  This paper presents a framework for the design and analysis of an
$\mathcal{L}_1$ adaptive controller with a switching reference system. The use
of a switching reference system allows the desired behavior to be scheduled
across the operating envelope, which is often required in aerospace
applications. The analysis uses a switched reference system that assumes
perfect knowledge of uncertainties and uses a corresponding non-adaptive
controller. Provided that this switched reference system is stable, it is shown
that the closed-loop system with unknown parameters and disturbances and the
$\mathcal{L}_1$ adaptive controller can behave arbitrarily close to this
reference system. Simulations of the short period dynamics of a transport class
aircraft during the approach phase illustrate the theoretical results.
