Old School Engineering versus New School Engineering

[SASless]

In another thread....or a couple of other threads....a thought was presented that begs expounding upon. A veteran poster to the forum here suggested that teaching methods of yore stand in contrast to more recent teaching methods and in some cases, time has caused a conflict in different concepts of physics.

The process of teaching precession that precedes current precedent seems at odds with theories presented as probable explantations. The poster pondered the question of the rightness of the various schools of teaching and its effect upon the students grasp of physical phenomenon.

I wonder if someone can expound upon the effect all most correct teaching can have on young minds being exposed to partially correct theories....does this mean a partial transfer of knowlege or a complete transfer of complete but wrong knowledge? In the absence of a qualified judge as to the validity of the knowledge being transfered and its practical application to rotating masses.....does an imperfect demonstration allow for an almost but satisfactory understanding of a nearly impossible topic with any real clarity?

If rotor dynamics and reactions to cyclic inputs vary from the theoretical does it mean the laws are imperfect or the teaching and understanding is imperfect. Is the old language and new concepts at odds there?

[Kyrilian]

SASless,
A very well stated question! ;)

As I see it, there is no old and new. The first rotors ever flown acted in extremely complex ways, ways I'm certain were not fully understood at the time. Knowledge was quickly gained by manufacturers/designers/academia--I just think that the engineering understanding has far outstripped the abilities of instructors to comprehend and then teach to students. Practical instruction has never been exact in any complex field. Usually the basics are covered, but those basic simplifications don't fundamentally conflict with reality.

In rotorcraft, instructors teach one aspect of a complex topic, neglecting other, significant factors that also weigh in. Teaching that the blades fly to a position or are governed solely by gyroscopics, while not really correct, has some basis in fact. The problem lies in the number of variables affecting the way the rotor behaves. Gyroscopic precession is a simplification of one very significant factor defining a rotor's behavior--rotor inertial mechanics--but leaving out everything else is a disservice to the truth.

does an imperfect demonstration allow for an almost but satisfactory understanding of a nearly impossible topic with any real clarity?

It depends on the need. As I see it, the primary point that pilots must understand is that rotor blades don't respond immediately. The more we add to this, the better. However, if the balance of knowledge means being able debate the intricacies of rotor dynamics at the expense of understanding weather, regulations, etc, then perhaps we can't expect everyone to be able to learn and understand this fully. A demonstration of gyroscopic precession is useful, as a gyroscope emulates much of the behavior of the helicopter rotor. However, the key is to instruct that it's much more complicated than that (even if you can't define how).

If rotor dynamics and reactions to cyclic inputs vary from the theoretical does it mean the laws are imperfect or the teaching and understanding is imperfect. Is the old language and new concepts at odds there?

What new concept? I'm relatively new to this (young engineer) but I don't believe this knowledge is new to the world. Forums like these and Lu's obsession with the R-22 brought it to our little corner on the 'net here, but I'm not so certain that instruction or what's known in industry or academia have changed recently.

....does this mean a partial transfer of knowlege or a complete transfer of complete but wrong knowledge?

Good question! I don't believe what's been taught (and presumably what will continue to be taught) can be called anything close to complete. But by teaching newbies that the rotor is not just a gyroscope I think we can move closer to a partial transfer of knowledge without it being wrong. It'll just be incomplete, with room for more knowledge to be gleaned without the old baggage that currently gets in the way.

[slowrotor]

I was taught in school that atoms had little round electrons spinning around a nucleus.
Now top physisists think electrons may be strings or waves or well... nobody knows!

They should not make up simple explanations when teaching without a disclaimer to notify the student that the ideas as presented may not be exactly true.

[Rotorbee]

The string theory (note: THEORY) gives us an explanation what a electron is made of, but it is still spinning around the nucleus. What you learnd at school is not wrong, but you can not teach kids the latest theories without beginning at the basics. Yes, some things we learn at school are simplified, but it would be to much for most kids to learn the latest news. You would have to explain them, that the string theorie only works, because it uses 10 dimensions, where 4 are visible and the rest are folded up. This is way to difficult for most people to understand - including me btw.

Lets take the centrifugal force as an example. I had long discussions with pilots about this concept. I find the world without that force way more logical, but most people fail to understand that concept, (probably because I am not able to explain it in a simple enough way). But ask them where the rotorblad would go, if the blade root would let go. Most will answer that it flies strait out because they believe that the centrifugal force will pull it away. But does it matter? No. Most pilots don't even bother about the physics of the ships they fly and they don't need it. We will not prevent any accident by making them learn something that they normaly just learn to pass the test. There are other things that are a lot more important to learn, to make flying save. But if we tell them, that what they learn is not really true, why should they learn it at all?
What they learn is enough to understand the basics, which is way more important then frustraiting them with explanations they will not understand because they miss the basics.

Anybody who is more interested in helicopter aerodynamics, should not be surprised, that the real world is way more complicated then the basics new pilots learn in ground school.
We should always be prepared to learn new things.

I read a draft of the FAA Helicopter Handbook and they do mention that the CF does not exist in reality, but I don't think that a lot of students will ever remember that footnote.

(Yes Shawn, there are other mistakes in there)

[212man]

Slow rotor, when I was at school it was called the "wave /particle duality" and simply meant that both concepts could be applied under different circumstances, not that either was correct in isolation.

SASless, I think that in reality, the concepts being discussed on that other forum, have always been known by those who need to (the designers and test personnel) but they are too complex to be taught in basic flight training. Some people have enough trouble dealing with electrical AC theory- how would you expect them to cope with the aerodynamics of the rotor? Do they really need to know anyway?

If you can impart a theory that seems to work, which is relatively simple to understand, then so be it. At least the pilots will have some understanding of how to treat their aircraft safely without chopping bits off; that' the important bit!

[Vfrpilotpb]

This is a very good and thought provoking question, and in reality it covers much of what we see today, both in hardware(the things that are big or spinning or controlling that item that moves) to the software( which is still in its infancy, but yet can control anything from the tiny hearing aids to the biggest machines man can make).

Take for example my generation Born in the fortie's, Steam trains were still the main tractive power items for moving the masses, a cleaver Sqdn Ldr called Whittle designed the jet engine which once given to America with their production ability's went on to conquer the World of avaition, hand held calculators didn't arrive untill the start of the seventies up to then the majority of us used slide rules and whizz wheels, machinery was (UK that is) was always held together with Whitworth threads.

So the evolution of technology eventually gets thru to us all, but the teaching of my generation must be superceeded, for like the Whitworth Thread it is old and based on so very few academics who made and gave us answers,... but who was there to counter such answers?

Peter R-B

[Droopystop]

Engineering of all types have taken huge leap forwards over the last 25 years or so, simply because of computing power. This has enabled engineers to predict dynamic situations where before they could only do static (snapshot) and quasi static engineering ("cineshot"). Remember the video clip taken by a camera looking down the length of a blade? I bet at the time noone could have predicted that. Now I am sure that this could be predicted and blade design adjusted accordingly.

So in other words, like in all parts of science, knowledge has improved from simple explainations that almost worked to high level mathematics which are the realms of the research engineers and mathematicians. If you were expected to understand this as a pilot, then pilot training would require a three or four year universtiy training before you even get to see a helicopter. Fortunately the basic understanding that we were taught is sufficient - it has after all served 2 or 3 generations of pilots well enough.

[Lu Zuckerman]

The reason for teaching rotor dynamics as related to gyroscopic precession and lead/lag and blade flapping was to give the student (mechanic) a basic understanding of what was going on in the rotor system during flight. This was to equip the future mechanic/pilot/maintenance officer with the ability to diagnose vibration problems.

In my day you tracked blades using a tracking flag and on a Bell you used a paintbrush dipped in paralketone and tied to a stick to track the main rotor and the tail rotor. Now vibration is detected using electronic devices and tracking is accomplished using strobe lights coupled with vibration detection equipment. Some blades do not require tracking as they are pretracked at the factory.

Now, these are the things taught at the factory schools however they still teach gyroscopic precession. Time marches on but in some cases it doesn’t.


:E :E

[spinwing]

Hang On ...Hang On ......

Everybody knows that just like the bumble bee the Helicopter is not supposed to fly ... its only good luck that keeps us up in the air ...No!

:p :p :p :p ;)