Hi. I'm not a pilot but find myself in a discussion with one who ...
1) insists that ground effect would have made it impossible for flight 77 to hit the first floor of the Pentagon on 9/11
2) that the top speed of a 757 at ground level would be far less than the 460 kts recorded by the FDR.
I would appreciate an objective opinion on these issues and also what would the top speed of a 757 be given the flight path it took that day.
I know there are a lot of variables that factor into this but I'm just looking for a ballpark. According to some info, radar shows that Flight 77 did a downward spiral, turning almost a complete circle and dropping the last 7000 feet in two-and-a-half minutes.
It clipped light poles on the way in. According to one analysis: Assuming that the ground at the base of the poles was elevated 18 feet relative to the Pentagon's foundation, and that the poles were clipped at a height of 20 feet, the aircraft's wings were 38 feet higher than the foundation at 600 feet before impact. Assuming that the plane's wings were at an average elevation of 8 feet upon impact, the plane would have lost 30 feet of altitude in 600 feet of travel, averaging one foot of altitude for each 20 feet traveled.
Hopefully this is enough info to give a ballpark answer.
Thanks a bunch,