Collision Avoidance Made Easy

Flying in the Los Angeles Basin or getting into Teterboro at the end of a long day can be tedious and harrowing, especially if you're flying VFR and not accustomed to a lot of traffic. With busy terminal airspace comes the possibility of a midair collision.

You've got to be on top of your game to fly comfortably in high-density environments. Everyone is busy, the sky is full of airplanes, and controllers don't have time to mess around with pilots who don't immediately comply with their instructions. Missing an ATC instruction, turning left instead of right, and failing to practice good collision avoidance are factors that stack the deck in favor of a collision.

Flying in a busy terminal area puts you on edge and increases your awareness. But how about rural, uncontrolled airports? Are you just as likely to have a potential collision problem there? Let's see.

To restate an old saw, "You'll probably never even see the one that gets you." So let's try to understand a little more about some of the pitfalls and remedies in avoiding midair collisions. Let's see what we can do to stay safe - and whether the image we have of a typical midair is anywhere close to accurate.

First, let's debunk the biggest myth about collisions.

Most collision avoidance literature usually features a very prominent closure rate chart. The chart graphically depicts just how little time pilots have to avoid hitting each other once one pilot spots the other aircraft. Those charts are frightening if you study them and think about their implications. They are also accurate. The math is simple and the numbers don't lie.

Regardless what the numbers are, the biggest problem with closure rate charts is they unintentionally and subliminally implant the visual image that high-speed closure rates are the primary cause of midair collisions. They send a clear message that speed is the real killer. That's usually not the case, and it's misleading because the mindset we have about collision avoidance is absolutely critical to solving the collision avoidance problem.

If you read most literature carefully, a vastly different picture emerges. Unfortunately, many pilots are "visual" people - impatiently picture-oriented. We don't often take time to read the fine print ,and the lasting impression about most collision avoidance literature is that closure-rate graphic. That's the wrong picture. At the minimum, it conveys a misleading message.

The picture that midair collisions are tragic is far from wrong, however. Between 1983 and 1995, 242 midair collisions occurred. That's nearly 20 a year. Half the airplanes involved were destroyed, and 440 people died in these accidents. So, the problem really is a problem. We all need to pay attention to it every minute we're in the air.

Profile Of A Midair

When are pilots most vulnerable to midair collision? Are the pilots involved flying VFR or IFR? Is it at night or in the daytime? At what altitude do most midairs occur? Is the traffic pattern more dangerous than other places? Is it more dangerous to fly in congested areas or in the boondocks? Are most collisions head-on? What's the typical closure rate?

Knowing the answers to these questions can help you to build a personal avoidance strategy and to evaluate the real hazards of where and how you do most of your flying.

For example, how often do you think about collision avoidance where you fly? Would you be able to answer the above questions? If you're an instructor, could your students answer them? Could you draw a profile of the typical midair collision for the airspace you fly in?

There would probably be as many ideas as there are pilots, but the important thing is to think about the typical collision scenario, to contrast that with the typical profiles you fly, and to make some decisions about what you think will work for you.

Here is the statistically typical profile of a midair collision. Half of all the midairs occur below 500 feet AGL. Less than a quarter happen above 3,000 feet AGL. More than 92 percent of midair collisions occurred in day VFR conditions.

Here's the real shocker about most midair collisions - the closure rate of the collision is slower than the speed of either aircraft. What does that say?

It says a faster aircraft overtakes a slower aircraft and hits it. Accident statistics show that 77 percent of all midairs occur when one airplane overtakes another from the tail or side. Only five percent of midairs are head on collisions.

A reasonable conclusion is that high closure rate is not the major culprit. On the contrary, an insidiously slow, "creep up on you" closure rate is the real danger.

Don't infer that closure rate isn't a critical factor in collisions - it is. But we must keep it in perspective. The important thing to remember is this - low rates of closure are much more dangerous than the high-speed, head-on.

It's important to remember that an airplane on a collision course will not appear to move in your field of view. The critical factor here is "apparent motion," which is what helps you find objects that otherwise blend into the background. If an airplane is in your field of view and it has no apparent motion in the sky, you probably won't see and recognize the danger - or the airplane you are about to collide with.

"Normal" Reaction Time

Let's say you do see a stationary object (airplane) outside your airplane. Experts tell us that it takes about 0.1 second to detect another airplane. It takes you another second to recognize what you've detected and think "That's an airplane." After another five seconds, you say "We're on a collision course." By that point, 6.1 seconds have elapsed.

Six seconds doesn't seem like a lot of time, no big deal. But, we're not finished yet.

It takes the average pilot about four seconds to decide whether to turn left or right, four-tenths of a second to react and apply control inputs, and another two seconds for the airplane to start moving in the direction the pilot wants it to go.

Combined, the total lag time from visual detection of another airplane on a collision course to the airplane starting to move away from the collision course is now 12.5 seconds. "No problem," you say? Wrong.

If the closure rate is 90 knots and you first detect an airplane on a collision course when it's a half-mile away, you only have a 7.5 second leeway to avoid a collision.

At this speed and distance, you have 20 seconds until you and the other airplane reach the same point in space. When you subtract the 12.5-second lag time, you have only 7.5 seconds before the airplanes collide. This isn't a lot of time. If you doubt it, the next time you fly - and see another airplane on a potential collision course - count 7.5 seconds and you'll realize how short a time it really is.

The only way to give yourself more time is to spot conflicting traffic when it's farther than a half-mile away - especially when you fly in midair danger zones.

See And Avoid

Several additional factors contribute to the need to see other traffic as far away as possible.

A pilot's reaction time is based on "normal" eyesight - which, unfortunately, has problems of its own. Light enters the eye from a field that spans more than 180 degrees, but our normal field of clear focus is only about 10 degrees wide. We'll discuss the remaining 170 degrees later.

Boredom and complacency resulting from uninterrupted straight and level flight can affect our perception significantly. It lulls our eyes into sluggishness, so to speak.

Refocusing Time

Normal eyes take time to refocus when we shift our view between objects at different distances. Even in urgent circumstances it can take from one to two seconds to shift focus from the instrument panel to another aircraft. Until our eyes are properly focused, we cannot, in effect, "see" that other aircraft.

Binocular Vision

Normal vision requires both eyes to focus on the same object. When something, such as a windshield post, blocks one eye's line-of-sight, it affects normal vision much the same as when one lens of a binocular is blocked. Both eyes need to receive the same visual cues. If a binocular cue is absent, problems arise.

Clutter And Lack of Contrast

With the exception of trainers, which are intended to be conspicuous, military aircraft usually are painted in camouflage or dull, flat colors. When seen against backgrounds of similar tone, their dull, neutral-tint paint makes them almost invisible - except for detected motion. Have you examined a sectional chart to see where the low-level military training routes are in the airspace where you fly?

Blossom Effect/Apparent Lack Of Motion

An aircraft on a collision course has no apparent motion in our field of view, but one collision motion phenomenon is pretty dramatic. It's the sudden, last-minute "blossom" when an unseen airplane on the collision course explodes into view - close up and full size - when the midair is imminent. This apparent motion is created by the dramatic increase in the apparent size of a colliding aircraft in the last seconds.

In addition to the normal vision problems already noted, other phenomena can seriously affect a pilot's ability to see other airplanes. Many of these are taken for granted. Use the following as a checklist to evaluate additional factors that can affect your ability to see at different times and phases of flight.

Added aggravations that contribute to deteriorated visual capability:

• Fatigue
• Oxygen deprivation
• Dust
• Obstructions
• Aircraft design
• Haze
• Alcohol
• Lightning
• Darkness
• Age
• Emotion
• Heat
• Optical illusions
• Weather
• Windshield distortion

Are Collisions Unavoidable?

From everything you've read so far, you might think that midair collisions are unavoidable. Think again. They are avoidable - and you can do many things to reduce the chances of having a midair collision. Here are some tips, paraphrased from an old friend, the Aeronautical Information Manual.

The most important thing you can do is constantly scan the sky in a 360 degree range - and above and below your altitude - for other aircraft. Realize the human limitations we described earlier and scan so you can actually see. For example, an average eye's focused field of view is 10 degrees, so scan the sky 10 degrees at a time. Scanning behind the aircraft may be inconvenient, and scanning above and below your altitude may seem unnatural, but that's where you need to scan. Remember, most midair collisions are caused when one airplane overtakes another.

Try to see other aircraft as far away as possible, and keep them in sight. Have you ever lost visual contact with a nearby aircraft after ATC has instructed you to maintain visual separation from it? Don't just give lip service to collision avoidance. Make it a priority in your flying. If you lose visual contact with the other aircraft, report this to the controller.

Once you have traffic in sight, don't dwell on it and stop scanning for other airplanes. That's like fixating on one instrument when you fly IFR. You're missing - not seeing - a lot of important information. Keep scanning for other airplanes, particularly when you're maneuvering and other airplanes are in the vicinity.

Once you recognize an aircraft on a collision course - it won't move in your field of vision - do something about it. Don't wait. After you change course to avoid the collision, make sure the other pilot didn't also change course toward you.

Most cockpits have their share of bothersome posts and other obstructions. When scanning for traffic, periodically change the position of your head to eliminate the obstruction from your view outside the cockpit. Without conscious head movement, that continuously obstructed spot is likely to be where conflicting traffic hides - until it blossoms.

Evaluate, think about, update, and use your airspace's midair-collision profile. Increase your vigilance when entering areas of increased risk, or avoid those areas entirely. Request flight following so an ATC controller can help you see-and-avoid other traffic. When receiving flight following, never assume that the controller's radar eyes and traffic advisories replace your see-and-avoid vigilance. Look outside the cockpit, particularly in airspace where you can expect other airplanes to be such as over VORs.

While discussing these see-and-avoid techniques with a student, I heard him say he didn't have a lot of time to look out because there was a lot to do in the cockpit. A pilot always has lots to do in the cockpit, but you can reduce your workload though good planning, cockpit organization, and thinking about where you're going to fly. You can do it on the ground. Study the appropriate charts, checklists, frequencies, and manuals before you fly. Organize your cockpit materials before starting the engine. Organization can reduce the time you spend looking for things in the cockpit and give you more outside-the-cockpit viewing time.

You can improve your ability to see-and-avoid by making sure the windshield and side windows are clean before you take off. Your eyes subconsciously focus on objects closest to them, such as dirt and bug spots. A dirty windshield can be a real problem when it's smoky, dusty, hazy, raining or you're flying into the sun.

One last tip - turn on your aircraft's lights whenever you're flying, night or day. Lights give an airplane added contrast against the surrounding sky or earth. This might be all that's needed to catch another pilot's eyes while there's still time to avoid a collision.

Once you realize that a midair collision really is a possibility, think about it, do the right things to avoid it, and stay on your toes. It makes flying safer, and more fun.

Collision Avoidance Quiz

You can find the answers in the body of the article.

Under what conditions do most midair collisions happen?

a. Day VFR

b. Night VFR

c. Night IFR

d. Day IFR

At what altitude(s) do the greatest number of midair collisions occur?

a. Below 3,000 feet AGL

b. 3,000 to 5,000 feet AGL

c. Above 5,000 feet AGL

d. Above 10,000 feet MSL

In what kind of airspace do most midair collisions occur?

a. Controlled airspace

b. Uncontrolled airspace

c. Neither of the above

d. Who knows?

With respect to airports, where do most midair collisions occur?

a. Directly over the airport

b. Within 5 miles of an airport

c. Farther than 5 miles away from the airport in uncongested airspace

d. None of the above

With respect to closure rate, how do most midair collisions occur?

a. Head-on at high speed

b. From the side at high speed

c. From the side or rear at a closure rate less than the speed of either airplane

d. From the rear at very high speed

How long does a pilot have to apply the controls to avoid collision with another aircraft (on a collision course) if the other aircraft is first seen one-half nautical mile away and the rate of closure is only 90 knots?

a. Less than 10 seconds

b. 30 seconds

c. 45 seconds

d. a minute and a half

Airplanes with exterior lights on are easier to see and avoid than are airplanes with their exterior lights turned off.

a. True

b. False

Which of the following contributes to the danger of having a midair collision?

a. Fatigue

b. Posts, dirty windows, and other vision obstructions in the cockpit

c. Cockpit disorganization

d. All of the above

One of the most important things a pilot can do to avoid a midair collision is:

a. Conscientiously look for other aircraft using a deliberate scan pattern

b. When an aircraft is sighted on a collision course, do something now.

c. Assume that the tower or approach control will keep you clear from other traffic in your area.

d. Avoid areas you know to be congested and hazardous, if you can.

e. a, b and d above

Even when not flying aerobatics, in which direction(s) is it especially important to "clear?"

a. Ahead and below your altitude

b. Ahead and above your altitude

c. Behind and to the sides of your aircraft, both above and below

d. All of the above