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.
Price of Cessna factory replacement system as compared
to Visual Instruments Flap Position Indicator System?
Cessna’s
flap position indicator systems were made by Stewart-Warner until this company
went out of business several decades ago. Since then these systems have been
made by Rochester Instrument Co. THE ORIGINAL GAUGES AND SENDER UNITS MADE BY
STEWART-WARNER ARE NOT COMPATIBLE WITH THE ROCHESTER GAUGES AND SENDER UNITS.
THUS, IF YOU OWN A STEWART WARNER COMPONENT AND IT GOES OUT, YOU THEN HAVE TO
PURCHASE BOTH THE FLAP INDICTAOR DISPLAY GUAGE AND THE SENDING UNIT AT A SALES
PRICE FROM CESSNA OF APPROXIMATELY $1,100.00 .
The good news is that you can purchase the
Visual Instruments Flap Position Indicator System for less than HALF of the factory
replacement system, it will have a 3-year warranty (much longer than Cessna’s
warranty), our system is much more modern with an LED light bar graph &
self-dimming capabilities. The price for our system is only $495.00 plus
shipping & handling!
Frequently asked Questions about the Visual Instruments Flap
Indicator “Click here”
