The preliminary is
here.
According to a Federal Aviation Administration inspector, the grass strip was 1,133 feet in length, oriented east and west, and had an approximate one percent upslope. The accident airplanes left wing impacted a tree branch 1,150 feet from west of the departure end of the runway.
So, the impact point was about 2300 feet from the approach end of the runway, but no way to know where the pilot started the takeoff roll.
The
DA40 POH says the ground roll is about 1000 feet, assuming 2300 lb GW (1650 lb EW, 30 gallons of fuel, 400 lb of people and baggage), 500 PA, and zero wind. The allowance for grass is "at least 20%," pushing the ground roll to at least 1200 feet. In addition, ground roll increases at least 10% for each 2% upslope, so let's add another 5% and we have at least 1260 ground roll. The field was only 1133 feet long, so even using the book numbers with no safety factor, they appeared to have been at least 130 feet short of enough runway to get airborne regardless of obstructions.
In addition, climb distance from liftoff to a 50-foot obstacle is another 400 feet, giving just about the 1700-foot distance Denny gave above. The POH says:
WARNING
For a safe take-off the available runway must be at least equal to the takeoff distance over a 50 ft (15 m) obstacle.
Emphasis on "must" rather than "should be" or "is recommended." Further, as this was just an "open field," not a real runway, "uneven terrain and in particular tufts of grass can...lead to a considerable increase in the takeoff distance." In this plane, on that day, with that load, all things considered, my personal safety factor would have been at least 150% of the computed 1660 feet, or about 2500 feet of usable runway surface, and even then, I would have needed an on-site confirmation of the condition of the surface. IOW, I would not have landed there in the first place, no less attempted a takeoff if an emergency had cause me to land there.
This sort of thing is a big issue for me as the AYA Safety Director, because we've had a long history of folks trying to operate AA-1x's out of short, often grass fields on hot summer days at high DA's -- unsuccessfully. That's why I push that 150% safety margin, and read reports like this one with great sadness and concern that there's something we're not doing right regarding teaching pilots about the issues surrounding short and soft field operations.
And it isn't helped when someone says only an incompetent pilot can't get a plane to make book performance, which is something I've heard said too often over the years.
