Carsten Wiethoff Wrote:On February 7, 2002 the NTSB published a Radar Data Impact Speed Study for UA175 and AA11. It is currently downloadable from here.

In it, the author, Daniel R. Bower, Ph.D. of the NTSB writes of UA175:

Quote:As the aircraft made its final descent to 1000 feet, it accelerated and impacted World Trade Center tower #2 at approximately 510 knots groundspeed.

At this low altitude 510 knots groundspeed is equivalent to 510 knots Calibrated Airspeed which equates to roughly 587 mph.
Taking into account the Design Diving Speed of 420 knots Calibrated Airspeed, this claims that a Boeing 767-200 could have exceeded the Design Diving Speed by 90 knots and remained intact and controllable.
I seriously don't think that is possible.

Peter Lemkin Wrote:I'm not a pilot nor an aeronautics engineer, but I am trained as a scientist and it doesn't seem logical to me either - more important it didn't seem believable to those pilots who had flown these types of planes and some who had even flown those very planes!......and WERE knowledgeable about aircraft and aircraft design and what is and is not possible or likely. 9-11 is a series of unlikely to impossible events one after another, just like 11-22-63...in my mind for the same reasons.

That said, a remote controlled plane or 'special' plane might have different capabilities. It should be possible to determine the exact speed from the FDR and some calculations based on the photos of the crash. I don't trust the government to give us the answers on any of this....:flute:

Carsten Wiethoff Wrote:

Peter Lemkin Wrote:I'm not a pilot nor an aeronautics engineer, but I am trained as a scientist and it doesn't seem logical to me either - more important it didn't seem believable to those pilots who had flown these types of planes and some who had even flown those very planes!......and WERE knowledgeable about aircraft and aircraft design and what is and is not possible or likely. 9-11 is a series of unlikely to impossible events one after another, just like 11-22-63...in my mind for the same reasons.

That said, a remote controlled plane or 'special' plane might have different capabilities. It should be possible to determine the exact speed from the FDR and some calculations based on the photos of the crash. I don't trust the government to give us the answers on any of this....:flute:

I don't see, how remote controlling an aircraft could change it's aerodynamic properties, so whether or not a pilot was at the physical controls does not matter. Of course, if it wasn't really a Boeing 767 ...
The FDR of UA175 was officially never found, so it cannot be used to determine the speed.
The study I quoted in the above post is based on the three dimensional radar returns of the plane, so as long as one trusts the raw data and there were no "plane swaps" or similar confusion, it should be fairly accurate.
Interestingly I tried to search for this paper at the NTSB website and could not find it, even if it certainly comes from that source.

[Update:] I found another NTSB speed study for UA175, based on video data. It can be downloaded here. The results vary between 473 Knots and 507 knots, depending on the method.