Nominal Stability Report
Preliminary FDM result: inertia, control derivatives, rate damping, and propulsion are placeholders; ADB v1.1 contains alpha-beta data only.
Database Metadata
- File:
adb_v1_1_drag_correction.csv - Moment/reference/CG:
(-0.150, 0.000, 0.150) m - rho:
1.090 kg/m^3, q_ref:340.625 Pa, S:1.805 m^2, b:3.950 m, c:0.457 m
Trim
- success:
True - alpha:
1.5005 deg - theta:
1.5005 deg - elevator:
1.5157 deg - throttle:
0.1563 - residual norm:
1.279e-13
Static Stability Derivatives
- Cm_alpha:
+0.985487 /rad(unstable longitudinal static sign) - Cn_beta:
+0.024349 /rad(stable directional static sign) - Cl_beta:
-0.010028 /rad(stable lateral static sign) - CL_alpha:
+4.858682 /rad - CY_beta:
-0.229180 /rad
Dynamic Modes
| Mode | Eigenvalues | wn rad/s | zeta | time constant s | Classification |
|---|---|---|---|---|---|
| phugoid | -0.091489+0.764909j; -0.091489-0.764909j | 0.7704 | 0.1188 | 10.9303 | stable |
| short_period | -11.7041+0j; +3.06093+0j | 3.0609 | -1.0000 | 0.3267 | unstable |
| dutch-roll-like lateral-directional | No clearly identifiable Dutch-roll-like lateral-directional oscillatory mode was found in this linearization. | n/a | n/a | n/a | not identified |
| roll | -30.229+0j | 30.2290 | 1.0000 | 0.0331 | stable |
| spiral | -0.00898588+0j | 0.0090 | 1.0000 | 111.2858 | stable |
Summary
- Static stability: longitudinal
unstable, directionalstable, lateralstable. - Dynamic stability among identified reduced-order modes:
unstable. - Weakly damped modes: phugoid.
- Unstable modes: short_period.
- No clearly identifiable Dutch-roll-like lateral-directional oscillatory mode was found in this linearization. Because the aircraft uses an inverse V-tail/ruddervator layout and the current lateral reduced eigenspectrum is entirely real, treat this as a model limitation and classification ambiguity to investigate before flight-test use.
Conclusion
The nominal database is not an acceptable fixed-wing stability baseline in the current FDM workflow. It is statically unstable in pitch and has an unstable longitudinal dynamic mode, although it remains useful as the aft/reference starting point for the CG sensitivity sweep.