Flying

spacemansteve: "[The CT4B] is a pleasure to taxi around in but has the flying characteristics of a brick."

I've never flown one. From what very little I know, the wing loading does seem a little high for a trainer. Is it unforgiving/mushy if you let airspeed decay? Maybe the Kiwis just want to instill early the skills that less wing demands.

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Some years back, I proposed Zlin 242Ls to the RNZAF, never realizing we were competing against a "brick". They weren't interested, but the Zlin is a delight to fly. As you can see, the Zlin has a more ample wing:

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Don't know too much about the Zlin, but yeah the wing loading on the CT4 is a bit too much. At the end of the day it suits its purpose and as long as you fly it by the book you have no problems.

There are two things the CT4 hates, speeding up and climbing. If you let speed decay away too quickly then its pretty hard to get it back up again. Like most aircraft tho, when you let speed decrease she'll be a bit sluggish but nothing overly problematic.

The Kiwi's bought the design off us aussies so although they like to claim it as an Kiwi aircraft, it is technically Australian.

At the moment we're looking at replacing the current CT4B trainers with F model which is an amalgamation of the A model (Wings moved a little bit forward) and the E model (300HP engine as opposed to 210) but also adding in a glass cockpit. Looks quite interesting but probably a bit too advanced for basic flying training

 

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This might seem out of place, but is bernoulli's theorem the same reason your ears hurt when the cabin pressurizes/depressurizes ? .

 

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Bernoulli's principle is more to do with the accelleration of a liquid (perfect fluid) through a venturi and the lower pressure that this creates...

It has more application in regards to the wings of aircraft.

The curvature of the aerofoil is similar to that of a venturi (half of one at least), therefore the air that travels across the top of the wing accellerates and subsequently the air pressure on the top part of the wing is lower than underneath. This then creates an upward force or, in aerodynamic speak, Lift... That is pretty much the basics of it, there is a hell of alot more involved such as boundary layers and seperation points etc etc, but generally speaking thats the reason for it

In regards to the "ear popping" experience every traveller has on aircraft. As you climb through the atmosphere the air pressure obviously decreases, When rapid ambient pressure increase occurs e.g. aircraft descent, this pressure tends to hold the Eustachian tubes closed, preventing pressure equalization across the ear drum, with painful results. To avoid this painful situation, most people normally attempt to open the Eustachian tubes by swallowing, which tends to open the tubes, allowing the ear to equalize itself.

If this fails, then the Valsalva maneuver may be used. A valsalva is simply holding your nose and closing your mouth then attempting to breath out.

Its a nifty tool when you're doing a rapid descent. I did a hypobaric chamber run and as we descended from 14,000ft at a rate of 4000fpm you could definately feel the effects of this and the valsalva became my best friend.

The highest i've flown in a non pressurised environment was 18,000ft. But the rate of descent was much easier on me

 

I know next to nothing (approaching zero, from the negative side)

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about flying, but once did some calculations of lift of a wing which were done, without using the Bernoulli's principle. I forget how now, but it was some mathematical approach built on the curl (type math derivative) and vortices etc.

I do know a little about sail boats (slightly above zero on the plus side) I think it was the New Zealanders who kept the keel of their America's Cup boat covered / secrete as long as they could as its tip had the perpendicular stubby extensions most modern commercial planes now have.

I notice that the plane of photo in post 46 does not have these perpendicular to wing stubby extensions. I think that they function to make flying more efficient, despite the extra drag (more "wetted area" in flow) by reducing the spill off of wing tip vortices. (There is a lot of energy spinning in air behind in these vortices and as I recall from the math, they are secondary to the lifting vortices, still attached to the wings in sub sonic flight at least. I.e. in this non-Bernoulli POV as I recall there is air circulating around the wings -up at the front edge, down at the trailing edge. - Probably only in the math. – It is all quite hazy to me now.)

Anyway, my question is:

With the modern, stubby, perpendicular-to-wing additions (Thanks to the N.Z. entry into the America's Cup) is it now less dangerous to land behind a big plane?

 

Winglets are a method of reducing drag without increasing wingspan. They do slightly reduce the energy in wingtip vortices, but not enough to significantly reduce the hazard- Winglets are no magic cure. Wake turbulence is an apt term, because aircraft leave a complex wake of multiple vortices, not only originating at the wingtips. Every discontinuity in the wing, such as fuselage and nacelle intersections tend to trigger multiple vortices, that can interact by combining and/or disturbing each other, depending on a lot of variable conditions. Eliminating large aircraft wakes can be thought of as a similar challenge to eliminating the wakes of large ocean vessels: Because a lot of mass is being dynamically displaced, a considerable wake is impossible to eliminate.

I wish I could find graphic of the interaction farther back in the wake, but there is a suggestion here of how similar rotation does develop further in the progression- the winglet vortex wraps into the wake of the wing, with only slightly diminished energy. Wake turbulence hazards do remain behind heavy aircraft with winglets, and as with all wing designs, the vortices are most intense and persistent when the aircraft is operating clean (flaps and leading-edge devices retracted) heavy and slow. The more uneven lift-distribution can be made, and the more vortices can be triggered, the more diffuse the wake. A clean-looking wing produces fewer, more defined, and more persistent vortices than a wing with lots of gadgets tripping multiple interacting vortices. Taking this principle too far would involve compromises in efficiency and safety. It's been far more practical for pilots to just avoid hazardous (but usually short-lived) heavy-aircraft wakes.

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Here's some coverage of an interesting NASA study that explored vortices and aerodynamic wake reduction. NASA and the industry sort of threw up their hands about wake-reduction aerodynamics, but a lot was learned about wake structure, and the environmental factors in wake persistence.

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BillyT

There are a number of concepts that are taught in regards to lift.

There is the pressure distribution concept which is basically applying bernoulli's principle over an aerofoil (wing). There is the Momentum theory which in a nutshell is about air hitting an aerofoil on an angle which imparts energy creating an upward vector. Then there is the Vortex/Circulation theory which is essentially what you just summed up in your post.

Hype, nice pics... I hate using the Dyson-Holland training books... too much writing and not enough pictures

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Thanks for the valsaaythingy maneuver, I still love flying but it's kinda hard to admire a city while your ear feels like it's being broken into with a piledriver.

 

No problems... Its something that all aircrew have to be able to do in my opinion... any problems then you're less effective in the air

 

Particularly when gliding, because you really have to pay attention to everything. From the damn yaw string (the simplest are the best), to the whole surrounding airfield and all the instruments.

It becomes subconcious after a while, but I had to fly instrument blind and it really wasn't good.

 

Ouch, yeah although my belief is that Powered flying is difficult because you have to monitor the engine on top of flying, plus the multitude of mechanical problems that can arise. I still think gliding would be one of the more difficult ways to fly. The concept of not having any ability to correct mistakes when low to the ground (landing) and even when flying seems pretty darn scary to me.

I'll stick to powered flight

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Yeah, I bled down to 500 feet AGL still thinking AMSL, and nearly cost me a glider.
Much more sensitive to fly though.

 

"I bled down to 500 feet AGL still thinking AMSL, and nearly cost me a glider."

Any masterful soaring bird is always ready to land.

Ah.

 

Anyone watch the red Bull Air race ?
I thought the Gs they pull would black out younger men, much less 40 year olds.

 

There is evidence that G tolerance does not decline with age. G tolerance certainly does increase with aerobatic proficiency and currency. There is a popular assumption in the aerobatic community that regular aerobatics actually promote vascular health.

In recreational, competition, and in exhibition aerobatics, sustained G is not the norm- neither do blackouts and G-LOC enter into the equation much. The Red Bull performers are highly accomplished and healthy pilots, but the physical demands of the display (including momentary +10 pulls) are nothing too physically extreme for any healthy individuals accustomed to the forces of exuberant flight.

It doesn't require any rare physical conditioning to endure the crowd-pleasing maneuvers displayed in the Red Bull races- just reasonably good health, and the physical acclimation of any proficient and current aerobatic pilot.

 

Oh ok. Fine, I won't take steroids to fly

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Is it scientifically proven that shorter pilots withstand G forces better? .

 

In the Chair Force, legless pilots would be ideal, if it were not for PR. But amputees aren't the right photogenic stuff. Fly-by-wire systems could easily do the LR yaw legwork without all the meat foibles. But along that train of thought is the wreck of a lot of hallowed mythos, bleating that it takes high consciousness to simply track and hit something.

 

This thread isn't exactly flying. Is it... Well with a little time on my hands, I'm going to toss in an offer to discuss formation flying. Right away, it's worth going over the reasons for flights of two or more, and the dangers involved because there is rampant confusion about that.

Q: Is this risky? What are the chances we might butt airplanes?

A: Not particularly, and the chances of collision are lower during this formation training than they are on normal single-ship cross-countries. Why? Because we are more aware. This kind of flying is going to help you become much more aware of your airplane and the sky around you than you have ever been before. I tell this even to high-time, experienced professional pilots- and if they haven't formally flown formation before, it does hold true.

Q: Why the hell are we going to fly within feet of another airplane?

A: Because there is strength in numbers. Whether your formation may be assailed by military, meterological, or procedural challenges, a gang can go where a loner might not be as safe, and a gang or even something of a gaggle can operate in a mutually-monitoring state of mind that elevates the focus of each aviator.

And this is aviation, on a higher mental plane. So clear your mind of everything but a simple mental windsocl: A sock with air rushing through it. Visualize sticking your hand into the center of a gigantic sock from downstream, and controlling the position and attitude of your hand in the sock, but in a very limp-wristed manner. Inside your mind's eye, fly your hand in the box. If you are a pilot, put yourself in your favorite airplane in the wind-tunnel box. Fly there. Play around in there some, like a trout swimming upstream. The Secret to formation flight is fully revealed from inside an easily-imagined sock.

Now let's take our sock into an imaginary sky like a kite. Put it up into the airspace of your head, and drag it, waggle it, dance it around some. Imagine its behavior: All the box does is behave like any windsock, or like big sock with a hole in the toes would, if you aired it out in the sky.

Pay attention now, if you want to fly beautiful formation, because this is important:

Fly your plane, literally and imaginatively, with a metally-visualized wind box surrounding the aeroplane.

It isn't static. I think I'll postpone discussing what comes next until someone beside just me expresses an interest.

 

Actually, I'll ramble on some more.

Straight and level flight. Visualize it with the imaginary windsock surrounding the airplane, the intake end of the windsock firmly in formation, the small downwind end of the windsock always going with the flow.

Now step on the left rudder -just a little- and keep the wings level.

What happens to the back of the imaginary windsock? How much does it move, if we're visualizing a windsock with a diameter equal to the wing span?

What happens when we stomp the rudder?

What happens when we release the rudder into trail?

If you can visualize the answer, you can become an expert formation flier.

 

After learning to always be aware of the relative wind, we become aware of many things, including a keen awareness of exactly where the airplane will be next, with surprisingly high accuracy.