"Jay Honeck" wrote in message news:vfrFb.617298$Tr4.1604490@attbi_s03...
The hobbs seems like a perfect, simple
device.

True, except most aircraft (outside of trainers) don't seem to have them.
Mine doesn't, and never did.

My aircraft (Mooney) came from the factory with one. Some argue that
its actually the legal way to count 100 hour ADs (since the tach
doesn't give 1:1).

That, and you're stuck using the ridiculous (to me) "1.4 hours" nonsense.
Why don't we just use "1:24", like the rest of the civilized world?

Gee, I thought that was the best reason for the 1.4 hours math. Its
hard to add up a line of "1:03", "1:23", "1:55". Seems like "1,4" +
"1.6" +"1.6" is easier to add. I guess if you're using a computer it
doesn't make any difference.

When I get this new transponder, I'm going to try using its internal "flight
time" clock. If it's too much of a pain, I'll go back to the tach time x
1.3.

In my plane (constant speed prop) I find that the hobbs and the tach
are almost 1:1. I don't often do pattern work though. On a typical 4
hour flight the tach will be within .1 of the hobbs. I tend to run the
engine around 2400 RPM. I would think 1.3 would be very, very
generous. In the J-3, I just use my watch since I usually ran the
engine way below the 2200 RPM where it turned 1:1.

-Robert