Differences Between the Cessna
Flap Indicator and the Visual Instruments Indicator
Cessna Flap Indicator Display
Cessna Flap transmitter (sender)
Visual
Instruments Indicator Display
Visual Instruments
Transmitter (sender)
The Visual Instruments Flap Position Indicator was developed because of frustrations and difficulties we had in maintaining the original flap indicators installed on older Cessna aircraft. This older style indicator system, evolved from adapted automobile fuel gauge technology used in the 1950’s and 1960’s. It has long been very problematic for many aircraft owners. Some owners simply fly with the indicator inoperative, rather than suffer from never ending repair costs. Here are some of the reasons these older style Cessna flap indicators fail, and the problems associated with them. We also explain how we have addressed each of these issues with the modern design of the Visual Instruments system
Electrolytic Corrosion
The Cessna system employed
a sending unit that was not hermetically sealed, causing the electrical wire
windings of the rheostat to become corroded. This happens especially fast if
you keep your aircraft in a wet climate. The corrosion is accelerated by
Electrolyses, as the windings are electrically energized whenever the master is
turned on.
The Visual Instruments Indicator employs a high quality
sealed potentiometer in its sender. The potentiometer is rated to 40,000
ft. It uses low-level electronic
signals to communicate with the display, so the higher currents employed by the
older style gauges are not necessary.
Transmitter coupling
The Cessna unit uses a thin wire rod to connect the sender transmitter to the flap pulley. This wire is easily bent and is difficult to adjust. It is the source of many reading errors.
The
Visual Instruments Indicator Design is quite clever. It uses a solid aluminum follower arm, which is connected to the
flap pulley. The arm is allowed to rotate on the shaft of the potentiometer
making the adjustment process simple. Three screws are tightened to secure the
position permanently.
Sinusoidal and low-resolution readings
The Cessna gauge is not linear. (The readings at ends of the scale are bunched up.) This is because the sender is connected to the rotating flap pulley, which moves in a sinusoidal motion.
The Visual Instruments Indicator corrects for
this error in its electronic circuits. Flap position is displayed on a linear bar graph. The Display has a much
higher resolution (5-degrees) for each bar as opposed to 10-degree markings on
the Cessna indicator. It is very
similar to the way commercial jets display their flap position on their Glass
Cockpit Displays.
Difficulty in reading the indicator, especially at
night
On
many model Cessna’s the flap indicator is located way off on the right side of
the instrument panel. This creates parallax errors and difficulties reading the
indicator. At night, the gauge is not internally lit, making readings even more
difficult.
Because of its LED display, the Visual
Instruments Indicator is not subject to parallax errors. It has an incredibly
wide viewing angle so the pilot will have no trouble reading it in the daylight
or at night. Its color-coded display makes it easy to identify the 10-degree
position for an emergency go-around procedure. The Indicator is equipped with
an internal light sensor that adjusts the display to the proper brightness
automatically.
Frequently
asked Questions about the Visual Instruments Flap Indicator “Click here”
