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We present results from a 2-epoch HST H$\alpha$ emission line survey of theAndromeda Galaxy that overlaps the footprint of the Panchromatic HubbleAndromeda Treasury (PHAT) survey. We find 552 (542) classical Be stars and 8429(8556) normal B-type stars in epoch # 1 (epoch # 2), yielding an overallfractional Be content of 6.15% $\pm$0.26% (5.96% $\pm$0.25%). The fractional Becontent decreased with spectral sub-type from $\sim$23.6% $\pm$2.0%($\sim$23.9% $\pm$2.0%) for B0-type stars to $\sim$3.1% $\pm$0.34% ($\sim$3.4%$\pm$0.35%) for B8-type stars in epoch # 1 (epoch # 2). We observe a clearpopulation of cluster Be stars at early fractional main sequence lifetimes,indicating that a subset of Be stars emerge onto the ZAMS as rapid rotators. Bestars are 2.8x rarer in M31 for the earliest sub-types compared to the SMC,confirming that the fractional Be content decreases in significantly more metalrich environments (like the Milky Way and M31). However, M31 does not follow aclear trend of Be fraction decreasing with metallicity compared to the MilkyWay, which may reflect that the Be phenomenon is enhanced with evolutionaryage. The rate of disk-loss or disk-regeneration episodes we observe, 22% $\pm$2% yr$^{-1}$, is similar to that observed for seven other Galactic clustersreported in the literature, assuming these latter transient fractions scale bya linear rate. The similar number of disk-loss events (57) as disk-renewalevents (43) was unexpected since disk dissipation time-scales can be $\sim$2xthe typical time-scales for disk build-up phases.

The Hubble Space Telescope Advanced Camera for Surveys Emission Line Survey of Andromeda. I: Classical Be Stars