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[IslandTractor]

can you refresh my memory on the different tach/clock times? I do remember reading something about this before. It does seem like my hours are flying by.

I think he was referring to the fact that engine hour measurement is based on assumed running for an hour at full PTO speed. Many tasks are done at lower RPM so technically the engine has been running for more hours than the hour meter documents.

I don't think it is a big deal and don't bother to make corrections as the factory recommended service intervals are very conservative. No big deal to change oil at 60 or 70 or even 100 real world operating hours instead of at 50 hrs at PTO speed.

The 50 meter hour figure correlates to total number of engine revolutions rather than real world operating time. Imagine a car that goes 60 mph for 50 hrs, that means changing oil every 3000 miles. Most every auto company today recommends 5000 miles between oil changes and even longer when using synthetic oil as many folks do. Going over the 50hr at full PTO speed is therefore not likely to cause any problem at all and certainly running at less than full PTO speed for an equivalent number of engine revolutions won't. Just check the oil every ten hours or so and change when convenient after the hour meter hits 50.

 

[ksbrdmkr]

An engine tach records time equal to a clock only when running at a certain rpm while clock time is recorded as straight clock time. On the engine tach when running at a low rpm it may take up to twice as long to record a hour.

 

[taw1126]

On the engine tach when running at a low rpm it may take up to twice as long to record a hour.

This is my "learn something new" for today. I thought the meter was simply tracking clock hours regardless of speed. Is the tracking proportionate...like 2 hours operating at half of rated rpm = 1 hour on the meter? Or it tracks every hour over some threshold rpm?

 

[ksbrdmkr]

It is my understanding that the DK 45SE changed from using a "tack" time recording to a straight clock time "hobbs" time. On some light aircraft one has to record both times, the "tachometer" time for the aircraft maintenance and the "hobbs" time for rental charges. The tachometer is based on the engine rpm.