Boeing 767 Low-altitude Top Speed Options

[Guest_Ningen_*]

Does anyone know how fast a Boeing 767 can fly at low altitude? The top speed at cruising altitude is over 500 mph, but I've heard the following about flight at 700 feet altitude:

The power plant will max out at 330 mph.

The plane will begin to shake itself apart at over 220 mph.

At 700 feet altitude, the air is so thick that if you go too fast you max the rotation of the turbines, the engines can't suck in air, and the engine starts acting as a brake.

Does this make sense?

Where could I get more detailed information about flight limitations (or whatever you call it) of the Boeing 767?

Thank you.

This post has been edited by Ningen: Sep 2 2007, 04:19 AM

[fransan]

I would like to tell you some of my own experience of high speed at low altitude flying.
Many years ago, we didn´t have the limitation of 250 kias max below 10000 feet in México, and oil prices where not a factor. The time it took to get to places however, somehow had become very important and attractive to people and our airline execs. So we flew all the time at max. speeds. I think about it now and find it hard to believe.
But we acctually flew (B.727 by the way) at up to 390 kias as low as a 1000 feet. (Yes one thousand feet) CRAZY.
What I´m trying to say, basically is, there´s no problem with those airplanes going up to max speed at any altitude.
Many times also we would go beyond "barber pole" (the max. speed shown on the indicator) on descent and hear the "tac, tac, tac, tac" (similar to a machine gun) warning, pull back a little to go back to within limits.
There was an incident, I believe it was an AA B727 that had a very scarry spyraling descent where the FDR went beyond the graph and there was speculation that it had gone beyond MACH 1 for a few secs. Maybe some of the pilots here can remember the case. (The pilots had deactivated the leading edge slats at cruise to extend 2 degrees of flaps, trailing edge only, and the FE came back from the bathroom, saw the CB out and pushed it in, they where something like FL350 and as the leading edge slats started to extend by this action, the airplane became uncontrolable, and kind of spyraled down, the pilot was able to recover from the dive after extending the landing gear, way above max. landing gear extension speed, at something like 12000 feet. The aircraft sustained some damage but still was able to continue for a landing basically in one piece.)
The speed at which a Boeing will start coming appart I would think is very hard to determine, they must have a ball park figure I guess (Boeing). I think it should be just beyond MACH 1 as these are not supersonic aircraft.

My $ 2c

[dMz]

But we acctually flew (B.727 by the way) at up to 390 kias as low as a 1000 feet. (Yes one thousand feet) CRAZY.
What I´m trying to say, basically is, there´s no problem with those airplanes going up to max speed at any altitude.

Hello fransan,

FAA type data sheet for B727 says:

http://rgl.faa.gov/Regulatory_and_Guidance...1C?OpenDocument

http://rgl.faa.gov/Regulatory_and_Guidance...6;FILE/A3we.pdf

"Airspeed limits: VMO/MMO - 390/0.9 (KEAS), Dual Mode 390/350/0.88 (KEAS)
For other airspeed limits see the appropriate FAA approved Airplane Flight Manual."

390 kts is right at V_mo, not ~150 knots over V_mo. (~142% of V_mo for B767-200 in the OCT "UA175" case).

My $0.02, and I'm still looking for sourced turbofan engine overspeed survivability evidence (refer to my air density vs. altitude post above).