  Boundary-layer instabilities for a finned cone at Mach=6, $Re=8.4 \times
10^6$ [m$^{-1}$], and zero incidence angle are examined using linear stability
methods of varying fidelity and maturity, following earlier analysis presented
in [doi.org/10.2514/6.2022-3247]. The geometry and laminar flow conditions
correspond to experiments conducted at the Boeing Air Force Mach 6 Quiet Tunnel
(BAM6QT) at Purdue University. Where possible, a common mean flow is utilized
among the stability computations, and comparisons are made along the acreage of
the cone where transition is first observed in the experiment. Stability
results utilizing Linear Stability Theory (LST), planar Parabolized Stability
Equations (planar-PSE), One-Way Navier Stokes (OWNS), forced direct numerical
simulation (DNS), and Adaptive Mesh Refinement Wavepacket Tracking (AMR-WPT)
are presented. A dominant three-dimensional vortex instability occurring at
$\approx$ 250 kHz is identified that correlates well with experimental
measurements of transition onset. With the exception of LST, all of the
higher-fidelity linear methods considered in this work were consistent in
predicting the initial growth and general structure of the vortex instability
as it evolved downstream. Some of the challenges, opportunities, and
development needs of the stability methods considered are discussed.
