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Ep 34 – Scan the Skies Effectively

Podcast | September 20, 2023

Pilots who fly IFR most of the time spend most of their day managing the autopilot or programming the flight management computer. On the ground we are completing checklists, communicating with ATC and taxing. Managing distractions are crucial in all phases of your trip. The news has been full of close calls, and I was cut off by an airliner while taxiing not long ago. If anyone has gone into Lake Havasu in the summer will understand managing VFR traffic and terrain simultaneously.


Nobody thinks they are going to collide with anything. We go about our day doing what our procedures say but how do you actually look for traffic? How do we ensure we are taking the correct taxi line in rainy conditions with lights creating a glare? How do we ensure we are taking off on the centerline of the runway and not the side lights? There are lots of things to run into.


Let’s start with airborne collision avoidance. The FAA produced a very good AC numbered 90-48E Pilots’ Role in Collision Avoidance which will provide the basis for this podcast. I’ll leave a link in the notes, and I will quote from that AC. Pilots say ‘see-and-avoid’ because it is actually a thing, and it should work when you are mixing it up with VFR pattern traffic or controlled VFR traffic or any traffic.


See and avoid does have limitations such as humans not looking out the window, weather conditions, aircraft blind spots and everything else that is going on inside the aircraft.


The FAA defines see and avoid as: When weather conditions permit, pilots operating IFR or VFR are required to observe and maneuver to avoid other aircraft.


I said before that humans may not look out the window, but this isn’t all the story. A basic understanding of the eye’s limitations in target detection is one of the best defenses against a collision.


Factors that affect vision in flight include atmospheric conditions, glare, lighting (exterior and interior), windshield deterioration and distortion, dead bugs on the windshield, aircraft design, cabin temperature, oxygen supply (particularly at night), and acceleration forces.


Pilots rely on their eyes to provide most of the basic input necessary for flying an aircraft such as the aircraft’s attitude, speed, direction, and proximity to opposing traffic. We fly fast aircraft and when entering the terminal zone, traffic density and aircraft closing speeds increase meaning we must scan the skies effectively.


This is directly from the AC… Detection of objects while airborne depends on six conditions: image size, luminance, contrast, adaptation, motion, and exposure time.


  • Image size—portion of the visual field filled by the object.
  • Luminance—degree of brightness of the object.
  • Contrast—difference between the object and background brightness, color, and shape.
  • Adaptation—degree to which the eyes adjust to surrounding illumination.
  • Motion—velocity of the object, you the observer, or both.
  • Exposure time—length of the time the object is exposed to view.


What is the number one cause of midair collisions?


The failure of the pilot to adhere to the see-and-avoid concept. But it’s not just looking out the window. There is some built in problems that we must account for. Rarely do we just look and see another aircraft right away.


The problem with the eye is the time required for accommodation or refocusing. It takes 1 to 2 seconds for eyes to refocus from something up close, like a dark instrument panel 2 feet away, to a bright landmark or aircraft 1 mile away.


The 1-to-2-second delay is significant. The US Naval Aviation Safety Center suggests it takes 12.5 seconds to identify, react, and avoid a midair collision.


The Navy breaks up the action into multiple steps.

Seeing the Object takes 0.1 seconds

Recognizing the Aircraft> 1.0 second

Becoming Aware of a Collision Course> 5.0 seconds

Decision to Turn Left or Right> 4.0 seconds

Muscular Reaction time> 0.4 of a second

Aircraft Lag Time> 2.0 seconds

TOTAL Time Before Aircraft Begins to Move> 12.5 seconds


In 12.5 seconds, two aircraft travelling at 250 knots will each cover one mile.

At a cruise speed of 450 knots, it’s 1.8 miles each so if two aircraft are at three and a half miles apart on a collision course the US Navy says you may not have enough time to refocus, recognize, and react before impact.


There are many other factors affecting the eye’s ability to detect objects.


What is Empty-Field Myopia?


If there is little or nothing to focus on, the eyes tend to not focus. This usually occurs on colorless days above a haze or cloud layer when no distinct horizon is visible.


What is binocular vision?


For our vision to be most effective each eye’s vision overlaps the other eye’s field of view. This creates perception of depth. If an aircraft is blocked from view from one eye, then the other has a more difficult time detecting the object, in fact it will be blurry. So, move your head to look around things blocking your vision.


There is the phenomenon called narrow field of vision or tunnel vision. We have a very narrow field of accurate vision. It’s only about 10 to 15 degrees of the 200-degree arc we can see out of. The eye cannot accurately identify what is happening in the distance when experiencing tunnel vision or narrow field of vision, even when the eye senses movement by its peripheral vision. Therefore, pilots tend to not believe what they see out of the corner of their eyes.


There’s the Blossom Effect.


Generally, the eye needs motion or contrast to attract our eyes’ attention. The “blossom effect” refers to the phenomenon where two aircraft on a collision course will appear to be virtually motionless to each other. The other aircraft will remain in a mostly stationary position, without appearing to move or grow for a relatively long time, and then suddenly bloom into a huge mass filling one of the windows. And watch out for dead bugs hiding aircraft.


Environmental Limitations.


The eye is also limited by the environment in that the atmosphere’s optical properties alter the appearance of aircraft, particularly on hazy days. VFR requires 5 statute miles of visibility, but on a hazy day, a pilot may have difficulty detecting opposing aircraft.


Ok what about glare.


Glare makes objects hard to see particularly on a sunny day over a cloud layer or during flight directly into the sun. Basically, the more contrast between the object and its background the easier it is to detect the object. Then there’s the dead bugs. A dirty, scratched, opaque, or distorted windshield will make matters worse.


What about nighttime?


Scanning at night uses your peripheral vision. There is a night-blind spot between 5 and 10 degrees wide in the center of the visual field. You can compensate for the night-blind spot by viewing an object “off-center”, which requires looking approximately 10 degrees above, below, or to either side of an object. So, scan the area around the object rather than looking directly at the object. Short stops of a few seconds in each scan will help detect the light and its movement.


How do we scan effectively?


Effective scanning is accomplished with a series of short, regularly spaced eye movements that bring successive areas of the sky into view. Scan across the same width from top to bottom then move on to the next area. Each area and therefore eye movement should not exceed 10 degrees, and each area should be observed for at least 1 second to enable detection. Develop a scanning pattern that is most comfortable for you and then keep it the same to ensure optimum scanning.


Don’t forget about Unmanned Aircraft Systems or UASs or sometimes called UAVs. Heads up below 400 feet in uncontrolled airspace and at all times.


Ok a bit on ground operations.


Check NOTAMs even when there are a hundred of them. Brief the hotspots on the taxi chart. Weather is always a factor of course, night or day. Airport lighting can be tricky as it changes from airport to airport. There is no centerline lighting at Las Vegas for example, but aircraft have lined up on the side lights of the runway.


Be aware of vehicle movements, taxiing aircraft, and aircraft being towed.


So, there is a lot going on and then there’s passengers. I had an FBO call us on the taxi out to tell us our passengers had left a gun in the rental car. The passenger said simply, “ask the FBO to store it for me and I’ll pick it up the next time I’m here.”


Watch your procedures during taxi and keep the chit chat to checklists only. Don’t become a statistic.


So your ability to detect objects depends upon:


  • Your distance from the object.
  • The size, shape, and movement of the object.
  • The amount of light reflected by the object.
  • The object’s contrast with the surrounding environment.


So, scan effectively!


In The News: Trajectory-based Operations


Ok let’s change gears for a moment. In the news is a section of the podcast where I talk about other happenings in aviation.


The FAA recently completed a six-day multi-country demonstration of trajectory-based operations or TBO which will be used by Air Traffic Control in various countries.

TBO enables regions to predict where an aircraft will be and at what time. The trial involved four flights between the U.S., Japan, Singapore, and Thailand.


How does TBO work? Countries will share data on aircraft trajectory—including latitude, longitude, altitude, and time—and air traffic managers from each country sequence flights to provide an optimal route, factoring in weather, airspace closures, and air traffic.


Air traffic controllers currently share flight information using voice. TBO uses data.  The AIN article quoted the FAA which said, “This will allow each country to be immediately aware of how changes in other countries will affect a flight and better plan for when an aircraft enters its area of responsibility”.


The demonstration showed how sharing and coordinating trajectory information across multiple countries could improve safety and efficiency, minimizing delays and reducing travel time. The result, the agency added, could reduce fuel burn and carbon emissions by up to 10 percent.

There’s a link to the AIN article in the notes.


Thanks for listening and have a great day!




AC 90-48E Pilots’ Role in Collision Avoidance


FAA Calls Trajectory-based Flight Demo a Success

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