The 1-4-1 system of jack movements for the flexible liners of supersonic wind tunnels.
by A. C. McIntosh and J. Pike.
The Aeronautical Journal of the Royal Aeronautical Society, January 1979, pp. 28-31.

Conclusions.
A new method has been proposed for finding the effects in supersonic flow of small movements of the plates of a flexible-liner wind tunnel. Previous methods involve moving the support jack on its own and have caused rippling in the plate, leading to a lengthy Mach number disturbance which is difficult to trace at low supersonic Mach numbers. Using beam theory, a system (known as the 1-4-1 system) has been derived which involves the movement of three adjacent jacks through displacements in the ratio 1:4:1. Such a system localises the rippling of the plate, and tests have clearly indicated both the shortening and smoothing effect that the system has on the resulting Mach number disturbance.

Comment.
The 1-4-1 system forms part of a highly successful wind tunnel calibration and flow correction procedure, which used a pitot rake to identify the source of the flow errors and the 1-4-1 system to correct them. The method has been used to calibrate and correct the working section flows of the 8' x 8' supersonic windtunnel at RAE Bedford. The full report referenced in the paper was never published.

Availability.
Royal Aeronautical Society Journals are held by large technical libraries, particularly in the UK
or email J A C K @ J A C K P I KE . C O . U K

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Last modified: Dec 2013.