Tachometer problems

Hi Jeffry,

1) My comments are not about variations in performance terminology (no idea where you got that from). They are about what should be the focus of the pilot/students attention - engine management/welfare first, prop a distant second. (Note: I am making a point, the PIC should be monitoring the entire aircrafts performance, not just two systems)

The USA Tecnam/Diamond POH you refer to, have been writen to satisfy a particular market (USA) To me this is an unfortunate accommodation that does nothing posative for the management of the Rotax engines. - In my view this is either actual or perceived "bullying" . In reality, the vendor must, if sales are required, attend to the whims of the (US) customer.

While it may not be within the power of the PIC to change the POH, that does not stop discussion on the matter. Tecnam/Diamond are no more infallible writers of documents, than any other individual/authority.

3) I mentioned constant speed/inflight adjustable props, to demonstrate the hierarchy of control - (1) power(engine) followed by (2) prop adjustment. Not to debate the pros/cons management needs of diffrent CS props.😈

So, I am right back where I was last week after changing the one P-lead wire and thought about changing out the Ignition Module.  That's where I am going to start on Monday when I can get right back at it!

I ran an external P-lead for the wire I hadn't replaced which I THOUGHT was the left switch because it was the switch that if I shut it off that would fix my tachometer readings after I changed what I thought was the right mag switch P-lead.   But the problem remained on the left switch which meant I had just disabled my original right mag switch, and I was holding a macgyvered external mag switch that incidentally took its place.   Problem remained then on the left switch which has that nice fresh wire.   I CHANGED THE WRONG WIRE!   That being said it worked quite well at any range ABOVE 1900 PRPM when not accelerating and was steady below 1400 PRPM

Absolutely stunned, I opted to install the right airframe mag switch P-lead to ignition module B and swapped the left airframe mag switch back to ignition module A.   

My problem is back on the right mag switch.   I KNOW prewire change it stayed on the right mag switch regardless of the module it was installed in meaning the issue has changed as before the only way to make it change which switch gave the error was swapping the connectors on the switches themselves.  The correct thing to do now is check either upstream or downstream of the ignition modules to determine if it is the modules or the coils now.

p.s. I also relocated the tachometer signal wire in the engine compartment as well to distance it from the ignition assembly and at this moment could hardly be further away, which in truth did I think help stabilize the readings to some extent but I also did that at the same time I goobered on another shielding ground for the remaining OG p-lead wire (the right one I guess) just for insurance