N1 gauge problem.

[flyby_heli]

Here is a question to all you guys.

We operate a 206.
Everything was working fine until yesterday, when one of the guys went to start it. The N1 gauge is not moving when you hit the starter, but you can tell everything is working by listening to the starter. When you light it off, the gauge jumps up when the speed hits 30% and works fine from there on up. Also when you shut off the engine, it spools down all the way like it should.

We checked the gauge at an avionocs shop, worked fine. We swapped the tach generator for a new one, and we checked all the wires in between for continuity. We also tapped the gauge to see if it was stuck.

Any ideas??

Flyby

[oldrotorhead]

Tell your pilot friend that he will learn a very expensive lesson real soon if he persists with the practice of lighting off an engine by using the "ear" method of determining N1 speed........stoopid procedure in my view!

[Arm out the window]

Might be worth swapping the gauge for another as well - when it was tested at the avionics place it might have been on its best behaviour and gone back to its old habits when back in the machine.

[paco]

If you insist on starting without an N1 gauge, when the blades start to move purely on airflow through the engine is around 15%, so let them move, wait a sec then open the throttle. Not recommended for long term use.

Phil

[long box]

Lots of 206's have sticky N1 guages, sadly years of pilots "tapping" the guage does not help, check the plug on the back of the tacho gene I have had it several times where the wires dont make too well but enough to work, by the time the engine is running up its enough to help the wires make contact, the guage will spool down correctly regardless of wiring or tacho gene hope it helps:ok:

[flyby_heli]

Thank you for all the tips.

We ended up pulling the gauge out again, and put new wires in the cannon-plugs on both ends. Then we hooked the gauge up directly to the tach generator, with new wires, to bypass the whole wire harness. Still no good. A new gauge is ordered!
It was working intermittent, one time it would work fine and the next it would act up again. Must be the gauge.

[chuckolamofola]

Check your ground, if too high resistance you'll loose one leg of the circuit. As the speed builds up the voltage will rise and thus overcome the resistance. Make sure the ground are clean at the engine and gage side, to include the shield ground. Changing just the connector won't fix this problem.

Regards,


Chuck

[Oracle]

Hi,
This problem is a classic impending failure of the Bell N1/Ng tacho internal instrument bearing. The guage should be changed out before you have to seek a new hot end - especially in your Baby Bell!

Cheers!

[flyby_heli]

Gauge changed this morning, works like a charm!!

Thanks for all the good tips!