Collision Avoidance Learned
Because you are inside a cockpit there are a number of inherent factors that will make it harder for you to see another airplane. Pilot fatigue, anoxia, a dirty windshield, cabin design, time of day, age, stress, temperature, illusions, window distortion, or distraction can make it more difficult for you, the pilot, to see another aircraft.
77% of mid airs occur between overtaking aircraft from tail or side. You will most likely never see the aircraft you hit or that hits you. Collisions are frequently caused by failure to follow ATC avoidance instructions. The charts tend to emphasize the element of high speed closure rates as being the hazard. This is not so, since only 5% of the mid airs are even partially nose to nose. The closure rate between a vast majority of midair accident aircraft is a speed less that the cruise speed of either aircraft. As you might expect the faster aircraft overtakes the slower. Knowing the facts can protect you. 50% of all mid-airs occur at less than 500' AGL. Another short 25% happen above 3000'. 92% happen in good VFR.
If you should have a view of the aircraft that you are going to hit, it will creep slowly into view and will not appear to move on the windshield. It is this lack of movement that makes the aircraft so hard to see. There is a lag time of over six seconds between looking, seeing and recognition of another aircraft as a problem. An additional six seconds is required to put an reaction into effect. At a 90-knot closure rate from a half-mile you will have less that eight seconds to avoid the collision. Not enough time. You must see the plane further away if you want a survival chance. You are unlikely to see a plane beyond a mile that is not moving on your windshield. In the final moments the other aircraft will blossom to fill the entire window. You are out of time.
The narrowness of our focused field of vision, only 10%, is a primary limiting factor in our ability to see an airplane. If you have not had an opportunity to focus your eyes to distance in the past 30 seconds your focal distance may be less than 50'. A window post that blocks from seeing with one eyes inhibits your vision.
You do have some options. You can deliberately avoid common altitudes. You can vary your aircraft course, attitude, and altitude. You can make a deliberate effort to move the head forward and back. You can know where to expect and look for other planes. You can do much of the work of the cockpit like copying the ATIS, looking at the charts by doing the copying and looking up near the windshield so that you can split your visual field. Under no conditions should you look down into your lap in a known traffic avoidance situation.. Even three seconds of instrument scan should be a maximum. Use your lights.
Additionally, avoid those areas, routes, and altitudes that are known to be frequented by other aircraft. Know that you have the total responsibility to see and avoid other aircraft. If you acknowledge an aircraft in sight that has been pointed out by ATC, you are responsible from that point forward unless you advise ATC that you have lost contact. Initiate your avoidance procedure immediately, don't delay. Use a deliberate scan pattern in 15° segments of the windshield.
If you must react, it is important that you pre-decide what you are going to do. For example, turning tends to expose more of your aircraft to the other aircraft and the bank increases the G-load on the aircraft. My personal choice is to climb since this is the best reaction with birds who fold their wings and dive. As a reaction to aircraft the dive/ climb/choice might be best weighted as to which mode
gives you the strongest G-load margin. Higher positive G-loads exist over negative G-loads in aircraft construction and that would mean that diving would be best.
Responsibility for traffic avoidance under VFR rests solely on the pilot. ATC may or may not provide warnings. Once you acknowledge having seen traffic to ATC the full responsibility rests with you. Keep this traffic in sight. If you lose sight of acknowledged traffic, advise ATC. When using radar advisories, the tendency to relax vigilance, don't. ATC is not responsible for your collision avoidance except when IFR and then only from IFR traffic. This includes airport traffic patterns without radar, as well. Don't trust ATC to have cleared the direction of a commanded turn, takeoff or anything else. Clear areas for your safety. A clearance lets you do something when YOU think it is safe.
Only the exceptional pilot can visually locate and identify a traffic conflict from two miles. You are more likely to locate that traffic if you are so familiar with the area that the direction of where to look is known from a given pilot or ATC reference point. If you are unable to locate a pointed out aircraft at one mile the problem may relate to difficulty deciding where to look for eleven o'clock, an ATC point-out error, or the relative course movement. Any one of the three could amount to a 30-degree; aggregate error. For this reason you must scan. You scan by moving your head, not your eyes. You cannot see when your eyes move.
For a period of years, midair collisions have averaged in the low twenties per year. Only half of these result in fatalities. Half of mid-airs occur below 500' and 1/3 in the traffic pattern. The causes of these are inherent in the visual limits of the cockpit, the limitations of the human eye, and a concentration of aircraft at airports and navigational facilities. Flight below 3000' has inherent dangers since most aircraft are below that altitude much of the time. You can't see faster aircraft coming into you from behind and above. Aircraft climbing into you from below are more likely to see you. Fly at altitudes other than even thousands or five-hundreds when you are below 3000' AGL. Use radar assistance whenever it is available.
See and avoid has psychological effects decreasing visual effectiveness. If we 'see' an aircraft called by ATC we tend to stop looking for other aircraft. Small traffic over two-miles out will not be seen. Large traffic can be seen out to seven miles. Outside of one mile a pilot is unlikely to spot an aircraft. Limited visibility really means limited ability to see.
Traffic is what you see, what you hear is advisory only. A relatively high proportion of aircraft are not where they say they are when communicating to ATC or otherwise. By knowing where you are at all times, you can avoid being part of the problem. Make your radio calls accurate as to position, altitude and intentions. Stating your intentions is not a clearance for you to stop looking. An altitude call is more likely to be accurate than a position call.
The closing rate of most mid-airs is relatively slow since it is most likely a faster aircraft merging from the rear 10-degees off center to either side. It takes a minimum of 10 seconds for you to spot, identify, react, and have the aircraft move. At any merging speed over 700 knots you will not have time to move. Any aircraft on a collision course within three miles may well be unavoidable. Any aircraft on a collision course will be on the horizon and appear motionless. Such an aircraft will 'blossom' in your window at the last moment. Banking for avoidance will be less effective than a dive or climb.
Avoidance Checklist
--Organize your cockpit
--Clean the windows
--Follow the altitude flight rules
--Avoid crowed areas like near VORs
--Use your lights and strobes
--Keep your altimeter setting current
--Keep your visual scan coupled to your brain
--Visual complacency is a killer
--85% of preventable flight accidents are caused by deficiencies of judgment or attitude
The way to use your eyes
The weak link in the see and avoid system is the eye. Dust, fatigue, feelings, illness, age, illusions, altitude, sun direction, glare, heat, lighting, and aircraft design affect vision. The eye has an accommodation function that enables it to change focus from far to near and back again. Even the best of eyes take one to two seconds to make this adjustment. If the weather or haze is significant the eyes may be unable to focus to a distance because there is nothing to see. You then have what is known as 'empty-field myopia'. If one eye sees something that the other eye cannot it gives a blurred or even rejected image to the brain. This happens when you have one eye dominant over the other. Movement is usually easily detected. While the eyes can get light from over 200° or arc, they can only focus on a 10-15-degree area. The eye can only focus while stopped. Move your eyes from side to side and you will only get a gray blur. Thus any scan must consist of a series of stops.
The system we practice is the one we will use. A good scan will make nine distinctive stops across the windshield with head turns to see to the rear at extreme left and right. Where you start is not as important as having a systematic method of looking. Drop the focus down and back up every third sweep to the flight panel and every fifth time to the engine/fuel panel. You must also move your head forward and back to see around the cabin posts and compass. No one scan works for everyone but the block scan that covers about nine sectors of the windshield is a good methodology. A fixation with a two-second stop is required to detect an existing target. You should devote 18 seconds to your external scan for every three seconds of cockpit scan. This means a 6 to l time difference, outside to inside.
Visual perception, as noted, is affected by many factors. An aircraft below you on final while you are on downwind may be lost in the mix of houses, trees and yards. Pilots tend to be optimistic and prone to overestimation of estimates of their visual abilities. Some people are entitled to this opinion however; Chuck Yeager was able to detect aircraft far sooner than other pilots of his
Scanning skill can reduce accidents that are expected by probability to happen every year. These thirty annual mid-air accidents can be reduced by seven or eight. We can learn to fly in those places and in such a way to bring about this reduction. Most midair collisions occur within five miles of an airport, below 3000' and in clear weather. Use standard 45-degree arrivals at uncontrolled airports. Learn to fly and practice where there are the fewest airplanes and the most space. As a student, do not stop clicking your eyeballs just because the instructor is aboard.
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