Flight Test Working Group

Lead: Alex Chin (Alexander.W.Chin@nasa.gov) & Jeffrey Ouellette (Jeffrey.A.Ouellette@nasa.gov)

Please contact Alex Chin or Jeff Ouellette for access to data depository.


Use X-56A as a case study for flutter prediction and ASE modeling improvements

  • Part 1: Predict blind flutter speed with flutter mode trends
    • Flutter analysis range from 0 to 200 KEAS
    • Flutter analysis based on mass condition (fuel) dependency
    • Document aero model formulation
    • Compare Vg and Vf trend plots
    • Leverage flight data as truth model for comparison studies (measured damping and frequency)
    • Although only the first flutter mode, Body Freedom Flutter, can be verified, secondary flutter modes at higher speeds can be analytically compared
  • Part 2: X-56 aeroelastic models for control
    • Compare with Low Order Equivalent System (LOES) models derived from flight data
    • Input/output control surface to sensor transfer function comparisons


  • Active control of flexible aircraft requires confidence in modeling formulation along with a thorough understanding of uncertainties and sensitivities to ensure appropriate controller robustness
  • The X-56A aircraft was designed with an active controller to suppress flutter and is heavily instrumented to provide flight data for better understanding flutter prediction models and increase confidence in aeroservoelastic modeling.

X-56 Vehicle Specifications

  • Specifications:
    • 500 lbs MTOW
    • (80 lbs Fuel)
    • 28 ft span
    • BRS parachute
    • two P-400 JetCat engines
    • 10 trailing edge control surfaces
  • Instrumentation
    • 3 axis high rate gyro
    • 10 z-axis accels
    • Fiber Optic Strain Sensing (FOSS)
  • Airspeeds:
    • Takeoff ~65KCAS
    • Max Level ~135KCAS
    • Open Loop Flutter 105-120 KCAS

Released Materials

Finite Element Model
Aerodynamic Panel Model

Pending Materials to Release for Comparison

  • Flutter speed derived from flight data
  • Low Order Equivalent Models based on flight data