I have an air pressure switch fitted to both my aircraft. Idea that came from
the
old Gliding spares company who I can't remember their name Maybe RD?
Measures Pitot/static pressure and is set to 40 knots. It switches a miniature
Farnell hour meter (RS in the old Jab but I couldn't find one 3 years back).
About
50 all in.
Radio Spares part number 317-443 Calibrated by gently sucking 40 knots on the
static
line reading on the ASI with a meter across the switch.
I find this is very accurate as it measures hours with the engine under 'load',
the only thing I care about.
The difference in actual engine running hours and flying hours is about 12%,
that
is an average over 1100 hrs (last time I looked).
That is flying from my base where engine running apart from flying is purely to
warm the engine up and less than 50% of the time back tracking (prevailing SW)
a 500 metre runway..
I do of course 'get about' and at some places taxiing can be a long time but
maybe
good average to use..
Oil pressure switches or anything else are just a compromise for engine load
hours
but the good thing is they will usually make you over maintain.
There are gadgets on the TV screen things that maybe can do this for you but I'm
still steam driven as I built before the TV thingy's were reliable.
Just myho, Regards, Clive
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