  An HST COS Far UV spectrum (1170 A to 1800 A) was obtained for the short
orbital period recurrent novae (T Pyxidis subclass), CI Aquilae. CI Aql is the
only classical CV known to have two eclipses of sensible depth per orbit cycle
and also have pre- and post-outburst light curves that are steady enough to
allow estimates of mass and orbital period changes. Our FUV spectral analysis
with model accretion disks and NLTE high gravity photospheres, together with
the Gaia parallax, reveal CI Aql's FUV light is dominated by an optically thick
accretion disk with an accretion rate of the order of $4\times 10^{-8}$
$M_{\odot}/yr$. Its database of light curves, radial velocity curves, and
eclipse timings is among the best for any CV. Its orbit period ($P$), $dP/dt$,
and reference time are re-derived via simultaneous analysis of the three data
types, giving a dimensionless post-outburst $dP/dt$ of $-2.49\pm 0.95\times
10^{-10}$. Lack of information on loss of orbital to rotational angular
momentum leads to some uncertainty in the translation of $dP/dt$ to white dwarf
mass change rate, $dM_1/dt$, but within the modest range of $+4.8\times
10^{-8}$ to $+7.8\times 10^{-8}$ $M_{\odot} /yr$. The estimated white dwarf
mass change through outburst for CI Aql, based on simple differencing of its
pre- and post outburst orbit period, is unchanged from the previously published
$+5.3 \times 10^{-6} M_{\odot}$. At the WD's estimated mass increase rate, it
will terminate as a Type Ia supernova within 10 million years.
