"Doug" wrote in message
om...
There is a way to tell if your tach is off. Move the plane so a street
light is shining on it from behind you. Run it up. A two blade prop
should appear to stop at 1800 rpm, a three blade at 1200 and 2400.
This is due to the strobe effect (the light blinks on and off).

Not outside the US...

Paul (running at 50Hz)