By Bjorn Fehrm

August 05, 2016, ©. Leeham Co: Last week we described Synthetic Vision and discussed why it hasn’t got its breakthrough yet. If we would have taken things chronologically, we should have started with Enhanced Vision systems.

Once again Gulfstream Business jets was the first to introduce Enhanced Vision Systems (EVS) into service. In 2001 it was certified as an option to the Gulfstream’s flight deck, using an infrared camera to generate a picture of what happens in front of the aircraft when visibility is bad, Figure 1.

Figure 1. Gulfstream Business Jet with Enhanced Vision IR camera. Source: Gulfstream.

Enhanced Vision

Enhanced Vision is today available for high end Business Jet aircraft and FedEx installed it on their DC-10/MD-11 fleet. The reason it found wider acceptance than Synthetic Vision is that FAA and other certifying authorities have credited the presence of the system with lower landing minima.

The typical minima for an ILS CAT 1 approach is a Decision Altitude of 200ft above the runway threshold, where the pilot can land if he has contact with the runway’s landing lights or he has to start a missed approach procedure.

The IR camera of an Enhanced Vision System makes the pilot able to see the landing lights in worse conditions, Figure 2, left picture. The right picture is what he sees with the naked eye.

Figure 2. Gulfstream’s Enhanced Vision System with (left) and without enhancement (right). Source: Gulfstream.

The pilot can then continue down to 100ft on the enhanced vision image in his Head Up Display. From 100ft, the pilot must have normal visual contact with the landing lights or he has to abort the approach.

Combined Vision System

I have got some feedback why the commercial airliner industry has not yet embraced Synthetic Vision. Different than an Enhanced Vision System, it has proved hard to get a decision height minima improvement for Synthetic Vision- assisted approaches.

The requirements on the system’s dependability gets very high (different to a situational awareness implementation) and it requires training of the pilots in the use of such a system. The airlines hesitate to foot the bill for such training without a clear operational benefit.

The business jet industry, which is leading the implementation of Enhanced and Synthetic Vision systems, now leans toward combining the two techniques into a Combined Vision Systems. The two images would be blended in on both the head down and head up display with slightly different purposes, Figure 5.

Figure 3. Synthetic Vision landscape layered on HUD ILS approach symbology. Source: Rockwell Collins.

Such a system would use Synthetic Vision to give the pilot superior situational awareness down to the ILS/LPV decision altitude, Figure 5, and then use the Enhanced Vision to lower the decision altitude threshold in bad visibility.

Combined Vision will find its way into Business Jets more and more. General Aviation will see Synthetic Vision come first as it’s a lower cost implementation, the IR camera of Enhanced Vision is of the cooled type and therefore expensive. When a new generation of pilots have grown up with Synthetic Vision the pressure on Commercial Aviation will be such that the one or the other system will be inevitable.