Originally Posted by
travelator
That is what the flight manual is being quoted as saying.
At 70000ft feet there is 24.5 times less px than at sea level. That means roughly you may only use 24.5 less fuel. This means the engine will not work. Clearly you have never done bgt.
Whislt as you decrease fuel as you increase alt the compressor has to work hard to give you enough air to continue the cumbustion. Basic gas.
Every gas turbine work on the same principles. The u2 is nothing special.
The n1 at 70000 feet would be at or near max n1 and not at sl n1 speed.
The engine will not work at sl n1 at 70000feet. My i suggest you go do basic gas
N1 is the dead give away for engine profromance. It is one of the very first t hings that is looked at when a drop in power is detected.
The higher the alt the faster for a give power setting the n1 must work, in other words whist at sl the n1 will give 1 to get to X whislt at 70000 it will have to work 24.5 times as hard to give X
Idle will be a few % above self substaining that % is the same at alt but the compressor must work harder to maintain it ie an increase in n1