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Clearing Turns

Clearing turns are very important

If you are getting your license, you probably have experienced your instructor being very adamant you do these clearing turns consistently and correctly.  It is mandatory you understand them for your flight test: if you show the examiner a lax attitude when checking for traffic, that is not only dangerous, but will constitute a fail.

So what is the proper way to do clearing turns, and why do we need to do them?

The real reason is safety.

When we do any maneuver practicing upper air work, be it slow flight, steep turns, stalls, spins, spirals, or whatever, we always do clearing turns.  We check for traffic by turning 90 degrees in each direction, using a consistent angle of bank (my instructor likes 30 degrees).   Then you roll around back to your original intended heading (you hope!) knowing that you have had a good look primarily behind you.    There is no real guide or standard as to how to exactly perform the clearance turns, but as long as something is done to actively check for traffic using turns.

To start always look to the right or left first, whichever way you intend to turn and verbalize that you are doing this.  Strain your neck, really have a good look, and say “clear for traffic on the left”.  Do your turn.  Then do this for the right side. Look, bend your neck to have a good look, and say “clear for traffic on the right”.  When you have completed the turn have a look around.

Before turning, always check for traffic, and verbalize that you are doing this.
Before turning, always check for traffic, and verbalize that you are doing this.

Generally, it is better to start from the left rather than from the right.  Overtaking aircraft are to pass on the right side; so if you take a right turn you may inadvertently cut an airplane off trying to pass you on the right. But regardless which direction you start from, make sure you have a good look around before changing your heading.

I used to think these turns didn’t accomplish much and was skeptical about how effective they are. I thought they left a section of sky unobserved.  But think about it,  you can see to the right or left without turning, and when you turn in either direction you can see behind you.   You can imagine it’s like doing a shoulder check.


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Wake turbulence

Have you seen the movie Argo?

If you have seen the movie Argo, and are a pilot, you know how unrealistic the scene is with the fleeing airliner near the end of the movie.  Though Hollywood pulls some highly impossible stunts, this one is really over the top in terms of how grossly impossible it is, and I’m sure I’m not the only one who noticed.  If you fly you probably picked up on it right away.  Cars chasing a 747 on the take-off roll? Right behind those engines which are operating at maximum thrust? They should be blasted into the taxiways.

Chasing a departing 747 in a Jeep is just a bad idea.

Jet scene from Argo. Image courtesy of
Jet scene from Argo. Image courtesy of

At the end of the movie, a fleeing 747 airliner is taking off rescuing U.S. diplomats during the Iran hostage crisis in 1979.  Once officials realized that these people were on the plane, they proceeded to chase after the plane while the plane was already on the takeoff roll. On the take off roll planes are at maximum power settings and the engines are pushing out a substantial amount of air. Maximum thrust in fact, is in excess of 50,000 lbs.

In a 747 aircraft, such as the one involved in the movie rescue has a take-off speed of about 155-160 knots (depending on load, field elevation, altimeter setting and temperature)  – that’s 290 km/h and 184 miles/h.  The first inaccuracy is that these cars are actually keeping up with the plane to the point it rotates.  Old Jeeps in the 70’s keeping those speeds? Very interesting.

The second problem with this depiction is the creation of wing-tip vortices or wake turbulence.  When a plane is accelerating down the runway, the engines are at full power,  set for maximum thrust.   As speed increases, air passes over the body of the aircraft faster and faster. Due to the cambered shape of the wing,  the shape of the wing causes the air on top of the wing to travel faster  than the air at the bottom of the wing. Because of Newton’s third law, the faster speed causes an area of low pressure at the top of the wing, and an area of higher pressure at the top of the wing.  This causes lift.

Airflow. Image from From the Ground Up, page 21.
Airflow. Image from From the Ground Up, page 21.

Also as air travels over the wing, it travels downwards as well as rearwards, causing downwash. Air traveling at the bottom of the wing is also deflected downward by the bottom of the wing.   This also contributes to creating lift.

Since the decreased pressure at the top of the wing is less than the atmospheric pressure around it, air over the top is deflected inward; air on the bottom of the wing is greater than the pressure of the air around it, hence it is deflected outward and curls upward over the wing tip. 

The two airflows unite at the trailing edge of the wing, creating eddies and vortices that unite into one large eddy at each wing tip, called wingtip vortices.

The heavier the airplane, the greater the span loading on the wing, the more air will be displaced downwards and the greater vortex will be generated.  The vortex created from a  Cessna 172 will be substantially smaller than one from a 747.  Anything caught in the path of the vortex will tend to roll with that vortex.

Vortices are a by product of lift. Image from
Vortices are a by product of lift. Image from

Since vortices are a by product of lift, they are only produced when the aircraft is in flight. Hence when the 747 jet takes off, it will start producing these vortices naturally.  Anything that is in the path of these vortices will be rolled – so if those vehicles in the movie were standing in the path of the vortices they should have ended up flying in all directions.

This is why many airplanes are now equipped with winglets – these tabs at the end of the wing actually prevent the two airflows from uniting, creating a barrier and preventing vortices from forming. Because vortices cause drag, preventing them from forming reduces drag and causes the airplane to use less fuel.

It is always very interesting to see how flying and airplanes are improperly depicted in movies for the sake of entertainment value.  Something to think about.


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Learning to Land

On approach for runway 34, CYBW

One of the hardest thing in flying is learning to land.  When I was struggling with the landing, my instructor made me feel better by letting me know this, and saying that she didn’t really “learn” how to land until she was doing her commercial license.  Of course she knew how to to it, but by that she meant that she didn’t really feel fully comfortable until then.

This put a few things into perspective, how long it will take until not only will it feel natural but you will not be so terrified and dry-mouthed every time you do it.  Since my first solo flight, I have really started paying attention how to possibly make the best landing happen consistently.  I haven’t been flying in the circuit much lately, so each flight I only get to do one of these landings so I try to make it as good as possible.

The landing sequence. This plane is about to flare.
The landing sequence. This plane is about to flare.

One of the things that is very apparent is the amount of right rudder needed.  As you cut power to idle, and flare, you are operating the aircraft at very low power settings. Asymmetric thrust will cause the aircraft to want to yaw to the left: recall that the aircraft has left-turning tendencies which cause left yaw. This is actually what I noticed very clearly on my first solo flight, thinking it was the wind that was causing my nose to yaw to the left on landing, my instructor quickly corrected me that it was not using enough right rudder.

Four things will cause left -turning tendency. These are:

1. Torque reaction from engine and propeller

2.  Slipstream causing a corkscrewing effect of air hitting the tail on the right, yawing the aircraft to the left.

3.  Gyroscopic action of the propeller, the propeller is a gyroscope and tries to “spin” the aircraft the opposite way.

4.  Asymmetrical loading of the propeller at high nose attitudes.

On landing, asymmetric thrust causes the left yaw.  When you touch the ground, be prepared to add even more right rudder. The engine torque will cause the left wheel to carry slightly more weight than the right, increasing it’s drag and causing even more yaw to the left.

So how can you strive to make each landing perfect? I’ve made a list of steps that I think are very important to note:

1.  Check winds. When flying in the downwind leg, when on final, or whenever you get a chance note the windsock so you know what winds you will be experiencing on the ground and on your final approach. Will you have a crosswind?

2.    Approach at a constant airspeed for your configuration (whether using flaps or not), do not “chase” the airspeed: that is, do not focus your attention on the airspeed indicator and try to correct deviations by switching attitudes.  Establish your airspeed well in advance on final, note how the horizon looks when you have reached the proper airspeed, and keep it there. Once you have your airplane in the right attitude, keep it there.

3.   Pick a spot on the runway. When you stare at this spot, this is where you will flare. It also allows you to break down your desired touchdown spot and keep you from focusing on the entire runway.

4.  Flare 5-9 meters (15 to 30 feet) from the ground.  Over time, you will “sense” where this point is. I learned that to recognize this point is to when the movement of the ground suddenly becomes very apparent, the whole landing area seems to expand, and the point where the ground seems to be coming up so rapidly that something must be done about it.

5.  Once you flare, wait for the sink.  You are trying to bleed off airspeed.  Once you feel the sink, pull back more, just don’t pull back more before you feel the sink. This will cause the aircraft to balloon – gain lift – and the high nose attitude can cause you to stall when still too high above the ground resulting in a hard landing.   You need to cover up the runway with the nose of the aircraft to get the proper high nose landing attitude.  It will feel uncomfortable at first – it did for me.  This will allow you to avoid touching down with your nose gear, or having a ‘flat’ (three wheel) landing, which increases the risk of wheelbarrow. Pull back slightly each time you feel a sink, this will allow you to check your rate of descent until all flying speed is lost and you can touch the runway as lightly as possible.

6. Get in the habit of keeping your hand on the throttle throughout the landing. If something happens, for example if the landing is not going well and you need to overshoot or if there is something else wrong and you require application of power, the time to get this power if your hand was not on the throttle is too long.

There are four different kinds of landings:

  1. Normal landing
  2. Cross-wind landing; where wind inputs will be needed
  3. Short field landing, and
  4. Soft field landing.

We learn each landing and we practice all of them until they present no difficulty.

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Chair flying pilot training

IFR Anyone? Even if we can't fly, we can still practice by visualization.

Chair flying is a recommended way to keep up with your pilot training

It’s the first day of spring in the Northern Hemisphere – March 21 – but you wouldn’t know it by looking outside.  We have snowstorms all across Alberta with the city of Edmonton under a snowfall warning.  When we have bad weather days and aren’t able to fly, all is not lost.  Aside from simulators or Microsoft Flight Simulator Software, there are other ways we can practice flying when we aren’t able to get up in the air.

Use bad weather days effectively

Most of flying is about procedures so a bad weather day is an excellent day to review them. My instructor gave me this tip a long time ago, that when I get grounded on weather days, we can still go “chair flying!” Chair flying is an important technique that helps in mental and physical preparation for a flight.

This technique is effective because it allows the pilot to memorize procedures, techniques, checklists and so on without the need of an airplane – saving time and money. It makes procedures feel so natural and familiar that they will become second nature.  Practicing chair flying will make you better prepared for a flight and should be done regularly.

How to “chair fly”

To chair fly, pick a quiet spot where you can concentrate. Decide on what procedure or task you want to focus on, and make sure you have all the necessary materials you need – checklists, notes, maps, or procedures that will help you.

Create a goal for yourself that you want to achieve in the session. For example, I found this very useful for learning precautionary and forced landings.  My goal at the end of the practice session to be able to go through everything without having to  look at my notes.

Take the exercise seriously

Run through the procedure as if you were actually flying, so make the hand gestures to adjust mixture control and so on, make your necessary radio calls. Replicate the environment as much as possible.  I find talking out loud about each step I am doing is very effective.

Effective flight preparation requires practice of the procedures involved.
Effective flight preparation requires practice of the procedures involved.

Chair flying will also help you dismiss anxiety of flying. When I was learning specialty takeoffs and landings, I would sit in a chair and run though everything that I needed to accomplish.

This imprinted the procedure in my mind and by the time I got out to do them I was relaxed and able to perform them without issue. When my instructor asked if I was ready, I could say yes and feel good about it. It saved me a lot of time, money and stress, and improved safety, too.

Good for learning airport procedures

When I was learning the taxi procedure at my new airport, I would sit in a chair and pretend I was taxiing running through the airport diagram and who I needed to call when.

Often, I will drive out to the airport in silence with the radio off, going through procedures while I drive.  I found this relaxes me and puts me in the mindset to fly.  When I get to the airport, I am centered, and ready.

Another good idea when we are weathered out and at the airport is to sit in the actual airplane and practice.  This is the most effective way to practice, it allows you to use the actual environment where you will be doing the procedures.  Once when I drove all the way out to the airport and couldn’t get off the ground, my instructor suggest that I sit in the plane anyway and practice my procedures.  I found it very helpful, and did not waste any time by driving out there and not being able to fly.

Practice frequently. Frequent, short sessions are more helpful than long, infrequent ones.

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The high key – low key landing procedure

The high key - low key landing procedure. Image courtesy of Transport Canada (Flight Training Manual)

This procedure is used to plan a forced approach in the event of an engine failure.

When we have an engine out emergency, our goal is the extend our glide as far as we can. The longer we can glide, the more time we have to evaluate our landing options and plan an approach.

Once we have established our glide and picked our field, we want to start turning into this field and planning an approach as fast as possible.  This may mean we are turning towards our field when planning which way we are going to land,  land into the wind if possible and avoid obstacles.  We are also likely doing our engine restart checks as we do this turn. This is explained in detail in the forced landing article.

Calgary VFR Navigation Chart
Calgary VFR Navigation Chart

We should note our altitude above ground level. This means we should note the altitude on our map. In the area where I am flying is near Cremona, Alberta, the elevation is around 4000 feet.  When I start the procedure, I am at 6000 feet.  I have 2000 feet of altitude to plan my approach and landing.  Of course this is just a simulation, so when I am up with my instructor we do get within a few hundred feet of the ground, but when  practice on my own I don’t go below 500 feet above ground, which is 4500 feet.

The procedure calls to start the high key abeam the threshold where we have chosen our landing spot. The altitude we should be above this threshold is calculated from whatever gives us a two-minute turn to our left in our aircraft and our rate of descent. The turn and bank coordinator and vertical speed indicator gives us this information.  In the Cessna 172, the two-minute turn gives us approximately 700 feet of altitude per minute.  This means in two minutes we can descend 1400 feet if we use the information supplied in the turn coordinator for a two-minute turn. The FTM suggests that we use this altitude plus 200 feet of “fudge factor” to plan our altitude, meaning that we should be at 1400 + 200 = 1600 feet above ground at our “high key” position.  Where I am flying, I am planning to be at the high key at 5600 feet.

This gives me about 400 feet to reach my high key position when I am flying at 6000 feet.

The low key position will be halfway around the turn, about a minute after entering the high key turn.  My altitude should be 800 feet above ground or around 4800 feet ASL on my altimeter.

A two-minute turn shown on the Turn coordinator. Image courtesy of
A two-minute turn shown on the Turn coordinator. Image courtesy of

A good trick is to pick a landmark where you estimate will be your low key position. Look to your left when you are starting your high key. Is there a landmark that is approximately 1.5 miles from your high key spot? You should aim to be over that spot in your low key, and this will give you an indication whether or not you are in the proper spot in your sequence.

Our “final key” will be around 500  feet.  Next we are at short final where we can decide if we are too high – and hopefully we are not too low!

Some things to note: be careful of the winds, these can affect your pattern and blow you off course.  Also if you think that you are way too high, do a turning slip to loose altitude before adding flaps. This will allow you to loose more altitude.  Remember, it is always better to be too high than too low. There are ways to loose altitude – such as a slip or using flaps – but there are no ways to gain it when we have no power. Also, the reason we turn left is because we are in the left seat we have better visibility of our landing spot on the left hand side.

The high key – low key landing procedure is only one way of planning the approach. It may sometimes be that we don’t need to do the key procedure, and can just do a series of turns to bleed off altitude, fly a “bow-tie” patten, or whatever system we think is best to get us on the intended landing spot safely. This means landing into the wind when possible, avoiding obstacles, and picking as smooth of a surface as possible.

This procedure is very difficult to do even when we are planning to do it in a simulation! I can imagine that when really loose engine power the situation becomes very real very fast, and coupled with the stress of knowing you have to put your plane in a field is very intense.  This is why practicing the procedure again and again is so important: your response is automatic and you know what steps you need to go through in a real engine-out emergency.


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The ‘six-pack’ flight instruments: gyroscopes

Continuing on our review of the ‘six pack’ of flight instruments from the instruments that are powered by the pitot-static system, below we review those that are gyroscopes.

A gyroscope is a rotor or spinning wheel rotating and high speed,  and exhibits two fundamental characteristics upon which all practical applications are based.  These are:

  1. Gyroscopic intertia –  or rigidity in space. This is the tendency of the rotating body to maintain it’s plane of rotation if undisturbed.
  2. Precession: This is the tendency of the rotating body, when a force is applied to it at a point perpendicular to the plane of rotation to react as if the force had been applied 90 degrees in the direction of rotation

The three gryroscopic instruments are:

  1. The heading indicator. The main instrument we use to detect heading of the aircraft.  Only operates when the engine is running.  It runs off a vacuum system so we have to adjust it to the magnetic compass every time we fly. Frictional forces in the gyro bearings cause it to precess, resulting in a creep or drift in reading approximately 3 degrees every 15 minutes.
  2. Turn and bank coordinator, sometimes called the needle and ball.  The needle shows the direction and approximate rate of turn. The ball shows the amount of bank in the turn and whether there is any slipping or skidding. The ball is controlled by gravity and centrifugal force.  In a coordinated turn, the ball will be in the center as the centrifugal force offsets the pull of gravity. The instrument reacts to yaw but can be used for roll control since the aircraft yaws when banked.  It can show a rate one turn which gives us 3 degrees per second or a two-minute turn.
  3. The attitude indicator. Modern attitude indicators have virtually no limits of pitch and roll and will be accurate indicate pitch up to 85 degrees, and will not ‘tumble’ in 360 degree rolls.

The instruments are typically powered by the vacuum system and an electrical system for redundancy in case one of the power sources fails.  Often the heading indicator and attitude indicator operate on the vacuum system while the turn and bank coordinator is electrically operated.