NOTE: SpaceAge Control offers (static cones) for use in RVSM (Reduced Vertical Separation Minimum) certification and general flight testing efforts. To be added to our mailing list for trailing cone developments, send an e-mail message with your complete contact details to firstname.lastname@example.org.
Trailing cones were first developed and tested in the 1960's. Much of this early testing work conducted by the Royal Aircraft Establishment, Douglas Aircraft, the FAA, and NASA is used as the basis for RVSM certification efforts today.
Trailing cones give an easy way of calibrating the static pressure error of a pitot-static system. It does this by giving an accurate measurement of the ambient atmospheric pressure (static pressure). The trailing cone system consists of a cone that trails at least one fuselage length behind the aircraft via a high-strength pressure tube. Static pressure is measured forward of the cone by static ports. The cone stabilizes and aligns the ports relative to the freestream airflow. This design eliminates the cost and complexity of retraction mechanisms. This design can also be used on aircraft that cannot use more complex systems.
A general RVSM flight test includes not only the trailing cone system but also a task-specific test system that includes pressure transducers, recording devices (PC), and displays.
A trailing cone is a seemingly simple device. It consists primarily of a cone with holes drilled into it, plastic tube, static ports, and other miscellaneous parts. It might seem that such a device could be put together rather quickly with parts obtained from a local hardware store.
However, designing and producing a trailing cone that will operate without leaks and without failures at Mach 0.9 and -65° C requires a dedicated engineering and manufacturing effort. As the leader in flight test air data products, SpaceAge Control has undertaken the task of developing a trailing cone solution for RVSM certification and general flight testing.
Why are trailing cones so popular in RVSM certification work? Primarily because the FAA and JAA specify them as one of several methods that can be used to perform flight calibrations. The trailing cone method is the most cost-effective and easiest of the methods to perform. Below are excerpts from documents referencing the trailing cone method.
Interim Guidance Material on the Approval Of Operators/Aircraft for RVSM Operations 91-RVSM with Change 1 (30 Jun 99) - Where precision flight calibrations are used to quantify or verify altimetry system performance they may be accomplished by any of the following methods. Flight calibrations should only be performed once appropriate ground checks have been completed. Uncertainties in application of the method must be assessed and taken into account in the data package.
- Precision tracking radar in conjunction with pressure calibration of atmosphere at test altitude
- Trailing cone
- Pacer aircraft*
- Any other method acceptable to the FAA or approving authority
* When using pacer aircraft it should be understood that the pacer aircraft must have been directly calibrated to a known standard. It is not acceptable to calibrate a pacer aircraft by another pacer aircraft.
Aircraft/Operator Approval for WATRS RVSM Operations -Non-group aircraft are those that cannot be considered as part of a group as defined in Note 1. For non-group aircraft the preceding procedures do not apply. Operators of these aircraft must apply for operating authority for individual airframes. Unless flight test evidence (e.g., trailing cone test results) can be provided to the State to show that each airframe is compliant with ASE targets, HMU, or GMU monitoring is required prior to RVSM (operational) approval being granted. If flight test evidence (trailing cone results) is provided, States are requested to forward it to the CMA for inclusion in the safety analysis.