Large Deflection Working Group

Lead: Markus Ritter (

Please contact Markus Ritter for access to data depository.


  • Apply nonlinear aeroelastic simulation codes for the prediction of:
    • Static equilibrium points (static coupling) with large deflections
    • Dynamic stability (flutter) about states of large deflection
  • Investigate nonlinear aeroelastic phenomena induced by large deflections:
    • Variation of structural characteristics (e. g. variation of mode shapes and frequencies)
    • Variation of static and dynamic loads (aerodynamic, inertia)
    • LCO onset (dynamic pressure, AoA), mechanisms, and amplitudes

Configuration: Technion Pazy Wing

  • Benchmark for static and dynamic (flutter) aeroelasticity of a very flexible wing (up to 50% elastic deflection w. r. t. semi-span)
  • Experimental data for validation of computational models
  • Chord - 100 mm, span - 550 mm
  • Main spar: 550 × 60 × 2.5 mm, at the center-chord
  • Airfoil - NACA0018
  • Wing-tip rod for attaching weights
  • Main spar - Aluminum 7075
  • Chassis - Nylon, PA12, 3D-printed
  • Cover - Foil (Oralight)
AePW-3 / LDWG benefits:
  • Simple, low-cost design
  • Easy generation of simulation models


  • Large elastic deflections are inherent in particular aircraft (HALEs, Sailplanes, modern jet transports) as the result of aerodynamic optimization
    • high aspect ratio to reduce induced drag → high slenderness
  • Bringing more flexibility into jet transport aircraft wings is even a future design goal of aircraft industry
  • Future aeroelastic analysis and design codes must account for aerodynamic (e. g. large rotation of surfaces and forces) and geometric (changes in mass and stiffness) nonlinearities
  • Standard - i.e. linear - analysis and design approaches are not suitable for highly flexible aircraft structures!

Existing Data

  • Sumulation Models:
    • CAD
    • FEM (Ansys, Nastran, w/ and w/o skin, calibrated with GVT data)
    • Beam models (cross-section data)
  • Experimental data:
    • GVT data of wind tunnel model
    • Static aeroelastic data (0-55 m/s)

Computational Analysis

Nonlinear static coupling simulations of the Pazy Wing for V0 and AoA combinations
  • Beam structural model (left) and full FEM (right)
  • Potential aerodynamic model (flat plate) for both plots

Computational and Experimental Plans

  • Stability analysis about states of large deflections
  • Gain experience with novel aeroelastic measurement techniques (optical fibers and motion tracking camera system)
  • Consider aerodynamic nonlinearities (viscous effects, stall) by high-fidelity aerodynamic methods and search for LCO regions

V-g plots of the Pazy Wing for V0 sweeps and two AoAs (each velocity corresponds to a state of static structural deflection and aeroelastic equilibrium)
1st Flutter Instability (43 m/s, AoA = 5°): 1st Torsion + 2nd OOP Bending
2nd Flutter Instability (71 m/s, AoA = 5°): 1st Torsion + 1st OOP Bending