And here we are meeting again! Nature has been so considerate today - the weather is just as perfect as I usually like it to be. A weather for two, a perfect bad-ass blonde twerking for me right now and no coffee to cool my temper. Tempting! If this keeps up, I may eventually loss my headless head. But not to worry guys, I am not losing my senses. Not to this blonde!

Who says you cannot build your own aircraft? || Pixabay image - (CCO Licensed)

A quick recap of our previous series:

The previous series saw of discuss the concept of Maneuvers in flight. A plane on a steady direction and constant attitude with wings at a lateral level is said to be in a straight and level flight. Such plane would be in Cruise Attitude. Increasing and decreasing airspeed while on straight and level flight will help you maintain correct space in the aircraft traffic circuit. While Climbing, a plane would be in continuous change in attitude, altitude airspeed and power settings. Talking of Descents, there two major categories: power on and power off descents. In Turning, the weight of the aircraft and centrifugal force push the plane away from the radius of turn while the wings lift and centripetal force pulls the plane inward.

Full post here.

Just joining us for the first time? I strongly request you check out our previous series: Series 1 | Series 2 | Series 3 | Series 4 | Series 5.

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So today we are going to have a pretty cool discussions. Well, you could thank the blonde. We have Slow flights and Stalls to discuss and trust me, those are a very interesting topics.. Let us get on it guys.

Slow flights

Slow flight is defined as the range of airspeed between the maximum endurance speed for an aircraft and a point just about its stalling speed for existing flight conditions.

We treat slow flights for three reasons:

• So you can master the proper flight technique to allow you precise control of an aircraft while flying in the speed range. Failure to take prompt corrective actions during flight can have dying consequences.
• So you can recognise when you are getting close to the slow flight range to allow you to avoid in-averted entry into this mode.
• To develop your coordination and give you confidence in handling the aircraft.

Slow flight is in accordance under certain conditions. These include take-off, landing, recovery from a misjudged landing, overshooting your approach and approach to the stall. You will not fly in slow speed mode while waiting for weather to clear, inspecting your potential landing area or searching for ground fixes. This is because flying in this mode requires the full attention of the pilot. Also keep in mind that fuel consumption during slow flight is higher and you could cause overheating of the engine from flying in this mode, particular when attempting a climb. It cannot be stressed enough that you must be aware of the effective controls at the bottom range of slow flight, especially altitude, airspeed and yaw.

Now let me get you into slow flight speed range. First, the aircraft may be in straight and level flight for maximum endurance. Now, bring the nose up beyond the nose-up limit for maximum endurance, note the airspeed decreases because of the increase in drag. This results in loss of height (altitude). To compensate the loss of height and maintain altitude, increase the power. You now have the aircraft in a slow flight range.

Some precautions before we go into the effect of slow flight on the aircraft:

• Slow flight should be practiced in slow and level flight, descending, level turns descending turns.
• When maneuvering close to the ground and wind conditions, exercise extreme caution and adjust the airspeed indicator upward to allow for the gas factor.
• Also, slow climb should be of short duration so as not to overheat the engine during this maneuver.
• The physical sensation in slow flight particularly a strong wind can result in a critical situation at a lower altitude. This means you must keep a close eye on the flight instrument to achieve a balanced flight and maintain a safer speed.
• Flying in a slow speed range does not necessarily imply serious controls difficulties or hazardous condition but any error of basic flight techniques will be exaggerated.
• We cannot stress enough the need for proper technique and precise control of the aircraft in this speed range.

Let us look at how the aircraft handles in this range. First, the relationship between power and altitude. During slow flight, a control decrease in airspeed without change in power settings results in dropping height. To maintain a constant altitude, you have to increase the power. Conversely, a control increase in airspeed without the change in power settings will result in decrease in the induce drag, raising your altitude. Therefore, power must be reduced to maintain a constant altitude at higher airspeed. There will be a slight drop in altitude during transition speeds. When flying st slow speeds. note the flight controls do not as effectively as at normal operating airspeed. Remember, as the airspeed decreases, the effect of controls decreases proportionally. Because when you get to stalling speeds, the greater you loss control. As well, the closer you get to stalling speed, the less stable the aircraft.

Why do these happen?

Look at the decrease velocity of airflow over the wing and increase effect of aileron drag. Combine these with slipstream and a symmetric propeller thrust and there is increase tendency of the aircraft to yaw. To maintain direction, you will have to use the rudder. When the aircraft begins to yaw, immediately apply the proper rudder pressure and increase power to maintain altitude. As the speed drops further, more power is required to maintain the rate of descent. When the nose pitches down with full power applied, you have dropped below the minimum controllable airspeed. The aircraft has now entered a stall flight condition.

Stall

A stall is when an aircraft has reached a point where there isn't enough lift to keep it at loft.

As you approach stalling speeds, air density, aircraft weight and the drag from flaps and undercarriage may make it impossible to maintain altitude. Perhaps, the most important point to remember here is that the unmindful approach into slow fight almost indicate you are approaching a stall.

Now, before we grab a cup of coffee, let us look at why a wing cannot provide enough lift to keep the aircraft at loft.

Remember what we discussed in our first sries (Serie 1) about the principles of flight. Lift depends on the Laminar airflow over the wing. As the angle of attack increases, you can see how the laminar layer becomes smaller and turbulent air predominate over the wing surface. By the time the angle of attack is at 16 degrees, you will notice the symptoms of a stall. At 17 degrees, there is no laminar layer and lift decreases. It is also important to remember the angle of attack unlike the angle of incidence, is a relative factor. The angle of attack is the angle between the Wing Chord and the Relative Airflow. And relative airflow is always parallel with an opposite to the Flight Path of the aircraft. And since the Flight Path direction is not always the same as the Pitch Attitude, an aircraft may stall in level flight if a high angle of attack is described.

From the above explanation, you can see that you cannot rely solely on the altitude of an aircraft to indicate the possibility of a stall. Remember, an aircraft can stall in practically any attitude and airspeed.

What about the term stalling speeds?

Flight manual lists stalling speeds for a specific aircraft in varying situations. But keep in mind. The stalling speed may be affected by the following factors:

• An aircraft that is clean and well maintained will have a better stalling characteristics than one in poor conditions.
• Balance and Weight can alter stalling characteristics. Power lowers the stall speeds because of the additional upward thrust.
• Increase in the angle of bank increases the stall speed.
• Extending the flaps increases the camber of the wing, thereby lowering the stall speed.
• Appropriate change of the pitch of an aircraft can raise the stalling speed.
• Extending the landing gear which increases drag can also have a slight effect on stalling speed.

But regardless of these factors and stalling speed, any aircraft will stall when the wing reaches a critical angle of attack, for most planes it is 17 degrees.

Now before we get into how to recover from a stall, let us discuss the symptoms of approaching a stall.

• First and foremost, is the decrease response of controls especially the elevator and ailerons.
• There is a loss of height despite attempts to maintain altitude with the elevator.
• You will hear and feel the beating of the turbulent air on the aircraft.
• most aircraft have warning devices which are activated prior to a stall.

To avoid a stall,use the elevator control to reduce the angle of attack. You should use a relatively small but quick forward movement of the control which will lower the nose. This will reduce the angle of attack and stability will return. You may also use additional power to reduce the angle of attack without changing the pitch attitude.

Now to intentional stall. Before you practice stall, there are few safety precautions to take. These are:

• The cockpit check.
• Make sure that the CARB HEAT is adequate.
• Seat belts are fasten, windows shut and other courses are secured.
• Look outside the aircraft and the ground below.
• You should practice stalls only over underpopulated area and at higher altitude.
• Keep in mind the objectives of practicing stalls.

This exercise is to teach you how to recognise an approach to stall conditions and take corrective actions, not how to stall an aircraft.

There are several types of stalls. They are:

• Power-Off stall.
• Power-On stall.
• Acceleration stalls.
• High-speed stalls.
• Secondary stalls.
• And Stalls during turns and Take-Offs.

Power-Off stall

A Power-off stall is generally entered from straight and level flight. First, close the throttle smoothly and keep the plane level by pulling back on the control column. As the airspeed decreases, you will enter a slow fight range. You will notice the diminishing responses from controls. Now, raise the nose as you would in a normal climb and the aircraft will stall. Use the rudder controls to keep the plane straight.

How do you access the stall condition?

Remember the basic rules. Reduce the angle of attack, and use the flight and power controls to correct the flight attitude. Firstly, as soon as you notice the flight condition, lower the nose. This reduces the angle of attack. In most cases, you should only have to push the control column forward to abort the neutral position. Pushing it too far forward may put too much load on the wing and slow the recovery. Second, increase the power but do not slam up on the throttle as this may cause the engine to spatter and you may lose power when you need it the most.

As soon as you recover from stalling, you gain cruise attitude. Set the power to normal. Recovery from stall should involve a little drop in altitude as possible. Use the rudder to control directions and level the wings with the ailerons.

One point to consider when practicing stalls: Do not raise the nose too far from the horizon to get the aircraft to stall. Using less pitch will give you more realistic feeling of what an accidental stall will feel and look like. In practicing stalls in descending turns, be sure to continue the turn at a constant rate until the stall occurs. Then use the standard procedure and recover straight ahead with a least loss of altitude. Failure to enter the stall properly could cause a wing to drop. If this should happen, use the same standard procedure, returning the aircraft to straight and level flight using coordination fight controls.

Power-On stall

Power-on stalls are very similar to stalls entered without power although there are some differences in maneuvers. You will notice that the pitching of the aircraft is more steep and rapid and the plane is more difficult to control. There is also a possibility for one wing to drop at the same time as the nose pitches down. The elevators and rudder are more effective in a Power-On stall because of the propeller slipstream. But the ailerons are less effective and tusk makes it more difficult to control a Power-on stall.

To enter a Power-on stall, smoothly bring the nose up to an attitude impossible for the aircraft to maintain. Hold it there until the stall occurs. Recovery is made in the same manner as before. Lower the nose and increase power. But because you are already at cruising or climbing power, the power increase will only be slightly.

Acceleration stall

An Acceleration stall occurs at a higher airspeed during certain turns, pull-ups or a high changes in flight path.

High Speed stall

High speed stalls can be reduced by pulling back appropriately on the control column at any speed the aircraft is possible of doing. This maneuver is not recommended because of the damages it can leave on the aircraft. A high speed stall may also occur in a steep turn when the angle of attack is greater than 60 degrees. Turbulence can also cause an increase in stalling speed. Here, a change is relative airflow results in a certain increase in the angle of attack.

You will notice that the aircraft flight manuals list what is known as the maneuvering speeds. This is the maximum speed at which flight controls can be fully obstructed without causing a fatal damage.

We have already covered the stall in descending turns in which the inside wing drops lower. But in a stall during a climbing turn, it is the outside wing that will drop because of less lift. This is because the outside wing needs a relative airflow at the steeper angle in the outward spiral.

One other stall we are going to take a look at in this series is the Departure Stalls. This occurs during take-offs. As the aircraft is rotated to achieve a greater angle of attack, it is in critical condition of flight for a short period of time. If the nose is too high after rotation, a stall may result. You may find yourself in a situation where you may be unable to recover from it or unable to climb higher to clear any obstacle on the flight path. To avoid this problem, be sure to establish the correct nose-up attitude for a climb after lift off.

Another critical departure procedure is the pull up following a missed approach. Usually, when you decide to abandon a landing, the aircraft is level instead of nose-down. The airspeed is lower and flaps are extended. You may also be faced to making a turn shortly after abandoning an approach. Take note of these mistakes that lead to a stall or near stall condition following approach.

Now to power. Since this is a form of take-off, you need enough power to climb. Make sure the attitude of the aircraft is correct and not too nose-high. Again, applying power plus nose-up pressure will force the plane into a very nose-high attitude. So compensate accordingly. Do not forget to retract the flaps or retract them too suddenly. Most aircraft cannot climb with aircraft fully extended and retracting them inappropriately can cause a sudden loss of height. Make sure the nose is not too high should you need to make an immediate turn.

So in general, when an aircraft stalls, the nose will come with one wing below and the other above because it loses lift. Eventually, the nose might come back to normal as the angle of attack is decreased so as to lower the critical angle of attack and the aircraft will no longer be in stall. So the angle of attack at which the aircraft stalls is designed at the wing of aircraft and it will remain constant regardless of the weight of the aircraft. It is the shape of the wing that determines the angle of attack in which an aircraft stalls, not the gross weight of the aircraft.

The gross weight of an aircraft might determine the speed at which you reach the critical angle of attack. So when the aircraft is heavier and get the same critical angle of attack at a higher speed and when it tries to get that same angle of attack at lower speed, it remains constant regardless of the gross weight of the aircraft.

The stalling angle of attack is independent of the speed of airflow over the wing.It is the angle of attack that makes the aircraft to stall, not the speed of airflow.

Now what happens as altitude increases? In a nutshell, the indicated airspeed at which an aircraft stalls will remain the same as at lower altitude as it is at higher altitude. What then happens when an aircraft stalls and the wings do not stall evenly? Anytime the wings stall unevenly, one wing will drop and the other will rise, regaining some lift and may eventually cause a rotation called a Spin. What happens here is that the wing that drops continues in a stalled condition while rising wing regains and continues to produce some lift and that causes a rotation - Spin, a very exciting thing. In order to spin an aircraft, first you must stall it. Hence, a stalled wing is a characteristic of Spin and not of spiral.

Conclusion

That completes our discussion on stalls. However, we cannot discuss on Stalls without eventually hinting on Spin. Our next series will cover absolute everything you need to know about Spins, Spirals and Slips. Gradually, we are closing in on understanding the techniques of flight. Let us take a break now but not to worry, we are meeting again in no time. Just stay with this blog and follow these series.

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References

• Slow flight
• Slow flight and stalls
• Stall
• How aircraft stalls and recovery
• Basic stall symptoms

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Previous Lessons In The Series

• Series #5: Understanding The Flight Maneuvers; Climbing, Descending & Turns
• Series #4: You've Got Attitudes, Aircraft Got Some Too
• Series #3: Understanding How Jet Engines Work And Effect Of Atmosphere In Flight
• Series #2: Understanding The Thrust Mechanism And How The Engine Works
• Series #1: Understanding The Mechanism Behind Airplanes And The Misconceptions

Till we meet again on my next post, well I am not changing my name. I am @teekingtv and I write STEM! THANK YOU FOR READING. GOD BLESS.

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