pplm exam principles of flight confusion
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pplm exam principles of flight confusion
Hello, I have been doing some mock exams on the Microisland website
Aircraft Techinal
And here, the answer to how much lift is generated from the upper surface of a wing, is opposite to what I have read in my textbook. As I understand it, two thirds of lift is generated from the lower relative air pressure on the upper surface of the wing, and one third from the airflow being deflected downwards by the lower surface of the wing.
The screengrab below however, has the answer different:
So, am i missing something, or is the exam wrong?
Cheers
Aircraft Techinal
And here, the answer to how much lift is generated from the upper surface of a wing, is opposite to what I have read in my textbook. As I understand it, two thirds of lift is generated from the lower relative air pressure on the upper surface of the wing, and one third from the airflow being deflected downwards by the lower surface of the wing.
The screengrab below however, has the answer different:
So, am i missing something, or is the exam wrong?
Cheers
There is a never ending argument about how a wing produces lift.
The conventional wisdom though, is that 2/3 of the lift is produced by the smooth airflow over the upper surface, and 1/3 by the downward deflection of the air by the lower surface.
In reality, the two effects cannot be treated entirely seperately, as they each affect the other.
MJ
The conventional wisdom though, is that 2/3 of the lift is produced by the smooth airflow over the upper surface, and 1/3 by the downward deflection of the air by the lower surface.
In reality, the two effects cannot be treated entirely seperately, as they each affect the other.
MJ
If you have any reasonable understanding of the principles of flight, then you come to realise that all of the exam syllabi are gross and often innacurate simplifications.
However, the objective in the short term is to pass the exams - and it is true that if you replaced the wing section with just the upper surface you'd lose about 1/3 of the lift. So, the answer works - but is still grossly simplistic and pointless.
Learn to pass the exam, then get a decent book on PofF like Kermode or Anderson, and learn it properly!
Daft, but the way to do it.
G
However, the objective in the short term is to pass the exams - and it is true that if you replaced the wing section with just the upper surface you'd lose about 1/3 of the lift. So, the answer works - but is still grossly simplistic and pointless.
Learn to pass the exam, then get a decent book on PofF like Kermode or Anderson, and learn it properly!
Daft, but the way to do it.
G
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The "trial" exam is wrong.
For this sort of exam question, the expected answer is:
The upper surface of the wing generates around 2/3rds of the total lift
Usually put that way, rather than "the lower surface of the wing produces about 1/3rd of the lift", since the idea is that in a stall the wing does not lose all its lift-generating ability.
You can always tell the smart student, they read this and ask: but what if the aircraft is flying inverted!
For this sort of exam question, the expected answer is:
The upper surface of the wing generates around 2/3rds of the total lift
Usually put that way, rather than "the lower surface of the wing produces about 1/3rd of the lift", since the idea is that in a stall the wing does not lose all its lift-generating ability.
You can always tell the smart student, they read this and ask: but what if the aircraft is flying inverted!
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You can always tell the smart student, they read this and ask: but what if the aircraft is flying inverted!
Read 'Stick & Rudder'. Everything you need to know about why an aeroplane flys (and sometimes doesn't) is in there.
Read 'Stick & Rudder'
This is my current favourite:-
G
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At £40 a copy I don't think I'll be reading that any time soon. Stick & Rudder is certainly dated, but I haven't come across another book that cuts through the crap quite as well as it does and tells a pilot what a pilot needs to know.
Should I start saving?
Should I start saving?
You spend how much a year on flying?
Or for something only 26 years old instead of 70 years old, you can have an earlier edition of Anderson for just over a fiver...
G
Or for something only 26 years old instead of 70 years old, you can have an earlier edition of Anderson for just over a fiver...
G
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As usual in all these exam questions - go have a look which software is used in final real exam and then learn the pushbutton answers. Afterwards switch on again your brain ...
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Genghis, there's a copy of 'Stick' on my bookshelf. It's far and away better than anything I've read before on 'pilot's aerodynamics'. Why do you think I'd need to supplant it?
I've no idea if those you've recommended are as good (the only thing 'Stick' falls down on is it's dated presentation). Since 'Stick', and not those other books, continues to be recommended, and it 'does it for me', it's the one I will stand behind as a recommendation. I'm not in the book review business so won't be buying those others to see if they're as good; I don't need to as I know 'Stick' does it just fine.
If you think the others are as good, by all means recommend them. But please recognise as well just how good 'Stick' is for someone who wants to fly aeroplanes, not design them.
I've no idea if those you've recommended are as good (the only thing 'Stick' falls down on is it's dated presentation). Since 'Stick', and not those other books, continues to be recommended, and it 'does it for me', it's the one I will stand behind as a recommendation. I'm not in the book review business so won't be buying those others to see if they're as good; I don't need to as I know 'Stick' does it just fine.
If you think the others are as good, by all means recommend them. But please recognise as well just how good 'Stick' is for someone who wants to fly aeroplanes, not design them.
I really do hope that we've learn a few things about aeronautics since 1944 however.
Newtonian physics and incompressible aerodynamics haven't changed yet, but our understanding of human factors, use of instruments, navigation, meteorology - certainly have.
G
Newtonian physics and incompressible aerodynamics haven't changed yet, but our understanding of human factors, use of instruments, navigation, meteorology - certainly have.
G
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Cheers guys, I have Brian cosgroves book call the microlight pilots handbook. Good to know the test answer is wrong in this case. Ive also come across afew other wrong questions from this site, so it might be an idea to avoid these online tests for now....
And to all those trashing the simplistic explanation of flight, well, we all have to start somewhere, and i think a simplistic explanation works for me now, much like a lot of GCSE chemistry and physics is not actually correct, and then retaught in a more complex (and contradicory) manner at A level.....
And to all those trashing the simplistic explanation of flight, well, we all have to start somewhere, and i think a simplistic explanation works for me now, much like a lot of GCSE chemistry and physics is not actually correct, and then retaught in a more complex (and contradicory) manner at A level.....
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Newtonian physics and incompressible aerodynamics haven't changed yet, but our understanding of human factors, use of instruments, navigation, meteorology - certainly have.
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The exam question that the OP refers to is ridiculous. Definitely one just to learn the answer for the exam and then forget about.
Genghis and Shaggy - you're discussing different things. "Stick" is no good for learning about the science of aerodynamics, but is brilliant at getting across enough info for a pilot to understand what s/he needs. You don't need to understand the detail of how a car works in order to drive one safely - but you do need to know a little bit about how it works: flying is the same.
Neither "Stick" nor a good aerodynamics text book will help answer the OP's question though.
No one has mentioned Bernoulli yet...
Genghis and Shaggy - you're discussing different things. "Stick" is no good for learning about the science of aerodynamics, but is brilliant at getting across enough info for a pilot to understand what s/he needs. You don't need to understand the detail of how a car works in order to drive one safely - but you do need to know a little bit about how it works: flying is the same.
Neither "Stick" nor a good aerodynamics text book will help answer the OP's question though.
No one has mentioned Bernoulli yet...
Daniel Bernoulli was a Dutch born mathematician (1700–1782), although he spent most of his working life in Switzerland. He studied mathematics and medicine, becoming professor of mathematics at St Petersburg in 1725.
In 1732 he became professor of anatomy at Basel University, continuing to become a professor of botany and finally physics. He worked on many areas including trigonometry, mechanics, vibrations and fluid mechanics—including anticipating the kinetic theory of gasses. His solution of a problem of gas properties became known as Bernoulli’s equation and was published in 1738.
In 1732 he became professor of anatomy at Basel University, continuing to become a professor of botany and finally physics. He worked on many areas including trigonometry, mechanics, vibrations and fluid mechanics—including anticipating the kinetic theory of gasses. His solution of a problem of gas properties became known as Bernoulli’s equation and was published in 1738.
G
Halfway through Stick and Rudder now. I thought I should read it, as some people rave so much about it.
I'll let you know what I think when I've finished it, but so far, if you can look past the rather dated style and language, it seems to explain things in terms that 'ordinary' people can understand, without falling into the trap of 'dumbing down' to a point where what it says is actually wrong.
From what I've read so far, I think you're a little harsh, Genghis. I think even Kermode, and Anderson seem a little highbrow to many.
Let's see how the other half goes.
MJ
I'll let you know what I think when I've finished it, but so far, if you can look past the rather dated style and language, it seems to explain things in terms that 'ordinary' people can understand, without falling into the trap of 'dumbing down' to a point where what it says is actually wrong.
From what I've read so far, I think you're a little harsh, Genghis. I think even Kermode, and Anderson seem a little highbrow to many.
Let's see how the other half goes.
MJ
...but there are vastly more up to date texts.
This is my current favourite:-
Introduction to Flight (Int'l Ed): Amazon.co.uk: John D. Anderson: 9780071086059: Books
This is my current favourite:-
Introduction to Flight (Int'l Ed): Amazon.co.uk: John D. Anderson: 9780071086059: Books
From 1978. Just sayin'.
SSD, an earlier edition is available as a PDF.