Hi Doug: The answer to the question is Density Altitude. On a 100 Degree day up there, the density altitude could be higher than the actual service cieling of the aircraft. With high density altitude you loose your engine performance and perfomance of all lift devices, Prop wings ...etc. in ground effect the drag vectors of the airflow is changed directionally so it becomes less. so you could get off the ground and then sink back down once you get out of ground effect. This all boils down to preflight planning. You should always calculate you density altitude before you get in the plane even if you are flying at sea level all the time for this one time you don't. You should always check your takeoff performance also. I don't know the specifics of the incident but I can assure you the NTSB put blame on the pilot for not accounting for Density altitude Airfreddy
There are many NTSB reports involving airplanes that got into the air but failed to climb out--often the result of overloading, high density altitude, and frequently some form of obstructions at the departure end of the airfield. One of the most recent involved a Bonanza A36 taking off from what should have been an adequate length strip, getting into the air, but stalling and cartwheeling off the end. The indications are that it was overloaded, and there may have been some engine problems as well. I've seen the video but I can't seem to locate it now. The problem really is that once you've overloaded an airplane, you're into test pilot status--you won't know what its performance (or lack of performance) will be. You're correct, that the airplane will accellerate better in ground effect than on the ground. But that still doesn't mean that it will accellerate to best angle before the obstruction comes--and when it is overloaded, best angle may be at a significantly higher airspeed than normal. One of the typical training issues is that much training is done on airfields that are huge compared to the actual needs of the training airplanes. Out here in the mountain west, many of our runways are more than a mile long--and yet, the typical trainer can safely rotate and climb out in a thousand feet or less, with no obstructions. So students don't get the feel of what happens when they have only a small strip to contend with. Let me give you a couple of examples. On Memorial Day, I invited a low time pilot friend to accompany me to a ranch strip near here for a "fly in breakfast". The strip is at 5500' and it's 2800' long, mixture of grass and gravel, so it's a little bumpy. I used to keep my airplane there, so I'm very familiar with it. It was a nice day, not too hot, probably about 70-75F when we took off later in the morning, with little wind. That made our density altitude about 7700'. My airplane is a very much modified C172 with 180hp, constant speed prop, droopy tips, flap gap seals--what I refer to as a semi-STOL airplane. On the hard surface runway at Greeley or Fort Collins, I can expect to easily break ground before 1000', same weather, same load. On the softer surface, even with 10 flaps, I expected to break ground at around 1200-1300', and that's what we did. I kept it in ground effect long enough to build to best angle (about 60 knots indicated), retracted the flaps, and then climbed out, gradually increasing speed to best rate (about 80 knots indicated)--and remember that my airplane is not a typical 172, so my V speeds won't be the same as other's. And because there are no obstructions off the end, I allowed the speed to build to best rate, which meant that we were only a couple hundred feet in the air by the end of the runway. My friend has flown with me many times, but always from hard, long runways. We've flown around the area here quite a bit and to and from OSH last year, so he's seen the performance of my airplane. Soon after we got into the air, he commented somewhat excitedly, "I didn't think we'd get off!" That's because he saw the end of the runway disappear much quicker than he was accustomed to, partly because I was doing a soft-field takeoff so that the nose was blocking it. On an occasion a couple of years ago, I had the airplane fully loaded with 4 people, no baggage, slightly more than half tanks. Without weighing everyone, I'm sure that we took off very near to gross. The morning was cool, around 60F. We easily broke ground at a little less than 2000' down the 4800' runway we were on, 5000' elevation. We were sight-seeing, so about an hour and a half or so later we landed in Laramie, borrowed a car, went into town for lunch, and returned around 2 p.m. The temp had climbed to 90F, and now we were well under gross, but the density altitude was over 10,700! I warned my passengers that we would take a long time before we would break ground, and that our climb out would not be very spectacular. We broke ground at roughly 3500', and our climb rate was about 300' per minute. I was expecting that, because I used to instruct at Laramie. But although I had warned my passengers, all of them were a bit surprised by the airplane's mediocre performance. My point here is that often students are not given adequate training in short field and high density altitude situations. There is no substitute for experiencing both of them in realistic situations. All too often, when the end of the runway is looming or there are obstructions, a pilot who hasn't had the experience will try to horse the airplane into the air, well before it is ready to fly safely. Does this help your understanding a little? Cary
The video you mentioned is in an AOPA Webinar "Takeoffs & Landings...The Expert Approach". On AOPA.com/webionears.
I almost did that.