Person dies in Southwest Plane after engine breakdown - Trump to blame!

[Elixir]

The bernoulli effect is NOT how wings work. Aircraft wings work by deflecting air downwards. This causes lift by plain old Newtonian equal and opposite reaction.

It's perfectly possible to build a wing that has a symmetrical cross-section. These work just fine and provide lift for any non-zero angle of attack.

Once again, my 8 year old gut was more correct than my 58 year old 4th grade teacher!
But I'm sure the Bernoulli effect has some ... effect... or they'd be building wings with a cross section that would be easier to construct than the foil shape, right?

Cheap light aircraft (and early designs) ARE built that way.

The design of the wing of a modern jet airliner is highly complex and balances construction and operating costs, drag, lift, the requirements to include equipment such as wheel wells and fuel tanks, icing, variable geometry components such as ailerons, flaps, slats, droops and air-brakes... There are dozens of reasons for a particular cross-section. But the fact remains that a wing with a symmetrical cross-section generates lift just as effectively as an airfoil. Angle of attack is all that's needed - if air is forced downward by the wing, then the wing is forced upwards by the air.

I'm surprised they don't have a "sharper" leading edge...

 

[bilby]

Cheap light aircraft (and early designs) ARE built that way.

The design of the wing of a modern jet airliner is highly complex and balances construction and operating costs, drag, lift, the requirements to include equipment such as wheel wells and fuel tanks, icing, variable geometry components such as ailerons, flaps, slats, droops and air-brakes... There are dozens of reasons for a particular cross-section. But the fact remains that a wing with a symmetrical cross-section generates lift just as effectively as an airfoil. Angle of attack is all that's needed - if air is forced downward by the wing, then the wing is forced upwards by the air.

I'm surprised they don't have a "sharper" leading edge...

Why?

 

[Jimmy Higgins]

Cheap light aircraft (and early designs) ARE built that way.

The design of the wing of a modern jet airliner is highly complex and balances construction and operating costs, drag, lift, the requirements to include equipment such as wheel wells and fuel tanks, icing, variable geometry components such as ailerons, flaps, slats, droops and air-brakes... There are dozens of reasons for a particular cross-section. But the fact remains that a wing with a symmetrical cross-section generates lift just as effectively as an airfoil. Angle of attack is all that's needed - if air is forced downward by the wing, then the wing is forced upwards by the air.

I'm surprised they don't have a "sharper" leading edge...

...and stickers!

 

[barbos]

I cited british statistics for 1990-2000. I doubt australian is better.

Neither is relevant to the USA in the last decade.

It's relevant to you.

 

[StoneRoad]

There are already preliminary reports (NTSB) that indicate they found fatigue damage on the hub where the fan blade separated. That's to be expected, in the sense that 90% of all fan failures are due to fatigue.

Yeah, I had a fan blade break on me at home. Sure, completely unrelated, but had to center the conversation about myself somehow.

Back on-topic, how much can maintenance prevent? In general, like NASA, isn't there a number of miles per incident? How do you inspect such things like fan blade fatigue? Is this X-ray'd or just looked at?

I'm guessing that non-destructive testing would be x-rays or ultrasound, or testing for cracks with penetrating dye. Interpretation and performing the first two methods are highly skilled jobs, dye penetration is easier but doesn't usually pick up the pre-crack fatigue changes.
(This is based on my memory from when I worked for a consulting engineer some years ago, and what I understand about checks on locomotive boilers and running gear)
I'm happy to be corrected by someone with more up-to-date information or practical experience.

 

[Malintent]

I was thinking about what the effort would be to pull a person in from an airplane window at 35,000 feet.

There are two main forces. Ambient pressure differential from the altitude, and the generated pressure differential from the airspeed.

The ambient pressure differential sounds low, at approximately 8 psi (half an atmosphere of pressure - estimated). With a window size of approximately 9 x 12, that is over 100 square inches... producing a total of 800 lbs of pressure.

To pull a stuck person out of an airplane window, you need to exert a force of at lest 800 lbs.

But it gets worse..

The speed of aircraft creates an additional pressure differential... exactly how the airplane's wings work... the force that is holding hundreds of people up in the air, along with the tons of aircraft weight itself, is all generated via lift produced by air simply moving over the top of the wing.
If you ever were in a fast moving car with the window open, I am sure you have experienced something getting sucked out by the pressure.

on top of that... the "wetted area" of the body itself... the part of the body that is being hit by oncoming wind. That produces additional force against pulling a body in.

It sounds to me that it takes at least half a ton (1000 or so lbs) of force to pull someone in. Even if two very strong people are able to pull that off (no pun intended)... some parts of that body are not going to still be attached.

The bernoulli effect is NOT how wings work. Aircraft wings work by deflecting air downwards. This causes lift by plain old Newtonian equal and opposite reaction.

It's perfectly possible to build a wing that has a symmetrical cross-section. These work just fine and provide lift for any non-zero angle of attack.

But don't take my word for it - NASA has a detailed explanation online, which is needed because this error is so widely believed. I was taught it at school; I expect you were too.

But then, my physics teacher also claimed that there was no such thing as centrifugal force. https://xkcd.com/123/

Ya, I was not only taught it in school while earning my degree in Aeronautical Engineering (with minor in Intermodal Transportation and Airport Management), but was required to design airfoils that solve specific problems. So I have used it in practice as well. I never heard of your "flat atmosphere" theory before... funny.

I suppose sailboats only move because of the air pushing directly against their sails too... meaning no one has ever or could possibly move a sailboat in any direction other than within 180 degrees of the direction of the wind.

What you are talking about is called "deflection". It has almost no effect during laminar flow. Turbulent flow of air over an airfoil will deflect more, but the exponential increase in drag due to failure of the laminar effect will stall the airfoil instantly.

Try it yourself... make or buy a cheap kit glider. Replace the wings with a slab of cardboard. Try throwing the glider a few times with the proper wings versus the flat regular piece of cardboard.

What you will find is that the proper airfoil will cause the plane to glide straight. The flat piece of cardboard will cause the plane to either pitch wildly up and then dive into the ground, or just dive straight into the ground, depending on where the center of gravity is.. normally that would be the center of lift, but if we are not generating lift (at least, not much) then it is all about center of gravity.

The Earth is more likely flat than airplanes don't really fly. I've built airplanes, I've flown airplanes.. but I never have personally been in space... so... flat earth possibly, Bilby's theory - no possibility..

 

[Malintent]

The bernoulli effect is NOT how wings work. Aircraft wings work by deflecting air downwards. This causes lift by plain old Newtonian equal and opposite reaction.

It's perfectly possible to build a wing that has a symmetrical cross-section. These work just fine and provide lift for any non-zero angle of attack.

Once again, my 8 year old gut was more correct than my 58 year old 4th grade teacher!
But I'm sure the Bernoulli effect has some ... effect... or they'd be building wings with a cross section that would be easier to construct than the foil shape, right?

Cheap light aircraft (and early designs) ARE built that way.

The design of the wing of a modern jet airliner is highly complex and balances construction and operating costs, drag, lift, the requirements to include equipment such as wheel wells and fuel tanks, icing, variable geometry components such as ailerons, flaps, slats, droops and air-brakes... There are dozens of reasons for a particular cross-section. But the fact remains that a wing with a symmetrical cross-section generates lift just as effectively as an airfoil. Angle of attack is all that's needed - if air is forced downward by the wing, then the wing is forced upwards by the air.

For there to be deflection, you need a wetted area. That is the area of the airfoil that is taking the direct impact of air.

Conservation of energy...

Let's say you pitch a "wing" (flat rectangle) 45 degrees to its direction of travel through an atmosphere. Half of the energy causes deflection and the other half causes deceleration. For every pound of force "lifting" the "wing" (pushing upwards on the deflector, to be more accurate) it is pushing against forward motion. That isn't flying...

Although... for a person with a great deal of submarine experience, I can see how deflectors could sound more universal than they are. Water is quite a bit more dense than air, and buoyancy (don't get me started on buoyancy*) appears to come into play.

** there is no such thing as buoyancy... boats float because of the deflection of their hull <rolleyes>

 

[Malintent]

There are already preliminary reports (NTSB) that indicate they found fatigue damage on the hub where the fan blade separated. That's to be expected, in the sense that 90% of all fan failures are due to fatigue.

Yeah, I had a fan blade break on me at home. Sure, completely unrelated, but had to center the conversation about myself somehow.

Back on-topic, how much can maintenance prevent? In general, like NASA, isn't there a number of miles per incident? How do you inspect such things like fan blade fatigue? Is this X-ray'd or just looked at?

I'm guessing that non-destructive testing would be x-rays or ultrasound, or testing for cracks with penetrating dye. Interpretation and performing the first two methods are highly skilled jobs, dye penetration is easier but doesn't usually pick up the pre-crack fatigue changes.
(This is based on my memory from when I worked for a consulting engineer some years ago, and what I understand about checks on locomotive boilers and running gear)
I'm happy to be corrected by someone with more up-to-date information or practical experience.

You are correct. X-ray is required, and is the current standard during manufacturing and after a set amount of production use. If a turbofan blade showed something on a dye test, that blade would fail the second it was used... so it is not really a test done after the initial phases of manufacture.
Current maintenance requirements include x-ray of blades, but extremely infrequently due to the complexity of removing each blade and individually analyzing.

 

[Jimmy Higgins]

** there is no such thing as buoyancy... boats float because of the deflection of their hull.

Wait... what?! Buoyancy is about the difference in mass of an object and the water it is displacing.

 

[Malintent]

Cheap light aircraft (and early designs) ARE built that way.

The design of the wing of a modern jet airliner is highly complex and balances construction and operating costs, drag, lift, the requirements to include equipment such as wheel wells and fuel tanks, icing, variable geometry components such as ailerons, flaps, slats, droops and air-brakes... There are dozens of reasons for a particular cross-section. But the fact remains that a wing with a symmetrical cross-section generates lift just as effectively as an airfoil. Angle of attack is all that's needed - if air is forced downward by the wing, then the wing is forced upwards by the air.

I'm surprised they don't have a "sharper" leading edge...

Why?

because your "deflection-based" aircraft is so incredibly inefficient that the need to reduce the wetted area (by sharpening the leading edge) is intuitively necessary. Pretty smart, Elixir...

One could make a plane work that way, I guess... you don't even need wings at all... just put enough rocket engines all around pointing in every direction and "fly" by brute force. A rock can "fly" if you throw it hard enough.

Of course, you will need engines with THOUSANDS of times more thrust to weight than exist.

 

[Elixir]

I was thinking about what the effort would be to pull a person in from an airplane window at 35,000 feet.

There are two main forces. Ambient pressure differential from the altitude, and the generated pressure differential from the airspeed.

The ambient pressure differential sounds low, at approximately 8 psi (half an atmosphere of pressure - estimated). With a window size of approximately 9 x 12, that is over 100 square inches... producing a total of 800 lbs of pressure.

To pull a stuck person out of an airplane window, you need to exert a force of at lest 800 lbs.

But it gets worse..

The speed of aircraft creates an additional pressure differential... exactly how the airplane's wings work... the force that is holding hundreds of people up in the air, along with the tons of aircraft weight itself, is all generated via lift produced by air simply moving over the top of the wing.
If you ever were in a fast moving car with the window open, I am sure you have experienced something getting sucked out by the pressure.

on top of that... the "wetted area" of the body itself... the part of the body that is being hit by oncoming wind. That produces additional force against pulling a body in.

It sounds to me that it takes at least half a ton (1000 or so lbs) of force to pull someone in. Even if two very strong people are able to pull that off (no pun intended)... some parts of that body are not going to still be attached.

The bernoulli effect is NOT how wings work. Aircraft wings work by deflecting air downwards. This causes lift by plain old Newtonian equal and opposite reaction.

It's perfectly possible to build a wing that has a symmetrical cross-section. These work just fine and provide lift for any non-zero angle of attack.

But don't take my word for it - NASA has a detailed explanation online, which is needed because this error is so widely believed. I was taught it at school; I expect you were too.

But then, my physics teacher also claimed that there was no such thing as centrifugal force. https://xkcd.com/123/

Ya, I was not only taught it in school while earning my degree in Aeronautical Engineering (with minor in Intermodal Transportation and Airport Management), but was required to design airfoils that solve specific problems. So I have used it in practice as well. I never heard of your "flat atmosphere" theory before... funny.

I suppose sailboats only move because of the air pushing directly against their sails too... meaning no one has ever or could possibly move a sailboat in any direction other than within 180 degrees of the direction of the wind.

What you are talking about is called "deflection". It has almost no effect during laminar flow. Turbulent flow of air over an airfoil will deflect more, but the exponential increase in drag due to failure of the laminar effect will stall the airfoil instantly.

Try it yourself... make or buy a cheap kit glider. Replace the wings with a slab of cardboard. Try throwing the glider a few times with the proper wings versus the flat regular piece of cardboard.

What you will find is that the proper airfoil will cause the plane to glide straight. The flat piece of cardboard will cause the plane to either pitch wildly up and then dive into the ground, or just dive straight into the ground, depending on where the center of gravity is.. normally that would be the center of lift, but if we are not generating lift (at least, not much) then it is all about center of gravity.

The Earth is more likely flat than airplanes don't really fly. I've built airplanes, I've flown airplanes.. but I never have personally been in space... so... flat earth possibly, Bilby's theory - no possibility..

I have a very bright nephew who is also an aeronautical engineer ... he's more into designing rockets than other aircraft, but has described different ways that airfoil cross-sections are tested in wind tunnels. According to him, it's like Malintent says - they are always trying to zero in on the optimal the lift/drag coefficient for operation at given airspeeds. That implies (to my ignorant self) that the Bernoulli effect is at least a significant, if not the dominant force in play with commercial aircraft wing design... correct me if I'm wrong.

 

[Malintent]

Ya, I was not only taught it in school while earning my degree in Aeronautical Engineering (with minor in Intermodal Transportation and Airport Management), but was required to design airfoils that solve specific problems. So I have used it in practice as well. I never heard of your "flat atmosphere" theory before... funny.

I suppose sailboats only move because of the air pushing directly against their sails too... meaning no one has ever or could possibly move a sailboat in any direction other than within 180 degrees of the direction of the wind.

What you are talking about is called "deflection". It has almost no effect during laminar flow. Turbulent flow of air over an airfoil will deflect more, but the exponential increase in drag due to failure of the laminar effect will stall the airfoil instantly.

Try it yourself... make or buy a cheap kit glider. Replace the wings with a slab of cardboard. Try throwing the glider a few times with the proper wings versus the flat regular piece of cardboard.

What you will find is that the proper airfoil will cause the plane to glide straight. The flat piece of cardboard will cause the plane to either pitch wildly up and then dive into the ground, or just dive straight into the ground, depending on where the center of gravity is.. normally that would be the center of lift, but if we are not generating lift (at least, not much) then it is all about center of gravity.

The Earth is more likely flat than airplanes don't really fly. I've built airplanes, I've flown airplanes.. but I never have personally been in space... so... flat earth possibly, Bilby's theory - no possibility..

I have a very bright nephew who is also an aeronautical engineer ... he's more into designing rockets than other aircraft, but has described different ways that airfoil cross-sections are tested in wind tunnels. According to him, it's like Malintent says - they are always trying to zero in on the optimal the lift/drag coefficient for operation at given airspeeds. That implies (to my ignorant self) that the Bernoulli effect is at least a significant, if not the dominant force in play with commercial aircraft wing design... correct me if I'm wrong.

Sounds about right... Although deflection is not desirable at all. It has a lift to drag ratio of 1. It's not flying... not anymore than a dead leaf is "flying" to the ground as is rocks back and fourth during its fall.

You would not be entirely incorrect for thinking about the Beurnaldi effect as what generates the lift and the deflection as what generates the drag.

 

[Malintent]

** there is no such thing as buoyancy... boats float because of the deflection of their hull.

Wait... what?! Buoyancy is about the difference in mass of an object and the water it is displacing.

Exactly. My statement sounds ALMOST as ridiculous as Bilby's and the Beurnaldi effect.
The Beurnaldi effect is about the difference in pressure between slow moving air and fast moving air.

 

[barbos]

Try it yourself... make or buy a cheap kit glider. Replace the wings with a slab of cardboard. Try throwing the glider a few times with the proper wings versus the flat regular piece of cardboard.

What you will find is that the proper airfoil will cause the plane to glide straight. The flat piece of cardboard will cause the plane to either pitch wildly up and then dive into the ground, or just dive straight into the ground, depending on where the center of gravity is.. normally that would be the center of lift, but if we are not generating lift (at least, not much) then it is all about center of gravity.

I guess you've never seen a paper glider.

 

[Worldtraveller]

There are already preliminary reports (NTSB) that indicate they found fatigue damage on the hub where the fan blade separated. That's to be expected, in the sense that 90% of all fan failures are due to fatigue.

Yeah, I had a fan blade break on me at home. Sure, completely unrelated, but had to center the conversation about myself somehow.

Back on-topic, how much can maintenance prevent? In general, like NASA, isn't there a number of miles per incident? How do you inspect such things like fan blade fatigue? Is this X-ray'd or just looked at?

I'm an aerospace engineer. I've worked at Boeing, and at and with several maintenance organizations. I've probably spent more time walking around on the wings of airplanes looking at maintenance issues than I have flying in them (and I fly a lot).

Engine fan blades are inspected usually with a visual inspection using a borescope. The actual level of detail and time between inspection intervals can required can vary by up to several hundred hours, and there are several types of inspections (labelled A through D by Boeing, with 'A' checks being daily/weekly walk arounds, do C and D heavy checks that require a lot of downtime and overhaul).

Engines (and APUs) are on their own separate schedule from the airframe and are often removed for heavy check and another engine swapped in, so the whole aircraft doesn't have to be down for the inspection. I don't know the exact time intervals on the CFM56 motor (I'm more of an airframe guy), but you might be able to google it.

Most of the time, inspections will catch a crack well before it becomes catastrophic. However, there are, and will always be, exception. It could be due to minor damage that wasn't noticed (say the engine sucked a small rock during taxi) or bad metallurgy, or any number of similar tiny, otherwise undetectable, causes.

Inspections are based on fatigue life, and assumed damage, and a lot of statistics. Engine, airframe and component failure in the US are well below the statistically required maximum for failure. This is one of the reasons that airlines in the US are so safe. You know, all those bad regulations that make businesses suffer so much.

 

[Worldtraveller]

You are still 50 times off.

No, I don't think that. I just do't think it has got as much better as you think.
And yes, I do think cars are about much much safer.

Well the facts disagree with you.

I think I will take their word over yours.

Facts disagree with you.

Actually, bilby is correct here. I work with the FAA, and with aviation safety, on a daily basis, and am intimately familiar with the regulations that drive that safety record. But you know, please keep telling us experts what you know.

 

[Worldtraveller]

Cheap light aircraft (and early designs) ARE built that way.

The design of the wing of a modern jet airliner is highly complex and balances construction and operating costs, drag, lift, the requirements to include equipment such as wheel wells and fuel tanks, icing, variable geometry components such as ailerons, flaps, slats, droops and air-brakes... There are dozens of reasons for a particular cross-section. But the fact remains that a wing with a symmetrical cross-section generates lift just as effectively as an airfoil. Angle of attack is all that's needed - if air is forced downward by the wing, then the wing is forced upwards by the air.

I'm surprised they don't have a "sharper" leading edge...

Why?

Aircraft wings that are designed for primarily supersonic flight have very sharp leading and trailing edges, but the design parameters are rather different for compressible (supersonic) conditions than subsonic flight. All of the lift curves and aerodynamic design assumptions for supersonic wings are based on an infinitely thin flat plate. Blunt body supersonic aerodynamics (like the space shuttle) are very different.

The F-104 had such sharp leading and trailing edges that the ground crews would put foam cushions on them whenever they were working around the plane.

As for the discussion on whether camber/airfoil design or 'deflection' create more lift: It's complicated, but with most modern airfoils, the angle of attack (aka deflection) is much more important than the Bernoulli effect. see: https://en.wikipedia.org/wiki/Angle_of_attack

Specifically, look at the lift vs. angle of attack curve: https://upload.wikimedia.org/wikipedia/commons/d/d1/Lift_curve.svg

At zero angle of attack, the lift coefficient is 0.5. By increasing the angle of attack to 5 degrees, it more than doubles to 1.1. Typical airfoils operate in the 3-5 degree angle of attack for 'straight and level' flight. There is a corresponding curve for the coefficient of drag. All airfoils have an optimum angle based on maximizing the first, and minimizing the second.

 

[bilby]

Ya, I was not only taught it in school while earning my degree in Aeronautical Engineering (with minor in Intermodal Transportation and Airport Management), but was required to design airfoils that solve specific problems. So I have used it in practice as well. I never heard of your "flat atmosphere" theory before... funny.

I suppose sailboats only move because of the air pushing directly against their sails too... meaning no one has ever or could possibly move a sailboat in any direction other than within 180 degrees of the direction of the wind.

What you are talking about is called "deflection". It has almost no effect during laminar flow. Turbulent flow of air over an airfoil will deflect more, but the exponential increase in drag due to failure of the laminar effect will stall the airfoil instantly.

Try it yourself... make or buy a cheap kit glider. Replace the wings with a slab of cardboard. Try throwing the glider a few times with the proper wings versus the flat regular piece of cardboard.

What you will find is that the proper airfoil will cause the plane to glide straight. The flat piece of cardboard will cause the plane to either pitch wildly up and then dive into the ground, or just dive straight into the ground, depending on where the center of gravity is.. normally that would be the center of lift, but if we are not generating lift (at least, not much) then it is all about center of gravity.

The Earth is more likely flat than airplanes don't really fly. I've built airplanes, I've flown airplanes.. but I never have personally been in space... so... flat earth possibly, Bilby's theory - no possibility..

I have a very bright nephew who is also an aeronautical engineer ... he's more into designing rockets than other aircraft, but has described different ways that airfoil cross-sections are tested in wind tunnels. According to him, it's like Malintent says - they are always trying to zero in on the optimal the lift/drag coefficient for operation at given airspeeds. That implies (to my ignorant self) that the Bernoulli effect is at least a significant, if not the dominant force in play with commercial aircraft wing design... correct me if I'm wrong.

Sounds about right... Although deflection is not desirable at all. It has a lift to drag ratio of 1. It's not flying... not anymore than a dead leaf is "flying" to the ground as is rocks back and fourth during its fall.

You would not be entirely incorrect for thinking about the Beurnaldi effect as what generates the lift and the deflection as what generates the drag.

Yeah, you would.

The minimising of drag by shaping the wing for laminar flow has fuck all to do with the use of the Bernoulli effect to generate lift. The blunt leading edge makes the flow accelerate on both top and bottom wing surfaces, and that helps to inhibit turbulence (in the absence of a shock wave - so not at supersonic speeds).

What matters for lift is that the air flowing across the wing changes angle, so that there is a downward component to the departing airflow off the trailing edge.

But you are forgiven both your error and your condescension, as this is not widely understood, even in the airspace industry.

The NASA information I linked to is fairly long and detailed; So I can understand your reluctance to read it.