Introduction
A synthetic vision system [SVS] is a means of increasing the situational awareness of pilots by creating an artificial representation of the terrain surrounding an aircraft on a display inside the cockpit. The eventual full development and widespread use of this technology will have a significant impact on reducing the number of controlled flight into terrain [CFIT] accidents such as the crashes of Air Inter Flight 148 and Crossair Flight 3597.
Operating principles
In order to produce an accurate representation of an aircraft's surroundings, SVS requires precise positional information, which is usually provided by GPS. This is then compared to an on-board terrain database to give pilots a clear view of the outside of their aircraft, no matter the weather conditions. The technology has been facilitated by the commonplace use of glass cockpit displays.
Current status
SVS technology is just beginning to enter use in some aircraft (Aircraft owners and pilots association, 20111; Helicopter association international, 20112), after having undergone trials including in a NASA Gulfstream GV business jet (NASA, 20043).
Use of SVS
Operational considerations relating to SVS are similar to those of most technological flight aids.
Advantages
Like GPS, TCAS, GPWS, and glass cockpits, SVS is designed to lower pilots' workloads, reduce errors, increase situational awareness, and make flying generally safer.
Increased situational awareness
The ability to clearly see the aircraft's environment in any weather conditions will undoubtedly improve situational awareness considerably.
Reduce workloads
The workload peak often experienced while on a difficult approach can be reduced by giving pilots an accurate visual reference point.
Mitigate errors
Errors such as flying approaches incorrectly will be able to be detected by pilots before the aircraft enters a dangerous situation.
Prevent controlled flight into terrain
The combination of the above three factors will help to reduce the occurrence of CFIT accidents, which will dramatically increase flight safety.
Improve efficiency
As well as the benefits from a reduction in accident rates, SVS may allow aircraft to operate in lower visibility conditions, which will increase the efficiency of aircraft operations.
Possible drawbacks
However, like GPS, TCAS, GPWS, and glass cockpits, SVS can also lead to problems very similar to those that can be encountered with the use of, particularly, glass cockpits.
Overuse
With the introduction of an artificial display of the aircraft's environment, the aircraft's actual environment (although so similar as to be practically identical) becomes less important and less used. In other words, the pilot spends too much time looking at the SVS display instead of out the window. While IFR flight does by its nature require most of the pilot's attention to be in the cockpit, there is still potential for overuse of SVS.
Overconfidence
SVS has the potential to significantly lower pilots' workloads in phases of flight where the aircraft is in close proximity to terrain. This could lead to pilots becoming overconfident about their ability to maintain situational awareness and fly the aircraft safely. Approaches could be flown almost literally as VFR even in zero visibility. As a result, pilots may be less careful with flight near terrain, and actually have less situational awareness as far as their location as measured by GPS and radio navaids is concerned.
Trust
While very accurate and reliable, any such system has the potential to provide erroneous data to the pilot. When SVS becomes commonplace in aircraft, such occasions will almost certainly be limited and insignificant, but the chance is always there. Pilots must still be ready to recognise if the system fails and take appropriate action.
Reliance
The combination of the above three points could lead to pilots relying on SVS to the point where they cannot fly the aircraft as well without the system. To be reliant on any flight system is not ideal and potentially dangerous. For example, a flight crew may become complacent on an approach by relying on SVS to determine their position. Should the system fail due to any number of problems including software faults, electrical faults, an avionics fire, GPS satellite malfunction, deliberate or accidental GPS jamming, or malfunction due to unlawful interference (bomb or missile strike), the pilots may not be able to respond to the problem effectively and in enough time to ensure the safety of the flight.
SVS in GA aircraft
The use of SVS in GA aircraft has many parallels to the introduction of glass cockpits in similar aircraft. SVS may reduce the frequency and effectiveness of lookouts, which could lead to an increase in mid-air collisions. The artificial environment it provides, while reducing pilot workload and situational awareness, could lead to pilots becoming overconfident about flying in bad weather, and could result in pilots taking risks they would not usually take.
Conclusion
Most technological advances have both advantages and disadvantages. For SVS to become an effective and widespread system, steps need to be taken to reduce and mitigate any drawbacks so that its advantages can help to increase to safety of aviation. If this is done, SVS could become one of the most important developments in the history of aviation.
