March 2002Features

Beyond See And Avoid

Reduce The Midair Collision Risk With Hot-Spot Vigilance

Let's face it, midair collisions are extremely rare events. In fact, according to the AOPA Air Safety Foundation's 2000 Nall Report, there were only 15 midairs in 1999. Considering that general aviation flew an estimated 27 million hours in the same year, that makes them exceedingly rare indeed.

But when midairs do occur, they often have tragic results. Those 15 midairs resulted in 16 fatalities. In this article we will attempt to replace the hearsay and hyperbole surrounding these mishaps with facts. We'll look at some midair collisions that illustrate typical midair scenarios and present strategies and techniques to minimize your risk of being involved in one.

The "Typical" Midair

The typical midair scenario hasn't changed much over the years. They occur mainly on good VFR days, close to airports, and at low altitudes. In fact, in 1999 all of the midair collisions occurred in visual meteorological conditions (VMC) and during the hours of daylight.

A recent AOPA Air Safety Foundation study of midair collisions revealed that 49 percent occurred in the traffic pattern or on approach to or departure from an airport. Of the other 51 percent, about half occurred during en-route climb, cruise, or descent, and the rest resulted from formation flights or other hazardous activities.

The "Big Sky" Theory

In the glory days of aviation, the FAA strongly emphasized the concept of "see and avoid" as a method to reduce the number of midair collisions. Basically, a pilot would scan the sky for other aircraft and simply maneuver to avoid a collision. The concept worked because 40 years ago there were far fewer general aviation and commercial aircraft sharing the same airspace, aircraft generally flew slower (giving a pilot more reaction time), and airports were considerably less congested. Even the vernacular of those times expressed the serene nature of aviation. Back then, airports were known merely as airstrips or fields, such as Zamperini Field in Torrance, California; Ryan Field in Tucson, Arizona; or Bowman Field in Louisville, Kentucky.

But those days are over. We can no longer depend solely on the see-and-avoid concept. The "Big Sky, Little Airplane" theory has serious limitations. To minimize our risk we must fly smarter. That means understanding the limitations of our eyes and aircraft, using all available resources, and being extra vigilant and proactive when flying in known "hot spots."

Scanning, Blind Spots, And Clearing

A complete discussion of visual scanning techniques is beyond the scope of this article. However, the Aeronautical Information Manual (AIM) is the official source of information on this subject. Essentially, the human eye has certain limitations, and to compensate for these limitations we should continuously scan the sky in 10-degree increments while focusing on each increment for at least one second. More important, however, we must be aware of our aircraft's blind spots. Numerous midairs have resulted from an aircraft climbing, descending, or turning into another aircraft. Most likely those aircraft would have been in plain sight had they not been hidden behind a wing or fuselage. In high-wing aircraft, the blind spots are above the wings. Conversely, in a low-wing aircraft, the blind spots are below the wings. Most aircraft have limited visibility directly above and below the fuselage. To compensate for these blind spots pilots should visually check (or "clear") these areas for traffic before changing the aircraft's flight path.

Clearing procedures should be used during all ground operations (taxiing) and during each phase of flight. For example, before taking the active runway for departure, it is a very good idea to visually clear the base leg and final for aircraft approaching to land. A common clearing procedure used during climbs is to make gentle turns to the left and right of the desired heading. Alternatively, the airplane's pitch attitude can be gently lowered every 500 feet or so to clear the airspace ahead.

During cruise flight, try to scan all the areas of the sky visible from the cockpit. Before making a turn, it is imperative to clear the respective side and rear quarter area. In high-wing aircraft, this requires raising a wing to clear the area. In low-wing aircraft, this requires lowering the wing to clear the area.

During descent, use alternating turns left and right to clear the area ahead of and underneath the aircraft. And before landing, check the entire length of the runway for other aircraft - especially at night. Don't rely solely on the fact you were "cleared to land" by the tower controller. They are only human.


Besides clearing, flying smarter also means using all available resources to avoid an in-flight collision. For instance, if you are taking passengers along, put their eyes to work for you. Before the flight, brief them on how they should advise you of potential traffic they may see.

During your preflight planning, identify potential hot spots along your route where a high number of aircraft may be concentrated. Examples include the airspace around airports, around and over VORs and designated VFR reporting points, known flight training practice areas, and near military training routes (MTRs). Use extra care when transiting these areas.

And don't be timid about using all available aircraft lighting to make your airplane more visible. On a hazy day, a bright landing light can be spotted many miles before an aircraft becomes discernable. And the same logic applies to strobes, navigation, and beacon lights. Common sense - and the federal aviation regulations - dictate that anticollision lights are a good idea anytime.

Of course the most effective tools onboard the aircraft are the communication radio and transponder. These two pieces of equipment open the door to a host of air traffic control services, including VFR traffic advisories. Unfortunately, for varied reasons, many pilots don't take advantage of these services. Some pilots are apprehensive about talking to ATC because it means dealing with a representative of the FAA. A few pilots are uneasy about talking on the radio. For them, a review of radio communications phraseology and practice with a certificated flight instructor may be beneficial. A complete description of the ATC services available to pilots and proper radio communications phraseology can be found in the AIM.

One of the most valuable skills a pilot can develop is to visualize the position of other traffic by maintaining a listening watch on frequency. By listening to the radio calls you can develop a picture of the traffic in your area. Listen for the position, type, altitude, and direction of the various aircraft. Determine whether an aircraft is a high-wing, low-wing, single, twin, or jet, so you'll know what to look for. Another useful concept is that of reciprocal positions. In other words, if your traffic is at eight o'clock, five miles, same direction, then you are at the other airplane's two o'clock position. You should listen for the other aircraft to acknowledge that you are in sight as you look for them. If your traffic is not in sight, it is imperative that you inform the controller. And don't hesitate to ask for regular updates on the position of conflicting traffic. With regards to potential traffic, it is essential to be proactive rather than reactive.

A Look At Some "Typical" Midairs

Being proactive may have changed the outcome of a midair collision between a Cessna 150 and a Piper Cherokee that occurred in San Diego, California, on December 24, 1996. Both aircraft were on final approach to parallel runways 28 Left and 28 Right at Montgomery Field. As in the "typical" midair scenario, the collision occurred about 1.5 miles east of the airport, at 1,400 feet above mean sea level, and in visual conditions. A special weather observation taken 15 minutes after the accident reported scattered clouds at 2,500 feet above ground level (agl), and visibility of 40 miles. By any measure, it was a textbook VFR day. According to the National Transportation Safety Board's preliminary report, a few minutes before the collision, the tower controller "instructed the aircraft (the Cherokee) to proceed southbound and issued traffic at 11 o'clock, and 2 miles, a Cessna aircraft descending through 2,100 feet, and further instructed the Piper pilot to report the Cessna in sight." There was no acknowledgment of the clearance from the Piper.

Likewise, the tower controller advised the Cessna pilot of "...traffic behind to your left, inbound for the parallel runway is a Cherokee." The pilot of the Cessna replied, "...we're looking for the Cherokee." The report states that the Cherokee "approached from behind and struck them (the Cessna) from above." Tellingly, the Cessna pilot never saw the Cherokee. Following the collision, the Cessna landed in a construction site with only minor injuries to its two occupants. Unfortunately, the commercial pilot and one passenger in the Cherokee were killed. In retrospect, the final approach paths of parallel runways are obviously potential midair hot spots.

Hot Spots

Other "hot spots" are known practice areas. About six miles south of Long Beach Airport, California, is the Port of Los Angeles. On the south side of the harbor is the breakwater, a roughly seven-mile-long, manmade rock structure rising up from the Pacific Ocean. Its primary purpose is to protect the harbor. But since it has long stretches that are absolutely straight, it's also ideal for practicing ground reference maneuvers. And almost every flight instructor in the vicinity uses it for that purpose. On February 15, 2001, a Cessna 172 and a Cessna 152 collided in midair over the breakwater, and tragically, four lives were lost. Onboard each airplane were a flight instructor and student. Both airplanes were rented and operated by the same flight school.

According to the NTSB preliminary report, visual meteorological conditions prevailed. The report states, "The Cessna 152 departed from the Long Beach airport about 1513, and the Cessna 172 departed from the Long Beach airport about 1500." Given this, it is likely that both aircraft received the same automatic terminal information service (ATIS) and altimeter setting. What's more, it's very common to practice ground reference maneuvers (turns around a point, S-turns) at a convenient altitude of 1,000 feet agl. It is quite possible these two aircraft were practicing ground reference maneuvers at exactly the same altitude when they struck each other. A few thoughts come to mind regarding this accident. First, obtain radar advisories whenever possible (the NTSB report does not mention whether either aircraft was receiving radar services). Second, use all available aircraft lighting. And third, in hot spots such as this, choosing an unusual altitude such as 1,200 or 900 feet agl for ground reference maneuvers may reduce the chance of an in-flight collision.

Clearly, there is no such thing as a typical midair, although most share some common characteristics. They occur mainly on good VFR days, near an airport, and at low altitudes. This means extra vigilance is required in these areas. On a more positive note, it's been said that the most dangerous part of any flight is the drive to the airport. With regards to midairs - and statistically speaking, of course - this old adage still holds true. Fly safe.