Aerodynamics thread

[Engineer]

Re: J-20 The New Generation Fighter Thread IV

You have said that according to your definition of the cross product and pitch and more important is obvious you do not understand the equation since you do not understand this detail

I said that because no where did I say "an aircraft is a wrench". It is that simple. You simply can't handle how right I am, since you are now making stuffs up and can't form a coherent sentence. ROFL!

If products of inertia are zero, (x, y, z)
are principal axes --->"
• All rigid bodies have a set of principal
axes"

source

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You do not understand the Matrix and it is obvious, since you do not understand what is written in the same source.

Your definition of cross product and pitch were like a wrench, however you do not understand the concept of vector and it is obvious since the products of inertia are zero at the Y axis and the pitch matrix shows the same with the 0s

You keep pathetically going in circles, yet you are unable to prove your little accusation of me claiming "an aircraft is a wrench". Meanwhile, your

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betrays your own ignorance on linear algebra and physics.

Since I am much more knowledgeable than you are, let me teach you an important concept about the cross product. A cross product must be perpendicular to the original two vectors:

Here, uxv is always perpendicular to both u and v, with the orientation determined by the right-hand rule.

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So, pitch moment as a result of thrust vectoring must be perpendicular to direction of the vectored thrust. Even

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says I am correct. Here is the proof:

The title said "pitch rotation about Y". The 1 within the matrix occupies the middle column, which can only be multiplied by Y. The Y axis lies in the span wise direction, so you obviously don't know what a pitch moment is when you claimed it is an "up and down" vector. You have even debunked your own claim when you said this:

the pitch matrix only have sines and cosines for X and Z and in the equations.

X and Z have sines and cosines while Y doesn't, meaning the rotation is about Y. ROFL!

 

[PanAsian]

Can anyone in the know enlighten me on why the Y-20 and other large transport planes such as the C-17 have vertical stabilizers that seem to be so top heavy?

Specifically why is the vertical stabilizer longer at the top than at the root where it is connected to the rest of the airframe? It just appears it would be structurally weaker the way it is than if the root is longer than the top.

 

[delft]

Can anyone in the know enlighten me on why the Y-20 and other large transport planes such as the C-17 have vertical stabilizers that seem to be so top heavy?

Specifically why is the vertical stabilizer longer at the top than at the root where it is connected to the rest of the airframe? It just appears it would be structurally weaker the way it is than if the root is longer than the top.

I think the root and tip chords of the vertical tail plane are the same, but on top of the tip is the tip body that carries the horizontal stabilizer and which makes the tip chord look larger. You want to save weight and drag on the vertical tail plane, so you make it "small", which is helped by having the fuselage and the horizontal tail plane act as end plates. But the horizontal tail plane must be high enough above the wing and it will have a considerable root chord that must not be larger than the tip chord of the vertical tail plane.
IIRC the first aircraft that tail planes looking like these was the Lockheed C-5A, although the earlier C-141 from the same company had similar looking tail planes. The other designs for the same function, by Boeing ( which let to the 747 - the same design but with the wing under instead of above the fuselage ) and Douglas had conventional horizontal tail planes. Since then all turbofan powered military transport aircraft except those by Antonov have T-tails.

 

[luhai]

Since then all turbofan powered military transport aircraft except those by Antonov have T-tails.

Don't forget the CN-235

 

[jobjed]

Don't forget the CN-235

Turbofan not turboprop. -facepalm-

 

[usaf0314]

did i mention i have finally graduated undergrad studies in Aeronautical Engineering!? The Aero industry is damn hard to get into, but I'm sure once I find a place, i'll be set for a while(been applying to Boeing and LM like crazy...). meanwhile i'll share my insights to the forum on aero matters...

 

[usaf0314]

Can anyone in the know enlighten me on why the Y-20 and other large transport planes such as the C-17 have vertical stabilizers that seem to be so top heavy?

Specifically why is the vertical stabilizer longer at the top than at the root where it is connected to the rest of the airframe? It just appears it would be structurally weaker the way it is than if the root is longer than the top.

as delft said, the tip cord of the airfoil approximately the same as the root cord. the reason it seems to be top heavy is because of the T-tail design, the "pod" at the top of the stabilizer house the motor or the power transfer mechanism from the motor to the elevator, the vertical stabilizer itself also have to sustain heavy torsional load from the elevator to the fuselage and the maximum load occurs at the top of the airfoil, therefore it will need extra strengthening material to support it.

 

[Equation]

did i mention i have finally graduated undergrad studies in Aeronautical Engineering!? The Aero industry is damn hard to get into, but I'm sure once I find a place, i'll be set for a while(been applying to Boeing and LM like crazy...). meanwhile i'll share my insights to the forum on aero matters...

Congrats and good luck on your job hunt!

 

[Air Force Brat]

did i mention i have finally graduated undergrad studies in Aeronautical Engineering!? The Aero industry is damn hard to get into, but I'm sure once I find a place, i'll be set for a while(been applying to Boeing and LM like crazy...). meanwhile i'll share my insights to the forum on aero matters...

I'll second that congrats from equation as well as best wishes in your job hunt, aerodynamics does remain where the "rubber meets the road" or " airfoil meets the air???" oh well, good job USAF and don't get discouraged, keep plugging away, in the meantime get some real world experience, and as I suggested to Mig, go take a few flying lessons. Take them in something slow where you can actually feel the lift as you gain airspeed, and feel it sink as you approach the stall, it will give you a much better perspective, and I think there are a few glider-ports in UP-state New York, that would be a blast....! brat

 

[usaf0314]

I'll second that congrats from equation as well as best wishes in your job hunt, aerodynamics does remain where the "rubber meets the road" or " airfoil meets the air???" oh well, good job USAF and don't get discouraged, keep plugging away, in the meantime get some real world experience, and as I suggested to Mig, go take a few flying lessons. Take them in something slow where you can actually feel the lift as you gain airspeed, and feel it sink as you approach the stall, it will give you a much better perspective, and I think there are a few glider-ports in UP-state New York, that would be a blast....! brat

I actually already have 6 hours logged into my book for single engine aircraft. Once i have a job and make some cash i'll finish the 30hrs and the written exam for a license. also thanks equation and air force brat!