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GPS Problem Areas
From SKYbrary Wiki
GPS equipment and its installation vary considerably.
- Most equipment designed for use in commercial aircraft is permanently installed in tested and approved locations with appropriate power supplies, and, crucially, is fully integrated with other flight systems.
- Some equipment, especially that used by general aviation, is portable with battery power and lightweight antenna design. Such equipment may create problems in use rather than aid safe navigation when used by pilots who do not fully understand its limitations and its capabilities.
At present, there is little formal guidance or training in the use of stand-alone GPS in General Aviation. This presents a serious problem for GA pilots who are often unaware how to properly use GPS as a supplementary VFR navigation aid. GPS equipment instruction manuals are often found to be complex and difficult to understand for some of those who acquire or plan to use such equipment; many pilots require assistance in applying the capabilities of the GPS to safe navigation.
To address these problems, some flying clubs organise sessions where experienced GPS users demonstrate and discuss the use of their systems, however, that merely guarantees that the 'instructor' knows more than the 'student' and may not necessarily ensure that the right ideas are being spread.
Challenges to successful use of GPS
The following paragraphs highlight particular technical problem areas in the use of GPS.
- Equipment Installation. Battery failure, unintentional aerial disconnection and poor internal aerial reception may be the causes of poor reliability and performance;
- These difficulties are absent when the equipment is correctly installed.
- Data Programming. GPS relies on correct data input, with effective cross checking against a map position to verify accuracy;
- Use of the “GO TO” Function. Following a deviation from track, care must be taken in using the “go to” function to ensure that the new track does not infringe controlled airspace.
- Poor Database Accuracy. Poor database accuracy may be due to incorrect depiction, the absence of some controlled airspace boundaries, or out-of-date information. American databases do not always cater for every European airspace category;
- Controlled airspace characteristics change from time to time; it is therefore essential that pilots maintain database currency by purchasing updates from the manufacturer. If hiring an aircraft, the GPS should be checked to ensure that it has the latest database up-date.
- Lookout. Re-routing usually necessitates re-programming of the GPS. This may require considerable time spent with “heads in cockpit”;
- Pilots must ensure that look-out is not compromised while programming GPS.
- Excessive reliance on GPS. Large navigational errors can arise where GPS is used as the sole navigation aid;
- Pressing on in Bad Weather. Because of the known accuracy of GPS, there is a tendency for pilots to “press on” in adverse weather, where previously, with map reading as their main source of navigation, they would have turned back or diverted. Some pilots also plan to fly very close to controlled airspace boundaries in the belief that GPS will deliver exceptional accuracy;
- Experience and reported incidents have verified the danger of these assumptions.
Airspace Infringement Safety Letters:
EUROCONTROL Airspace Infringement Initiative:
- European Action Plan for Airspace Infringement Risk Reduction;
- Airspace Infringement Initiative website;
EUROCONTROL Guidance Notes for GA pilots
- Rules for VFR flight;
- Flight preparation;
- Getting aeronautical information before flight;
- Reading and understanding NOTAMS;
- Getting meteorological information before flight;
- Reading and understanding weather reports and forecasts;
- Using meteorological information for planning;
- Visual navigation;
- VOR/DME/ADF Navigation;
- GPS Navigation;
- Getting aeronautical and meteorological information in flight;
- Entering controlled airspace;
- Getting the most out of your transponder;