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Sunday, 11 May 2014


Meanwhile, I'm also taking flying lessons, of course!
I may not write each and every time about my lessons, but they do continue. I have had my seventh lesson as I write this, which is also lesson number 7 in the syllabus, so I am progressing as planned. Lesson 7 is all about slow flight and stalls. Stalling is effectively flying so slowly, that the wings reach that critical point where they stop producing lift.
So, yes, you start to fall from the sky, and no, that's not scary :)


As you progressively fly slower, you need to point the nose more upward to retain altitude. That will increase the angle of the wing profile, relative to the air flow, which increases the lift per quantity of air flowing around the wing. This quantity, of course, decreases as you fly slower; hence the need for an increase in the so called "angle of attack". However, there is a maximum to the angle of attack. At that angle, the airflow over the top of the wing becomes "separated" over too much of an area of the wing; it does not cling to the top of the wing anymore, so the lift is reduced dramatically.
So if you close the throttle, and keep your altitude by pitching up as needed, you will inadvertandly meet that situation where lift drops abruptly. That moment, you enter a stall situtaion.
The moment you start to "fall from the sky", the little wings at the tail end of the airplane (the horizontal stabilo) will cause the nose to be pointed further down again, much like the tail of a dart. A small amount of pitch down will improve the airflow along the wing profile in the correct direction already, and the plane becomes controllable again. The remedy therefore is to put the stick in the neutral position (it was strongly pulled already when entering the stall), and apply full throttle.

So stalls it is! The main purpose of my lesson at the 9th of april. It had already been a month or more since I last flew, so I wondered if It would all come back to me soon. "Q" was already booked before and after my flight, so not too much time for extras. Luckily, my work and traffic cooperated nicely, so I was at the club early enough to get settled, and prepare the Weight & Balance. The one before me came in ealy too, so while he was debriefed, I did my walk-around. All nuts and bolts accounted for, and in place, moving parts free to move, and enough oil, only a little short on fuel. About 1/4 full in the left tank, less than that in the right tank (the dipstick starts at 1/4 tank). So we would need to fill her up; also good excersise :) It really isn't all that complicated, as long as you don't forget the ground cable, it's all pretty similar to fueling up with a car. Except for the two tanks, that is ;) It comes in handy if you figure out how and where to park, so that you can actually reach both tanks with the hose, you can see the pump while fueling up both tanks, and so that you can simply drive out of there.

I'm starting to get the hang of things, so Piet did not have much to do, until just before take-off. As there was a fair bit of (cross) wind, he talked me through the take-off, and initial climb, before entering the runway. But that was about all. We started out doing some climbing excersises at Vx, and Vy. That are the speeds for best angle of climb (comes in handy when trying to clear nearby objects, such as trees) and best rate of climb (feet per minute, handy for reaching a higher flight level as soon as possible). So we descended to 500 ft, and start to climb, descend again, and climb again... you get the picture. Clouds were at 2200ft, so that's how far we'd climb. That was also the altitude for stall recovery excersises.

We practiced stalls with and without flaps, both with recovery at the sound of the stall horn, and at the onset of a fully developed stall. 4 Different excersises. Fully developed, without flaps is, of course, the most difficult one to recover, because the instability seems bigger, and more airspeed recovery is needed to regain control than with flaps.
Because the effect is bigger, and the recovery effort is more extensive, the difference between the one wing and the other will be more pronounced too. Most likely, one wing will stall before the other, and that's why you get a so-called "wingdrop". By moving the stick in the oposite direction, you only worsen the situation: the stalled wing gets stalled deeper, while the unstalled wing gets a little more reserve towards stalling. It is the natural reaction to countersteer a wingdrop, though. So you need to suppress that reflex, and steer along with the roll, in order to regain control quicker. That only applies when bank angles are not too steep, of course.
This situation can also lead to a spin, where you turn towards the stalled wing so fast, that the "outside wing" does not stall at all, while the "inside wing" remains stalled (thus producing no lift). This can lead to an equilibrium state too (albeit a very dynamic one) where you spiral downwards with one wing stalled; the spin. This equilibrium state requires control inputs to recover from; in this case stick neutral, and full opposite rudder - kick yourself out of the spin. This will give the stalled wing some airspeed, while the stable wing looses some airspeed. Anyway, "intentional spins are not allowed", according to the pilots operating handbook, so we're not supposed to get to that stage.

None of that happened during my excersises, just some sloppiness of the controls, and a distinct sinking feeleng. Nose just under the horizon, full throttle, close the carburettor heat in the same movement, and up flaps one notch while you have your hand near the handle anyway (with full flaps only). I lost only some 200 feet in altitude, so that's OK. Especially for a first-timer ;)

I had another lesson planned to do stalls, but the weather was just not good enough, then. Too much crosswind on the day itself. The days before and after were beautiful flying weather, but hey, you can't win 'em all.

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