Care and Feeding of the Database

Managing electronic updates of navigation and airport data


Modern FMS are capable of a large number of functions including basic en route navigation, complex departure and arrival navigation, fuel planning, and precise vertical navigation. Unlike stand-alone navigation systems, most FMS use several inputs. Typically, they formulate the aircraft’s current position using a combination of conventional DME signals, inertial navigation systems (INS), GPS receivers, or other RNAV devices. Like stand-alone navigation avionics, they rely heavily on airborne navigation databases to provide the information needed to perform their numerous functions.

The capabilities of airborne navigation databases depend largely on the way they are implemented by the avionics manufacturers. They will provide data covering a large variety of locations, routes, and airspace segments for use by many different types of RNAV equipment.

Databases can provide pilots with information regarding airports, air traffic control frequencies, runways, special use airspace, and much more. Without airborne navigation databases, RNAV would be extremely limited.

Electronic flight bag

The advent of the electronic flight bag (EFB) adds yet another twist to the complexity of avionics databases. The respective FMS and EFB databases remain independent of each other even though they share much of the same information.

For example, FMS and GPS databases both enable the retrieval of data for the onboard aircraft navigation system. Additional data types that are not in the FMS database are extracted for the EFB database, allowing replacement of traditional printed instrument charts for the pilot. The three EFB charting applications include terminal charts, en route moving map (EMM), and airport moving map (AMM).

The terminal charts EFB charting application utilizes the same information and layout as the printed chart counterpart. The EMM application uses the same ARINC 424 en route data that is extracted for an FMS database, but adds additional information associated with aeronautical charting needs and can even provide a means for overlaying digital weather on the charts, thereby enhancing the pilot’s awareness of the route of flight.

The EFB AMM database is a new high-resolution geo-spatial database only for EFB use. The AMM shows aircraft proximity relative to the airport environment. Runways depicted in the AMM correlate to the runway depictions in the FMS navigation database. The other information in the AMM such as ramps, aprons, taxiways, buildings, and hold-short lines are not included in traditional ARINC 424 databases.

Other data storage issues

Other systems on aircraft employ significant data storage systems. The Terrain Database provides the latest generation of landscape data for prevention of controlled flight into terrain (CFIT) and terrain avoidance warning systems (TAWS) to be used by pilots, dispatch, and other flight operations planners. In addition, cabin management systems (CMS) may include a moving map system complete with city names and topographical features including numerous zoom levels similar to Google Maps. Custom Component Concepts offers one such system incorporating updatable data bases with capacities in the terabyte range.

A common yet often overlooked component of a data storage system is an internal battery. Frequently the energy storage device is a common place commercially available unit and in some cases is an approved field replaceable unit. There should be a procedure published by the equipment manufacturer providing detailed step-by-step instructions to ensure success. In some cases improper battery replacement techniques can result in the loss of custom information.

As with most computerized systems, shutdown processes often take time above what may be needed to power down the aircraft. These internal batteries provide the “glass of warm milk” to assist the database in going to sleep. Sometimes the battery will expire without warning resulting in unexpected anomalies associated with the FMS operation. It is worth investigating if such a battery exists in each system operated along with anticipated life expectancy. If a defined replacement program does not currently exist a proactive approach can prevent an ugly situation during a launch.

Another concern is the storage capacity of legacy flight management systems and their ability to cope with all the additional information to support functions such as wide area augmentation systems (WAAS). There are currently 2,000 airports that have this capability and the list is growing. One question to ask an equipment manufacturer prior to initiating any kind of equipment upgrade would include memory capacity.

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