HFS
Well Known Member
In the old days, before the advent of all of the electronic information gathering devices we have today, we relied on mechanical "trickery" to help slow down the hands of time. Most of us used the rise of oil pressure on startup to start the Hobbs - nothing new there.
But, on the mechanical tach/hour meter side, you could get tachs that logged hours at two different rates. For a fixed pitch propeller, 2500 rpm was considered the norm for cruise; and, for a CS propelle,r 2300 rpm was the accepted standard.
Now, if you wanted to "fudge" a little bit on the rate at which your tach hours were logged; and, ran your engine at a lower rpm in cruise, you got the benefit of slower hours logged - not much, but some.
On my (ancient) Rocket I have the 2500 rpm tach/hour meter, but only run the engine in cruise at 2200 - effectively slowing down the accumulation of hours by about 12%. Sleight of hand, maybe, but - oh well.
YMMV - and I am sure it does.
I see Mitchell still makes mechanical tachs that actually go up to 3000 rpm cruise - even more deception!
HFS
HR II S/N 002
But, on the mechanical tach/hour meter side, you could get tachs that logged hours at two different rates. For a fixed pitch propeller, 2500 rpm was considered the norm for cruise; and, for a CS propelle,r 2300 rpm was the accepted standard.
Now, if you wanted to "fudge" a little bit on the rate at which your tach hours were logged; and, ran your engine at a lower rpm in cruise, you got the benefit of slower hours logged - not much, but some.
On my (ancient) Rocket I have the 2500 rpm tach/hour meter, but only run the engine in cruise at 2200 - effectively slowing down the accumulation of hours by about 12%. Sleight of hand, maybe, but - oh well.
YMMV - and I am sure it does.
I see Mitchell still makes mechanical tachs that actually go up to 3000 rpm cruise - even more deception!
HFS
HR II S/N 002
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