On a Sunday morning in March a 150-hour private pilot, 61 years old, and his wife went for a short flight in a rented Cherokee Warrior. It was a nice blue-sky day. The nearest weather reporting point, 20 miles to the south, was calling the visibility 10 miles — which meant, for all practical purposes, unrestricted — with a few scattered clouds scudding along at 3,600 feet. Though the first day of spring was still around the corner, the temperature was an unseasonable 77 degrees. A blustery wind was blowing: 16 gusting to 23, with a peak gust of 28 knots. There would be some bumps — but it would surely be a fine day for flying.
The couple told the airport manager that they were going out to “do maneuvers.” They took off at 11:15 from Runway 18; the wind then, the airport manager recalled, was between 14 and 20 knots, directly out of the south.
The next sighting of the Warrior, about a quarter of an hour later, was at a small private strip on a farm 10 miles away to the southwest. The farmer’s son was climbing onto his tractor when he saw an airplane fly low over the runway. Not recognizing it, he assumed it was just a pilot having fun making a low pass. A few minutes later, however, the airplane returned and landed on Runway 26, taxiing to the west end, where the tractor was. When the couple emerged from the Warrior, he recognized them as old friends whom he had not seen in several years.
He chatted with them for 20 minutes before climbing back onto his tractor to resume working. He last glimpsed the Warrior beside the approach end of Runway 8, facing south and, as he supposed, doing its run-up. It was not until an hour later, when he was leaving the farm in his car, that he saw the wreckage of the airplane. Both wings torn from the fuselage, it lay on its left side, just north of the departure end of the runway. He found the couple alive and responsive and called for help. They were taken to the hospital, where the pilot died the next day. His wife survived.
The National Transportation Safety Board gave the following probable cause:
The pilot’s failure to maintain airplane control during takeoff, which resulted in an aerodynamic stall and subsequent collision with trees. Contributing to the accident was the pilot’s inadequate preflight performance planning before departing on the soft, grass field with a quartering tailwind.
The NTSB investigator, examining the scene on the day after the accident, found clear tire marks along the grass runway and concluded that the Warrior had become airborne after rolling approximately 1,900 feet. It then “veered to the left, stalled, and collided with trees before it came to rest in a field.” No evidence was found of any mechanical failure of the airplane; he noted, however, that the flap handle was in the fully retracted position.
The investigator described the runway as a “soft” 2,600-foot strip on which the grass stood between 6 and 10 inches high, and went on to say that extrapolation from the published performance chart indicated that with retracted flap and on a paved, level and dry runway the airplane would have required “about 2,312 feet” to take off “under the existing wind conditions.”
The investigator could not know what the wind conditions had been at the moment of takeoff, but probably assumed the worst case, which, considering the outcome, seems reasonable. If the wind at the farm was about the same as at the nearby public airport, it was out of the south at 15 to 20 knots.
The pilot can hardly have been unaware of the wind; he had been standing in it for 20 minutes. But he probably felt that it was nearly a direct crosswind to Runway 8/26; that would explain why he felt justified in landing one way and taking off the other. The manager of the public airport had said the wind was “directly” out of the south, but if we assume that it might have been from, say, 190 rather than 180 degrees, then the tailwind component on Runway 8 would have been 5 to 7 knots.
I have a “Take-off Weight Chart” from a PA28-161 POH that was probably prepared for Great Britain or Australia, since takeoff distances are in meters and weights in kilograms. It is more detailed than the standard American chart, with corrections for runway surface and slope, and it is more difficult to use. Nevertheless, a couple of things about it jump out at you. One is the sensitivity of takeoff distance to surface type. The difference in runway requirement between a “hard sealed surface” and “long wet grass” is about 50 percent. The part of the chart dealing with the wind does not allow for tailwind components of more than 5 knots, but it appears from extrapolation that a 7-knot tailwind component might add another 20 percent to the takeoff distance. These factors don’t add to one another; they multiply, so that 50 percent and 20 percent make 80 percent, not 70 percent.
Taken together, the grass, the soft condition of the surface, and the tailwind component made the runway length marginal. Most probably the pilot did not realize how much runway he would need. His leaving the flaps retracted suggests that he may have underestimated the retarding effect of the grass, and in that case he may not have used a nose-high soft-field takeoff technique either.
That he got off the ground in 1,900 feet proves, at least, that it could be done. It could suggest that the airplane was light, that the tailwind component was less than expected, or that, seeing that he was nearing the end of the runway, he lifted off prematurely in ground effect.
An airplane will become airborne and fly in ground effect at a speed below its normal takeoff speed, but unless it is a good deal more powerful than a Cherokee Warrior it will accelerate only as long as it remains just clear of the ground; if the pilot tries to fly it out of ground effect too soon it will mush, and if he continues to try to make it climb against its will it will stall. A gust from behind would cause it to settle back toward the ground.
By choosing to take off on Runway 8 the pilot had set up another problem that he probably didn’t recognize until he was halfway down the runway. The farm buildings were clustered at the east end, and around them were a number of trees; there was also an east-west line of trees along the north edge of the property, converging with the departure end of the runway and, with the trees around the buildings, in effect surrounding the northeast corner of the property with an unbroken screen. Another line of trees ran north-south along the western edge, but there was a gap in that barrier at the end of the runway for a groundhugger to slip through. There was no such gap at the east end.
Most likely, when the pilot decided to begin his takeoff roll at the west end of Runway 8 the trees at the east end, half a mile away, did not look imposing. He expected that, in any case, he would be airborne and climbing well before he reached them. By the time he realized he would barely have flying speed when he neared the end of the runway, it was too late to abort; and now the screen of trees loomed in front of him, so that he not only had to get off the ground but had to clear them as well. Time was doubly against him. When the pilot realized he was going to need the whole runway, it was too late to stop; and when he realized that there was a screen of trees in front of him, it was too early to climb. He had put himself in an impossible situation.
The runway length, the surface condition, the wind and the trees were all, taken separately, ambiguous counselors. None of them, by itself, pointed conclusively to the choice of one runway or the other. Taken together, they called out for caution; but the pilot did not hear.
This article is based on the NTSB’s report of the accident and is intended to bring the issues raised to our readers’ attention. It is not intended to judge or to reach any definitive conclusions about the ability or capacity of any person, living or dead, or any aircraft or accessory.
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