Harmon Technologies, Inc.

Airspeed Indicator

The Airspeed indicator measures how fast the airplane is moving through the air.  The picture above is similar to the one in N4907J but is from a slightly slower type of airplane.  On N4907J it is calibrated in miles per hour (MPH) although it has a second scale calibrated in knots as well.  The indicator works by comparing ram air pressure with regular outside pressure.  Although this method sounds rudimentary, modern airliners use the same technique.  This speed is different from how fast the airplane moves over the ground because there might be a tail wind or headwind.

The airspeed indicator has colored bands indicating important speed ranges for the airplane.  The white band indicates the permissible operating range with full flaps. This is slower than the normal operating range and is normally used for approaches and landings (and sometimes takeoffs).  The green band is called the normal operating range and is normally used with flaps up (these ranges overlap quite a bit).  The yellow band is not really a warning band but is only to be used in relatively smooth air.  Most airplanes cruise near the top of the green band.  This is normal.  The lower portion of the yellow range is used for descents unless turbulence is present so seeing the needle flick into the yellow range should not be a cause for concern.  At the top is a red line that represents the maximum speed that should ever be used.

We normally take off at around 65 t 70 MPH, approach to land around 90 MPH and touch down at around 60.  The speeds during operations near the ground are similar to automobile highway speeds.

The airplane climbs at around 100 to 110 MPH and cruises at between 150 and 160 MPH depending on weather conditions and altitude.

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