AVIATION SAFETY NEWSLETTER
Thought for the month.....
For every human problem there is a neat, plain solution-and it is usually wrong.
IT'S THE MIDAIR SEASON AGAIN.... Midair collisions in the U.S. have
stabilized since 1995 at about 16 per year. The number has decreased significantly and steadily for at least 35
years, even as traffic has increased. In the airline world, between 1946 and 1978, there was a steady average
of about one fatal airline midair per year. However, following the 1978 midair collision in San Diego, the once
common accident scenario has disappeared. The principal factors explaining this change include: on-board Traffic
Collision Avoidance System (TCAS), better ATC equipment, and the requirement to be equipped with Mode C. Since
1995, GA has averaged one midair collision per 1.6 million flight hours. 56% of the 329 midairs that have occurred
during that time involved fatalities and 40% of the 658 aircraft had fatalities. 60% of all aircraft involved
managed to land safely, while both aircraft manage to land safely in 44% of all midairs.
All 329 midairs from 1983 through August 2000 occurred in visual conditions (VMC). Bright sun was the only commonly cited factor related to weather. Inadequate visual lookout - failure to see and avoid, remains the most common causal factor identified by the National Transportation Safety Board (NTSB). Most midairs involve relatively low closing speeds, as one aircraft usually strikes the other aircraft from the rear, from above, or from a quartering angle.
Most midairs occur near airports, especially nontowered airports. The typical midair occurs at low altitude on approach and landing or, somewhat less frequently, on takeoff and climbout. Accident reports indicate that about 88% of pilots involved in midairs never see the other aircraft in time to initiate evasive maneuvers; only 12% of the 658 pilots appear to have begun reacting to an impending collision. The second most common factor, was failure to follow procedures. These procedures most commonly include inappropriate entry into landing patterns and failure to use the CTAF at nontowered airports.
Midairs at high altitude are rare events. Most of those that do occur at altitude involve formation flying. If you plan to fly formation, comply with §91.111 by briefing clearly stated communication procedures and flight paths relative to each other, and allow for major differences in aircraft performance. Student pilots are involved in 36.5% of midairs. They account for 22.5% of pilots involved in midairs, and about 7.25% of all midairs involve students in both aircraft. The high frequency of students may reflect their relative lack of experience. Yet, despite the high percentage of student midairs, the data indicates that experience is not a very effective insurance policy. Half the pilots involved in midairs since 1983 had more than 1,500 hours total flight time, while one-third of the pilots had more than 3,000 hours.
Most of the technological fixs that are now used by the airlines are too expensive for GA aircraft. The best hope for a pilot to reduce his or her risk of a midair collision is with strategies that are low tech and not so very new. A disciplined adherence to procedures (proper entry into landing patterns, proper departure patterns) and proper use of the CTAF frequency at nontowered airports could go a long way towards reducing the number of midairs. Flight instructors can reduce their risk by resisting the temptation to turn off the radio and by choosing to conduct some initial training at airports and in airspace that have very little traffic. Yet, old fashioned scanning (see-and-avoid) remains the primary strategy. The problem is that, as a basic tool for avoiding midair collisions, see-and-avoid has its limits.
The human eye can detect and recognize an aircraft the size of a PA-31 or a comparable Cessna at a maximum of 1.5 miles. If the closing angle is head-on, or nearly so, even two small and relatively slow civil aircraft close at speeds in excess of 200 knots. This allows a maximum of 25 seconds for evasion under ideal conditions. However, the ideal is reduced by various factors, including the following.
First, substantial time is required to scan the horizon properly. To scan just 130 degrees of the horizon and focus on interim target areas, a pilot requires up to 20 seconds. A target aircraft may not be visible when the pilot scans and focuses on a sector and, by the time the pilot returns to that sector, closing time may be very short.
Ideal conditions also are reduced when a pilot's attention is focused inside the cockpit, where workload reduces the time a pilot spends scanning. Workload is highest during approach/landing and takeoff/climb-out, when most midairs occur.
In addition, high-wing aircraft restrict a pilot's ability to scan above his or her altitude, while low-wing aircraft restrict the ability to scan below the aircraft. Any of the factors identified above can reduce the effectiveness of see-and-avoid. The combination of any two or more factors can reduce the practical time available for a safe, evasive maneuver to just a few seconds or less. This is true even where closing speeds are relatively slow due to closing from the rear, from above, or from quartering angles.
Catfish Wharf Restaurant
7 to 9 PM
Giving and Getting a Good Flight Review
Spirit of St. Louis Airport
9 to 11 AM
FRED P. HARMS
Operations Safety Program Manager
1-800-322-8876 extension 4835