Section 905
Digital RPM Indicator
Page Date: 20. April 2002 905 - 5
PilotĀ“s Operating Handbook
EXTRA 300S
magneto ignition system.
While performing a magneto check during engine run-up, the red alert indicator lights will
illuminate, thus identifying the grounding of the respective right or left magneto systems.
Tachometer Magneto
Ignition switch Right Left
Both OFF ON ON
Left ON, Right OFF OFF ON
Right ON, Left OFF ON OFF
Both ON OFF OFF
Between the left and right magneto ignition system alert indicators is a yellow RPM Syn-
chronization indicator. This small yellow indicator is illuminated when there is a difference
of more than 50 RPM between the right and left tachometers.
This indicator also may flicker during extreme RPM excursions of the engine.
OPERATION BUTTONS
There are three panel buttons. Each button has two modes of operation.
PRESS-AND-HOLD operation mode
(press and hold for more than 2/3 of a second)
This operation mode is placarded above each button. (Hours, Clear,Trap)
Engine time (Hours)
The left button, upon depression, will cause the tachometer to display the non-fractional
portion (0000.) of the current accumulated engine hours. When the button is released, the
fractional part of the engine hours (.00) is displayed for a short period of time. The clock is
started whenever the engine RPM exceeds 800 RPM and is recorded in real hours.
Clear (Clear)
The middle button clears the RPM trap. During depression of the switch, the RPM trap is
zeroed. When the button is released, the trap will record the current engine RPM.
Engine RPM (Trap)
The right button will cause the tachometer to display the current contents of the RPM trap.
This trap records the highest engine RPM achieved before the button was pressed.
PRESS-AND-RELEASE operation mode
(press and release in less than 2/3 of a second)
This operation mode is placarded below each button.( L , DIM , R )
Masks ( L , R )
During normal operation, the tachometer presents the average of the left and right internal
tachometers on the display. However, a mechanism exists to mask either tachometer from
the display, leaving the remaining tachometer to determine magneto/ignition problems.
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