So - I understand the wing shape gives lift to jets and planes. Got it.

When a jet or plane turns sideways - does it start slipping earthward ? Do you have to tilt it slightly upwards to keep level flight if sideways ?

photo like this prompted question:

https://www.pinterest.com/pin/96686723222261991/

gracias.

The Bernouli effect (air pressure differential caused by the shape of an air foil) is only a minor component of lift. Most of the lift of a wing is due to pushing air against gravity, like when you stick your bladed hand out the window of your car at speed. Engine thrust vector can also be a significant component. The fighter jockeys will have to confirm this, but I think the factor that is preventing a plane from falling out of the air when it is flying in a wings vertical attitude is mostly inertia, but probably some component of thrust vector as well.

Do you remember vectors from physics? Wings generate lift vertically perpendicular to the wing. When you bank (lean) you now have a horizontal component of the lift vector, which is what causes the plane to turn. As such you have decreased the vertical component of lift, so the plane will want to lose altitude. To compensate you have to increase total lift by raising the nose so that the vertical component is again equal to the weight of the plane to maintain altitude.

The more you know!

In a bank you have to pull back slightly on the stick if you want to stay at the same altitude. The ailerons cause the plane to climb a little compensating for the less vertical lift component because you tilted the plane. The more bank and tighter the turn, the more lift needed. Once you get it banked to 90 degrees from horizontal, no amount of ailerons are going to help!

The lift generated by the wings acts perpendicular to the chord line of the wing (call it perpendicular to the wing, it will be close enough). This is why one must pull back on the stick to maintain altitude in a turn. Part of the lift is going toward holding the airplane up (vertical component of lift) and part of the lift is going toward turning the airplane (horizontal component of lift). Contrary to what some might think, the rudder does not turn the airplane, the horizontal component of lift turns the airplane.

Now the picture you posted is interesting. The airplane appears to be in what is called "knife-edge flight". All lift coming from the wings is horizontal and is doing absolutely nothing to hold the airplane up. Looking carefully at the picture though, you can see that the fuselage is not parallel with the horizon. Likely the fuselage is acting a bit like a wing and producing a small amount of lift. The bigger effect keeping the airplane up though is most likely thrust. The exhaust coming out of the turbine engines is not pointed horizontal, but slightly down. The equal and opposite reaction would be to push the airplane up.

This effect is more visible in some turbo-prop aerobatic aircraft used in airshows as the angle is much steeper as is needed with the slower speeds.

Note, the amount of lift generated by the wings is relative to the angle of attack of the wings. Pull back on the stick to increase the (positive) angle of attack, push forward to decrease the (positive) angle of attack (not getting into negative angles of attack and inverted flight here). My guess from looking at the picture you posted is that the pilot is flying at a neutral angle of attack with the wings not generating significant (all horizontal) lift in order to make a straight pass along the deck.

quote:

Originally posted by tsmccull:
In a bank you have to pull back slightly on the stick if you want to stay at the same altitude. The ailerons cause the plane to climb a little compensating for the less vertical lift component because you tilted the plane. The more bank and tighter the turn, the more lift needed. Once you get it banked to 90 degrees from horizontal, no amount of ailerons are going to help!

Did you mean elevator when you said ailerons?

Ailerons roll the airplane around its longitudinal axis (roughly a line from the spinner to the tail end of the fuselage).

The elevator pitches the airplane around a horizontal line drawn through its center of gravity. This changes the angle of attack of the wings and either increases or decreases total lift generated by the wings.

The rudder yaws the airplane around a vertical line drawn through its center of gravity.

For completeness, the angle of attack of a wing is defined as the angle between the chord line of the wing and the relative wind. A simple description would the be angle between where it is pointed and where it is going. When one is in high speed level cruise, the angle of attack is low. When one is in slow flight, the angle of attack is high.

it takes a lot more power to maintain altitude in a 90deg bank in airplanes or helicopters.

You could ask the hotshot pilot of the 1994 B-52 crash at Fairchild Air Force Base- but he ded.

quote:

Originally posted by slosig:

quote:

Originally posted by tsmccull:
In a bank you have to pull back slightly on the stick if you want to stay at the same altitude. The ailerons cause the plane to climb a little compensating for the less vertical lift component because you tilted the plane. The more bank and tighter the turn, the more lift needed. Once you get it banked to 90 degrees from horizontal, no amount of ailerons are going to help!

Did you mean elevator when you said ailerons?

Ailerons roll the airplane around its longitudinal axis (roughly a line from the spinner to the tail end of the fuselage).

The elevator pitches the airplane around a horizontal line drawn through its center of gravity. This changes the angle of attack of the wings and either increases or decreases total lift generated by the wings.

The rudder yaws the airplane around a vertical line drawn through its center of gravity.

For completeness, the angle of attack of a wing is defined as the angle between the chord line of the wing and the relative wind. A simple description would the be angle between where it is pointed and where it is going. When one is in high speed level cruise, the angle of attack is low. When one is in slow flight, the angle of attack is high.

Yep, my bad. Thanks for the correction. Getting old’s a bummer!

quote:

Originally posted by airbubba:
it takes a lot more power to maintain altitude in a 90deg bank in airplanes or helicopters.

Is it even possible to _maintain_ altitude in a 90 degree bank for any length of time in a helicopter?

In an airplane where the thrust is off-axis to the wings, given sufficient thrust, sure it is doable. I'm not familiar with helos that put out their thrust except through their "wings" (the rotors) though.

quote:

Originally posted by kkina:
You could ask the hotshot pilot of the 1994 B-52 crash at Fairchild Air Force Base- but he ded.

[FLASH_VIDEO]<iframe frameborder="0" height="315" src="https://www.youtube.com/embed/7-S_NM--evM" width="560"></iframe>[/FLASH_VIDEO]

Slid sideways didn't he...

As others noted, wing shape is in part contributing to lift, but angle of attack (angle between wing and local airstream) is what's creating lift, relative to velocity (airspeed). Lift overcomes gravity and also creates drag, and airflow is affected by speed, change in shape (configuration; flaps, slats, spoilers or speed brakes, mach effects, boundary layer energizers, surface contamination, slots, etc).

The aerodynamics and effects of a swept wing are not the same as a straight wing, and affect stall behavior, flight control effectiveness, and aerodynamic and flight control criteria like center of lift and center of pressure, which vary more with changes in angle of attack. Given that most jet aircraft are swept wing, and experience these effects to varying degrees, it could be said that jet behaviors are somewhat different than most propeller driven aircraft (in some, not all, respects).

In general, in knife-edge flight (bank 90 degrees), the lift produced by wing, which can be thought of as acting perpendicular to the line that runs from the front of the wing to the back (chord line), is no longer acting upward. The greater the bank, the greater the horizontal component of lift, until in a 90 degree bank, the lift component is entirely horizontal. It's for this reason that aircraft bank when making a turn; the turning force, or the force that causes the airplane to change heading and make the turn, is effected by the degree of bank and the degree of horizontal component of lift. Bank more, turn faster (more or less).

At 90 degrees of bank, the horizontal component of lift is greatest, the vertical component of lift is least, and in one sense, there's a change in the way the flight controls effect the path of the aircraft. Increasingly lift comes from the side of the fuselage and the fuselage becomes the "wing," so far as vertical lift. The rudder becomes the "elevator," commanding vertical motion, or increasing or decreasing the angle of attack of the fuselage, while the wings are "pushing" the aircraft around the turn. Some aircraft have the capability to do this, others don't.

Another important factor in keeping the airplane up, in that 90 degree turn, is thrust. The thrust vector is slightly down, thought of as pushing the airplane "up." Think of it as the more the nose angles up in that 90 degree banked turn, the and the greater the thrust, the more thrust there is acting vertically. Aircraft with a lot of raw thrust (relative to weight, and that required to maintain level flight in a given condition and speed) have more capability to sustain a 90 degree bank. Inertia, or centripetal force, won't make an airplane hold altitude; it's got to have a force sustaining it throughout the turn; a combination of lift from the fuselage, and thrust, does it.

It may go without saying that the use of the flight controls as the aircraft transitions through a roll change their use and meaning, to a degree. The elevator, for example, in level flight, is raised (or stick pulled back) to go up. Once inverted, one pushes on the elevator to go "up" or away from the ground. Likewise, the rudders have a different function (or additional function) in a 90 degree bank, from level flight. They still move the aircraft about the "vertical axis" or yaw axis, but take on the impromptu role of elevators, with respect to the angle of attack of airflow on the underside fo the fuselage, and changing that angle.

In a roll, these uses and effects are continuously changing; how, and how much depends on the type of roll, the continuity, and duration. There's a lot less seen in a fast roll than a slow roll. In jet aircraft with considerable thrust, there's far less use of the rudders (in most cases) than straight wing, slower aircraft, and thrust takes on a much greater role.

In large, swept wing aircraft, stall speed/angle of attack climbs rapidly with increasing angle of bank. There will quickly come a point when a large airplane may exceed it's capacity for lift in a given circumstance, as we see in the B52 example above with Col. Holland (or the more recent C-17 crash at Elmendorf), both eerily similar in cause, and effect (the cause was human factors manifest as aerodynamics and fire). Thus is the result when one runs out of airspeed, altitude, and ideas at the same time.

I think what you were asking is covered in the description of a forward slip. The photo you show is something completely different and a plane that has such high performance power/thrust that it can overcome some of the other aerodynamic issues.
In the type of general or commercial aviation plane where airflow over the wing creates the lift, the direction of that airflow over the wing is critical.
In other words, airflow ninety degrees to the side would result in no lift in straight flight.

quote:

Originally posted by slosig:

quote:

Originally posted by airbubba:
it takes a lot more power to maintain altitude in a 90deg bank in airplanes or helicopters.

Is it even possible to _maintain_ altitude in a 90 degree bank for any length of time in a helicopter?

In an airplane where the thrust is off-axis to the wings, given sufficient thrust, sure it is doable. I'm not familiar with helos that put out their thrust except through their "wings" (the rotors) though.

no, for a quick 90-180 course reversal, pretty high g turn @ 100knots.

Want to really make it fun? Vector your thrust 90 degrees in a 90 degree angle of bank.

quote:

Originally posted by airbubba:

no, for a quick 90-180 course reversal, pretty high g turn @ 100knots.

Tom Cruise could do it.

quote:

Originally posted by airbubba:
no, for a quick 90-180 course reversal, pretty high g turn @ 100knots.

Not saying it is smart (avoid curve, what avoid curve?), but the cropduster turns I've seen in helos spraying involve what looks like a reasonably high G pull up, then a wingover/pedal turn, then diving right back into the next line. Next to no airspeed at the top, would be a real bad time for the engine to cough 50-100' off the ground with next to no airspeed. It is efficient for getting onto the next line though...

quote:

Originally posted by sns3guppy:

quote:

Originally posted by airbubba:

no, for a quick 90-180 course reversal, pretty high g turn @ 100knots.

Tom Cruise could do it.

Yeah, that guy who said a Pitts is unstable. Pshaw.

quote:

Originally posted by mojojojo:
Want to really make it fun? Vector your thrust 90 degrees in a 90 degree angle of bank.

Says the guy who got to fly the cool toys.

quote:

Originally posted by slosig:

quote:

Originally posted by airbubba:
no, for a quick 90-180 course reversal, pretty high g turn @ 100knots.

Not saying it is smart (avoid curve, what avoid curve?), but the cropduster turns I've seen in helos spraying involve what looks like a reasonably high G pull up, then a wingover/pedal turn, then diving right back into the next line. Next to no airspeed at the top, would be a real bad time for the engine to cough 50-100' off the ground with next to no airspeed. It is efficient for getting onto the next line though...

h/v curve for bell 206:
at the top of the pull up, a torque turn to the next line, all made in in the area by the longer blue line.

the crosshatch area is to be avoided.