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convexengineering / SPaircraft

Models for commercial aircraft design
http://spaircraft.readthedocs.org
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Some arbitrary constraints pushing the model, oops. #84

Closed 1ozturkbe closed 7 years ago

1ozturkbe commented 7 years ago

Hey @mayork, I noticed this constraint today within D8:

CruiseAlt >= 35000. * units('ft'),

Oops. Putting this here as a reminder to scrub the entire model for constraints like these, because I'm pretty certain this was pushing both 737 and D8 (altitude was lower-bounded).

mayork commented 7 years ago

not an oops....TASOPT requires cruise alt to start there so I was enforcing that. To get a realistic design we need a constraint like that because we have ot have the capability to fly at that kind of cruise altitude

1ozturkbe commented 7 years ago

We definitely should not set this, and the model works fine without it. It is totally arbitrary; I don't see why 35000ft is better than 30000ft. The D8 and M072_737 want to fly low and slow, so we should let them.

1ozturkbe commented 7 years ago

I remember why we decided to set this, but now I'm backing out on that decision. I think it is a bad idea. Instead I think we should constrain the flight time to cruise altitude or the distance to cruise altitude or neither.

mayork commented 7 years ago

I see what you're saying but I think it's really more of a capability thing...any realistic aircraft is going to have to be able to fly in the upper 30,000s...one option is to set a singly constraint that like rate of climb at x altitude is greater than some value we choose and then let cruise altitude be totally optimized

1ozturkbe commented 7 years ago

Actually, to give a better idea, here's the cruise segment altitude for the std_killer_chart. D8_standard_morphing_chart_CruiseAlt.pdf

1ozturkbe commented 7 years ago

So I had actually added a top of climb minimum climb gradient to D8 from TASOPT, so I think we should be good. I just don't want a minimum cruise altitude to skew results.

1ozturkbe commented 7 years ago

I've reduced the altitude to 25,000 ft, just so we can accommodate the M0.72 73 flying just under 30kft. Otherwise, the lower bound in no way influences the results. Closing.