SAFA Skysailor Magazine

28 SKY SAILOR July | August 2020 I n Australia (and typically around the world) there are two sets of rules one can fly by: VFR and IFR. IFR (Instrument Flight Rules) is where an aircraft can take off in fog, climb in controlled airspace to a pre-planned flight level then descend to the airport approach corridor and finally land – all this happens within controlled airspace, with air traffic control providing clearance for the aircraft to proceed into each sector of flight. The clearance enables separa- tion for aircraft to ensure there’s no conflict, that is, no two aircraft can occupy the same bit of airspace at the same time. The pilot might not need to look out the front window until late final to confirm the runway is actually where he expects it to be. VFR (Visual Flight Rules) on the other hand is where a pilot flies an aircraft utilising visual refer- ences. In order to make this happen, a few require- ments must be met. The flight must stay within Visual Meteorological Conditions (VMC). Pilots, if flying and navigating with visual references, need to fly in conditions that allow the pilot to see those references. Bad things happen when you try and fly a plane using VFR in non-VMC conditions. When it comes to separation of aircraft, Air Traffic Control do not provide separation between aircraft flying under VFR rules in the type of airspace in which we operate. It’s up to the pilots involved to See-and-Avoid other aircraft using the right of way rules you would have covered during your training. See-and-Avoid has been the mainstay of pilots flying VFR aircraft. See and Avoid is how pilots maintain separation from other aircraft and avoid collisions. See-and-Avoid has worked for many years relying on the fact that it’s a ‘big sky’ with plenty of room for aircraft to fly wherever they want. However, there are a number of factors that make See-and-Avoid flying less than ideal. Airports, particularly aerodromes without air traffic control, tend to concentrate large numbers of aircraft into a smaller area with a potential cause of conflicting flight paths. Using GPS tends to have pilots fly accurate flight paths, point to point, causing a potential for conflict along these routes. Quadrantal flying levels are not manda- tory below 5000ft (although they are encouraged), meaning that it is possible to encounter an aircraft on a reciprocal heading at the same altitude you are flying. The visual scanning technique that pilots use takes time and cannot cover all of the directions that a potential conflict can arise from, and detect- ing an aircraft on a collision course is difficult. If you are on a collision course with another aircraft, due to the speeds aircraft fly at, there is very little time to take evasive action. The truth is that See-and-Avoid doesn’t actu- ally work very well, particularly in crowded airspace where there is a higher possibility of collision. In 1991, the Australian Transport Safety Bureau (then the Bureau of Air Safety Investiga- tion) released a report called the ‘Limitations of the See-and-Avoid Principle’ [www.atsb.gov.au/ publications/1991/limit_see_avoid/] . It was a watershed moment – the primary system of visual navigation ‘See-and-Avoid’ was shown to be inad- equate for most of the general aviation flying that was happening. Originally, See-and-Avoid was a maritime concept developed for slow moving ships, but the modern aircraft cockpit workload reduces the time a pilot can devote to looking outside the cockpit. It’s estimated that VFR private pilots spend about 50% of their time on outside traffic scan while airline pilots spend 20%. Factors Field of vision The average person has a field of vision of around 190 degrees. The field of vision begins to contract after about age 35 and is reduced markedly after 55 years of age. The quality of vision varies across the field, with sharp vision occurring in the centre of the eyeball’s field of vision and lessening at the periphery. Therefore, a pilot must look directly at or near the target to have a good chance of detecting it. Obstructions and field of view An enclosed aircraft cockpit can include many obstructions to a clear field of view, e.g. window posts, aircraft structure such as wings, and even passengers. In aircraft such as hang gliders, para- gliders and microlights, forward vision is quite good, but all of these aircraft have limited ability for the pilot to see up and to the rear. Glare Glare is unwanted light entering the eye. Al- though SAFA aircraft seldom have windscreens, windscreen glare is a problem for GA pilots. SAFA pilots can suffer from glare from dirty sunglasses, visors, or instrument reflections. When the glare source is five degrees from the line of sight, visual effectiveness is reduced by 84%. In general, older pilots are more sensitive to glare. Limitations of visual scan Just scanning the forward 180 degrees a pilot can see, the ability to do a proper scan of each 10 degree arc would take three seconds per arc at the very least, adding up to 54 seconds per scan. Pilots cannot maintain that level of scan while piloting the aircraft effectively. Threshold of acuity Most aircraft will be detected in the eye’s pe- ripheral vision, yet this is where visual acuity is poorest. Empty field myopia If you are performing a scan of open sky where there are no visual cues, your eyes will default to a focus of about 56cm, which means that any aircraft will appear to your eye first out of focus. Aircraft characteristics “In determining visibility, the colour of an aircraft is less important than the contrast with its Why use VHF? How VHF plays a role in Alerted See-and-Avoid. Peter Allen