Coffin Corner, is it there?

I've understood that when flyin' high and fast coffin corner comes into equation, which means that you go a bit too slow, you'll stall, you go bit too fast, you (mach) stall. Or so i've understood. The higher and faster, the more significant. The U2 spyplane had only 10 knot window to fly in.

Now when i reduce the throttle at very high altitudes, the plane stalls pretty much at same speed (IAS) it would on sea level. This is true not only in DCS but also in FSX's higher end fighter planes models i've tried. But i've heard that PMDG passenger planes do model coffin corner.

So, in these simulations generally, is the coffin corner there or not? I just like to know...

Now when i reduce the throttle at very high altitudes, the plane stalls pretty much at same speed (IAS) it would on sea level.

That's correct and the key word here is "IAS". As you go higher the same IAS will correspond to a higher TAS. At one point your stall speed (IAS) will get very close to your critical Mach number (TAS).

Like a U-2 "Dragon Lady" at FL700

Heard it said that they (at operational altitudes) operate in a very small window (like 5 Knots Indicated) between Stall Speed and Mach Buffet onset.

IAS stall speed should be about constant. However, fighter mac Mach numbers are so high that you can't really get to the corner (also for fighters, it might not be aero issues that raise a limit, but heating and engines). The U-2's problem was that it flew so high and had a low M_crit.

It's not about 'is the coffin corner there in simulations' - certainly some simulations may not model mach buffet, but the real question would be 'is this aircraft subject to mach buffet'.

For a supersonic fighter, this problem just flat out does not exist.

For a passenger aircraft, you could certainly over-speed both engines and wings, but that's their design limit.

The A-10 is also subject to this condition with its straight wing, but you'll just never get an A-10 into a situation where it can travel high and fast enough for this to be a problem in straight and level flight. You will certainly encounter compression issues in a high-speed dive though, and you may over-speed the engines in that case as well.

So, in these simulations generally, is the coffin corner there or not? I just like to know...

IAS stall speed should be about constant.

okay thx ... but in passenger planes the IAS Vmo comes down, but the clean config stall IAS speed remains the same, hence the smallish margin in the IAS indicator like in this picture:

http://m2.i.pbase.com/g3/23/582523/2/124628692.bNVc3wKR.jpg

The only planes in DCS to which this applies atm would be the MiG-15 and the F-86. All the others cannot fly high enough or are supersonic by design. On those two planes, high altitude fighting is a bit frustrating at times as you stall out trying to turn while simultaneously popping the airbrakes out trying to keep it under mach .9. A dogfight at 10km+ in either the MiG-15 or F-86 is a rather unique experience in DCS because of this.

The only planes in DCS to which this applies atm would be the MiG-15 and the F-86. All the others cannot fly high enough or are supersonic by design. On those two planes, high altitude fighting is a bit frustrating at times as you stall out trying to turn while simultaneously popping the airbrakes out trying to keep it under mach .9. A dogfight at 10km+ in either the MiG-15 or F-86 is a rather unique experience in DCS because of this.

Gonna test this today!