Textron Aviation Cessna 172S NAV III Skyhawk SP, Information Manual

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CESSNA SECTION 7
MODEL 172S NAV III AIRPLANE AND SYSTEM DESCRIPTION
KAP 140 AUTOPILOT
U.S.
ENGINE
(Continued)
ENGINE INSTRUMENTS
(Continued)
RPM (TACHOMETER)
Engine speed (RPM) is shown by the tachometer indicator found on all
EIS pages. The tachometer indicator uses a circular scale with moving
pointer and a digital value. The pointer moves through a range from 0
to 3000 RPM. The numerical RPM value is displayed in increments of
10 RPM in white numerals below the pointer.
The normal engine speed operating limit (top of green arc) changes
with altitude. For standard-day conditions, between sea level and 5000
feet, 2500 RPM is the upper limit of the normal operating range. From
5000 feet to 10,000 feet, 2600 RPM is the top of the normal range. And
above 10,000 feet, 2700 RPM is the upper limit of the normal operating
range.
When engine speed is 2780 RPM or more, the pointer, digital value,
and label (RPM) turn red to show engine speed is more than the limit.
The digital value and label (RPM) will flash. The engine speed
(tachometer) is displayed in the same configuration and location on the
LEAN and SYSTEM pages. If engine speed becomes 2780 RPM or
more, while on the LEAN or SYSTEM page, the display will return to
the ENGINE page.
A speed sensor, mounted on the engine tachometer drive accessory
pad, provides a digital signal to the engine and airframe unit which
processes and outputs the RPM data to the EIS. A red X through the
RPM indicator shows the indicating system is inoperative.
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172SPHAUS-05 7-31
For
Training
Purposes
Only