How do you check a Tech to see if it is right

Hey guys looking to check and see if my tech is right in my plane. Any one know easy way to do this ???? I do not think it is right

Hello OldFox

I borrowed one of those "lazer type hand held tachometers" and put a mark on the spinner. I had to stand fairly close. Be sure your a/c is well secured!

Don

There are several easy ways to check a tachometer that do not endanger you during the test.
You can check your aircraft tachometer with a digital unit available at hobby shops for model airplanes. Most of them sell for about $25. Although the instructions are for a model airplane they work well with full size aircraft. You don’t need to hold the tach within 12 inches as directed. Simply aim the sensor at the prop from the safety of the cockpit with the sun in front of the aircraft. The model tach will measure the flickering prop speed. With a known prop speed you multiply the rpm with your prop speed reduction unit ratio, if installed on your motor.


Thus if the prop is measuring 2000 rpm and you have a gearbox ratio of 2.43 your engine is turning 4860 rpm.



The other method is to check your aircraft tach at night using the 60 hertz flicker of lighting on the ramp. Just position the aircraft so you see fluorescent or mercury vapor lighting through the prop arc. If you have a 2 blade prop the shadow will appear to stop at 1800 rpm. A three blade prop will appear stationary at 1200 rpm.


Adding your correction factor for a two blade prop at 1800 rpm with a 2.43 gearbox would have an engine rpm of 4374 rpm.


A three blade prop at 1200 rpm with a 2.43 gearbox would have an engine rpm of 2916 rpm.


Either method is easy, safe and cheap.

JP

Excellent tips John.

Thanks guys for all the help !!!! this place is great :):) Chris