THE DAY THE IMPOSSIBLE HAPPENED

Sunday 25th. November 2007 was one of the last good flying weekend days of the year. The sun shone through a cloudy sky and the wind was around 10 mph.

There were around eight of us at the flying field and our normal frequency control was in use. Peg on the board for 35 MHz. and name on the board for 2.4 GHz.

A young member, who had recently passed the Club flying test was getting help from a very experienced pilot and instructor, because he wanted to fly his newer model a Cougar. The radio was a Futaba 2.4GHz.

The instructor was flying the model when he experienced a great deal of what seemed like interference but he managed to put the model down in a partly controlled way. The ground contact was hard and the airframe was damaged.

After bringing the model back to the pits the radio was checked and worked correctly but then the control surfaces began to move when the transmitter was not operated.

The immediate conclusion was a transmitter to receiver linking failure. (binding for those used to Spektrum phraseology) However this was challenged because the equipment had been bought as a set and with this, according to the handbook, the linking was done by the manufacturer.

Then another member who was setting up his trainer in the pits complained that his control surfaces were moving abnormally. He was also using Futaba 2.4 GHz equipment bought as a set. Although he had previously checked and re-done the linking procedure at home.

Further checking and testing showed that we had the “impossible” situation.

Transmitter “A” would control receiver “A” and receiver “B”.

And even worse transmitter “B” would also control receiver “A” and receiver “B”.

Which ever transmitter was used the green light on either receiver was solid green.

This was more than a “linking” problem.

Each transmitter should have a unique identifying code to which the receiver links. More than one receiver can link to a transmitter. A receiver can be re-linked to another transmitter.

But according to the manufacturer it is impossible for a receiver to link to more than one transmitter at the same time. On Sunday 25th November we witnessed the impossible.

The equipment has been returned to the supplier and we are waiting for an explanation.

Until we know more I suggest that all 2.4 GHz equipment is checked with any other on site before flying.