The Human Factor: Be Predictable

Many people are not aware that one of the most dangerous practices when riding a bicycle is traveling against the flow of traffic. The problem is that drivers are not expecting anyone to approach from the right at any pace faster than a walk, so they focus on the traffic approaching from the left and may not notice a bicycle approaching from the right until it is too late.

If traffic coming from an unanticipated direction is dangerous in the two-dimensional world of driving, it is a much bigger risk in the three-dimensional world of flying. When driving a car, you don’t have to worry about anyone approaching from above or below, and aside from the rare drunk driver, the same goes for another car approaching head-on. When flying an airplane, traffic can approach from almost any direction at any time, and it may be traveling at a vastly different speed than you are. This is not much of a factor in cross-country cruise flight, when the big-sky theory is in full effect — there is so much space that the odds of two airplanes being at the exact same location at the same moment are very small.

However, flying in the vicinity of an airport greatly increases the chances of sharing the same bit of sky with another airplane due to the concentration of aircraft at the same approximate altitude approaching or leaving the same location. Because it is so hard to search for traffic in all directions, and impossible to see traffic from above, below or behind the airplane, it is critical that pilots follow a predictable flight path so other pilots in the vicinity can anticipate where to look for traffic, reducing the amount of sky to search. Airplanes also have an advantage over cars. While drivers can only communicate with each other through the use of a horn, turn signals and the occasional hand gesture, pilots have the ability to talk to each other about where they are located and where they are headed.

I have personally experienced how effective this system of following a prescribed pattern and communicating with each other can be. I was approaching Oshkosh one summer during the EAA fly-in at a time when the airport was supposed to be open. However, when I contacted the controller, I was told the airport was still closed for the airshow, and that I should hold outside the airport traffic area. Other pilots approaching Oshkosh were given the same message, and soon there were quite a few airplanes holding over various lakes and other prescribed holding points. Everyone was very good about announcing where they were holding and at what altitude, so while still keeping a sharp eye out for traffic, I was fairly certain there was nobody else holding at the same location and altitude as me.

The regulations covering airport patterns are amazingly simple. FAR 91.126 specifies that each pilot of an airplane must make all turns to the left, unless there are markings indicating that turns should be made to the right. It also says that pilots of helicopters must avoid the flow of fixed-wing traffic. While not regulatory, the Airman’s Information Manual provides a little more guidance, recommending a midfield entry on the downwind leg at a 45-degree angle.

Advisory Circular AC 90-66A, which covers “Recommended Standard Traffic Patterns and Practices for Aeronautical Operations at Airports Without Operating Control Towers,” provides even more detailed advice, such as:

• Avoid the flow of traffic until established on the entry leg.

• Proceed to a point well clear of the pattern before descending to the pattern altitude.

• Aircraft should be at the appropriate traffic pattern altitude before entering the traffic pattern.

• Entry to the downwind leg should be at a 45-degree angle abeam the midpoint of the runway.

• Smaller airplanes should observe a 1,000-foot agl traffic pattern altitude, whereas larger and turbine-powered airplanes should enter the traffic pattern at an altitude that is 500 feet above the established pattern altitude.

• The traffic pattern altitude should be maintained until the aircraft is at least abeam the approach end of the landing runway on the downwind leg.

• When departing the traffic pattern, airplanes should continue straight out or exit with a 45-degree left turn (right turn for right traffic pattern) beyond the departure end of the runway after reaching pattern altitude.

The danger of not maintaining the recommended pattern and altitudes was illustrated by a midair collision that occurred in December 2010, about a half mile northwest of the Shenandoah Valley Regional Airport in Virginia. This airport has a single runway oriented northeast to southwest, with a standard left pattern for both Runway 5 and 23. The National Transportation Safety Board report states that as an EMS helicopter descended toward the airport helipad from the southeast, the crew was communicating with other aircraft on the CTAF, monitoring the traffic on a traffic collision avoidance device (TCAD), and visually tracking the known traffic while watching for any other traffic in the vicinity.

The helicopter crew and the pilots of the other airplanes thought that they were aware of all the aircraft operating in the vicinity of the airport. However, radar data showed that a Cessna 172 had departed Runway 23 about 20 minutes earlier and had flown a right downwind departure, which was contrary to the established traffic pattern. After flying north of the airport, the Cessna reversed course and approached the airport from the northeast, heading toward the west side of Runway 23 at 500 feet agl. Thus the airplane was in an unexpected location, going in an unexpected direction at an unexpectedly low altitude, and was breaking just about every traffic pattern rule and advisory.

Because of the low altitude and the location of its transponder antenna, the airplane’s transponder signal was not received by the TCAD in the helicopter. The helicopter passed northeast of the airport on a modified left base about 500 feet above the traffic pattern and then turned to parallel Runway 23 on the west side of the runway as it descended toward the helipad. Thus the helicopter was in compliance with the requirement to avoid the flow of fixed-wing traffic. There was no reason for the helicopter pilot to expect an airplane to be flying 500 feet northwest of the airport; the airplane was not being shown on the TCAD, and it was blocked from being visually acquired by the cockpit structure of the helicopter. However, it still would have been possible to avoid a collision if the pilot of the Cessna had simply picked up the microphone and announced where he was and what his intentions were.

Nobody in the pattern or at the airport that day remembered hearing the voice of the Cessna pilot on the frequency, and nobody could come up with an explanation for the unusual flight path and the lack of communication. You can imagine how shocked the helicopter crew members were when they “felt a bump and a shudder,” and the flight nurse and pilot saw a white rectangle under the helicopter “for less than a millisecond.” The helicopter suffered only minor damage to the skids, but the airplane crashed, killing both the instructor and the student.

Our aviation system functions as well as it does only because we have a pretty good idea of what other pilots are going to do. Anytime someone “goes rogue” and does something unexpected, the risk for everyone in the vicinity goes way up. It is well worth the reduction in risk to follow all the regulatory and nonregulatory advice, and to be especially conscientious about communicating your location and intentions whenever you are doing something that other pilots would not anticipate.

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