Many, if not most, competition pylon racing wings are now coming with, or have an optional Speedbar Trimmer Interconnect (STI) system. It is intended to put most speed control, including trimmers, in the speedbar. Basically, pressing the speedbar activates the speedsystem AND lets up the trimmers.
As this is a test question on the new PPG 3 exam, we wanted to provide some educational material on it for reference. Please do not copy or redisplay this illustration; it is provided here by permission.
It is a schematic to illustrate the basic concept of system operation. Since pressure is so much higher on the A’s, the default condition when armed is no speedbar, trims slow (or neutral depending on glider).
A failure of the interconnect line will let the wing go to the trimmer selected setting which would normally be fast if the system is in use.
In a front tuck situation the system would allow the trimmers to go full fast on the tucked side. This is clearly a design for experienced pilots who will react properly to dynamic situations with quick and appropriate responses. Even then, it is largely experimental (as are most pylon racing wings) and is not likely to be certified in any way.
As always, pilots should base their understanding on a careful reading of the wing’s Pilot Manual.
This is commonly called the PK System, named after its inventor Paap Kolar.
Speedbar Trimmer Interconnect System
