The DT Series of strain sensors from Columbia Research Laboratories allows critical undercarriage structures and surfaces to be monitored more accurately than with counting accelerometer methods. The sensors incorporate the proven technology of the flight-qualified DTD2684. They are designed to monitor fatigue loading experienced by aircraft under various conditions of flight speed, weight, and mission configuration. DT3625 sensors, designed to measure fatigue in tight spaces, are 0.45 x 0.25 x 0.14 in and have a mass of 13 g. DT3617 foil strain sensors measure planar shear strain forces when the axis of principal strain is identified. DT3715 sensors measure both strain and temperature on curved mounting surfaces, while DT3716 sensors measure both strain and temperature on straight mounting surfaces.