Coffin Corner
Have had this mind boggling question on my mind for months, and I can't seem to get to the bottom of it.
Coffin corner comes about at high levels as Vstall approaches/meets MMO. My understanding is that as the aircraft climbs, MMO translates itself into a lesser IAS value since the temperature gets colder and therefore the airspeed value of Mach 1 itself decreases. This explains the high speed limitation.
I also understand that as the aircraft climbs, it needs a higher true airspeed to sustain lift. Therefore, stall speed in TAS increases.
What i'm not getting is that whilst stall speed in TAS increases, in straight accelerated flight, stall speed in IAS should remain the same provided that the aircraft maintains the same configuration. Therefore, why does the low speed limit on the ASI (which indicates IAS!) increase at high levels?
Any ideas?