  We present a study of the central engine in the broad-line radio galaxy 3C
109. To investigate the immediate surrounding of this accreting, supermassive
black hole, we perform a multi-epoch broad-band spectral analysis of a joint
NuSTAR/XMM observation (2017), an archival xmm observation (2005) and the
105-month averaged Swift-BAT data. We are able to clearly separate the spectrum
into a primary continuum, neutral and ionized absorption, and a reflection
component. The photon index of the primary continuum has changed since 2005
($\Gamma = 1.61 \substack{+0.02 \\ -0.01} \rightarrow 1.54 \pm{0.02}$), while
other components remain unchanged, indicative of minimal geometric changes to
the central engine. We constrain the high-energy cutoff of 3C 109
(E$_{\text{cut}}= 49 \substack{+7 \\ -5}$\,keV ) for the first time. The
reflector is found to be ionized (log $\xi$ = $2.3 \substack{+0.1 \\ -0.2}$)
but no relativistic blurring is required by the data. SED analysis confirms the
super-Eddington nature of 3C 109 initially ($\lambda_{Edd} >$ 2.09). However,
we do not find any evidence for strong reflection (R = $0.18 \substack{+0.04 \\
-0.03}$) or a steep power law index, as expected from a super-Eddington source.
This puts the existing virial mass estimate of 2 $\times 10^{8}$M$_{\odot}$
into question. We explore additional ways of estimating the Eddington ratio,
some of which we find to be inconsistent with our initial SED estimate. We
obtain a new black hole mass estimate of 9.3 $\times 10^{8}$M$_{\odot}$, which
brings all Eddington ratio estimates into agreement and does not require 3C 109
to be super-Eddington.
