Who Says You Cannot Make your Own Airplane? Series #8: Understanding The Airport Circuit, Control Zone & Dealing With Flight Conditions Illusions

Welcome back here buddies. Oh so this will be the 8th time we are meeting on this series? Wow! How time flies. But com to think to it, we are progressing so fast and pretty well. It is my belief that we are all understanding the concepts being discussed o these series. Do not worry, in no time we will be having our self-made aircraft on the sky.

A brief recap of the previous series here:

Spinning is the rotation of the aircraft s it loses lift. This occur following a stall. There three stages for Spin maneuver. They the incipient stage, the developed stage and the recovery stage. Recovering from a Spin is to upset the balance between the aerodynamic and the movement that makes the spin possible.
When an aircraft has an excessive nose-down attitude with a steep descending turn, it is said to be having a Spiral Dive. To recover from a Spiral Dive, the throttle is closed and almost simultaneously, level the wings with the Power added to maintain lift. Side Slip gets the aircraft in bank attitude.
There are certain conditions necessary for take-off.

Full article 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 | Series 6 | Series 7.

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Today we will be dealing with two topics. In the first section we will be talking about the circuit. In the second part, we will be looking at how to cope with illusions that can be created by different flight conditions.

The Circuit

The Circuit is the specified path to be flown by aircraft operating in the vicinity of an airport. The primary purpose of the circuit is safety. The Circuit is rectangular in shape and has five arbitrarily defined legs. These legs are:

• The Climb after take-off Leg.
• The Crosswind Leg which is not to be confused with Circuit Joining Crosswind which will be talked about later.
• The Downwind Leg which is 90° to the Crosswind Leg.
• The Base Leg which is another 90° turn from the Downwind Leg.
• The Final Approach Leg

Unless you are told otherwise, all Legs are 1000ft above theground level. Let us start from the beginning. After take-off, there is straight climb into the wind normally to 500ft. Then, there is a 90° turn onto the Crosswind Leg where the aircraft climbs to the second height and levels up. Another 90° turn brings the aircraft onto the Downwind leg which runs parallel to the landing path. On this leg you will do any pre-landing checks. From there, you make a 90° turn onto the Base Leg and the last 90° turn puts you on the Final Leg. The aircraft is placed straight until the landing is completed.

The heading you will stay on the Crosswind and Base Legs will be determined by the strength of the wind. When flying the Circuit, keep a good lookout on both sides as well as above and below. You do not want to collide with other aircraft that may be heading to or proceeding fro the airport area.

At controlled airport, everything you do around the Circuit area needs to be reported as the control tower will be monitoring your movement. You will be directed as you move around the Legs. A typical radio transmission would be like: "Report Downwind Left Hand.... Rwy16"

Still on the subject of radio communication, if you head on unfamiliar airport, you might be asked to report on a point unknown to you. If you are unfamiliar with the local area, advise air traffic control immediately. When flying the circuit, it is crucial that you judge the whole pattern and relation of the runway all to other points on the ground. This will help you judge the type of landing approach you should need.

Another part of the Circuit is usually called The Approach. Exactly where you will turn from Downwind to Base will depend upon the wind. The stronger the wind, the steeper your angle of descent will have to be during the final straight approach. Therefore, you will have to make the turn to Base sooner.

Once you are flying Base, adjust your heading to compensate Drift then decide where to begin your descent. After descent has begun, you will have other decisions to make about the use of flaps and power to find you an approach. This will be done with on another series on Approaching Landing.

Spacing of aircraft in Circuit is something you must be aware of as well. You must always be aware of your positioning in relation to other aircraft. An unforgivable sin is to cut off a proceeding aircraft by turning Base or Final out of sequence. Following too close may mean you will have to abort and go around again before you can land.

On the other hand, at a busy airport, you do not want to tie up traffic by allowing too much space between yourself and a proceeding aircraft. Correct spacing comes with experience. You will have to account for wind and Circuit speed of other aircraft. Your spotting a queue may be adjusted by widening or narrowing your circuit and decreasing or increasing your airspeed.

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You will now be taught the correct procedures for leaving and joining the circuit at controlled airport. Later we are going to deal with uncontrolled fields. In the mean time, I need to ease myself. Yeah, like use the gent. But do not worry, my shii does not stink. So relax.

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You know I told you it will not take long. Now I am back. Sprayed the surrounding. Now let us continue.

Leaving And Joining The Circuit At Controlled Airport

Control Zone

A Controlled Zone is the controlled airspace of the defined dimension. It extends upward from the ground to a specified height. The Designation Positive Control Zone means special regulations applied within the zone. For all practical purposes, several airport with control towers may be considered Positive Control Zones. After take-off, if you fly outside of the circuit, you will either remain in the Control Zone or leave it all together. If you remain in the Control Zone, the tower will ask you to stay on the tower frequency and to advise what type of exercise you plan to do.

The tower also want to know what altitude you will be flying at and what are the exercises that will be carried out. If you plan to leave the Control Zone, you will need permission from the tower to quit monitoring the frequency.

On leaving a circuit with Left Hand traffic tower, you must have permission from the tower to make a Right Hand turn. If this permission cannot be granted, continue on the runway heading until you are cleared of the traffic pattern and abort circuit height before turning right.

Keep in mind that as you leave the circuit, you may find yourself in the Control Zone of another airport you do not intend to land at. Remember, you must establish a radio connection with the tower of the second airport. You will remain under the control of this second airport until you are cleared of the Control Zone again.

Returning To The Circuit At A Controlled Airport

Now we will deal with returning to the circuit at a controlled airport. There are some procedures you need to follow when doing that:

• First, advise the control tower of your identification, direction and distance from the airport as well as altitude and other requests. This should be done prior to entering the Control Zone.
• When given clearance by the tower, you are expected to join the circuit Downwind at circuit height which is 1000ft.
• The "clear the circuit" extraction from the control tower allows you to make a Right turn if you joined in Crosswind or it allows you to make a partial Right turn Downwind.
• You may also be given clearance to join the circuit on Base or for a straight in Approach which means you will join it on Final.

Leaving And Joining The Circuit At Uncontrolled Airport

At uncontrolled airport, you are more or less on your own. Some may have the transport candler to flight surface station or locally based aircraft operators with whom you must check in with. Although they have no control over aircraft, they can provide you with information regarding Surface Winds, Runway Conditions, Ground Traffic and Weather. Remember, you are also expected to transmit your intentions while in the circuit. And because you do not have the watchful eye of the control tower, be especially alert for other aircraft.

If you want to leave the circuit at an uncontrolled field, continue climbing on the runway heading until you are well cleared of the Circuit. All turns in the vicinity of the airport should be due to Left unless a Right Hand circuit is designated.

When returning to uncontrolled field, take full advantage of any on-the-ground communication for landing advice. Ground conditions change in a very short period of time. Should you plan to cross over the airport, do so well above the circuit height. Then descend the circuit height on the Upwind Leg and enter the circuit Crosswind. You may also enter the circuit Downwind at circuit level where the Downwind and Crosswind Legs intersect.

Spacing yourself in traffic is your responsibility. Normally, there is only one runway in an uncontrolled filed. However, the pilot may make decisions on which runway to use where there are more than one runway.

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Illusions That Can Be Created By Different Flight Conditions And How To Avoid Them

In this section, you will be shown how two types of illusions occur and how to avoid them. The first type is Visual Illusions and occur on approach to landing. Illusions are frequently mentioned as contributing factors on approach to landing accidents. Researchers determined that how you happen to see things while approaching landing is very important. What you think you are seeing might be totally the opposite of what you are actually seeing.

If the unfamiliar runway is wider than normal, you may descend too low and crash if the errors are not corrected in time. A wider runway will make you think that you are higher than normal and you might stall over the runway. Another illusion that might occur is caused by the slope of the runway. In mountainous country, this could range from 3° to 6°. A small up-slope gives you the illusion of being higher than you really are. Conversely, a down-slope will deceive you to believe you are lower.

Sloping problems occur especially at night where the only visual references are the runway lights. To avoid problems with illusions at unfamiliar airport, the followings will help:

• Note the runway size and surrounding terrains.
• Use any any visual aid that might be available.

The other types of illusions you might experience are those created by drift. They occur in strong winds when you are flying at lower altitude. This is something you will do during a first landing approach when carrying out off-airport procedures or in deteriorating weather. At lower altitudes, movement relative to the ground becomes more apparent. In strong winds, illusions are created which if misinterpreted, may develop into dangerous situations. The closer you are to the ground, the greater the dissection. Because you are on lookout for other aircraft at these altitudes, there is a little time to monitor the flight instruments. It is therefore important that you anticipate the false impressions that are created by the set of appearance of the ground.

If visibility is good, you can fly low at normal cruising speeds. However, in low visibility, it is recommended that you reduce your speed. To maintain a lower speed, extend the flaps. This will allow you a tighter turning radius which you may need to avoid obstacles. And because you are using more power with the flaps extended, the extra slipstream of the elevators and the rudder will give you better control of the aircraft.

Illusions That You May Be Confronted with Under Different Conditions

Now, let us look at some illusions which you may be confronted with under different conditions. Remember, you are flying low with a strong wind. If you are flying into the wind, a reduced ground speed produces an illusion of a reduced airspeed. when you are flying downwind, the opposite occurs. The increased ground speed produces an illusion of increased airspeed. Resist the temptation to reduce your airspeed since if carried to the extreme, it could cause you to stall.

If you are turning from Upwind to Downwind, it would appear that the aircraft is slipping inwards. This is an illusion created by drift over the ground. You can confirm this by glancing on the turning ball indicator which should have the ball centered. Do not use the rudder to attempt to correct what appears to be a slip. But because the drift is real, you must allow plenty of room to avoid any obstacle that might be inside the turn.

In the opposite situation when you are turning from Downwind to Upwind, you will think the aircraft is skating outwards. Again, confirm that your turn is accurate and coordinated by checking the instruments. Remember, the skate is an illusion and you will have to compensate for the drift to avoid any obstacle out of the turn. The illusion effect increases as the airspeed decreases and the wind velocity increases.

Some precautions to take when flying low:

• Look well ahead and maintain a safe airspeed.
• Turn accurately to get rid of deceit of illusions.
• Maintain coordinated flight.
• Keep a good look out for other aircraft and obstacles.
• Fly in a safe altitude and observe local regulations.
• Avoid annoying others and frightening livestock.
• Do not turn too steeply.
• Allow yourself sufficient space to maneuver and never practice this exercise unless there is an authorised flight instructor aboard.

Another illusion that usually disturbs pilots during landing is atmospheric illusions. Here, rain and other atmospheric factors threaten the pilot with illusions. These factors my make the runway look farther away than it really is. As you continue piloting and gaining experience, you should know how to avoid this illusion causing your aircraft serious problems.

Conclusion

Just as it is necessary to understand the procedures involved in take-offs and landing, it is very important to understand what the airport Circuit is all about and how it is ran. The primary reason the control tower is there is to guide the landing and proceeding aircraft to safety. So is the airport controlled to provide adequate ground help to the aircraft. We will have to take break here. In the next sires, we will be discussing about approaching and landing.

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References

• Airfield traffic pattern
• Understanding the VFR Airport Pattern Circuit
• Control zone
• Approach and landing illusions
• Pilot Perception: Runway Illusions

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Previous Lessons In The Series

• Series #7: Understanding The Aerodynamics; Spin, Spiral, Slip And The Concept Of Take-Off
• Series #6: Understanding The Concept Of Slow Flight and Stall
• 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

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