In Vietnam one of the problems the Migs had was that the US aircraft were all faster than they were at the lower altitudes. A Mig-21 could not catch our fighters down low. I recall reading that our F-105's would sometimes go into attack a target with a Mig-21 flying formation. The Mig could not get into position to fire because if he backed off on the throttles for a second or did a maneuver to get behind the 105's they would leave him.
I also recall one Indian pilot saying that while the Mig-21 was theoretically a Mach 2 airplane every time he got much past Mach 1 the low level fuel light came on. But our Red Eagles unit flying Soviet equipment at Tonopah said that it was very impressive how you could get a Mig-21 up just past Mach 1 and then back off on the throttles and it would stay supersonic for quite a while.
And the other reason the Mig engines had short service lives was that it fit their philosophy. You had to keep people working in a Communist county, where the Govt owned everything, so you built stuff designed not to last very long. You had to keep the factories going and you did not expect equipment to last very long in combat anyway. They did not build Migs with lots of access panels because they would be sent back to be rebuilt, not fixed in the field. Of course, one bullet in the wrong place and the airplane was as good as destroyed.
At 10,000 ft air pressure is 10.1 PSI. At 20,000 ft air pressure is 6.76 PSI. I can tell you from personal experience that it makes a hell of a lot of difference if you are trying to breathe!
Mlflyer,
I don't think much could keep up with an F105. I've heard of 900+ KIAS and that a small bit of damage could be catastrophic at those speeds. I've seen 740KIAS at about 6000' but that was after ramping down but with a high drag tank on. However a few guys got kills with them!
Cheers,
Biff