Just what information is needed to fly an aircraft in the information age? It seems modernization of avionics systems continually delivers copious amounts of data to the flight crew. But how do these systems know what they know and how do they get current data? They are of course programmed to know. Airport and navigation data periodically changes which, in the past, required pilots to pay regular visits to their local pilot supply store and purchase up-to-date charts.
In 1973, National Airlines installed the Collins ANS-70 and AINS-70 Area Navigation (RNAV) systems in its DC-10 fleet marking the first commercial use of a required navigation database. Nowadays commonplace, portable GPS units have more memory and computing power than those early systems.
The criteria for the navigation database is defined by the ARINC 424 enabling industry standardization.
The means of obtaining current information has also changed drastically. Instead of a trip to the pilot store, the update now most frequently requires receiving electronic media either from a trip to the Internet or obtaining a package through the mail. Floppy discs are still employed for this process by some avionics manufacturers and more recent systems use means that will load a bit faster with fewer challenges and include CD/DVD or USB portable storage devices.
Supplied by FAA, DOT, etc.
The majority of the official flight navigation data in the United States is supplied by the Federal Aviation Administration and supplemented by various civil aviation authorities as well as the Department of Defense (DOD). Outside the United States this information comes from various sovereign states and is collected in an aeronautical information publication (AIP). Distribution to aircraft operators includes service providers such as Jeppeson. Once the distributor has the information, it will be applied to various media devices required by their customers to facilitate loading in specific avionics platforms.
The database update occurs at a 21-day cycle. The edited content is sent to the avionics manufacturer or prepared with the avionics-packing program. Data not coded by the 21st day will be contained in the database for the next date cycle. In order for the information to be in the database at this 21st day the actual cutoff is more like 28 days.
Who is responsible for loading data?
So just who can legally load navigation database revisions? In the United States the FAA considers this action to be preventative maintenance and thereby allows a properly trained and qualified pilot to accomplish the procedure. This method is not categorically implemented industrywide. In some operations, qualified maintenance technicians will install, test, and sign off the update in the appropriate maintenance record.
Pilot authorization for loading databases is found in Federal Aviation Regulation (FAR) Part 91 Appendix “A” and reads as follows: “Updating self-contained, front instrument panel-mounted air traffic control (ATC) navigational software databases (excluding those of automatic flight control systems, transponders, and microwave frequency distance measuring equipment (DME)) provided no disassembly of the unit is required and pertinent instructions are provided. Prior to the unit’s intended use, an operational check must be performed in accordance with applicable sections of Part 91 of this chapter.
Types of RNAV systems
There are many different types of RNAV systems certified for instrument flight rules (IFR). The two common ones include global positioning systems (GPS) and multi-sensor flight management systems (FMS).
Most GPS operate as stand-alone RNAV systems. A modern GPS unit accurately provides the pilot with the aircraft’s present position; however, it must use an airborne navigation database to determine its direction or distance from another location unless a latitude and longitude for that location is manually entered. The database provides the GPS with position information for navigation fixes so it may perform the required calculations to determine the appropriate tracks, headings, and distances to be flown.
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.
This by no means implies that older equipment may be loosing memory function.
I have been told more than once, memory function diminishes with age and the older you get the longer it takes to complete the thought process. In my view the memory/mind is like a closet. The more that’s packed into it the longer it takes to locate something. AMT
Jim Sparks has been in aviation for 30 years and is a licensed A&P. He is the manager of aviation maintenance for a private company with a fleet including light single engine aircraft, helicopters, and several types of business jets. He can be reached at email@example.com.