Stalls in turbulence

[WLIU]

You should go take an hour of aerobatic dual to start to get an understanding of how "G", airspeed, and aircraft inertia interact.

But I will note that on final approach, you are unlikely to encounter 2G turbulence. That is really severe. Having a lot of experience with both sustained and momentary G's from flying aerobatics, I will offer the opinion that moderate turbulence is maybe +1.5G to -0.5G. And it is the minus G that gets folks most concerned. Getting jerked against the seat belts makes most straight and level pilots really uncomfortable.

Light airplanes float up and down more on final where airplanes with heavier wing loading, which means a higher approach speed, "punch" through a "bump" with less change to their flight path. But the airplanes with the higher wing loading typically stall at lower angles of attack! So what is going on? Due to the higher speed and higher weight, the time exposure to the "bump" is less and the greater inertia means that the airplane reacts less. In turbulence, mass and inertia are your friend.

Best of luck,

Wes
N78PS

[martymayes]

On final you are 65 kts, I would say you'll stall if 2G load is applied. Sustained? I don't know here, but sometimes it feels like the updraft load is sustained 2-3 seconds when you encounter it suddenly.

An inflight load applied for 2-3 sec is a transient condition.

Steve, when the plane encounters an updraft on final, the pilot pushes the stick forward to keep from ballooning above glidepath which unloads the airplane. A stall would be more likely if you encountered a downdraft on final, cause the pilot would pull back on the stick, which increases load + angle of attack. When wind shear, updrafts/downdrafts/gusts and turbulence is expected on final, you fly a higher approach speed which gives extra padding for those things.

[Steve Jeff]

When wind shear, updrafts/downdrafts/gusts and turbulence is expected on final, you fly a higher approach speed which gives extra padding for those things.

Usually 5 or max 10 kts above normal app speed. I would say that is small difference for updrafts, downdrafts.

[WLIU]

Increasing your approach speed from 65 kts to 70 kits is 7%. That is large in airplane stall margin terms. Going from 65 kts to 75 kts the increase is 15%.

If you fly with a G meter and an AoA display on a bumpy day you will find that you are overestimating the effects of the turbulence that you have encountered. Perhaps there is a homebuilder near you that has the gear and would go flying on an otherwise bad day to let you observe the data.

You will overcome your fears by simply flying on less than idea days. Start easy and work up.

Fly safe,

Wes
N78PS

[martymayes]

Usually 5 or max 10 kts above normal app speed. I would say that is small difference for updrafts, downdrafts.

Considering that updrafts/downdrafts have little impact, small difference = more than adequate. Can't keep adding speed because it impacts landing distance. How many airplanes have stalled and crashed on final in the last 10 yrs due to turbulence? I suspect the number is very, very small.

[Steve Jeff]

Increasing your approach speed from 65 kts to 70 kits is 7%. That is large in airplane stall margin terms.

Yes, there is a substantial changde in 1G stall, but considering gust also increases G, the difference will be smaller in stall margin terms. Perhaps it will give you just 0.1G in plus.

How many airplanes have stalled and crashed on final in the last 10 yrs due to turbulence? I suspect the number is very, very small.

Don't know, there are lots of crashes due to stall/spin in traffic pattern. But I hope all of them are due to maneuvering, inadequate speed maintained by pilot etc.

[WLIU]

The statement "Perhaps it will give you just 0.1G in plus." is based on your fear, not on looking at the V-N diagram for your airplane.

I get the distinct impression that the original question is posed in a manner that is looking for support for the notion that flying in weather that is less than perfect is far too dangerous for a mere mortal in a light aircraft. The folks contributing to this thread are using logic and fact based information, but the info provided isn't being accepted as the answer to the question.

I will suggest that none of the folks who have provided info in this thread started out as masters of the subject, but rather started flying on nice days, studied the performance of their aircraft, and flew on progressively more challenging days. Not instant gratification. Can't get it all from a book or an internet forum. You have to fly.

Perhaps flying only on nice days is appropriate for now? After all, that is a perfectly fine approach to enjoying aviation.

Fly safe,

Wes
N78PS

[Steve Jeff]

The statement "Perhaps it will give you just 0.1G in plus." is based on your fear, not on looking at the V-N diagram for your airplane.

Right, it's about 0.25G.

I get the distinct impression that the original question is posed in a manner that is looking for support for the notion that flying in weather that is less than perfect is far too dangerous for a mere mortal in a light aircraft. The folks contributing to this thread are using logic and fact based information, but the info provided isn't being accepted as the answer to the question.

No way, I just want to understand exactly what is the margin and how likely is to have problems.

[Frank Giger]

The only turbulence I fear in the pattern or on final is wake turbulence - and it's fairly simple to avoid.

However, get bit once and you'll add quite a bit of distance more than what the book suggests from then on, particularly if one is piloting a Champ! Or so a friend tells me.

OTOH, I've had wind change directions on me while on final more than a couple of times - heck, I've had wind from two directions on the runway (kinda funny when the two windsocks on the ends of the runway are pointing in different directions) - and it's not that big a problem if one is sticking to the basics and not trying to do anything fancy. A little more power (just a little) helps out a lot. "Squirrely" air and gusts are actually more challenging and have resulted in more go-arounds than changing wind conditions for me.

But my advice is to find a day that is outside of your personal minimums and put a trusted CFI in the rear seat for some pattern work. I've done it and it's worth gold in terms of understanding where my skill level was and how much I underestimated myself - as well as pointing out how much more I have to learn. And also when it's time for me to throw in the towel and put it in the hangar.

The bonus is that with a few other simple tasks thrown in one can get WINGS credit and have it count towards the biannual (er, flight review). I've already given this guy a wheelbarrowful of cash for the basic license; might as well throw in a few more bits of paper and have him really do some work for me after all.

Then again, I have no shame and zero pride when it comes to becoming a safer pilot. There's a Champ driver at our field that is simply amazing at slipping to a super short field landing and I basically begged him to take me around the patch and show it to me first hand. Maybe when I have 30 years behind the stick of one I can pull it off like he can; until then I'll just be jealous.

[Steve Jeff]

Sometimes I felt the G lasts few seconds when you suddenly ecounter the gust. So I figured out in 2-3 seconds you may even get a spin, if the turbulence also induces some yaw. What if just one wing is hitted by a strong gust and it exceeds its critical angle of attack? The differential lift will be large due to the other wing is still flying. Maybe these scenarios are far away from how things really happen. I don't know, that's why I have these doubts.

Btw, usually, in a spin, how large is the difference in lift between the two wings? How much differential lift is the rudder able to overcome to recover from a spin? Although slightly embarrassed, I'll confess what I figure out: if a strong gust makes you spin, is it possible to not have enough rudder to recover? I guess the differential lift in a normal spin is not very high, cause you can't induce differential lift larger than using full ruder, but I guess if only one wings is stalled due to gust and the other is flying, that is larger than whatever spin you induce with controls. Again, maybe I have a very wrong idea of how a spin works. I'm sure you can clarify my strange doubts. Thank you so much!