future777captain
New Member
Part 1: Understanding the Basics of the Airplane and Flight
If a seafaring explorer from 500 years ago was caught in a time warp and transported to this day and time, he would naturally be perplexed by the ‘ships of the sky’ that we call airplanes. After all, most of what we put into aviation is taken from shipping; the captain and first officer, stewards, rudders, nautical miles, knots, etc…..) In essence, driving a power boat through the water would give some idea of how a plane works in relation to air.
However, the seafaring man has changed careers and now wants to be a 777 captain, just like me. But, we have take him from the beginning, ‘from the Greg up’.
We stand in front of a cessna suspended in mid-air, like a hologram.
At the front we have the propeller, the body of the plane is the fuselage, two wings, a vertical fin, and a horizontal stabilizer.
A) We start with the propeller, or ‘prop’ for short. The prop itself is designed as a spinning wing. What happens is that the turning prop will force air behind it, therefore causing a forward reaction with the rest of the plane.
B) The fuselage doesn’t need much explaining. It is essentially the body of the aircraft that is holding everything together.
C) Remember we talked about the effect of what the prop does? Well, it moves the plane forward, but doesn’t create the lift we need to get off the ground. That is where the wings come into play. It works in 2 ways.
1) First, we have the Bernoulli effect. At the leading edge of the wing meets the airflow, the air will accelerate over it as it seeks to remain constant with the air molecules that have been compressed below it. The faster air over the top is therefore creating less pressure, allowing the aircraft to leave the ground. A car at high speeds, on the other hand, would not be able to generate this kind of lift.
2) Secondly, we have the Newton effect. It states that an action will create a reaction. Essentially, according the wingfoil design, as it cuts through air, it creates a downwash of air, while at the same time compressing the air below the wing down. By compressing the air below it, otherwise pushing it down, the opposite reaction is that the wing will be forced up in an opposite reaction.
3) The ailerons. The ailerons are what we call a ‘control surface’. One of many actually. The purpose of the ailerons is to deflect the airflow in order to produce a turn. In a right turn, for example, the right aileron will go up, and the left goes down. The left down aileron is producing more lift, while the right up one is deflecting the wing down, therefore resulting in a right turn. An opposite situation would have the opposite effect.
D) Here we have flaps. Flaps have a couple of functions. They act as both lift and drag forces, which can be confusing to some. On takeoff, for example, speed is relatively low, and to produce as much lift as we can, we want to increase the wing area as much as we can. Therefore, there is a moderate level of take off flap. Remember, for take off, we want maximum lift and minimum drag. On landing, we want a low speed and more drag to keep that speed as we descend, so we have a larger output of ‘landing’ flaps to achieve that.
E) Next we have the vertical stabilizer, or fin. The purpose of this vertical fixed wing is to keep the aircraft stable in flight, basically preventing left-right yawing motion of the front of the aircraft. Attached to it is the rudder. Unlike a ship, the rudder on an airplane is not there to produce a turn. That is what the ailerons are for. The purpose of the rudder is to control various types of yaw (which we will get into later). But a practical example would be our right turn. When the right wing is down and the left wing is up, the higher wing (left) is causing more drag, therefore the plane will try to go left instead of right. The rudder is then put into the direction of the turn to
co-ordinate it and keep the plane on it’s proper flight path.
F) Here we have the horizontal stabilizer. As the vertical stabilizer is used to control yaw, or left-right motion, the horizontal stabilizer is used to control pitch, or up-down motion. The control surface here is called the elevator. It’s deflective properties work in much the same way as ailerons, except both the left and right elevators move in unison. When we pull up, the elevators go up, which causes the airflow deflection to force the tail down, therefore the nose goes up. If we push down, the opposite effect happens. As well, we have an additional ‘anti-servo’ tab. It moves with the elevator, making it heavier and requiring more force in climbs and descents. However, although it seems anti-productive, it is not. It is needed in aircraft where the controls are too light and we need more stability along our lateral axis.
Forces in Flight
When the plane is in the air, we generally say that there are 4 forces acting upon it: Thrust, weight, lift, drag.
1) As we discussed, thrust is the forward movement of the plane caused by the propeller. Thrust is a little different between jets and props, which we don’t need to get into.
2) Weight: Weight is the downward force of gravity on the aircraft. Weight can be confusing because the weight of an airplane in the air is not necessarily the weight it is on the ground. For example, if a plane weighs 1,000 lbs on the ground, it is likely to be that weight in straight and level flight. However, in a turn, the gravity load of the airplane increases to gravity x 2, which means in the turn the plane is now 2,000 lbs. As we also think of weight as the combined sum of all the airplane parts plus fuel, people, and baggage, we can think of weight meeting and acting at the center of gravity (c of g). The c of g, located ahead of the lift in straight and level flight, is found by engineers by measuring from a datum point, and finding the average location where the sum of all weights will be located. This is very important for us, because the weight of the airplane will constantly change during flight, mostly due to fuel being burned. For example, me and the sailor sitting in front, with the fuel tank behind us. As the weight in the tank becomes less, the center of gravity will move forward, which means we have to pull back on the stick to remain level, thereby increasing the weight on the tail, which makes the plane think it is heavier. Our stalling speed increases, but we will get more into stalls in a little bit.
3) Lift: As we discussed before, there is Newtonian and Bernoulli lift. Let’s look at the wing design for a second. First, from the left to right of the wingtips, we have the wing chord. The curvature of the upper and lower surface is called the camber, divided into upper and lower camber, and at the end near the flaps and ailerons we have the trailing edge. Now, if we look at a little animation, we can see the air flowing over the top and the bottom of the airfoil. You notice that the air over the top is faster than the air at the bottom, which means lower pressure. Here, the wing is in straight at level, so the way at which the air is meeting the leading edge of the wing, otherwise known as relative airflow, is parallel to the flight path. If we move the wing down or up, the relative airflow will remain parallel. Our various angles are called angles of attack.
Now, as relative airflow is parallel to the angle of attack, lift is perpendicular. Basically, we have the higher pressure under the wing, and lower pressure on top. The sum of all the pressure forces acting on a wing, if we consider it to be equal to a single force, will act in a straight line up through the cord. We call this the center of pressure, acting up in a 90 degree line, which we can call our lift.
4) Drag: We can call drag any forces that are ‘resisting’ the movement of the airplane trough the air. Drag can be divided between parasite and induced drag.
a) Parasite drag is caused by resistance by any part of the airplane that is not contributing to lift. They include the fuselage, landing gear (without wheel pants) antennas, and open cowlings, among others. Simply put, form drag is related to the shape of the body of the aircraft, and skin friction is caused by air sticking to the surface of the skin of the airplane. It can never be eliminated completely, but aircraft designers have found ways to reduce it as much as possible. Depends on the airplane. However, rule of thumb is that as speed increases, parasite drag also increases.
b) Induced drag is caused by the forces that produce lift and can never be eliminated, like the wings. In the end how much induced drag we experience depends on the shape of the wing of the individual aircraft. Basically, low pressure air over the wing flows inwards, and high pressure air under the wing flows outwards. When the 2 meet at the trailing edge, their unison causes the 2 to form into a circular eddy that we call wing-tip vortices. This disturbed air resists the forward motion of the wing, hence we have induced drag. The amount of induced drag is dependent on the aspect ratio of the wing. That is, the ratio between the wing span and the wing chord. For example, a glider with a span of 36 feet: 6 feet= aspect ratio of 6. Another glider that is 36: 4= aspect ration of 9. The glider at aspect ratio 9 will have less induced drag since the upper and lower airflows have less distance to travel. Rule of thumb is that induced drag decreases as speed increases.
c) Aileron drag is a third category that is fairly straightforward. The drag of the down going aileron causes more drag because it is being put down into a compressed airflow. The aircraft designer will usually correct for this in the aircraft design, in order to prevent yawing in the opposite direction in which we are turning. Differential ailerons are designed so that the down going aileron moves down less, while the up going one moves higher into the airflow. Frise ailerons are streamlined into the wing so that the down going aileron will cause less drag.
The 3 Axis of the Airplane
If we look at the plane from the top, we can cut it into 2, and imagine a 3rd line going up. The line from the nose to the tail is called the longitudinal axis. The axis between the wing tips is called the lateral axis. And the line extending upwards is called the normal (vertical) axis.
1) Longitudinal axis: When the rotate the plane on this axis, we call it the bank (or roll). This rotation is controlled by the ailerons and to a certain extent the rudder.
2) Lateral Axis: The rotation here is called pitch, which is the up and down moving motion of the aircraft. This is controlled by the elevators.
3) Normal (vertical) axis: Here, the aircraft’s nose moves left to right. We call this yaw, and it is controlled by the rudders.
Yaw is a very prevelant force on an aircraft, especially on single engine aircraft.
The first type of yaw is slipstream yaw. The motion of the propeller causes air to be pushed back in a corkscrew motion, causing the fin to turn from the high pressure to the low. This is what we call slipstream yaw. It is corrected by offsetting the engine thrust line (in the case of the diamond katana 2 degrees to the right), adding rudder trims, or a combination of both.
Another type of yaw is turbulence yaw. In turbulence yaw, the plane is being buffeted by the air beneath it (much like a ship in the water). This causes the right and left wing to off balance, resulting in one wing at a higher angle of attack than another, causing more drag on the upgoing wing, causing it to yaw in that direction.
Tension yaw may occur when the pilot is unknowingly putting unnecessary pressure on the rudder, especially in a tense moment, like difficult situations on short finals.
These 3 axis meet at the center of gravity (c of g). Remember that an axis will change with flight. For example, when an aircraft is in a 90 degree bank turn, the vertical axis becomes parallel with the ground.
Stalls
Stalls deserve their own section because it is extremely important to be able to identify the symptoms of a stall, causes of stalls, and stall recovery.
Let’s look first at the wing design. You notice that on the Katana, the wing is twisted at the end. This is a feature we call washout. In this design, lift is designed to be greatest at the root, and decrease until we eventually get 0 lift on the wingtips. The idea is that the wing root will reach the critical stalling angle of angle of attack before the tips, thereby reducing the chances of the airplane entering into a spin.
Let’s look at a little video John made about what is going on during a stall.
In this video, you can see the right wing of the Cessna in flight. You notice that seafaring man has taped confetti all over the wing to demonstrate airflow. Now, at this moment, all the confetti is lying flat representing the smooth flow of air over the wing. Now, our pilot is increasing the angle of attack. As it increases, notice how the confetti is becoming turbulent on the inboard section. What’s happening is that at this angle the smooth airflow is unable to follow the upper-camber like it was before. The airflow is pulling away from the wing and is becoming turbulent. At this point, the center of pressure that is causing lift is moving forward, away from the separation point between turbulent and smooth air. Also note that the confetti on the wing-tips remain smooth. Washout has made sure that the inboard will stall before the tip can stall. At this time, the turbulent air is also hitting the elevators, making John notice that the stick is shaking.
Now, we pull past the critical angle of attack, and the confetti stops on the inboard section. No more airflow is flowing over the upper camber, which means no lift as the center of pressure has moved all the way back to the trailing edge. The nose will now drop, allowing airspeed to build up again. At this point John will apply full power and ease out of the dive.
In which conditions will we likely encounter a stall?
1) Increased weight, especially loaded over gross weight. What happens is that in this case, to maintain straight and level flight, we have to increase our angle of attack higher in direct relation to our weight. The heavier the plane, the more we increase the angle of attack. Each increase in angle of attack takes us closer to the critical angle.
2) The location of the center of gravity also plays an important part. When we have more weight at the front then the back, for example, we are unbalanced. In this case, the center of gravity will move forward, farther away from the tail, which will have to be moved down to prevent the plane from descending. This downward motion is increasing the weight of the tail, therefore the weight of the airplane. The stalling speed will then increase. The opposite is true with too much loading in the back. However, this is not recommended for safety’s sake. Always keep the plane properly loaded.
3) Turbulence changes the angle of attack as the plane is bouncing. This is why we move at Va speed (maximum manouevering speed) through turbulence, because we don’t want a situation where we are at low speed and a high angle of attack.
4) A turn is also where we may encounter stall. In a turn, our horizontal lift is divided into vertical and horizontal. This is where we start to feel G’s. It depends on our angle of bank. Essentially, in a turn, both the vertical and horizontal lift are combined into a total lift weight, creating equal centrifugal force trying to pull the plane the other way. This is increasing the weight of the airplane, therefore a higher stalling speed. As well, since the downgoing wing is not moving as fast through the air as the up going wing, in a stall it will stall first, perhaps leading to a spin or spiral in the direction of the stalled wing.
5) Icing or any inconsistencies on the wing are major factors. This is where ‘clean-wing’ concept comes into effect. Essentially, when we have icing or even dirt on the wing, we are essentially changing the wing design. Imagine we are flying at-15 degrees celcius and someone overflys us and pours water onto our wing. The boundary layer of air, which is the thin layer of air that sticks to or ‘coats’ the airfoil, is essentially destroyed. That means that any air passing over the ice will become turbulent, much like the confetti demonstration, eventually, or at least very potentially, destroying our lift. Even if the ice is everywhere on the plane except the wing and horizontal stabilizers, the aerodynamic structure is compromised, also adding to the drag on the airplane, as well as weight. Therefore, increased stall speed.
If a seafaring explorer from 500 years ago was caught in a time warp and transported to this day and time, he would naturally be perplexed by the ‘ships of the sky’ that we call airplanes. After all, most of what we put into aviation is taken from shipping; the captain and first officer, stewards, rudders, nautical miles, knots, etc…..) In essence, driving a power boat through the water would give some idea of how a plane works in relation to air.
However, the seafaring man has changed careers and now wants to be a 777 captain, just like me. But, we have take him from the beginning, ‘from the Greg up’.
We stand in front of a cessna suspended in mid-air, like a hologram.
At the front we have the propeller, the body of the plane is the fuselage, two wings, a vertical fin, and a horizontal stabilizer.
A) We start with the propeller, or ‘prop’ for short. The prop itself is designed as a spinning wing. What happens is that the turning prop will force air behind it, therefore causing a forward reaction with the rest of the plane.
B) The fuselage doesn’t need much explaining. It is essentially the body of the aircraft that is holding everything together.
C) Remember we talked about the effect of what the prop does? Well, it moves the plane forward, but doesn’t create the lift we need to get off the ground. That is where the wings come into play. It works in 2 ways.
1) First, we have the Bernoulli effect. At the leading edge of the wing meets the airflow, the air will accelerate over it as it seeks to remain constant with the air molecules that have been compressed below it. The faster air over the top is therefore creating less pressure, allowing the aircraft to leave the ground. A car at high speeds, on the other hand, would not be able to generate this kind of lift.
2) Secondly, we have the Newton effect. It states that an action will create a reaction. Essentially, according the wingfoil design, as it cuts through air, it creates a downwash of air, while at the same time compressing the air below the wing down. By compressing the air below it, otherwise pushing it down, the opposite reaction is that the wing will be forced up in an opposite reaction.
3) The ailerons. The ailerons are what we call a ‘control surface’. One of many actually. The purpose of the ailerons is to deflect the airflow in order to produce a turn. In a right turn, for example, the right aileron will go up, and the left goes down. The left down aileron is producing more lift, while the right up one is deflecting the wing down, therefore resulting in a right turn. An opposite situation would have the opposite effect.
D) Here we have flaps. Flaps have a couple of functions. They act as both lift and drag forces, which can be confusing to some. On takeoff, for example, speed is relatively low, and to produce as much lift as we can, we want to increase the wing area as much as we can. Therefore, there is a moderate level of take off flap. Remember, for take off, we want maximum lift and minimum drag. On landing, we want a low speed and more drag to keep that speed as we descend, so we have a larger output of ‘landing’ flaps to achieve that.
E) Next we have the vertical stabilizer, or fin. The purpose of this vertical fixed wing is to keep the aircraft stable in flight, basically preventing left-right yawing motion of the front of the aircraft. Attached to it is the rudder. Unlike a ship, the rudder on an airplane is not there to produce a turn. That is what the ailerons are for. The purpose of the rudder is to control various types of yaw (which we will get into later). But a practical example would be our right turn. When the right wing is down and the left wing is up, the higher wing (left) is causing more drag, therefore the plane will try to go left instead of right. The rudder is then put into the direction of the turn to
co-ordinate it and keep the plane on it’s proper flight path.
F) Here we have the horizontal stabilizer. As the vertical stabilizer is used to control yaw, or left-right motion, the horizontal stabilizer is used to control pitch, or up-down motion. The control surface here is called the elevator. It’s deflective properties work in much the same way as ailerons, except both the left and right elevators move in unison. When we pull up, the elevators go up, which causes the airflow deflection to force the tail down, therefore the nose goes up. If we push down, the opposite effect happens. As well, we have an additional ‘anti-servo’ tab. It moves with the elevator, making it heavier and requiring more force in climbs and descents. However, although it seems anti-productive, it is not. It is needed in aircraft where the controls are too light and we need more stability along our lateral axis.
Forces in Flight
When the plane is in the air, we generally say that there are 4 forces acting upon it: Thrust, weight, lift, drag.
1) As we discussed, thrust is the forward movement of the plane caused by the propeller. Thrust is a little different between jets and props, which we don’t need to get into.
2) Weight: Weight is the downward force of gravity on the aircraft. Weight can be confusing because the weight of an airplane in the air is not necessarily the weight it is on the ground. For example, if a plane weighs 1,000 lbs on the ground, it is likely to be that weight in straight and level flight. However, in a turn, the gravity load of the airplane increases to gravity x 2, which means in the turn the plane is now 2,000 lbs. As we also think of weight as the combined sum of all the airplane parts plus fuel, people, and baggage, we can think of weight meeting and acting at the center of gravity (c of g). The c of g, located ahead of the lift in straight and level flight, is found by engineers by measuring from a datum point, and finding the average location where the sum of all weights will be located. This is very important for us, because the weight of the airplane will constantly change during flight, mostly due to fuel being burned. For example, me and the sailor sitting in front, with the fuel tank behind us. As the weight in the tank becomes less, the center of gravity will move forward, which means we have to pull back on the stick to remain level, thereby increasing the weight on the tail, which makes the plane think it is heavier. Our stalling speed increases, but we will get more into stalls in a little bit.
3) Lift: As we discussed before, there is Newtonian and Bernoulli lift. Let’s look at the wing design for a second. First, from the left to right of the wingtips, we have the wing chord. The curvature of the upper and lower surface is called the camber, divided into upper and lower camber, and at the end near the flaps and ailerons we have the trailing edge. Now, if we look at a little animation, we can see the air flowing over the top and the bottom of the airfoil. You notice that the air over the top is faster than the air at the bottom, which means lower pressure. Here, the wing is in straight at level, so the way at which the air is meeting the leading edge of the wing, otherwise known as relative airflow, is parallel to the flight path. If we move the wing down or up, the relative airflow will remain parallel. Our various angles are called angles of attack.
Now, as relative airflow is parallel to the angle of attack, lift is perpendicular. Basically, we have the higher pressure under the wing, and lower pressure on top. The sum of all the pressure forces acting on a wing, if we consider it to be equal to a single force, will act in a straight line up through the cord. We call this the center of pressure, acting up in a 90 degree line, which we can call our lift.
4) Drag: We can call drag any forces that are ‘resisting’ the movement of the airplane trough the air. Drag can be divided between parasite and induced drag.
a) Parasite drag is caused by resistance by any part of the airplane that is not contributing to lift. They include the fuselage, landing gear (without wheel pants) antennas, and open cowlings, among others. Simply put, form drag is related to the shape of the body of the aircraft, and skin friction is caused by air sticking to the surface of the skin of the airplane. It can never be eliminated completely, but aircraft designers have found ways to reduce it as much as possible. Depends on the airplane. However, rule of thumb is that as speed increases, parasite drag also increases.
b) Induced drag is caused by the forces that produce lift and can never be eliminated, like the wings. In the end how much induced drag we experience depends on the shape of the wing of the individual aircraft. Basically, low pressure air over the wing flows inwards, and high pressure air under the wing flows outwards. When the 2 meet at the trailing edge, their unison causes the 2 to form into a circular eddy that we call wing-tip vortices. This disturbed air resists the forward motion of the wing, hence we have induced drag. The amount of induced drag is dependent on the aspect ratio of the wing. That is, the ratio between the wing span and the wing chord. For example, a glider with a span of 36 feet: 6 feet= aspect ratio of 6. Another glider that is 36: 4= aspect ration of 9. The glider at aspect ratio 9 will have less induced drag since the upper and lower airflows have less distance to travel. Rule of thumb is that induced drag decreases as speed increases.
c) Aileron drag is a third category that is fairly straightforward. The drag of the down going aileron causes more drag because it is being put down into a compressed airflow. The aircraft designer will usually correct for this in the aircraft design, in order to prevent yawing in the opposite direction in which we are turning. Differential ailerons are designed so that the down going aileron moves down less, while the up going one moves higher into the airflow. Frise ailerons are streamlined into the wing so that the down going aileron will cause less drag.
The 3 Axis of the Airplane
If we look at the plane from the top, we can cut it into 2, and imagine a 3rd line going up. The line from the nose to the tail is called the longitudinal axis. The axis between the wing tips is called the lateral axis. And the line extending upwards is called the normal (vertical) axis.
1) Longitudinal axis: When the rotate the plane on this axis, we call it the bank (or roll). This rotation is controlled by the ailerons and to a certain extent the rudder.
2) Lateral Axis: The rotation here is called pitch, which is the up and down moving motion of the aircraft. This is controlled by the elevators.
3) Normal (vertical) axis: Here, the aircraft’s nose moves left to right. We call this yaw, and it is controlled by the rudders.
Yaw is a very prevelant force on an aircraft, especially on single engine aircraft.
The first type of yaw is slipstream yaw. The motion of the propeller causes air to be pushed back in a corkscrew motion, causing the fin to turn from the high pressure to the low. This is what we call slipstream yaw. It is corrected by offsetting the engine thrust line (in the case of the diamond katana 2 degrees to the right), adding rudder trims, or a combination of both.
Another type of yaw is turbulence yaw. In turbulence yaw, the plane is being buffeted by the air beneath it (much like a ship in the water). This causes the right and left wing to off balance, resulting in one wing at a higher angle of attack than another, causing more drag on the upgoing wing, causing it to yaw in that direction.
Tension yaw may occur when the pilot is unknowingly putting unnecessary pressure on the rudder, especially in a tense moment, like difficult situations on short finals.
These 3 axis meet at the center of gravity (c of g). Remember that an axis will change with flight. For example, when an aircraft is in a 90 degree bank turn, the vertical axis becomes parallel with the ground.
Stalls
Stalls deserve their own section because it is extremely important to be able to identify the symptoms of a stall, causes of stalls, and stall recovery.
Let’s look first at the wing design. You notice that on the Katana, the wing is twisted at the end. This is a feature we call washout. In this design, lift is designed to be greatest at the root, and decrease until we eventually get 0 lift on the wingtips. The idea is that the wing root will reach the critical stalling angle of angle of attack before the tips, thereby reducing the chances of the airplane entering into a spin.
Let’s look at a little video John made about what is going on during a stall.
In this video, you can see the right wing of the Cessna in flight. You notice that seafaring man has taped confetti all over the wing to demonstrate airflow. Now, at this moment, all the confetti is lying flat representing the smooth flow of air over the wing. Now, our pilot is increasing the angle of attack. As it increases, notice how the confetti is becoming turbulent on the inboard section. What’s happening is that at this angle the smooth airflow is unable to follow the upper-camber like it was before. The airflow is pulling away from the wing and is becoming turbulent. At this point, the center of pressure that is causing lift is moving forward, away from the separation point between turbulent and smooth air. Also note that the confetti on the wing-tips remain smooth. Washout has made sure that the inboard will stall before the tip can stall. At this time, the turbulent air is also hitting the elevators, making John notice that the stick is shaking.
Now, we pull past the critical angle of attack, and the confetti stops on the inboard section. No more airflow is flowing over the upper camber, which means no lift as the center of pressure has moved all the way back to the trailing edge. The nose will now drop, allowing airspeed to build up again. At this point John will apply full power and ease out of the dive.
In which conditions will we likely encounter a stall?
1) Increased weight, especially loaded over gross weight. What happens is that in this case, to maintain straight and level flight, we have to increase our angle of attack higher in direct relation to our weight. The heavier the plane, the more we increase the angle of attack. Each increase in angle of attack takes us closer to the critical angle.
2) The location of the center of gravity also plays an important part. When we have more weight at the front then the back, for example, we are unbalanced. In this case, the center of gravity will move forward, farther away from the tail, which will have to be moved down to prevent the plane from descending. This downward motion is increasing the weight of the tail, therefore the weight of the airplane. The stalling speed will then increase. The opposite is true with too much loading in the back. However, this is not recommended for safety’s sake. Always keep the plane properly loaded.
3) Turbulence changes the angle of attack as the plane is bouncing. This is why we move at Va speed (maximum manouevering speed) through turbulence, because we don’t want a situation where we are at low speed and a high angle of attack.
4) A turn is also where we may encounter stall. In a turn, our horizontal lift is divided into vertical and horizontal. This is where we start to feel G’s. It depends on our angle of bank. Essentially, in a turn, both the vertical and horizontal lift are combined into a total lift weight, creating equal centrifugal force trying to pull the plane the other way. This is increasing the weight of the airplane, therefore a higher stalling speed. As well, since the downgoing wing is not moving as fast through the air as the up going wing, in a stall it will stall first, perhaps leading to a spin or spiral in the direction of the stalled wing.
5) Icing or any inconsistencies on the wing are major factors. This is where ‘clean-wing’ concept comes into effect. Essentially, when we have icing or even dirt on the wing, we are essentially changing the wing design. Imagine we are flying at-15 degrees celcius and someone overflys us and pours water onto our wing. The boundary layer of air, which is the thin layer of air that sticks to or ‘coats’ the airfoil, is essentially destroyed. That means that any air passing over the ice will become turbulent, much like the confetti demonstration, eventually, or at least very potentially, destroying our lift. Even if the ice is everywhere on the plane except the wing and horizontal stabilizers, the aerodynamic structure is compromised, also adding to the drag on the airplane, as well as weight. Therefore, increased stall speed.
