Posted: 5/1/2025 10:29:54 AM EDT
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MSFS 2024 Max 8 has the N2 over 100% during much of Level Change climb. N1 is in the high 80's to low 90's % during Level Change climb. Using Vertical Speed and setting it to keep N2 below 100% results in slow climb rates. Is this the actual situation in real aircraft? Thanks in advance. |
Two thirds of the way to being fat, dumb, and lazy
Joined:
Oct 2008
Posts:
7934
EE: 100% (17)
MS, USA
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N1/N2 is determined (really estimated) as 100% of a semi-arbitrary RPM while the engine is on the drawing board. On a Williams FJ44, 100% N1 was 17,245 and N2 41,200 RPM. Later, during certification testing, it's very common to arrive at acceptable power settings with N1s above 100%. On the FJ44, I remember takeoff power settings as high as 104.4% N1 if I recall, but the max allowable N2 was 99.3%. Designing, testing and certifying a turbine engine still have some guesswork involved. I've often wondered why they don't go back and change the N1/N2 numbers during the course of the process, so that N1 and N2 max limits are 100% when they're done, but neither Williams nor Pratt & Whitney seem to do so. The PWC engines I fly now are substantially derated (which is cool, because it means they can carry their SL thrust up to a higher altitude than one that isn't, and have longer TBO and theoretically better reliability compared to one that's not), and don't approach 100% N1/N2, normally hovering in the 80's and occasionally (based on temperature/altitude) having a place on the chart that gets into the 90's. |