  There are very few reports of flare signatures in the solar irradiance at H i
Lyman {\alpha} at 121.5 nm, i.e. the strongest line of the solar spectrum. The
LYRA radiometer onboard PROBA2 has observed several flares for which
unambiguous signatures have been found in its Lyman-{\alpha} channel. Here we
present a brief overview of these observations followed by a detailed study of
one of them, the M2 flare that occurred on 8 February 2010. For this flare, the
flux in the LYRA Lyman-{\alpha} channel increased by 0.6%, which represents
about twice the energy radiated in the GOES soft X-ray channel and is
comparable with the energy radiated in the He ii line at 30.4 nm. The
Lyman-{\alpha} emission represents only a minor part of the total radiated
energy of this flare, for which a white-light continuum was detected.
Additionally, we found that the Lyman-{\alpha} flare profile follows the
gradual phase but peaks before other wavelengths. This M2 flare was very
localized and has a very brief impulsive phase, but more statistics are needed
to determine if these factors influence the presence of a Lyman-{\alpha} flare
signal strong enough to appear in the solar irradiance.
