Lecture 12: Aircraft Performance

[@danielnofal]

Thanks MIT for this wonderful course. Essential for pilots.

[@gehirnx]

This is exactly what I needed!! Go MIT!

[@princetonjoshua3028]

I dont mean to be so offtopic but does anyone know of a way to log back into an Instagram account?? I was stupid lost the login password. I would appreciate any help you can give me.

[@bobbybrantley8298]

@Princeton Joshua Instablaster :)

[@princetonjoshua3028]

@Bobby Brantley I really appreciate your reply. I got to the site through google and Im in the hacking process now. I see it takes quite some time so I will reply here later when my account password hopefully is recovered.

[@princetonjoshua3028]

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[@bobbybrantley8298]

@Princeton Joshua you are welcome :)

[@abigabaamos6842]

Good lecture for young pilots

[@HossainRonnie]

I think the reason air density is reduced with higher humidity under atmospheric conditions is because of the lower molar mass of H2O (18u per molecule) relative to N2 (28u) and O2 (32u). If you model the air as an ideal gas of non-interacting point particles (reasonable assumption under these temperatures and pressures), then every molecule in the air should occupy the same volume. Since density is more or less the mass per unit volume, having a higher proportion of water molecules in one cubic metre of gas/air means you'll have less mass of the particles all added together (compared to having more nitrogen and oxygen), hence lower density. And as a consequence the rotor and airfoil will displace fewer kilograms of air per second (at the same speed) and have somewhat degraded performance. I would expect around 2.5% lower density considering I think even 100% humidity only means like 4% of the air mass consists of water vapour, so perhaps there is some quadratic term that explains the 7%, or maybe the 7% incorporates less efficient combustion. Let me know if you know what the 7% is based on, I am curious! 🙂

[@MohamedIbrahim-nx5jy]

Exactly, a higher water vapor content also means more condensation is present in the atmosphere which releases heat since condensation is an exothermic reaction and the heat increases the energy of the molecules making the occupy more volume and thus being less dense.

[@buckyperchski-mc2vo]

So ur sayin i dont need to calculate landing distance if i land my C152 at JFK?

[@STEM671]

ENGINEER PILOT PHYSICIAN AND SPACE WALK WITH DUE ACHIEVEABLES

[@conned]

In real flying, there is no time to interpolate...

[@aronbijl4109]

Yes Phil, we know, you are smart, but when had to read the graph about densities, you asked the crowded. Please stick to the content you are presenting and bloat less bout yourself!

[@georgiagant4992]

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