What is a Trailing Cone?

Trailing cones (aka trailing wires or trailing static cones) is a testing device used to calibrate the static pressure (i.e. altimetry ) of an aircraft. It provides accurate atmospheric pressure measurements surrounding the aircraft. To accomplish accurate measurements, the trailing cone sits clear outside of the pressure disturbance region around the aircraft fuselage or at least one fuselage length behind the aircraft and it is connected to the control system thru a pressure tubing.

During the product development phase of new aircraft, the cone is fixed on to test planes during early test flights to measure static pressure or ambient atmospheric pressure.

How to measure trailing cone drag force?

In some critical flight test validations, aeronautical engineers need to determine the aerodynamic drag forces on the cone and compare them to analytical predictions. In those instances, in-line load cells are installed in the trailing cone system to measure the axial tension in the pressure tube caused by the cone drag force.

These in-line force measurements allow flight test engineers to validate analytical models and accurately determine in-flight loads exerted on the cone attachment point.

In this application, two types of in line load cells were used to measure the tension in the tube. The first type, LCM325, is solid and prevented the pressure transducer from sensing static pressure. The second type, QLA317 is hollow and allowed the static pressure to flow through the load cell to the pressure transducer. The load cells were installed between the attachment point and the pressure tube.