Aviation Safety Corner

GREETINGS! For this month's topic, I would like continue our discussion on, "Wind at Your Back." The record shows that pilots should not discount the effects of a tailwind on takeoff and landing performance. This is Part III of IV.

Now let's start our discussion, "On the Record." While most of the pilots with whom I talked seemed to indicate that they don't think tailwinds cause many accidents/ incidents, an examination of NTSB Accident/Incident Data reveals otherwise.

Data from 1983 through May 1996 includes 1,102 reports in which "tailwinds" are ascribed as factors. They represent about three percent of the 36,421 aircraft accidents and incidents that occurred in the U.S. during the period.

This results in an average of about 85 tailwind mishaps per year, with about two-thirds being classified as accidents. Compared to other environmental factors, tailwinds are reported as a factor in aircraft accidents with about the same frequency as high-density altitude, fog, and low ceilings. They occur about twice as often as accidents involving carburetor ice and about half as commonly as crosswinds.

In terms of where tailwind accidents occur more frequently, Colorado, Idaho, Nevada, Oregon, and Vermont came out with percentages significantly higher than the average. Delaware, Kentucky, and North Dakota had markedly lower-than-average percentages. The other states came pretty close to the average percentage: 3.03.

The types of aircraft more frequently involved in tailwind mishaps seem to be consistent with overall fleet distribution. Of the 1,102 accidents/incidents, Cessna's were involved in 447 (40.5 percent of the total), Pipers in 216 (20 percent), Beechcraft in 70 (6.5 percent), "Grumman's" in 46 (four percent) and Mooneys in 18 (1.5 percent).
Of the specific aircraft, the Cessna 172 was listed most frequently, with 132 occurrences (12 per-cent of the total). The Cessna 150/152 series came in second with 90, and the Piper PA-28 series was third with 70.

What is interesting is to compare these accident trends with the AFM performance corrections for each specific aircraft. For most of the high-wing Cessna's, the correction factor is to increase distances for takeoff and landing performance by 10 percent for every two knots of tailwind component. The Cessna 150/152, 172 and 182 fleet accounted for 274 accidents and incidents (25 percent of the total). For the Cessna 210, which was involved in 22 reports, the correction is 10 percent for every 2.5 knots.

For most Twin Cessna's, the correction is five percent for every two knots. The entire Twin Cessna fleet accounted for only 12 occurrences. It would seem that these aircraft are affected by tailwinds on takeoff and landing somewhat less than the single-engine fleet. Higher airspeed aircraft have a higher wing loading and generally are aerodynamically cleaner. Also, a 10-knot component is a lower percentage of the airspeeds involved.

Now let's discuss, "Phases of Flight." Let's take a closer look at the data for the years 1990 through 1995. There were 429 tailwind accidents and incidents. Of the total, 284 were classified as accidents, an average of about 47 per year.

Since accident reports provide much greater detail than incident reports, focusing on them gives better insight into what really happens in a tailwind mishap. Most of the takeoff and landing accidents involved overruns on short runways. These tended to have few fatalities or serious injuries; the usual results were loss of the aircraft or substantial damage. Many of these accidents involved pilots already engaged in dealing with other emergencies or forced landings.

The situation producing the most serious injuries and fatalities involved aircraft attempting go-arounds.
Now, in conclusion, remember, if an unexpected tailwind is encountered on landing; go around if there is any doubt about being able to stop the aircraft on the runway.

Don't miss next month's Aviation Safety Corner, when we'll finish our discussion on "Phases of Flight" and "Landing, Takeoff Accidents" in Part IV of IV.

Larry G. Harmon
FAA AVIATION SAFETY COUNSELOR

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