The B-2 wing configuration was close to neutral stability.[^3] It had a very light wing loading.[^3] As the aircraft increases speed, the pitch stability decreases.[^1] In the event of a stall the aircraft would tumble backward.[^1] This can cause a coffin corner situation as the aircraft accelerates if the pilot runs out of sufficient angle of attack to level out and slow down.[^1] This was encountered in a wind-up turn compliance event.[^1] It has near neutral pitch stability and as very light wing loading.[^2] This makes it susceptible to turbulence.[^1] At low altitude and high speed the short period mode can approach 1.5 Hz.[^3]
A 384-element half-span box model was used to generate the subsonic aerodynamic forces and moments using a 2D Doublet Lattice method.[^3]
A correction factor weighting was used to make sure that the model matched the wind-tunnel data.[^3] These weighting factors were added directly to the NASTRAN box forces.[^3] The frequency of 0.4 was chosen as the point where all of the correction factors would become 1.[^3] Therefore the correction factors were linearly interpolated so that they would become 1 at the frequency of 0.4.[^3]
The flying-wing design needed to be self-trimming.[^4] The spanwise lift distribution is non-optimal and the twist and tailored leading-edge camber was used to create good stall behavior at low speed and low compressibility drag at high-speed.[^4] The wing planform area was held to the absolute minimum for volume of the payload, crew, fuel, and propulsion system.[^4] The airfoil thickness was increased as much as possible to the limit of incipient flow separation.[^4] A supercritical airfoil was designed ahead of the engine inlet as it expands to supersonic speed and is then compressed before it enters the inlet.[^4] The nacelle cowling is also a supercritical airfoil as the flow accelerates to supersonic and then becomes part of the recompression extending to the outboard wing.[^4] The airfoils for the wings were based on supercritical airfoils.[^4] The aerodynamic design provides better efficiency than contemporary subsonic transport aircraft.[^4]
[[B-2 Residual Pitch Oscillations]] – happened at high speeds
[[X-31 Envelope Expansion Tests]] – used wind-up turns for envelope expansion testing
[[B-2 Wind Tunnel Models]]
[[B-2 Aerodynamic Guesstimation]]
Sources
- [1] PeninsulaSrsVideos, B-2 Flight Test, (Jul. 07, 2017). Accessed: Jul. 08, 2024. [Online Video]. Available: https://www.youtube.com/watch?v=l-Fo44a5oOQ
- [2] Aeroservoelastic Analysis of the B-2 Bomber.” Accessed: Jun. 23, 2024. [Online]. Available: https://arc-aiaa-org.colorado.idm.oclc.org/doi/epdf/10.2514/2.2674
- [3] R. T. Britt, J. A. Volk, D. R. Dreim, and K. A. Applewhite, “Aeroservoelastic Characteristics of the B-2 Bomber and Implications for Future Large Aircraft”.
- [4] “B-2 aerodynamic design.” Accessed: Aug. 04, 2024. [Online]. Available: https://arc.aiaa.org/doi/epdf/10.2514/6.1990-1802
Backlinks
[[B-2 Flight Control Laws]]
B-2 Spirit
[[Doublet Lattice Method]]
[[F-15 Speed Brake Design]]
F-22 Flight Control System
[[Flow Separation]]
[[Interpolation]]
[[Short-Period]]
[[Supercritical Airfoils]]
[[Transonic Flight]]
[[Turbulence (Aircraft)]]
[[Wing Loading]]