B747 performance question...
 

My brother was listening to an internet radio show that began discussing the recent crashes with Air France and 9/11. One of the hosts on the show is absolutely positive that a B747 can not fly at 400mph at 700' MSL. It sounds like he is on the conspiracy train and that 9/11 didn't really happen, and the flight data recorders were tampered with and gave "massaged" data.

He asked me if it possible for a B747 to fly at that speed at such altitudes... So I do what I do best, got on Microsoft FSX and set it up. The simulator let me do it, even flew faster than 400mph before it gave me the structural damage crash. Granted it's only a desktop game and not the real jet or even a full motion simulator. I also immediately thought of the FAR violations for such speeds and altitudes...

So I asked a friend that has 30 years of Boeing time, and he told me it could be possible, but he has not flown the 747 so he isn't sure of when the clacker would come on. I do know someone that was a FE on a cargo 747, so I was going to ask him too, but I figured I would start here first.

Is it possible to fly a B747 @ 400mph @ 700' MSL causing damage or not? It seems as if the host is convinced that a 747 would self destruct before it reached a target, say a building.

For those who want to hear it, this is the link to the radio show:
No Agenda | With Adam Curry and John C. Dvorak | In The Morning Discussed in the early minutes of the 6/11/09 show.

I think so..
 

I flew 747-100s and -200s at my first airline, then -400s at United. It's been 8 years since I flew the -400, but I think so.

At the first company, I watched a cockpit-video of a maintenance test-flight, in Tuscon, at about 10,000 ft. They needed to take it past redline and get the overspeed warning. Keep in mind,there is a warning for exceeding IAS, and also one for exceeding Mmo (Mach). The 10,000 ft check was for IAS warning.

As best I remember, IAS redline was 386 kts; Mmo was 0.92 Mach. I think that is true on all models.

I was amazed watching the video: they set takeoff power, and let it accelerate. Not only did it hit 400 kts IAS, the rate of acceleration at that speed made it look like it could have hit 450!! They terminated the speed run right as they hit 400 kts.

Now, to address the 700 MSL question: Probably. I won't go into the full explanation of the four significant types of drag, but for the same IAS, the drag is the same regardless of altitude or density altitude....except for Mach-wave drag. But if the 747 can hit 400 IAS at 10,000ft, then it should be able to at sea level...where the mach number is lower, and therefore, wave-drag is lower. (And the engines have even more thrust).

Not sure why the hosts were discussing a 747 and 9/11, since it wasn't involved.......

Thanks for the answer, that is what I thought.

Then again, I was wondering why he picked the 747 too. Maybe just because it's easy to remember for those in the non-flying community? Like every sports car is a Corvette, or every motorcycle is a H-D...