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Limiter History

The introduction of the limiter from 2008 was one of the most profound, interesting and controversial developments for F5B (and F5D). This section goes into more detail. It describes the hardware and software available, installation hints, testing results and operational results as they become available.

A bit of history. The limiter was proposed at the CIAM Technical Committee 5 meeting at the 2006 World Championship in Pitesti. To verify the possibility, and for fun, Mark Haig and George Shering decided to build one. Two different approaches were used. Mark built a simple limiter from scratch, doing all the hardware and software himself. This is shown below and was the first limiter to “limit” on the bench.

limit_1

George took a different approach. In flight loggers had appeared on the market. So it was decided to modify a BnB DPR-1 logger to add limiting capability. This resulted in the device shown below.

limit_2

The current capability was more than doubled by adding shunt wires, an input cable from the receiver was added, using a Medusa opto and a Kontronik filter toroid for good measure. The controller connection was taken from the modified white socket. The big problem with this approach was the software. Probably for good commercial reasons BnB would not provide a circuit diagram or the software, so it was necessary to reverse engineer the hardware and completely re-write the software, good fun!

Anyway this was all finished and the unit flown before the March 2007 committee meeting in Lausanne. This limiter retains the logging capability so it was possible to demonstrate the flight on the PC to the committee. They were convinced that the limiter was a viable option and it was adopted in the rules for 2008.

Just in time for the 2008 world championship commercial limiters became available. One like Mark’s designed from scratch by Steve Neu, and one like George’s made by modifying an already existing logger by Stefan Merz. He had an easier job, however, as he already knew the hardware and software.

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