QUOTE (too low @ terrain,Sep 26 2007, 03:13 PM)
Speed limits B767:
turbulent airspeed: 290kt/.78M
gear extend: 270kt/.82M
gear retract: 270kt
alternate gear extension: 250kt/.75M
max tyre speed: 225mph (= 196 kt)
min speed above FL250: Vref30+100 kt
min speed for clean LDG: Vref30+50 kt
took me a little time to answer - I am working rather a lot these days.
VMO/MMO = maximum operating limit speed is a speed that may not be deliberately exceeded in any regime of flight (climb, cruise, or descent)
Question: Why are there two speeds, i.e VMO-slash
Answer: VMO/MMO refers to "Airspeed or
Mach Number, whichever is critical at a particular altitude
(Remark: Mach no. is usually not calculated below 25,000 ft)
VMO is based on the IAS (indicated airspeed), which is simply speaking measuring the plane's aerodynamic drag.
This aerodynamic drag gets lower in thinner air = on higher altitudes.
A constant indicated airspeed results in a higher Mach number and a higher True Air Speed=TAS, the higher a plane flies.
___500ft 290kt 290kt 334 0.44
_1,000ft 290kt 296kt 340 0.45
10,000ft 290kt 348kt 400 0.54
25,000ft 290kt 435kt 501 0.72
35,000ft 290kt 493kt 567 0.86 = speed limit
So if a 767 is flying 645 mph at 700 ft MSL see NTSB Report On Ua 175 - thread
it is exceeding it's maximum operation limit speed of 360 kt by 55%
__ 700ft 360kt 360kt 414 0.54
__700ft 560kt 560kt 645 0.85
Make your own calculations:
Mach Number calculator http://www.grc.nasa.gov/WWW/K-12/airplane/mach.html
True Airspeed calculator http://www.csgnetwork.com/tasinfocalc.html
The other speeds indicated by TLT are self explanatory. Vref has nothing to do with the govt loyalist site, but rather with a calculated take-off speed depending on take-off weight and flaps setting (hope I am correct here).
Final thing: ZBAA is Beijing, just in case you were wondering.
*EDIT* forgot to mention: the fact, that the max. gear retract (extend) speed and the max. speed in turbulent air are considerably lower than Vmo is a clear indication, how 'vulnerable' the airframe can be in case of a speed exceed.