When flying as an uncontrolled flight in visual meteorological conditions, pilots practice, "see-and-avoid" as a primary method of minimizing the risk of collision. "See-and-avoid" directly links with the pilot's skills of looking outside the flight deck/cockpit and becoming aware of his/her surrounding visual environment lithe pilot can acquire skills to compensate the limitations of the human eye, then the see-and-avoid practice can be greatly improved and effective in facilitating a safer flight environment altogether.
The skills that compensate for the limitations of the human eye are; application of effective visual scanning, development of 'good airmanship,' and the ability to selectively listen to radio transmissions from ground stations as well as other aircraft's, so as to be able to create a good mental picture of the traffic situation around.
No pilot is immune to collision, thus this circular is there to benefit and aid each pilot.
Mid-air collisions can occur in all phases of flight and at all altitudes. Nearly all mid-air collisions occur during day light hours and in excellent visual meteorological conditions. Most collisions occur near aerodromes and are caused mostly by aircraft's operating VFR and uncontrolled.
Collisions can involve even the most experienced pilot. A study that was carried out on over two hundred reports on mid-air collisions revealed that, pilots involved in collisions ranged in experience from those flying their first solo to pilots with over fifteen thousand flying hours of flight time.
There is no determining factor to reveal which pilot is more prone to mid-air collision. It could happen to any pilot whether a novice or experienced pilot. This is because you may have a case where a pilot with only a few flight hours (novice pilot) has so many tasks to perform in the cockpit and so much to think about for example all the checks he/she has to conduct, that adequate look out is forgotten altogether. On the other hand you may have a pilot with thousands of flying hours (experienced pilot) who is so used to routine flights where he/she has never experienced any hazards that they become complacent and forget to scan the environment around them looking for any hazards.
Learning to use your eyes and maintain vigilance through proper awareness, aids in the avoidance of mid-air collisions.
Causes of Mid-Air Collisions
Traffic congestion and aircraft speeds are part of the contributing factors to mid-air collisions. It takes a minimum of 10 seconds for a pilot to spot traffic, identify it, realize it's a collision threat, react and have the aircraft respond.
In some cases radar facilities and air traffic contra is overloaded and limited.
Apart from the above paragraphs, the reason most often found to cause mid-air collision is, "failure of the pilot to see other aircraft" in other words, failure of the see-and-avoid system. When collisions occur it is always wondered why at least one of the pilots involved in the collision failed to see the other aircraft, if truly they were practicing situational awareness. It can therefore be said that it is really the eye which is the leading contributor of mid-air collisions. Below are limitations the eye has that affect flight.
Limitations of the Eye
The eye is the prime means of identifying what's happening around us, as 80% of our information intake is through the eyes.
During flight we depend on our eyes to provide basic input necessary for flying such as; proximity to opposing air traffic, direction, speed and attitudes. A basic understanding of the eyes' limitations in target detection is the best insurance a pilot can have against collision.
In flight, vision is influenced by atmospheric conditions, glare, lighting, windshield distortion, oxygen supply, cabin temperature, aircraft design, acceleration forces and so forth.
The eye is vulnerable to the vagaries of the mind. We "see' and acknowledge only what the mind allows us to. A day dreaming pilot, who is staring into space, is a prime candidate for a mid-air collision.
The problem with the eye is the time rewired for accommodation or refocusing of objects both near and far. It takes 1 to 2 seconds for the eyes to adjust during refocusing. Considering that you need 10 seconds to avoid a mid-air collision, 1 to 2 seconds can be a long time.
Other focusing problems arise when there is nothing specific to focus on. This is common at very high altitudes as well as at lower levels on vague, days above cloud where there is no visible distinct horizon. In such cases the pilot experiences empty-field myopia, (staring but seeing nothing).
It is important during the scanning for pilots to move their heads around obstructions, so as to avoid the effects of, 'binocular vision', which are a causal factor of mid-air collisions.
Another eye problem is narrow field of vision.
Motion or contrast is needed to attract the eye's attention, and tunnel vision limitation can be compounded by the fact that at a distance an aircraft that is on a collision course, appears to be motionless. Then almost out of nowhere a sudden bloom huge mess as the aircraft's collide, this is known as the 'blossom effect'.
The eye is limited as well by the environment. Optical properties of the atmosphere such as; limited visibility which actually just means 'limited vision' afters the appearance of the aircraft.
Light affects visual efficiency. On a sunny day, glare for example is worse. Glare makes it hard to see what is at a distance as well as making the scanning process uncomfortable.
The mind can act as a distraction to the pilot to the extent of hindering the pilots vision altogether or causes cockpit myopia staring at one instrument without even° seeing it").
Visual perception is affected by many factors. The best way to avoid collisions is by learning how to use your eyes for efficient scanning, as well as understanding the eyes' limitation and not over estimating our visual abilities.
Visual Scanning Techniques
Avoiding collisions requires effective scanning, that is from the moment the aircraft moves till it comes to a stop at the end of a flight.
Before take-off visually scan the airspace and the runway. Assess traffic from radio transmissions. After take-off, properly scan outside of the cockpit to ensure that no aerodrome traffic will be an obstacle to your aircraft.
Before and during the tum to departure heading, focus attention to the direction of the turn.
In climb and decent listen carefully to radio exchanges between ATC (Air Traffic Control) and other aircraft's, so as to form a good mental picture of the other traffic's position.
How to Scan
The best way to perform as scan is by removing any bad habits that you may have been implementing before, and conduct a contentious scan.
Scanning once without stopping to focus on anything is practically useless.
There is no one scanning technique that works for all pilots. The most important thing is for all pilots to develop a scan method that's comfortable and works for them.
Scanning properly requires the pilot to know how and where to concentrate the search during a scan. It is very critical especially in the traffic pattern to always look out before a turn, and ensure the path is clear. Also look for traffic making an improper entry into the circuit as well. During the climbing and when climb-out make a gentle clearing turn so as to ensure that there is no traffic on your path.
During final approach, don't forget to scan around to avoid tunnel vision.
In normal flight scanning an area at least 60 degrees left and right of your flight path aids in avoiding the threat of a mid-air collision.
Probability of spotting collision threats increases with the time spent looking outside.
To increase the effectiveness of the scan the following should be implemented:
- The gaze should be shifted and refocused at regular intervals.
- The pilot should realize that his/her eyes rewire several seconds to refocus when switching views between items in the cockpit and distant objects.
- Good scanning needs constant attention sharing with other piloting tasks, although pilots should remember that good scanning is easily degraded by conditions such as; boredom, illness, fatigue, preoccupation as well as anxiety.
Effective scanning is achieved through short regular and spaced eye movements that bring successive areas of the sky into the central visual field.
They are two scanning patterns;
- Side-to-Side Scanning.
- Front-to-Side Scanning.
Both of these scanning methods involve the 'block' system of scanning.
This system is based on the premise that traffic detection can be made only through a series of eye fixations at different points in space. In application the windshield is divided into segments and the pilot methodically scans for traffic in each segment of airspace sequentially.
Side-to-Side Scanning Method
With this method scanning starts from the far left of the visual area and methodically sweeps to the right, pausing briefly on each block of viewing area to focus. At the end of the scan the pilot returns to the instrument panel inside of the cockpit and then repeats the outside or external scan again.
Front-to-Side Scanning Method
With this method scanning starts at the centre of the windshield, more to the left, focusing briefly on each block, than back to the centre block, after reaching the last block on the left the scan is repeated from the centre but now to the right. Once complete the pilot returns to the instrument panel inside of the cockpit and then repeats the outside or external scan again.
There other scanning methods apart for the two mentioned above, however these are the two commonly implemented.
The Time-Sharing Plan
To achieve maximum efficiency in flight, a pilot has to establish good internal scan and learn how to allocate time for the external and internal scan.
Average time needed for an instrument panel scan is 3 seconds and for an outside scan 18-20 seconds.
Efficient instrument scanning is good practice for a pilot even if he/she is flying VFR.
Developing a good time-sharing plan takes work and practice. The best way to start developing a time-sharing plan is to start on the ground in your own aircraft that you are used to flying and then use the scan in actual practice at every opportunity.
During flight if one crew member is occupied with a task in the cockpit the other can continuously carry out the scan ahead and on both sides of the aircraft as well as internally.
Collision Avoidance Checklist
This involves more than just a proper scanning technique. You may be the best conscientious scanner but still experience a mid-air collision if you neglect other factors in the, "see-and-avoid', technique. It is important to use a collision avoidance checklist as routine that you implement as you perform your pre-take-off and landing procedural checklist
A Collision Avoidance Checklist Includes:
- Check yourself: IMSAFE and Eyesight
- Plan ahead: Doing activities such as; removing clutter in the cockpit, neatly storing charts, familiarization of frequencies, distances, headings and so forth enables the pilot to have less to do in the cockpit and hence leave enough time for internal and external scanning.
- Clean windows: Make sure windshield is clean.
- Adhere to procedures: Follow correct regulations and procedures; such as correct flight levels and proper pattern practices.
- Avoid crowded airspace:
- Compensate for blind spots: Know where your aircraft blind spots are as they are at different places for each aircraft.
- Equip to be seen: Aircraft lights can aid in avoiding collision. In high traffic density, strobe lights are often the first indication another pilot has received you presence.
- Talk and listen: Use your eyes as well as your ears in flight. Take advantage of the information you receive over the radio. When a pilot reports his/her position to ATC they are also reporting it to you.
- Make use of information: ATC often tell you where traffic is, for example," three miles one o'clock', look for this traffic and once you find it, do not forget to scan the rest of the sky.
- Use all available eyes: If flying with a co-pilot, have an established procedure in place to ensure that at all times an effective scan is maintained.
- Scan: This is the most important part of the checklist.
Implementing good airmanship, ensuring you and your aircraft are in good condition, developing an effective scan time-sharing system, these will give you the basic tools needed in avoiding mid-air collisions.