Stall Training

[aro]

I don't believe any pilot has been taught "you mustn't exceed 30 deg", but is usually told to do rate 1 turns in the circuit because that gives a bigger margin of error

 

30 degrees angle of bank is not a rate 1 turn, unless you are doing somewhere in excess of 200 knots. A rate 1 turn is 180 degrees per minute, not a specific angle of bank.

 

It's easy to say that you should just follow your training, but these accidents tend to happen when things happen differently to what you did in training. Maybe a few things combine, e.g. a tailwind on base, a slower aircraft in front of you and a heavier load and further aft c.g. than you are used to. You delay turning final a few seconds to increase the separation with the aircraft in front, then you need a tighter turn because of the tailwind but you remember your instructor warning about steep turns in the circuit. Some subtle rudder pressure brings the nose around a bit quicker, some back pressure to avoid catching up with the slow guy ahead and ... oops!

[turboplanner]

........ then you need a tighter turn because of the tailwind but you remember your instructor warning about steep turns in the circuit. Some subtle rudder pressure brings the nose around a bit quicker, some back pressure to avoid catching up with the slow guy ahead and ... oops!

You certainly can spin in this way, but that's not what I was getting at wne I brought this up. The following is from "The Killing Zone, how and why pilots die" by Paul A. Craig.

 

"Aerodynamics of the Turn.

Avoiding low-altitude steep turns and low aerobatics all together is the safest course of action. But what is it about these maneuvers that become deadly at low altitude? Why does the airplane seem to fall out from under a pilot when in these maneuvers?

The airplane's wings must provide lift to counteract all "down" forces. Weight or gravity is the "down" force that we easily understand, but while flying other forces come into play. These additional forces can team up with gravity and reduce the effectiveness of lift. [When an aircraft is flying straight and level the lift exactly opposes weight]. These lift and weight vectors are fairly simple, but things get complicated when the airplane turns.

In a medium bank turn the first problem is that the lift vector is now leaned over, in the turn. [When the lift vector is leaned over we lose effective lift because the lift vector no longer directly opposes weight.] So in a turn we lose lift.

Meanwhile the turn wil also produce centrifugal force. This is the swaying force you feel in your car when you make a fast turn. Centrifugal force joins forces with gravity to form a resultant load. This is more commonly called the G force. The actual force of the earth's gravity does not get stronger when you turn, but when you add gravity and centrifugal force together it places an extra load on the wings. From the wing's point of view it is being asked to carry a greater load.

The wing is being asked to carry a greater load at the exact moment when lift is reduced and the wing is less able to carry a greater load.

Something has to give. The accelerated stall takes place . Ordinarily the stall speeds are painted on the airspeed indicator. The slow end of the white arc is the stall speed with flaps down and the slow end of the green arc is the stall speed with the flaps up. But in a turn the colors of the airspeed indicator can no longer be trusted. The airplane can and will stall even though the airspeed is well within the green arc. It stalls faster than the indicator says it should; that's why it's called an accelerated stall.

At shallow banks, the G force is not much above 1G. But when a pilot makes a 60-degree level turn, the G force jumps to 2Gs. That means a 2000 pound plane now effectively weighs 4000 pounds in the turn. More importantly, the wings must support 4000 pounds. That is a great deal to ask - to get 4000 pounds of lift from the wings of a 2000-pound airplane. The wings probably will not be able to do it and lift is lost; the airplane stalls."

 

After being trained on how to turn an aircraft with aileron, and how to turn more sharply if needed, and after reading recent posts, I'd be surprised if anyone here would be tempted to try and sharpen a turn using rudder, but let's say they do; they have misused the controls and they probably know it.

 

However, in the example I've given above, when you start playing with steep turns from about 45 degrees, you need to know the factors, like throttle settings you are going to use, you need to know what you can and can't do from theory lessons, not from something simple like keeping the ball in the middle, and that's why I give the angle of bank much more attention than I did in my first few years. Reading those paragraphs changed my attitude to showing off my tight turns overnight.

[facthunter]

I don't think any experienced person would disagree with your extract but like all things it's not the only way to look at these things. You don't fly with your eyes constantly on an airspeed indicator when in a busy circuit with say 5 aircraft in it not, widely spaced.. You are also taught when going into a turn to increase power or do something about the extra lift required. If that's automatic, you are much safer. Nev

[M61A1]

I'd be surprised if anyone here would be tempted to try and sharpen a turn using rudder, but let's say they do; they have misused the controls and they probably know it.

This is part of the mystery.....Like the turnback with an engine fail on takeoff. Everyone knows about it, but for some reason it still happens and way more often than we would like.

This article is not particularly about stalls, but later in the article it looks at illusions and why people may do some of these things that cause an inadvertent stall.

https://www.australianflying.com.au/news/dragons-of-the-downwind-turn

[Guest Machtuk]

I'm enjoying this thread, by all accounts there ought to be bodies and airplanes littering the countryside!?

[turboplanner]

I'm enjoying this thread, by all accounts there ought to be bodies and airplanes littering the countryside!?

Good point; there seems to be an absence.

[M61A1]

there seems to be an absence.

Perhaps the absence is why the media and others jump on it when it does happen. Even car crashes are statistically rare, but not many people give a damn unless it involves them, then they want move the world.

[facthunter]

They are frequent enough, and mostly avoidable . That's the issue. When issues turn up world wide, Airlines do something about their training if there's a case to do so. . The base to final thing keeps on being there. Nev

[MPB]

You raise some very interesting points. As someone who has NOT done any indepth practice on stalls / spins / spiral dives - only to the "incipient" stage, I have been seriously considering finding an instructor with the right rating and A/C in order to expand my skill set. I wonder if that fact that RA-Aus registered A/C are not allowed to perform intentional "aerobatic" maneuvers is a factor here? Thanks for your post :)

Consider taking some gliding instruction. Stall and spin training is conducted routinely. Its an annual requirement.

[M61A1]

Stall is about AoA & load factor, few understand this.

One might argue that it's all about AoA. The load factor just means increased AoA.

I don't know why few would understand the relationship between between stall and AoA and the effect of load factor. It's right at the very beginning of BAK and you need to understand it to pass.

[facthunter]

Stall is the ANGLE (to the relative airflow) at which a "specific" aerofoil ceases to do the right thing with the airflow pattern over it, loses lift rapidly and has a marked drag increase. It's usually somewhere around 14 degrees. You generally can't read AoA,.unless your instruments are pretty sophisticated. Load factor is increased by more speed or more angle of attack

. In a glider you don't have thrust. It's good stall/ spin practice but THRUST is another "control" available for stall recovery and can be an issue with spin and spiral recovery..

A "G" meter reads load factor.. Your elevator controls the AoA. Nev

[kgwilson]

Consider taking some gliding instruction. Stall and spin training is conducted routinely. Its an annual requirement.

Gliders are always looking for thermals and circle in them to gain height. Turns can be very tight and awareness of stalling in the turn (which can rapidly evolve into a spin) is vital for a successful height gain as often the core of a strong thermal is very small and the tighter you can turn the greater the height gain. This is the main reason that stall and spin training is part of the gliding syllabus.

[Bruce Tuncks]

A wise old instructor once told me that 27 degrees was the threshold of feeling G forces, which feel uncomfortable, and so many people avoided more bank than this all their lives.

While they could get away with this in powered aircraft, you need to turn steeper to thermal a glider.

Surprisingly, gliders do not often stall/spin while thermalling. A relaxation of back stick is all that is generally done. ( 45 degrees bank and 45 knots is my aim for a Libelle)

In 50 years, I have never seen an inadvertent spin from a thermalling glider, but it must have happened. There was a fatal accident in the US where a Nimbus 4 glider broke up midair. It is thought that it spun while thermalling and oversped during the recovery. Mind you, the Nimbus 4 is a huge wingspan high-performance glider, worth about ten Libelles.

[Guest Machtuk]

One might argue that it's all about AoA. The load factor just means increased AoA.

I don't know why few would understand the relationship between between stall and AoA and the effect of load factor. It's right at the very beginning of BAK and you need to understand it to pass.

 

Well if that's the case why do pilots still kill themselves if it's that easy?

[M61A1]

Well if that's the case why do pilots still kill themselves if it's that easy?

That's what I said earlier......For some reason everyone knows about it,base to final stall/spins, stalling in a turn back etc, but they still happen.

There was a well known instructor who frequented this forum, that began a thread about the turn back, so clearly he knew about it, then it happened to him.

I don't know what the answer is, but I'm quite sure that the vast majority of certificated and licenced pilots understand these things, but fail to apply them when it matters.

 

https://www.recreationalflying.com/threads/the-impossible-turn-a-known-killer.5984/

 

https://www.recreationalflying.com/threads/pilot-dies-in-light-aircraft-crash-south-of-townsville.30952/