[kip51035]

DIHEDRAL:
Say your aircraft has 10 deg. dihedral each wing. With the aircraft traveling straight you bank it 10 deg. to the right. Now the right wing is level and 100% efficient. The left wing is sticking up at 20 deg. angle very inefficient. This causes the aircraft to level itself. I had an ultra-light aircraft that had 2 deg. or less dihedral. In a 30 deg. bank it would do a perfect turn with only a little elevator. Anything less it would roll out and anything more it would roll in. I gained some altitude one day and let it roll in. I stopped it at wings vertical. I think it would go right upside down.

[kip51035]

Describe laminer flow!

Answer:
Please read the previously prepared PDF file.

[Mike Sebastien]

Originally Posted by Mike Sebastien

Next question. Why do aircraft designers put a small amount of dihedral in the wing when it isn't required?

Designers will put a small amount of dihedral in the wing even though it has no effect on aerodynamics of airplane to prevent Droopy WING SYNDROME. If the wing had no dihedral and viewed from the from the front or rear the wing will look like the wingtips were sagging. Pattern or Aerobatic aircraft designs don't want any dihedral so that when rudder is input all you get is pure yaw. That makes less work for the pilot by removing roll coupling. But they also want to the airplane to look aesthetically pleasing. If you look at a Carden wing the top of the wing will be straight and the bottom will be cut to give dihedral in the wing.

[Mike Sebastien]

Originally Posted by kip51035

What dramatic reaction does the air accomplish at the high point of the wing?

Answer:
The simple answer is it changes direction. The leading edge of the wings purpose is to separate the air. Anything that has weight has inertia. The air that is moving apart is now sucked back together due to the aft section of the airfoil. This rapid change of direction causes lift. The wing moves through the air, the air does not flow over the wing.

I disagree. The upper wing has a high point so that the air traveling over the upper surface of the wing has father to go so it must go faster to keep up with the lower surface air. With increased velocity over the upper surface and thus air pressure decreases (Bernoulli's theorem)and you get lift.

[Warbird_ace]

Originally Posted by rotormonkey13

What happens when a tandem helicopter like a chinook has a retreating blade stall? And why?

Retreating blade stall is a phenomenon where airflow over the retreating blade fails to generate adequate lift - corrected by designing blades that "flap" (retreating blade develops a greater AOA hence more lift).
Usually, this happens with extremely fast forward speeds, where advancing blades can hit near supersonic speeds and the retreating blade essentially stops moving (relative to the air its in). If this were to happen, the helicopter would fall to the side of the blade stall. Thus, the vNE (never exceed speed) is determined.
From a tandem helicopter standpoint (like a chinook), theoretically its sheer size and aerodynamic profile should prevent this from ever happening.

Now, I'll take it one further. Those fancy Russkie co-ax machines could in fact hit their stated vNE's. What happens when you get a double retreating blade stall on a co-ax machine? Technically, nothing! The coax design (while counteracting torque effects) also cancels out the effects of retreating blade stall (unless some extreme G maneuvers are performed, at which point blade stall is the least of the crew concerns).

[Warbird_ace]

How does the density of the atmosphere affect the performance of rotor blades?

What causes vibrations in a helicopter during the transition to hover phase?

[kip51035]

Originally Posted by Mike Sebastien

I disagree. The upper wing has a high point so that the air traveling over the upper surface of the wing has father to go so it must go faster to keep up with the lower surface air. With increased velocity over the upper surface and thus air pressure decreases (Bernoulli's theorem)and you get lift.

This old theory does not work, Mainly because the air is dead calm and not flowing anywhere. As a matter of fact some of the air close the the airfoil is dragged in the same direction as the wing passing through it. It was about the seventh time I had the theory of flight lecture and during the question period one of the guys walked up to the board and drew a dozen dots on the board and said " That is dead calm air, how does the wing produce lift?". After coffee all the instructor could come up with is a wing pushes air down to cause lift.

[kip51035]

Some wings have the high point as far back as 42% and others have the high point as far forward as 18%. What purpose does this offer?

Answer:
The wing with the 40% high point is a high speed wing. First wide use was on the WWII Mustang. It usually has a quite sharp leading edge. This allows it to separate the air with less resistance. Keeping the laminar flow intact and the point of a stall or separation comes at an early angle. You will also find the trailing edge pinched together like the material was too wide for the ailerons and flaps. This allows the wing to lay the air back together at a very low angle causing less drag and a small wake.

The airfoil with an 18% high point like some of the Yak aerobatic aircraft usually have a very blunt leading edge and can achieve much higher angle of attack before separation and a stall occurs. The wing after the high point is usually flat and therefore when separation or stall occurs it will cover all of this area in a very short time and the aircraft will drop like someone cut the string.

[davidmc36]

Lift has more to do with Newton than Bernoulli. Or at least explanation is incomplete using Bernoulli alone. A wing does much more than alter pressure, it deflects air downward.

https://www.youtube.com/watch?v=UqBmdZ-BNig

http://www.allstar.fiu.edu/aero/airflylvl3.htm

[Mike Sebastien]

Originally Posted by kip51035

This old theory does not work, Mainly because the air is dead calm and not flowing anywhere. As a matter of fact some of the air close the the airfoil is dragged in the same direction as the wing passing through it. It was about the seventh time I had the theory of flight lecture and during the question period one of the guys walked up to the board and drew a dozen dots on the board and said " That is dead calm air, how does the wing produce lift?". After coffee all the instructor could come up with is a wing pushes air down to cause lift.

Then why bother with a airfoil on a wing. Just hang a board on each side of the fuselage, give it little bit of positive angle of attack and viola you have a airplane that flies.


Yes there is dead calm air on the surface of the wing but each molecular layer of air moves which then creates lift.

I agree Newton's explanation accounts for a lot of the lifting force created by a wing. Only issue with Newton's theory is that it doesn't explain why a wing stalls at high speeds such as a snap roll.