Timeline for Does lift equal weight in level flight?
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| Dec 14, 2018 at 4:12 | comment | added | AirCraft Lover | @Stankinator, there are clear force direction. Lift force consists of two component: Lift force, which is L * cos (AoA), which AoA=Angle of Attack. This force is oppose the w=mg. While induce and parasitic drags are opposing the thrust. to make airplane fly (i:e: cruise), the L * cos(AoA)=mg. But, L * cos(AoA) itself is produced by the thrust which must be much greater than the drag components. | |
| Jul 12, 2017 at 17:57 | comment | added | Gypaets | @MSalters There are infinite directions (aka plane) perpendicular to the fluid flow and lift points in one of them. The good thing about having a consistent lift definition is that you don't have to change it depending on the flight attitude- it remains the same even in a nosedive in Mars. Admittedly, there are special situations where you need to define reference directions or quantities yourself, but it's not the case now. | |
| Jul 12, 2017 at 17:43 | comment | added | Gypaets | @Stankinator I have no problem using simplifications such as "thrust is parallel to aircraft axis", but referencing a flow magnitude (lift) to a random unrelated variable (gravity direction) doesn't make sense at all. How would you answer the lift statement question in my first comment? I really couldn't explain basic concepts such as "lift coefficient" or "increased stall speed in a turn" with your lift definition. Changing the definition depending on the question is for sure more confusing than just using the correct one. | |
| Jul 12, 2017 at 15:59 | comment | added | Stankinator | Lift as a scientific term is clearly defined, but in practical terms for myself as a pilot, answering questions like this, that definition often leads to more confusion than clarity. Yes, the true lift forces on an airplane rarely equal its weight; a propeller's thrust, and much of a jet engine's as well, comes from the lift force, but it opposes drag instead of weight, and no one ever refers to thrust as "forward lift." It is much easier to speak of lift as "the force that opposes gravity" in many cases. | |
| Jul 12, 2017 at 12:43 | comment | added | MSalters | I'm not so sure lift is clearly defined. Sure, in the easy case of an infinite fluid flow without turbulence, the direction of fluid flow is well-defined. Reality is somewhat more complex, with wind and convection. And I'm not sure lift is even defined at all for that "falling body" example. There are two directions perpendicular to the fluid flow, after all. | |
| Jul 12, 2017 at 7:39 | comment | added | Gypaets | Lift is clearly defined. Why do you need to make up your own definition (which is neither logical nor intuitive) for it? Would you say the statement "lift needed to perform a 60° bank turn is equal to the lift needed for level flight" is true? | |
| Jul 11, 2017 at 22:34 | vote | accept | lemonincider | ||
| Sep 25, 2017 at 13:46 | |||||
| Jul 11, 2017 at 16:36 | history | edited | Stankinator | CC BY-SA 3.0 |
Clarified that 'lift' as I use it is not the same as the definition of the lift force
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| Jul 11, 2017 at 16:32 | review | First posts | |||
| Jul 11, 2017 at 16:43 | |||||
| Jul 11, 2017 at 16:30 | history | answered | Stankinator | CC BY-SA 3.0 |