The staged rich-lean gas turbine engine combustion system has been the subject of numerous investigations directed at substantiating the capability of burning nitrogen bearing fuels without producing high emissions of nitric oxides. Many tests conducted to evaluate the potential of this combustion system when operating with coal-derived liquid fuels have been conducted using subscale burners because of the high cost and limited quantities of fuel available (e.g., (1–3). Questions arise as to the applicability of the subscale test findings when predicting the capabilities of full scale devices. In order to evaluate the efficacy of applying subscale results to large scale devices, a program was undertaken to test a 25-cm dia staged rich-lean combustor having similar characteristics to a previously tested 12.5-cm dia combustor and to identify areas where scale effects prove to be critical.