The influence of spark plug orientation on early flame kernel development is investigated in an optically accessible gasoline direct injection homogeneous charged spark ignition engine. This investigation provides visual understanding and statistical characterization of spark plug orientation impacts the early flame kernel and thus combustion phasing and engine performance. The projected images of flame kernel were captured through natural flame chemiluminescence with a high-speed camera at 10,000 frames per second; and the ignition secondary discharge voltage and current were measured with a 10 MHz system. The combustion metrics were determined with a piezo-electric in-cylinder pressure transducer and real-time engine combustion analyzer. Three spark plug orientations with two different electrode designs were studied. The captured images of the flame were processed to … ensemble average and 2-D probability distribution and 1-D probability distribution. The results revealed that the two electrode designs produce the same trend across the three spark plug orientations, with double fine wire spark plug resulting higher probability of fast growing flame kernels, compared with the oval ground spark plug. The orientation of the spark plug electrode gap facing the intake manifold resulted in higher probability of fast growing initial flame kernels, followed by the cross flow orientation and the orientation of the electrode gap facing the exhaust. Charge motion interaction with kernel development was characterized. The data was segregated according to the initial flame kernel propagating directions and investigation was conducted to understand how the different spark plug orientations influence the flame kernel propagation cycle-to-cycle.