For convenience, I repeat Bellerophon's diagram of the flight envelope here.
Mike's earlier question had me scratching my head too, hence my question.
What are the fundamental reasons for each of the limitations, and what were the consequences of going outside them?
Going clockwise from the left, we have :
VLA (lowest admissible speed)
One would expect a curve for constant alpha max against IAS and altitude, not the staircase in the diagram.
Was this for simplicity of use of the diagram?
Max altitude (60,000ft)
This is the 'simplest' one: it was the highest 'safe' altitude from which an emergency descent could be made, in the case of a window blowing out, without having the blood of the pax boil....
Test flights (without pax, and with the crew pressure-breathing oxygen) did go as high as 69,000ft.
Mmo (max operating Mach number)
Mach 2.04 is usually quoted as having been chosen to assure an adequate life of the airframe.
But what effect does a higher Mach number
as such have?
Or are Mmo and Tmo (127°C) directly related?
Vmo (max operating speed) = 530kts until 43,000ft
I suppose this is related to structural limits (qmax)?
Vmo reducing to 380/400kts at about 33,000ft
What is the limiting factor here (other than qmax)?
Vmo constant at 380/400kts down to 5,000ft
What is the limiting factor here? The answer will no doubt also explain why this is slightly weight-dependent.
Vmo reducing to 300kts between 5,000ft and 0 ft
Why the sudden change below 5,000ft?
CJ