Laser induced ignition was applied in a turbulent two staged aeronautical combustion chamber. It was coupled to extensive on-line spectroscopic measurements to determine the local equivalence ration within each spark. This value was found correlated to the probability of ignition and it was shown that establishment of the complete flame in the combustor required not only the creation of an initial kernel but also favorable flow patterns. Criteria for ignition based on experimental results are proposed in a particular combustor but the techniques and subsequent analysis developed may be applied to other injection devices.