Sooooo, PILOTS ...You Think You Know Why Aircraft Can Stay In The Air???

[Kip Powick]

This is quite interesting, and I would think, opens the door to lively discussion

 

https://getpocket.com/explore/item/no-one-can-explain-why-planes-stay-in-the-air

PS...I always thought the answer was PFM.

[conehead]

That's pretty interesting stuff, particularly the part about inverted flight. How does an aircraft remain aloft while inverted if all the lift is being created on the top of the wing, which is closer to the dirt whilst inverted?

[Kip Powick]

How does an aircraft remain aloft while inverted if all the lift is being created on the top of the wing, ........

 While inverted the " flat bottom of a wing" ... (now being the "top" of the wing), can generate lift if the correct angle of attack is flown, normally a much higher angle of attack than flown when the aircraft is in level upright flight.

Fully aerobatic aircraft have "special wings " which allow it to fly either upright or inverted but even then the critical factor is angle of attack, especially while inverted.

 Aerobatic aircraft are able to fly inverted by changing the angle of attack and based on my experience, one has to push the nose skyward to maintain  level flight  while inverted and maintaining the correct angle of attack. Depending on the aircraft type, that is an uncomfortable  pilot position, but with practice it becomes bearable .

 

 

 

[boestar]

a flat board can generate lift at the correct angle of attack.  It will not be efficient.

A flat bottomed wing will generate lift with a VERY small angle of attack and very little if any deflection.

What about a symmetrical airfoil?  The airflow over the wing and under the wing travel at the same velocity and pressure with an AOA of 0 deg.  rendering it neutral. increasing the AOA is what causes the area of low pressure to develop on top of the airfoil. However the argument could also be made that the air on lower surface is now being deflected downward.  So which one has the greatest effect the pressure or the angle of deflection?

Interesting topic as I think in certain cases Bernoulli wins and in other cases the deflection theory plays into it.

 

[Vsplat]

Well an ALPA rep explained it best, at least for large airline equipment.

Airliners fly because the world hates money and pilots are overpaid so the earth repels them.  This also explains why wide body pilots must make more than narrow body drivers do.  The wide bodies need far more lift.

Now as I recall this fellow was a 747 driver so perhaps there was another agenda. 

Vs

[W5]

When reading that my eyes glazed over....

[IFG]

3 hours ago, W5 said:

When reading that my eyes glazed over....

Not everybody's taste in literature, for sure . But some of us nerds lap this sort of stuff up. This article, tho', maybe not so much. The writer seems to conflate mystery with complexity.

The various physics keeping us all aloft are each quite well understood (outside the ALPA walls ), but the interactions here are extremely complex, as anybody who deals with simulation would be happy to tell you. There's a lot of 'this'll work" to cover for the gaps in math - subject to verification by flight test, which is why we should be careful about drawing any conclusions from simulator behavior outside the prescribed envelope. e.g., was once told that anything beyond 2° sideslip is guesswork.

Cheers. IFG - 

p.s. re; Inverted, symmetrical airfoils don't care - altho' upside-down does feel a bit funny at first like Kip says. Wing is fat dumb and happy, but the airframe bolted on to it is pretty nose-up because of constructed (right-side-up) angle-of-incidence; less so on aerobatic birds with 0 built-in AOI (as they never really know which way is going to be up ).

Edited April 18, 2023 by IFG