With the remnants of 2004 fading into history, the dawn of 2005 brings with it a significant list of new challenges. Many of the rules and regulations that influence the worldwide aviation community have been modified, amended, or otherwise changed. These changes not only influence the in-flight operation of the aircraft but often impact maintenance practices. The first step in understanding the changes involves interpreting the acronyms: RNAV, PRNAV, BRNAV, ELT, TAWS, RVSM, and Mode S; why it sounds like some sort of exotic extraterrestrial language.
Even though some of the upcoming changes have come about in the European community they may require compliance from all aircraft planning to operate in this airspace. In some cases operation may be allowed without conformity but increased air traffic delays could be expected.
Precision radio navigation
Precision radio navigation (PRNAV) is one such rule. RNAV, a method of navigating that uses waypoints established by merging multiple radio navigation signals and basic radio navigation (BRNAV) methods, has been in use since the time when an aircraft could follow a radio signal. PRNAV will allow aircraft to operate on a more direct path from point of departure to destination rather than flying over classic ground-based navigation stations.
This action is intended to establish consistent or standardized aircraft operations in the various states making up the European community. And by combining the known accuracy of the navigation equipment with radar monitoring and air traffic surveillance, a higher level of safety can be achieved inspite of the fact the total number of aircraft using the airspace at a given time has increased. There are currently 39 countries comprising the European Civil Aviation Conference (ECAC) where the Required Navigation Performance (RNP) in terminal airspace is in place. The one significant variable here is the wide variety of aircraft types utilizing different methods and equipment to determine position and with the rule limitations are placed on the integrity of the equipment providing navigation data. To qualify, position information must be accurate within one nautical mile for at least 95 percent of the flight.
Types of equipment
High levels of accuracy can be achieved by using several different types and combinations of navigation equipment. Included in this list are global positioning systems (GPS), multiple distance measuring equipment (DME) systems and a combination of very high frequency omni directional range (VOR) and DME. Inertial reference systems (IRS) may also be used, providing the predicted level of accuracy without external updates was within the prescribed tolerance at the time of system certification.
A database including waypoints and obstacle clearance is an integral part of a modern aircraft navigation system. The integrity of this data base is critical to safe operation and will be under scrutiny and as a minimum the aircraft operator must put in place a means for validating the information accuracy. Many of these data bases are commercially available and distributed. Part of the plan is to approve the agencies that create and dispense the navigation information.
Basic RNAV (BRNAV) became mandatory in the ECAC in April 1998 and required an accuracy of five nautical miles, which again means the aircraft would have to remain within five nautical miles of its determined lateral track for at least 95 percent of the flight. This capability is described as RNP-5 compliant. Eventually the RNP plan is to have an accuracy of 0.3 and 0.1 nautical miles; however, no mandate is planned before the year 2010.
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