane (horizontal stabiliser). If the wing is set at an angle to that then they will simple shift the Cl vs alpha curve to allow for it.I attach another diagram showing a wing at an angle to the relative wind with three alternataive datums, blue, green and red. The lift and hence lift coefficient is independent of the refrence datum rwegardless whether or not the chord line is used. All that happens is that the graph of Lift Coefficent vs Angle of Attack is simply shifted horizontally. The actual and maximum lift coefficients are unchanged. Therefore the Angle of Attack can be measured relative any of the datums and the appropriate curve used to determine the lift coefficient and lift force.http://forums.avsim.net/user_files/194643.jpgAnyway, your point is simply a smokescreen. Replace Airraft Datum with Chord Line in my diagrams and there is absolutely no change in the basic principles."Relative wind is opposite velocity... read that again... opposite velocity. Lift and velocity are not assured to be at right angles."Yes,Relative wind is opposite velocity and I never said or implied otherwise. However, lift by definition is a right angles to relative wind: drag is parallel to it.When an airfoil or a wing or a glider is moving relative to the air it generates an aerodynamic force that is partly parallel to the direction of relative motion, and partly perpendicular to the direction of relative motion. This aerodynamic force is commonly resolved into two components: Drag is the component parallel to the direction of relative motion. Lift is the component perpendicular to the direction of relative motion.http://en.wikipedia.org/wiki/Full_aerodynamic_forceIn effect there is only one aerodynamic force on a wing. As Wikipedia says, this is resolved into two components; one at right angles to the airflow that other parallel to it. What's your definition?

[phjvh 0]

Hi,"Small Pause", just fun, has just a little to do with the subject and probably known:

http://video.google.com/videoplay?docid=-1994695142386399860About angle of attack and inverted flight.Jan"Beatus ille qui procul negotiis..."

[WarpD 824]

Holy toledo... you're using wiki as your source??? I can't compete with wiki... I'm only human. To make THAT many mistakes takes a whole bunch of humans!There are so many things wrong with your latest post, I honestly wouldn't know where to begin.I hope you don't design real aircaft, seriously.And yes... I'm done with the "discussion". There is no point in further wasting my time. So, feel free to toss out more childish internet insults... but, I strongly recommend you use a far more reliable source for aerodynamics than a wiki. Seriously.

[mgh 89]

I quote Wikipedia because in this instance it is correct. You, as usual, fail to provide any evidence to support your erroneous claim that "Lift and velocity are not assured to be at right angles". What's your source for that? Anyway, I'll give you another reference to prove you're wrong again from a university website:"An object in an air stream is subjected to a force, F, from the air stream made up of two component forces: a drag force, D, acting in line with the direction of air flow; and a lift force, L, acting at 90

[WarpD 824]

>I quote Wikipedia because in this instance it is correct.>You, as usual, fail to provide any evidence to support your>erroneous claim that "Lift and velocity are not assured to>be at right angles". What's your source for that? Anyway,>I'll give you another reference to prove you're wrong again>from a university website:>>"An object in an air stream is subjected to a force, F,>from the air stream made up of two component forces: a drag>force, D, acting in line with the direction of air flow; and a>lift force, L, acting at 90

[mgh 89]

Microsoft shows a table titled CL vs Alpha which runs from Alpha = -3.142 (-180 deg) to Alpha = +3.142 (+180deg) with a maximum CL = 2.096 and a minimum CL = -1.528. I presented a graph using the exact values from that table. What parts of that can't i prove?My second statement (not my first I freely admit) was "An aircraft pulling negative g - such as in steady inverted flight - will have a negative angle of attack.".Your reply was "Incorrect. Once the aircraft is inverted, the angle of attack is referenced to the bottom surface of the wing.I still maintain my second statement and that you have failed to disprove it.

[WarpD 824]

>Microsoft shows a table titled CL vs Alpha which runs from >Alpha = -3.142 (-180 deg) to Alpha = +3.142 (+180deg) with a>maximum CL = 2.096 and a minimum CL = -1.528. I presented a>graph using the exact values from that table. What parts of>that can't i prove?>>My second statement (not my first I freely admit) was "An>aircraft pulling negative g - such as in steady inverted>flight - will have a negative angle of attack.".>>Your reply was "Incorrect. Once the aircraft is inverted,>the angle of attack is referenced to the bottom surface of the>wing.>>I still maintain my second statement and that you have failed>to disprove it.>>>Yes, I already conceeded that particular point many posts back. However, the rest of your conclusions regarding angles are incorrect. 90* is the maximum value for AoA. No aircraft can operate outside that limit. In fact, Cl_max's AoA is reached far before that angle.

[mgh 89]

Agreed then that an aircraft in steady level inverted flight has a negative Angle of Attack.However, what is the Angle of Attack of an aircraft in a tail slide?I agree the maximum Cl ocurs at a relatively low Angle of Attack for a conventional aircraft but that says nothing about the [bmaximum[/b] Angle of attack

[WarpD 824]

>Agreed then that an aircraft in steady level inverted flight>has a negative Angle of Attack.>>However, what is the Angle of Attack of an aircraft in a tail>slide?>>I agree the maximum Cl ocurs at a relatively low Angle of>Attack for a conventional aircraft but that says nothing about>the [bmaximum[/b] Angle of attackAngle of attack in a tail slide will be referenced from the rear surface of the wing due to the fact the relative wind is now from the rear.Maximum angle of attack and Cl_max are one and the same. If an aircraft's Cl_max is at +12* angle of attack... any higher angle will result in a stall.

[mgh 89]

"Angle of attack in a tail slide will be referenced from the rear surface of the wing due to the fact the relative wind is now from the rear."Why?. you defined "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." There's no mention of a rear surface of a wing - whatever that might mean. If the direction of the relative wind changes then the AoA changes by the same amount by your definition. If the relative wind changes by 180 deg then AoA changes by 180 deg. Let's apply some numbers. An aircraft in a steady vertical climb has no lift because otherwise it would diverge from the vertical. The most general case is for an aircraft with a cambered wing. At Cl = 0 the AoA for such an aircraft will be a small negative number, say -5 deg. (The actual number isn't critical - chose another if you like.) When the aircraft enters a tail slide the relative wind changes through 180 deg and so the AoA becomes 175 deg. If during recovery the aircraft pitches by, say, 10 deg the AoA will become 185 deg (-175 deg). What numerical values do you say these these AoAs will have? "Maximum angle of attack and Cl_max are one and the same. If an aircraft's Cl_max is at +12* angle of attack... any higher angle will result in a stall." You contradict yourself in two sentences. If Maximum AoA occurs at ClMax then how there be a higher AoA? In fact in a spin the AOA exceeds the AoA at ClMax. For example, NASA defines a flat spin as one where the AoA is greater than 60 deg, which is well above the AoA for ClMax. (Source: NASA Technical Paper 1009 - Spin-tunnel Investigation of the Spinning Characteristics of Typical Single-engine General Aviation Airplane Designs)