AVL Tutorial (4) - Stability, Lift distribution, Stall, Trim Calculation

This AVL Tutorial - Part 4 - is all about calculating in AVL. We will cover static (longitudinal) stability, talk about the optimum center of gravity, the lift-distribution and how you can foresee, where stall occurs and finally we will calculate three trimmed flight conditions (Landing, Turn and Looping flight).
The Athena Vortex Lattice (AVL) Code is very useful for quick and reliable Aerodynamic Analysis, Trim Calculation and Dynamic Stability Calculation. I used this program extensively in my Bachelor Thesis and further works on the battery-electric touring motorglider FVA 30 (www.fva.rwth-aachen.de/), as a research assistant at the Flight Systems Dynamics Institute of RWTH university (www.fsd.rwth-aachen.de/) and for personal UAV and model aircraft design.
This is the list of contents covered in this video
Topic: Stability, Lift distribution, Stall, Trim Calculation
Static Stability
* What is static stability?
- Derivative Cma, Moment coefficient curve
- Zero Lift Moment Cm0
* How can I calculate that (in AVL)?
- no-trim run case
- output stability derivatives
* Estimating the correct Center of Gravity (CoG)
- Rule of Thumb - 1/3 of x_MAC
- Aircraft Neutral Point
* Outputs, Stability Derivatives
Lift distribution, Treffz-plane
* Elliptical lift distribution
* Stall prediction, Taper
* Oswald Factor
Trim Calculations - control surface deflection
1. Landing configuration, Flaps down
2. Turn, banked flight
3. Looping flight
AVL was written by Mark Drela and Harold Youngren (Massachusetts Institute of Technology).
"AVL is a program for the aerodynamic and flight-dynamic analysis of rigid aircraft
of arbitrary configuration. It employs an extended vortex lattice model for
the lifting surfaces, together with a slender-body model for fuselages and nacelles.
General nonlinear flight states can be specified. The flight dynamic analysis
combines a full linearization of the aerodynamic model about any flight state,
together with specified mass properties."
More information on web.mit.edu/drela/Public/web/avl/

[@harshniket3454]

Please upload the next tutorial video... its really helpful.

[@hostkakamay2577]

I have downloaded your 4 series tutorials about avl and I have watched it in boucle, that was very instructive and I’m grateful for your work! Thanks.

[@BenjaminKelm]

Thank you for the encouragement!

[@praveenpratap1194]

Kindly upload next AVL tutorials.

[@cmduartes]

Best tutorial ever! Please upload more great content!

[@BenjaminKelm]

Thank you! I'm thinking to do another series on XROTOR or QPROP/QMIL.

[@Chamorristaxd]

Great stuff, world class

[@BenjaminKelm]

Great, I'm very happy! What exactly helped you?

[@joelivanmartinez3660]

Hi, very useful tutorials, thaks!!

[@cfd2050]

Thank you, I have learned a lot from your tutorial.

[@BenjaminKelm]

Great, can you give me a hint what was most useful for you? What exactly helped you? I'd like to learn how to improve things.

[@cfd2050]

@@BenjaminKelm The whole example from modeling to analysis makes me quickly master the basic operations of AVL. And in practice, I find I'm confused about the difference between the drag and the drag on the trefftz plane. Looking forward to your answers, thanks!

[@sohamphatarphod4960]

Hey can u make on on dynamic stability? like modes and stuff?? Would love to see that as well!!!

[@NAMANSACHDEVABME]

These tutorials are really helpful. Thanks a lot. I have one question:- If I want to add the moment , say generated by engines in the file so that I can trim the aircraft for that condition, How can I do that? Thanks in advance

[@alevarona7]

Is there any fast way to calculate the plane polar, not the airfoil? or I have to iterate and extract the data by myself

[@davidvazquezmasero4020]

Hi there. Thank you so much for the tutorials, first and foremost. Once I've watch all the videos I have a few questions that maybe you or someone watching the comments can solve for me: - Is it possible to obtain the plots as a set of data, like a data file? - Is it possible to obtain plots for the chordwise lift distribution? - Is it possible to obtain the Cp distribution? Thank you

[@BenjaminKelm]

yes, just see the AVL documentation. The data is available through the many output options in the OPER menue the lift distribution plots are available through the OPER/Treffz the CP distribution is the same as the lift distribution

[@yacoob24]

Really very useful video bro, Thanks. I want to find Xcp in AVL can you help me with it?

[@BenjaminKelm]

X_cp meaning the center of pressure? You can do that by integrating all forces or by computing the neutral point (see video) and then adjusting it with the Cm0 value (more information on that in standard literature)

[@shashwatsripunj]

When is your next tutorial coming?

[@BenjaminKelm]

I'm glad you show interest in this. What exactly would you like to see? I have some plans to upload some tutorials for QPROP or XFOIL

[@deprecated96]

@@BenjaminKelm MSES would be a nice option. Is the next level of AVL I think

[@donfung8665]

@@BenjaminKelm Dynamic stability and stability derivatives!

[@raisfadillah3166]

Great and very useful tutorial! Thanks. And I want to ask you about Cmtot in the result file of stability derivative calculation. What is the meaning of Cmtot ?

[@BenjaminKelm]

Cm_tot is the total pitch moment coefficient

[@goldenfang57]

Will you show how AVL can calculate dynamic stability modes?

[@BenjaminKelm]

not planned. I think the "session2.txt" tutorial on the MIT AVL website showcases the dynamic calculation quite well. Try that tutorial ;)

[@hedleyfurio]

here is carbon dragon.avl that I am trying to locate -> drive.google.com/file/d/1yweICNo4-d2jgsu1Dt1uF6Cgwk2sGgID/view?usp=sharing

[@pelotonlopezmuro]

Hi Hedley! That is a very interesting lesson too! Do you have access to the full playlist? I would be very much interested in it :)

[@kenancici2677]

hi, I dİd everything same but it not converge in trim condition

[@BenjaminKelm]

Check for formatting errors (especially TABs in Windows version)