Sensors are a vital enabling technology for gas turbines and are critical to validation of design tools, new products, engine control, and health monitoring. The limitations of sensors in terms of survival temperature, accuracy, stability, and degradation limit where measurements are made during development and the operating ceiling of the gas turbine. Engines are run with safety margin in order to safeguard components against mechanical failure. Consequently, they are not run at their most optimal, which impacts overall efficiency. For example, a 10C uncertainty on turbine entry temperature changes the specific fuel consumption by 0.2%. Also a 0.2mm change in turbine tip clearance changes the specific fuel consumption by 0.4%. It is believed that with better sensing techniques, in excess of 500,000 tonnes of kerosene could be saved per annum, which equates to a CO2 saving of over 1.5 million tonnes. Despite some successes in recent research, it has become clear that the capability gaps are not closing quickly enough. Further research in to sensors and instrumentation is, therefore, absolutely essential if the capability gaps are to be filled at an adequate rate.