djpacro

No adverse yaw with the Airtourer and its flaperons. I haven't flown a Callair - I bet that Herb Andersen would appreciate Contact Flying's feedback. My last Pitts was an early model S-2A with differential frise ailerons - "spades" added more recently and it feels and rolls as good as many Pitts.

These notes about Spillman's work may help explain the thrust extracted from some surfaces. https://books.google.com.au/books?id=X4pkFU-iRD0C&pg=PA146&lpg=PA146&dq=spillman+sails&source=bl&ots=t63ZlVF0Ol&sig=kB8NZL9whQgRIXIs6qqRpZo1wr4&hl=en&sa=X&ved=0ahUKEwjp_8mrzMvJAhUDiKYKHSRaCpcQ6AEIJTAB#v=onepage&q=spillman%20sails&f=false Like many things we can change the datum and it is actually quite useful to talk about negative pressure wrt aeroplanes because the static pressure on the upper surface of the wing (in normal flight) will be less than the static pressure inside the cabin of the aeroplane. Static pressure under the wing will likewise be higher than pressure inside the cabin. So, it all depends on your frame of reference - sitting inside the cabin if you put a tube into the wing connected to a hole on the upper surface near the leading edge - put the other end into your mouth - you will feel the suction.Reminds me of a test I as asked to witness many years ago - the engineer connected a manometer up something like that tube - whoooosh - all the fluid was sucked out. He turned and looked to me, disbelieving what he had just seen. You need a suction gauge, I said. He was a mechanical engineer.

Ahh! Aspect ratio - one of my pet subjects. Span loading considerations have benefit. Wing loading considerations have benefit. Doesn't leave many benefits to consider for aspect ratio alone. Who would've though that we'd be discussing stuff like Biot-Savart and Prandtl here.

NASA does a pretty good job with their educational info online for school children.

I flew the Airtourer and Austers at Lovely Banks, don't recall the Chipmunk. Lovely Banks disappeared very many years ago.

is easy.

CASA is the problem - from the new aeronautical knowledge standards in the Part 61 MOS Schedule 3 Unit 1.3.1:"2.2 Bernoulli’s theorem and Coanda theory 2.2.1 Apply Bernoulli’s theorem of constant energy flow to describe how an aerofoil produces lift, limited to the variation of kinetic energy (dynamic pressure) and potential energy (static pressure) as air flows through a venturi or over a aerofoil. 2.2.2 Explain Coanda theory and the effect on lift production." Only CPL, aerodynamics is not required in much depth at RPL and PPL level so, I agree, pilots do not need to know much detail. It wasn't quite as bad in the old Day VFR Syllabus: "6.3 Bernoulli's theorem 6.3.1 Apply Bernoulli's theorem of constant energy flow to describe how an aerofoil produces lift. Note: Limited to the variation of kinetic energy (dynamic pressure) and potential energy (static pressure) as air flows through a venturi or over a wing. Student should also be aware that the upper surface of a wing generates the majority of lift." "Pre-PPL background knowledge only PPL basic principles should be known CPL should be known in considerable depth." Yep, had to be tested because that is what CASA has mandated in their rules so Australian providers of pilot theory must, unfortunately, present info consistent with that.Some people read vague snippets of information with limited applicability in the good book Aerodynamics for Naval Aviators then quote it out of context as general theory. Incidentally, that book of 400+ pages is free online at the FAA website http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/00-80t-80.pdf

good practice in wind tunnel tests to have a moving ground board for ground effect nope, Bernoulli is exactly right, the only problem are those who misrepresent his theory

G'day Dick. DJP

and https://www.raa.asn.au/storage/151111-amb-airspace-changes-wef-12-nov-15.pdf with phone number to ask further advice - they prefer to speak to people earlier rather than later.

I meant to state: only partly consistent - unable to correct the text now that I am home from hols and reading all of this on something bigger than my iPhone. My style is more like that of http://www.dylanaviation.com/ I like his philosophy: "To be a flyer, students need to master only two skills: do not cause the airplane to stall and control yaw. Specifically pilots should know how to turn an airplane. Until the FAA requires CFIs to teach and pilots to master and demonstrate that skill, I fear the bad safety record will continue."Jim of Contact Flying, by contrast, seems to be more like http://billquirkbooks.com/blog/2014/06/30/landing-insights/ who is in Alaska and somewhat critical of the technique by Mountain/Canyon Flying in Idaho - I lived in Wyoming for some years and did some backcountry flying in a Husky in Idaho etc. I'm certainly not of the "elite Alaskan pilot’s aviation sphere".

Had to wait until I got home to flick through my copy of the book - that extract was a general comment - he then went on to explain how the lag may be demonstrated with that 30 deg bank exercise.

nb: to clarify - divide by G pulled

agree disagree

Good Kaz although Kamloops didn't need to apologise in that situation - he was just going down a particular track with the discussion and I suddenly turned it on its head.Incidentally, the situation that I described was not an inverted stall although we were inverted at the time i.e. we had a positive angle of attack.

A simulator can provide an easy demo of performance comparisons for people to see for themselves.

It takes a bit of effort to engage in technical debate online, esp discussing aerodynamics at pilot level. I recall a long (perhaps esoteric) argument here about boundary layers with a mechanical engineer (so background in different textbooks) and it seemed to me that he hadn't encountered the term momentum thickness which we used in airfoil design. And don't mention Bernoulli! Suggest that you find a young lad with a Flight Simulator and get him to run through some flight exercises and compare the energy states. Or ask Matt Hall to explain how he turns to win a Red Bull race.

I will never forget an instructor who did indeed show me that technique quite recently, after briefing me on the technique when I queried it. Just coming over the back side of a loop we were extremely slow and he stalled it then pulled the nose down and the aeroplane responded with a sudden spin entry. He was obviously well versed in this as he recovered in a neat 1/2 turn and pulled out of the dive. My turn next. Same stall exercise. Small forward movement of the stick to reduce the angle of attack and we are unstalled so continue to fly the loop. That instructor agreed that my technique of moving the stick forward was better than his of suddenly getting the nose down. Seems to me that he had confused his own instructor's teachings on unusual attitude / stall recoveries. I wonder what key words his instructor used to describe the correct actions that work in all situations? "Learn to recognise that it is a stall ..." not as easy as it sounds to many people, when I ask how they would recognise a stall they typically rattle off all those standard symptoms of an approaching stall but that doesn't answer the question.

depends on the attitude

Just a little annoying for engineers but if many people use that term for a useful flight exercise then so be it. I did some training once with an ex-USAF Colonel whose nickname was Dutch - he loved to call his wave the Dutch salute and ..... sorry, but he would be quite entitled to roll around the floor and call that a Dutch roll. The certification requirement is for a specific level of positive DR stability. The PC-9 is one type which does not meet that requirement (at high altitude). The Airtourer is one example of a type which exhibits an annoying DR in a little bit of turbulence - I've always wanted a bigger rudder and fin on an Airtourer.

i would never train to drop the nose instantly

strine

CASA's MOS has lots of specs on required flying tolerances but nought on balance that I can see apart from words like "balance and trim the aeroplane accurately". First of all the instrument has to be accurately mounted in the panel. Secondly, consideration of the behaviour of the ball in dynamic conditions - refer the text in the attached photo. Worth repeating that first sentence: "Many pilots are under the mistaken impression that coordinated flight and ball-centered flight are always synonymous" with the result that, unless absolutely steady conditions, they fly down final in a state of perpetual uncoordination. The Pitts standard instrument package does not include a slip ball yet it can easily be flown accurately in balance - except normal landings when many of us prefer to sideslip just so that we can see the runway. As for flying the approach in calm conditions or direct headwind vs a crosswind - the discussion is irrelevant as there is always a crosswind component, its just that sometimes it is NIL.