Rotor Tach Switch
Rotor Tach Switch
This is a microswitch mounted at the rotor brake arm on the head, that shorts out the Rotor Tach signal when the rotor brake is on. This is to help assure you don't go flying with the rotor brake on. When prerotating, you are first watching for 100 RRPM to let you know you can pull the stick full aft getting ready for takeoff roll. The next RRPM we use is 220 RPM - ready for full throttle, stick back takeoff.
So, if you are watching for these RRPMs and the rotor tach just shows 001, you know something is wrong. It normally takes about 1/2 nanosecond to realaize you still have left the rotor brake on.
This is my own design. The Magni normally comes with a switch on the rotor brake lever at the front seat - which lights a red light on the dash to let you know the rotor brake lever is on. This works also, but the red light is sometimes hard to see in the bright sunlight. And, myself and some others have accidentlally flown with the rotor brake activated. (This does not endanger flight, but it turns the paint on the rotor head drum a bit brown. Do much flying with the rotor brake on - over about 2 hours total, can ruin the brake pads and require replacement.)
The normally closed contacts on the micro switch are connected across the rotor tach pins. To do this, we remove the pins from the RT connector and solder in a short 1/8 phono connector to plug the microswitch in. See pics.
You don't need any of these if you religiously make sure the rotor brake is off when you start to prerotatoe - checklists please!
See pictures to see the microswitch installation at the rotor head.
- Greg