MCD-100 PAGE

MCD-100   DESCRIPTION

The MCD-100 is a light-weight, solid-state instrument that provides a digital display of the altitude information generated by an encoding altimeter or electronic "blind" altitude encoder to a transponder.  The MCD-100 monitors the altitude data lines between the encoder and transponder, decodes the altitude with a microprocessor, and displays it on a large bright LED display.  This allows the pilot to see the altitude that is transmitted to ATC at all times.  The MCD-100's microprocessor also can calculate and display a "corrected" altitude based on the local barometer setting.  This is similar to the calculation done by the ATC facility.  The barometer setting can be adjusted to a known local barometer value or calculated by entering a known altitude such as the field altitude during run-up.

Like the MCE-100 Altimeter, a useful feature of the MCD-100 is its Altitude Alert function.  While flying at a desired cruising altitude, simply activate the Altitude Alert function and the MCD-100 will notify the pilot with a flashing display when the set altitude varies more than + / - 200 feet.

Like all Adaptive Interfaces instruments, the MCD-100 has a built-in white LED backlight for low-light and nighttime operation.  The digital display also has a special, polarizing filter for much improved readabilty in bright sunlight.

WHY AN MCD-100

Besides providing a way to confirm the correct operation of an aircraft's altitude encoder, the MCD-100 provides a great, easy to read secondary altimeter.  A digital altitude is so much easier to interpret that you may find yourself referring to this display more often than to the old mechanical altimeter.  Knowing in advance when the controller asks you to 'say altitude' that your altimeter and blind encoder are providing the same information will give you much more peace-of-mind when you respond with your altitude.  Also, the built-in Altitude Alert function makes it easy to avoid venturing away from your assigned altitude or up into Class B airspace while navigating around busy airspace.

MCD-100   TECHNICAL DESCRIPTION

The MCD-100 is a solid state instrument that monitors the standard (SIF/ATCRB) parallel digital lines that provide altitude infomation between an aircraft's altitude encoder and its transponder.  This is done by attaching a "Y" cable between the encoder and the transponder and routing the signals to the MCD-100.  The inputs to the MCD-100 have a very high electrical impedance (>30k ohms) that minimizes electrical loading and any possible interference with the signals.

For altitudes below 62700 feet, altitude is encoded in 100 foot increments on 10 digital signal lines using a Gillham or "Gray" code.  The 10 signal lines are sampled by a microcomputer, decoded using software, and presented as an altitude on a 5-digit LED display.  The altitude displayed on the MCD-100 is limited to 32000 feet.  Mode C altitude information is always based on a standard pressure of 29.92 inches of mercury, not the actual local air pressure.  Local air pressure can be entered by buttons on the front panel as a barometer value or by entering known current altitude.  A logarithmic and exponential formula is then used by the microcomputer to calculate a "corrected" altitude that better represents the actual altitude of the aircraft.  A function button on the MCD-100 allows display of either the Mode C altitude or the "corrected" altitude.

The MCD-100 is has an aluminum case and fits a standard 2-1/4 inch round panel cut-out.  The MCD-100 is controlled by a set of 4 buttons on the front panel and by a set of menus and functions.

MCD-100   SPECIFICATIONS