Light Aircraft Association

Hello

I have been working on my instrument panel and as such taken my panel out. To make that possible I had to disconnect the (mechanical) tachometer.

After putting everything back together I noticed an issue with the tachometer and that is that the hour meter on there seems to be registering around 1 hour for 10 minutes that the engine has been running e.g. the engine meter is running fast..

Although it still seems to be showing me to correct revs. I guess I can't be sure.

Its a mechanical tachometer that is connected to a 1200 CC Rectimo (VW Beetle) engine fitted in a Fournier RF-3.

Does anyone have any idea what this could be / experienced a similar issue?

Thanks!

Rogier

Hi Roger,

You have hit the 'average tacho' problem! Mechanical tachos are designed to log hours at an 'average' (cruise) rpm, which is usually about 2400 to tie in with Continental / Lycoming cruise rpm's. When used with a VW, the cruise rpm will be much higher, typically 2800 rpm, thus your tacho hours will be running fast. There is nothing you can do about it except to fit a Hobbs meter running from either the alternator if fitted, or a battery connected to the master or magneto switch if engine electrics are not available. There is no adjustment fitted to the mechanical tacho.

I take it the tacho is an 'AC' manufacture or similar? Hope this helps.

Robin Morton
LAA 000144