Tacho counter

[Dude~]

Does anyone know what drives the tacho counter on a PA28? Is it mechanical or electrical and thus does it stop if the master switch is off?

[tmmorris]

I'm not an engineer but...

To the best of my knowledge it's mechanical, connected by a cable like a car speedo cable. I.e. it's not dependent on electrical power. One failed on me once and the club said that it had come disconnected (and had done it before!)

That said, you don't exactly need it in an emergency - i.e. it's not as essential a bit of kit as some. You can just do it on the engine noise and performance (and throttle position) - I flew from Sibson to Oxford on that occasion, though the takeoff at Sibson was a little nerve-wracking wondering if it was developing full power without any way of checking...

Tim

[A and C]

Are you talking about the counter on the RPM gauge or a hobbs meter ?

[Dude~]

I am refering specifically to the numbers that count engine running time, inside the rpm dial. Not the hobbs, air switch etc.

Basically, what I'm getting at is this:
Does the tachometer reading show a true figure for engine life? Because if a pilot can prevent the tachometer from counting whilst the engine is running, then there is great scope for fraud on a maintenance level, and pilot level.

If it is a mechanical linkage, such as is found on many motorcycles (tachometer merely indicates rpm but doesn't count it) then the engine life can accuratly be determined via the tacho reading on the rpm dial.

[A and C]

The counter inside the tacho is part of the RPM indication system and could only be stopped by going inside the gauge and disconecting it.

If the taco stops indicating RPM then the counter will stop You could stop the tacho by disconecting the cable but you would be without RPM indication.

Fraud is not to much of a problem because there are usualy a number of logbooks filled in by diferent people and if a fraud is taking place then a quick look at the pilots logbook , the aircraft logbook ans airfield logs soon show this up.

The first place that fraud is usualy picked up is on the fuel log because fuel consumption is always a good indicator of flight time.

The CAA take a very dim view of this type of fraud and the last time they prosicuted someone ( cardiff based i think ) if I remember correctly the fines came to about £ 32,000 .

[Fujiflyer]

...and not to even mention the legal ramifications if there was an accident resulting from mechanical failure on an A/C which had exceeded its maintenance check.

I should think that if this activity was suspected it would be fairly easy to prove even if someone supplied fuel separately (ie paid for the fuel but not for the aircraft hire as a whole). I don't intend to go into any more detail on that though, here.

Rich

[Flyboy-F33]

What are the circumstances that prompted you to ask that question?

GG:hmm:

[IO540]

Presumably fraud could be detected because the larger fields keep records, and also many plane spotters operate websites that record registrations and arrival/departure times...

The only way to operate a plane "off the books" and be fairly sure to get away with it would be to only fly solo, and only between private sites. This probably happens with helicopters rather more...