Case M8 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_m8.csv
• Moment/reference/CG: (-0.080, 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: 1.8458 deg
• theta: 1.8458 deg
• elevator: -3.3242 deg
• throttle: 0.1630
• residual norm: 3.985e-14

Static Stability Derivatives

• Cm_alpha: +0.155594 /rad (unstable longitudinal static sign)
• Cn_beta: +0.028648 /rad (stable directional static sign)
• Cl_beta: -0.011018 /rad (stable lateral static sign)
• CL_alpha: +4.886141 /rad
• CY_beta: -0.227202 /rad

Dynamic Modes

Mode	Eigenvalues	wn rad/s	zeta	time constant s	Classification
phugoid	-0.745163+0.728641j; -0.745163-0.728641j	1.0422	0.7150	1.3420	stable
short_period	-7.91482+0j; +0.574806+0j	0.5748	-1.0000	1.7397	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	-30.2275+0j	30.2275	1.0000	0.0331	stable
spiral	-0.00116757+0j	0.0012	1.0000	856.4773	stable

Summary

• Static stability: longitudinal unstable, directional stable, lateral stable.
• Dynamic stability among identified reduced-order modes: unstable.
• 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

Case M8 is close to the static pitch-stability transition but has not crossed into acceptable behavior. It remains statically unstable in pitch and dynamically unstable in the identified longitudinal response.