Stalls in turbulence

[pacerpilot]

Actually all airplanes will behave that way. Think back to stall training, most instructors jump on us for trying to aileron the wings level, we use rudder. By trying to pick up a wing in a stalled condition will worsen the condition. Also, the spin/rotation is effected by the rudder. You're yawing round and round the vertical. That's why we don't-or shouldn't be-picking up speed once stabilized in the spin. A spiral is twirling around the roll axis, usually not stalled. I re-read your original post and wasn't sure if anyone had answered your first question too: "Let's say I took off, climbing at 65kts and there is a 15 kts headwind. If at 100ft, SUDDENLY the wind direction changes and becomes a 15 kts tailwind, my airspeed will suddenly drop to 65-30=35 kts, right? I guess it will end up in a spin and being too low to recover...". The answer is no. You'll still be flying 65. Your ground speed will go from 50kts to 80kts though. Remember, your airplane is moving through the airmass-with the airmass. If you're indicating 65mph, the wind could be blowing 100 mph, and you'd be flying backwards over the ground at 35 mph. The airplane is still flying 65mph through the airmass. If the windspeed changes, you're still going 65. But as Wes and Marty described, it may be possible-although remote-to see a momentary airspeed change. Which is actually a true wind shear condition, i.e. a sudden wind speed change or gust (not a vertical column of air blasting up or down). There was an article in our magazine a while back addressing the "downwind turn". Refering to a potential airspeed reduction from crosswind to downwind. It just don't happen. To sum up, use your training, don't chase the airplane through every little bump or "feeling" of vertical accelerations and keep the ball centered-you'll be fine.

[Steve Jeff]

Don't understand. You sad initially that ailerons don't change AOA and after you seem to agree with me.

And reagrding my first question, it was about a sudden gust, I know that steady wind means nothing to airspeed.

[pacerpilot]

Well, just trying to help but it seems I'm not. I'd suggest a flight instructor at your local field.

[Matt Gonitzke]

The ailerons do affect the local angle of attack for the region of the wing where the ailerons are located. However, most airplanes are designed such that the wing root stalls before the tip so that there is still aileron control after the wing (root) has stalled. This is done by either twisting the airfoil leading edge downward over the length of the wing, or with different airfoils along the span so that the angle of attack at the tips is lower.

Example: my glider stalls at about 40 mph, and on landing rollout, I still have aileron control down to about 20-25 mph or so. Look at a single engine Cessna wings sometime...the wing twist is very visible and obvious.

[Steve Jeff]

However, most airplanes are designed such that the wing root stalls before the tip so that there is still aileron control after the wing (root) has stalled. This is done by either twisting the airfoil leading edge downward over the length of the wing, or with different airfoils along the span so that the angle of attack at the tips is lower.

Example: my glider stalls at about 40 mph, and on landing rollout, I still have aileron control down to about 20-25 mph or so. Look at a single engine Cessna wings sometime...the wing twist is very visible and obvious.

Do you think airplanes not designed so, will have a wingdrop tendency when having a full stall landing during decrab in crosswind?

[Bill Greenwood]

Steve, Wind does not shift instantly, it is not like driving a boat over a waterfall, except maybe if you flew into a tornado.

Also there is some kind of stall warning in most planes, the best kind may be airframe buffet such as from the tailplane when turbulent air from the wing hits it; there are also warning horns bells, stick shakers in jets, etc. so that a pilot should know when a stall is near.
If you release stick back pressure at the first sign of a stall, good airplanes recover quickly and don't continue into a stall or spin.

I think you are overanalyzing and worrying about a stall too much; go out and fly and practice stall approach, stalls and recoveries and I think you'll find that while you need to be aware of it, you don't need to be on the edge of your seat about a stall sneaking up on you, IN NORMAL FLIGHT. Now, if you are doing acro or have just lost the engine after takeoff that is another realm.

[Cary]

Steve, you're getting a lot of good advice here, but you're not responding that you understand it. One of the best pieces of advice was to take some aerobatic lessons. It sounds to me as if your initial private pilot training really left out a whole lot about aerodynamics, because many of your questions should have been answered long before you went for your checkride. So now you owe it to yourself and to your passengers to make up for those deficiencies, but to do that, you have to pay attention to what you're being told. While you don't think you're arguing with the advice you're getting, in fact you are. So before you respond again, go back and re-read everything that has been said. Honestly, it's good, and it's accurate. I did not see one inaccurate item.

I speak from the perspective of 40 years of flying mostly singles, a few years of instructing back in the late 70s and 80s, and gobs of hours in turbulence. Don't try to reinvent the wheel--but learn from those who have been doing it, and the only way to do that is to pay attention--and stop arguing.

Cary

[Steve Jeff]

I have no intention to argue. I just want to understand how things really work. I pay attention and I really appreciate any advice, but I want rational help for my doubts. Just saying don't worry and listen to what we say it's not enough. I don't understand what's wrong to clarify these doubts. Of course I haven't understand some things as long as they were pointed to what I wanted to find out. When I came back with my thoughts, you stop answer and think I'm arguing with you, which is wrong. Don't try to reinvent anything.

[martymayes]

Why on some airplanes opposite aileron induces a spin or at least further wingdrop if you try to pickup the wing at stall using ailerons?

Because an aileron does two things; it makes lift and it makes drag. A spin requires yaw to be imparted at the stall. Using the rudder to do that usually works pretty well, however, using ailerons can certainly exacerbate the situation, because they are working on a long lever arm. A couple of similar looking trainers, one by Piper and one by Beechcraft made for very interesting lessons when misusing ailerons during stalls.

BTW, I don't think you're being argumentative, I don't think you need aerobatic lessons (although you might enjoy it), you just have some misconceptions that should have been cleared up when you were training. No big deal. Live and learn.

[Steve Jeff]

Thank you very much, I really appreciate.

If you have time and patience to help me with some questions that, as you also said, were not clarified during my training, actually because I haven't know about them then.

Regarding my first question, headwind shifts to tailwind, you said 15 kts and sincerely I don't get it why it's so. I figure out that if the headwind will decrease suddenly, there should be a change in airspeed, e.g. 15kts headind changes to 5 kts headwind, if it's suddenly, the airspeed decreases 10 kts. So, why when it suddenly shifts from 15kts to 15 kts tailwind there is no a 30 kts drop?

Also, what is not clear to me is the difference between a wingdrop and an incipient spin. I figure out that you may have a wingdrop even if you are coordinated, because the wingdrop may be induced by engine power effects and other factors, not necessary yaw, so, with ball centered you may have a wingdrop, but not a spin, right?

If that wingdrop is abrupt, what be will be the outcome? The wing will tuck under and the result will be a spiral with nose pointing down?

During a coordinated turn descent, I know that the AOA of the inside wing is higher than of the outside, in this case, you may have a spin even if you had ball centered?

And during decrabbing, when you introduce pro-spin controls, i.e. rudder to decrab and opposite aileron just to prevent banking in the direction of the rudder, why there is no wingdrop? Considering a stall landing, the airplane is very close to stall when we introduce these controls.