|
The tachometer plays a very important role in
ensuring proper engine cooling and performance. An engine allowed
to over rev will result in a lean fuel mixture and can will
overheat, resulting in an engine failure due to seizure.
If the
engine is not allowed to rev up to its proper RPM this can cause
engine overheating, or engine failure, due to the engine not being
able to burn the fuel the way it was designed to.
A pilot taking
off on an engine that can only develop 5900 RPM can attest to the
fact that his engine will loose power and eventually quit. So what
role does the tachometer play in all this?
The
tachometer is used to properly pitch the propeller. A properly
pitched prop means the engine will have the correct load. If everything else is
in the system is correct,
the engine will then provide the best climb, cruise, engine performance
and reliability.
To achieve this you most
know what RPM your engine was designed to do in straight and level
flight under full power application. Since you can't do this
safely in the air, you must do it on the ground, with the craft
tied down.
A problem we have is since
a craft moving through the air is provide clean air entering the
prop at whatever speed you are doing, and a plane tied down has to
pull the air into itself, you must allow for this when
setting the propeller.
Example:
A 503 and or 582 Rotax twin carbed two stroke engine
should rev up to 6500 RPM in straight and level flight under full
power. Experience has shown that this can be achieved if the craft
is tied to the ground and the prop is set so that under full power
the engine can only pull about 6200 to 6300 RPM.
This should give
you 6500 in the air. Since all Rotax engines are supplied with a
break in procedure and it is required that it be done before the
engine is put into service, the first time you will use your
tachometer is to set the pitch on your prop for the break in.
An
engine that is allowed to pull 7200 RPM tied down on the ground is
not likely to make it through the whole break in procedure,
without seizing up!
Just as an engine that is set for 5500 RPM will start to loose
power and RPM after about 10 minutes.
For tachometer pricing click here.
|
