Summary of the Second AIAA Stability and Control Prediction Workshop

Summary of the Second AIAA Stability

and Control Prediction Workshop

Benjamin M. Simmons , NASA Langley Research Center Andrew J. Lofthouse , Air Force Life Cycle Management Center Dan D. Vicroy , Adaptive Aerospace Group AIAA SciTech Forum 12 – 16 January 2026

Contents ➢ Workshop Overview Credit: NASA ➢ Model Geometry and Reference Quantities ➢ Test Cases ➢ Wind - Tunnel Testing ➢ Stability Derivative Calculation ➢ Comparison of Results ➢ Conclusions ➢ Questions/Discussion

Overview

AIAA Stability and Control Prediction Workshop II (S&CPW2) ➢ Applied Aerodynamics and Atmospheric Flight Mechanics TCs Credit: NASA ➢ Establish best practices for prediction of S&C derivatives ➢ Impartial forum for evaluating CFD predictions for S&C ➢ Identify areas requiring further research and development ➢ Workshop II (SciTech 2025): static and dynamic stability derivatives ➢ Website: www.sandcpw.com , Email: sandcpw@gmail.com

Model Geometry

➢ Common Research Model (CRM) th ➢ 4 Drag Prediction Workshop OML ➢ ONERA vertical tail design Credit: AFLCMC ➢ No engine nacelles or pylons Clean S&CPW2 CRM geometry.

➢ Geometry provided as . igs /. stp files Credit: AFLCMC ➢ Common meshes generated using HeldenMesh and Pointwise tools ➢ Full - scale geometry Credit: AFLCMC Example S&CPW2 mesh.

➢ Wind - tunnel - scale flow conditions Credit: AFLCMC

Definitions and Reference Quantities

➢ Body - axis coordinate system

➢ Standard orientation definitions

➢ Force accounting: only model surfaces (no sting)

➢ Force and moment coefficients: 𝐹 𝑧

▪ Normal force: 𝐶 = 𝐶 =

𝑁 𝑧 ത 𝑞 𝑆 𝐹 𝑥

▪ Axial force: 𝐶 = 𝐶 =

𝐴 𝑋 ത 𝑞 𝑆 𝐹 𝑦

▪ Side force: 𝐶 = 𝐶 =

𝑆 𝑌 ത 𝑞 𝑆 𝑀 𝑦

▪ Pitching moment: 𝐶 = 𝐶 =

𝑚 𝑀 Property CFD WT 𝑦 ത 𝑞 𝑆 ҧ 𝑐 − 𝑀 𝑧 Model scale 100% 2.40%

▪ Yawing moment: 𝐶 = − 𝐶 =

𝑛 𝑀 𝑧 ത 𝑞 𝑆 𝑏 Wingspan ( 𝑏 ), ft 192.8 4.627 − 𝑀 𝑥

▪ Rolling moment : 𝐶 = − 𝐶 =

𝑙 𝑀 𝑥 Mean aerodynamic chord ( ҧ 𝑐 ), ft 22.98 0.552 ത 𝑞 𝑆 𝑏 Wing reference area ( 𝑆 ), ft 4130 2.379

Summary of S&CPW2 Test Cases

𝑓 = 𝜔𝑙 / 2𝑉 𝑟 Static Test Cases Dynamic Test Cases ∘ ∘ ( 𝑀 = 0 . 052 ; 𝑅𝑒 = 200 , 000 ; 𝑇 = 518 R ) ( 𝛼 = 3 ; 𝑀 = 0 . 036 ; 𝑅𝑒 = 140 , 000 ) 𝑜 ∘ ➢ Case 1a: 𝛼 - sweep with sting ➢ Case 2a: pitch oscillation ( ± 5 ) with ∘ 𝑓 = [ 0 . 04 , 0 . 06 , 0 . 08 , 0 . 10 ] 𝑟 ➢ Case 1b: 𝛽 - sweep with sting ( 𝛼 = 0 ) ∘ ∘ ➢ Case 2b: roll oscillation ( ± 5 ) with ➢ Case 1c: 𝛽 - sweep with sting ( 𝛼 = 4 ) 𝑓 = [ 0 . 2 , 0 . 4 , 0 . 6 , 0 . 8 ] 𝑟 ➢ Case 1d: 𝛼 - sweep with sting and no tail ∘ ➢ Case 2c: yaw oscillation ( ± 5 ) with ➢ Case 4: repeat Case 1 without sting 𝑓 = [ 0 . 2 , 0 . 4 , 0 . 6 , 0 . 8 ] 𝑟 ➢ Case 3: use alternative methods to Participants report/submit: determine static/dynamic derivatives ➢ Data for each test case ➢ Case 5: repeat Case 2 without sting ➢ Static/dynamic stability derivatives Red text = required case

Test Case Geometry

Static and roll oscillation (Case 1 and 2b) Pitch oscillation (Case 2a) Yaw oscillation (Case 2c) Clean/stingless (Case 4 and 5)

Wind - Tunnel Testing

➢ NASA Langley 12 - Foot Low - Speed Tunnel ➢ Static and forced oscillation data for a 2.4% scale CRM ➢ Flow angularity and blockage corrections ➢ CFD results are blind (wind - tunnel data publicly released at S&CPW2) ➢ Full presentation and data: https://ntrs.nasa.gov/citations/20240016282 𝑽 𝑽 Pitch Oscillation Roll Oscillation Yaw Oscillation

S&CPW2 Participants

Participant Names Organization Method Adaptive Aerospace Group and Dan Vicroy, Benjamin Simmons Wind Tunnel NASA Langley Daniel Enriquez Altair Engineering FlightStream Wei Liao, Collin Strassburger Bihrle Applied Research FUN3D Kelly Laflin, Steven Klausmeyer Textron Aviation FUN3D Air Force Life Cycle Andrew Lofthouse, William Vogel Kestrel Management Center Mehdi Ghoreyshi, Pooneh Aref US Air Force Academy Kestrel NASA Armstrong Flight Seung Yoo STAR - CCM+ Research Center Zhuoneng Li, Andrea Da Ronch, Xupeng Sui University of Southampton STAR - CCM+ • Participant ID numbers have been removed for public release of this presentation • Participants are not ordered by their ID number on this slide

Stability Derivative Calculation Approach

Static stability derivatives Vicroy, D. D., “A Guide to Forced Oscillation Data Processing and Analysis,” NASA TP – 20210023569.

➢ Central difference approximation ➢ Differentiation of local polynomial fit Dynamic stability derivatives ➢ Integration method 4𝑉 𝑇 ➢ 𝐶 ( 𝛼 ) = 𝐶 𝑡 cos ( 𝜔𝑡 ) 𝑑𝑡 ׬ 𝑚 𝑜 𝑚 𝑞 ҧ 𝑐 𝜔 𝐴𝑇 ➢ Legacy method; only valid in linear regions ➢ Specific point method 𝑉 ➢ 𝐶 ( 𝛼 ) = 𝐶 𝑞 − 𝐶 ( 𝑞 ) 𝑚 𝑜 𝑚 𝑚𝑎𝑥 𝑚 𝑚𝑖𝑛 𝑞 ҧ 𝑐 𝐴𝜔 ➢ Preferred method; valid in nonlinear regions CFD forced oscillation data processing ➢ Remove initial transients (if applicable) ➢ Resample to 5 Hz th ➢ Apply a zero phase - shift digital low - pass 6 order Butterworth filter ( 𝑓 = 5 𝑓 ) 𝑐 𝑜𝑠𝑐 Example linear model hysteresis loop.

➢ Trim data to include full cycles for analysis

Comparison of Results

• One dataset was selected per participant per test case • Sign corrections were applied to match the expected trends • Meshes were renamed coarsest to finest (e.g., A = coarse, B = medium, C = fine, etc.)

• Distinguishing information is provided in the plot legends to inform participants on which dataset is shown • Full comparison of results: https://ntrs.nasa.gov/citations/20240016445

Case 1a: 𝜶 - Sweep with Sting and Tail

Required data ∘ ∘ ( 0 ≤ 𝛼 ≤ + 20 )

∘

Case 1c: 𝜷 - Sweep with Sting and Tail ( 𝜶 = 𝟒 )

Case 2a: Time Histories ( 𝑓 = 0 . 04 )

𝑟

Case 2a: Hysteresis Loops ( 𝑓 = 0 . 04 )

𝑟

Case 2a: Dynamic Stability Derivatives ( 𝑓 = 0 . 04 )

𝑟

Case 2a: Dynamic Stability Derivatives ( 𝑓 = 0 . 04 )

𝑟 Percent Difference From WT

Case 2b: Dynamic Stability Derivatives ( 𝑓 = 0 . 4 )

𝑟

Case 2b: Dynamic Stability Derivatives ( 𝑓 = 0 . 4 )

𝑟 Percent Difference From WT

Case 2c: Dynamic Stability Derivatives ( 𝑓 = 0 . 4 )

𝑟

Case 2c: Dynamic Stability Derivatives ( 𝑓 = 0 . 4 )

𝑟 Percent Difference From WT

Concluding Remarks

➢ S&CPW2: CRM static/dynamic stability derivative prediction ➢ Static angle of attack and sideslip sweeps ➢ Roll, pitch, and yaw forced oscillation maneuvers ➢ Blind comparison of CFD results to low - speed wind tunnel data ➢ 7 participants submitted final CFD results (4 different CFD codes) ➢ Community engagement and lessons learned for dynamic predictions ➢ Reasonable overall agreement, but room for improvement ➢ Best practices for dynamic derivative predictions are needed ➢ Determine next steps and future S&C prediction workshops

Acknowledgements

➢ Stability and Control Prediction Workshop II Organizers

➢ Andrew Lofthouse, Air Force Life Cycle Management Center ➢ Benjamin Simmons, NASA Langley Research Center ➢ Dan Vicroy, Adaptive Aerospace Group, Inc.

➢ William Vogel, Air Force Life Cycle Management Center ➢ Norman Princen, The Boeing Company ➢ Adam Clark, The Boeing Company ➢ Brett Johnson, The Boeing Company ➢ Matthew Prior, General Atomics – ASI ➢ Steve Klausmeyer, Textron Aviation ➢ Kelly Laflin, Textron Aviation ➢ Charlie Harrison, Gulfstream Aerospace Corporation

➢ Workshop Participants (see earlier slide)

➢ AIAA Stability and Control Prediction Discussion Group

➢ Applied Aerodynamics and Atmospheric Flight Mechanics TCs

Website: Email: www.sandcpw.com sandcpw@gmail.com