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Stalls and angle of attack: a very important relationship

The relationship between stalls and airspeed is often misunderstood.   It is not actually the airspeed of the aircraft that will determine when the wing will stall, but rather the angle of attack.

Stall recognition is generally taught with reference to airspeed only.  Students are taught to pull up to stall the aircraft and continue doing so, watching the airspeed bleed off, watching the needle go from the green arc, through the white arc where this ends, and the airspeed at which that aircraft (in that particular configuration) is known to stall.  Instructors drill into us the importance of angle of attack, and that the aircraft can stall at almost any airspeed. In fact, my instructor and I stalled the aircraft at full power settings. It was surprising and intense, and very important to recognize that this can happen.

There is no instrument to show the relationship between angle of attack and airspeed determining stall due to the complex forces that determine when an aircraft will stall, including weight of aircraft, load factor, the aircraft’s center of gravity, and other factors such as altitude, temperature, aerofoil contamination (frost or ice on wings) and turbulence.   The airspeed indicator alone cannot measure when a stall will occour.

Your POH will give you stall speed with flaps up and flaps down configurations, for a certain weight. We learn in ground school that stall speed increases with weight forward center of gravity (which acts like an increase in aircraft weight), load factor (such as in a turn) and when there is surface contamination.  Once you know the basic stall speeds, it is up to you, the pilot, to be able to recognize when you are increasing or decreasing the stall speed.

It’s not the airspeed, it’s angle of attack

A typical lift curve, showing where lift angle is reached, which is about 16 degrees in this example. Image from
A typical lift curve, showing where lift angle is reached, which is about 16 degrees in this example. Image from

Angle of attack is the angle at which the relative airflow meets the wing. This is what determines when a wing will stall. It’s important to understand relative wind – this is the way the air flows over the wing – when this is disrupted, air can no longer flow the way it’s designed to over the wing, and lift decreases.  The critical angle of attack is reached when the maximum lift coefficient is obtained, after which lift will drop off when the angle is exceeded, and the aircraft will loose lift. After the critical angle of attack is reached, the aircraft is said to be approaching a stall.

The aircraft will always stall at the same angle of attack, called the critical angle. Many modern jets have an instrument that prevents the pilot from increasing the angle of attack past the critical angle, this is called the angle of attack limiter or alpha limiter.

Dangers of being low and slow

However this type of tool, or similar instrument is not in most general aviation planes. This leads to the pilot having to be very careful in making sure they don’t push their airplanes in into this flight envelope. When is a stall most dangerous? When you are low and slow.  Typically, the base to final turn can be very hazardous, and this is corroborated with the amount of stall-spin accidents that happen during this circuit sequence (for general aviation airplanes).  On this turn, you are low, and your airspeed is decreasing since you are on approach. When you turn, you increase the load on the aircraft, and if you push it into a stall (say, by executing a steep turn) you can enter a deadly stall-spin from which recovery is difficult due to the proximity of the ground.

ICON Aircraft GuageRecently I’ve discovered the aircraft manufacturer Icon Aircraft. This company has created an angle of attack instrument for general aviation airplanes.  This instrument measures angle of attack and presents it to the pilot showing when they are flying within the proper range.  This is a very interesting development that should go a long way into increasing safety.

I recommend watching the video about the concept below. Very cool!

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Top ten reasons why you should never learn how to fly

Flying? Boring! Why would I ever want to do it? Aside from being expensive and time consuming,  it’s also pointless. Why would I want to shoot around the sky in a metal tube?  It just seems like a poor use of time. Seriously, only those with poor judgement would consider getting a pilots’ license.  There are just so many reasons why you should never do it, but here are the top ten that I could think of.

1.  The view sucks.  Why would I want to see the world from 3000 AGL?  I have such a hard time picking out my house from the plane, it’s so much easier if I’m driving around in my car.  The world just looks so big from the air and it’s really not that interesting.  I’m just not interested in seeing the bigger picture.

These guys are always bossing us pilots around. You'd think they own the airspace or something.
These guys are always bossing us pilots around. You’d think they own the airspace or something.

2.  Airports are boring.  Nothing interesting happens at airports. Seriously, flight schools talk about teaching you soft field landings and precautionary/forced landings, but never actually let you do them, always forcing you to return to the airport. How about some danger? I’ve seen Top Gun – I’m ready!

3.  Air Traffic Controllers are bossy.  They constantly tell you what to do and they talk so fast that you can barely understand them most of the time.  And they always tell you to switch frequencies and get upset if you don’t call them.

4.  Too many calculations. You really have to learn how to flight plan to learn how tedious and pointless it is.  Just point the airplane in the direction you want to go – how much harder does it have to be, people? Fuel, schmuel. I’ll just keep an eye on the fuel gauge like I do when I drive. What could possibly go wrong?

5.  No in-flight entertainment.  Unless you count your instructor, there is no real source of entertainment when you’re flying.  No movies, TV, music or anything. No hot coffee. The service stinks.  Why would I want to sit in an old uncomfortable 30 year old Cessna when I can comfortably stretch my legs out on the couch like a human being.  When I stretch my legs out in the Cessna I just end up hitting the rudder pedals, which causes yaw and I have to do more work to correct it.  Can’t relax in the thing for a second.

6.  Flight instructors are annoying.  They are always telling you what to do and bossing you around. It’s worse than ATC because you can’t really get away from them.  Once you leave the control zone you are free of the claws of terminal control but you can’t get rid of your instructor once you let them in the plane with you.  They really don’t know that much … How much can there possibly be to know??

7. Too much safety emphasis.   Do you know how long it takes to prepare to actually go on a flight that lasts less than an hour? About two hours. Checklists, meetings, briefings, log books, journey log books, sheesh. So much paperwork and so many safety checks. I mean, did you know when you’re at the hold short line that you have to check your engine is operating? It started, so why do you need to check it again? Obviously it’s working and the plane is ready to go.  If it wasn’t it wouldn’t start. Obviously.

8.  Trainer planes are old.   Trainer planes are so old, I think they must have been built when dinosaurs roamed the earth.  They are loud and uncomfortable.

9.  It’s too hard.  The instrument panel in your car has only a few sources of information: speed, fuel quantity, engine temperatures and some have a tachometer.  The most basic airplane panel has six highly confusing instruments which are really hard to understand, ever mind all the other engine instruments, radios, direction finding equipment, navigation tools, approach systems, and the little floaty thing on the dash.  There are so many maneuvers, attitudes and movements too learn, it’s just seems like way to much work.

10.  It’s scary.  The whole concept of flying just seems like a bad idea.  There are just too many planes of movement.  It’s not that rewarding, and not really fun to be in control of the thing.   Constant briefings, meetings, exams, preparations, paperwork and safety checks.  Soaring through the air?  Make a career out of it? Seriously why bother. I’d rather just sit on the couch eating chips.

We hope you had a good laugh reading this.

Sarcasm aside, ever try to talk yourself out of getting a license?  So many reasons. The fact is that flying is hard, committing wonderful and very rewarding.  Like many things in life, if it wasn’t hard, it wouldn’t be worth doing.   Challenge yourself and don’t give up.  Search your soul and if you discover flying is right for you, you will have the time of your life and you will not regret it!



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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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A review of weather reports for pilots

Mountain wave cloud from the edge of the rocky mountains

Let’s review some basic concepts in meteorological reports for Pilots.

Cloud cover: measured in oktas, or out of eighths of the sky coverage:

  • SKC – sky clear of cloud
  • Few 1-2 out of 8
  • Scattered 3-4 out of 8
  • Broken 5-7 out of 8
  • Overcast 8 out of 8 – full sky coverage

METAR: Aviation routine weather reports are coded weather observations that are taken each hour at over 200 aerodromes and other locations in Canada.

SPECI: Special Weather Reports – these amend METAR observations, whenever weather conditions fluctuate or are below criteria.  What are these criteria?

  • Sky condition: (1) the cloud ceiling height changes either up or down from 1500 feet, 1000 feet, 500 feet, 300 feet or 100 feet, or to the published IFR limits for that aerodrome. Also, (2) the first occurrence of cloud under 1000 feet is noted.
  • Precipitation
  • Temperature: if above 20 degrees, an increase of 5 degrees; or if the temperature decreases to 2 degrees or colder.
  • Visibility: up or down any of these thresholds: 3 SM, 1.5 SM, 1 SM, 3/4 SM, 1/2 SM, or the limits for the aerodrome.
  • Wind: Wind doubles to exceed 30 knots, or shifts.
  • Severe weather: thunderstorm, tornado, funnel cloud.
  • Other: these can be incidents at the aerodrome, such as an accident or a special request from a weather forecast office, or if the weather observer feels it’s just to take initiative to issue this alert.

TAF: Terminal area forecast. Limited to aerodromes where METARS and SPECIs are published.  There are about 180 TAFs in Canada.  Generally prepared four times daily with up to 30 hour validity.

GFA: Graphical Area Forecast. There are seven GFA areas in Canada, these weather charts depict the most probable weather conditions expected to occour on the ground up to FL240 (flight level 24,000 feet).  There are six charts prepared for every period, issued daily at 2330, 0530, 1130 and 1730 UTC, valid from 0000, 0600, 1200 and 1800 UTC respectively.   Each chart has 12 hours of forecasting plus a 12 hour IFR outook, giving us a total of 24 hours of forecasting.  Of the six GFAs listed for each forecast period, three contain cloud and weather information and three contain icing, turbulence and freezing levels.

The GFA can also be amended by AIRMETs or SIGMETs. AIRMETs are short term weather advisory for aircraft in flight, alerting pilots to possible hazardous flying conditions, but not severe enough to require a SIGMET.  SIGMETS  are short term warnings of certain potential hazardous weather phenomena, and are limited to more serious hazards which are important to all types of aircraft.

FDs – These provide upper level wind forecasts. They are provided for seven specific regions in Canada, and are further broken down for specific areas.  Forecast for the 3000, 6000, 9000, 12,000 and 18,000 foot levels are provided, and these are the low-level FDs. They are also given for flight levels above 18,000 feet (FL180).

Radar: Radar is provided on the Environment Canada webpage. It will show you developing precipitation. It is very accurate.

Satellite: Satellite is shown on the AWWS webpage, and is useful for long term weather forecasting and planning. You can use it to find low and high pressure systems. Recall that air rotates clockwise around a high and counterclockwise around a low.

PIREP: Pilot reports can be filed at any time. They should be regularly checked for your region. In fact, one that I received from a controller at Calgary terminal saved me from going into an area of severe turbulence.

A sample RVR for CYBW (Springbank)
A sample RVR for CYBW (Springbank)

RVR Index: Another great tool is the RVR index. The Runway Visual Range shows real time the current wind speed and direction at your chosen aerodrome. It is so accurate I often check it when I am already at the airport getting ready for a flight.  The image on the left it shows a sample of what you will see.  The wind speed and direction is displayed according to the magnetic compass.  Here the wind is blowing from 130 at 9 knots.  The wind direction is overlayed with the actual runways to get a sense of where exactly the wind is coming from, and if we can expect a crosswind.  In fact the cross wind component for each runway is calculated in a table next to the image.  Wind given is the average for each minute.


It is important to understand how to read these reports and understand how they are created.  After awhile, it becomes second nature.   Pilots after all, are lifetime students of weather.

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Forward Slip

Forward Slip - Transport Canada photo

The other day I was out flying with my instructor reviewing soft field procedures. We were doing circuits on runway 25, and on the turn from the downwind to base leg of the circuit, we were  hit with strong turbulence every time.  The leg goes close to the river so we assumed it was something to do with that.  It was a bit much for me and I lost my concentration, so I kept coming in too high and fast.  After a few we landed and the controller immediately announced a runway change to runway 16.   I decided that I still wanted to try it, given that the circuits we did on 25 weren’t really that great.

After takeoff from runway 16 the turbulence hit us again only a few hundred feet AGL. I decided that it was probably best to ask for a full stop and end the lesson.  The turbulence was too distracting and kept me from being able to concentrate on the maneuver.  Inadvertently on the landing again, I came in too high.  So my instructor told me to use a forward slip – which is something that I’ve done numerous times – but I hesitated and my mind went blank.  I eventually did it, but think this is a procedure I need to practice still, particularly when I go solo.

What is a forward slip?

It is a turn that is prevented by use of rudder.  The airplane moves in straight, drag inducing position that increases rate of descent and doesn’t increase airspeed – because of all the drag that is created by the airplane in that configuration. The aileron holds the bank while the opposite rudder causes the nose to point in the other direction.

To enter a forward slip, power to idle, turn the aircraft into the wind, and use opposite full rudder. The configuration feels somewhat awkward to me since the airplane is steeply banked and pointing in the other direction. Like everything in flying, it is all about practice until it feels natural!

Another thing is I REALLY need to start bringing my camera and maybe my video camera to my flights! I am always too lazy to take photos but it is great to have them particularly so I can share them here.


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The perfect landing

Normal landing touchdown attitude

The perfect landing technique explained

The most difficult part of learning to fly is, I think, the landing.  It is a precise series of steps that, when individually understood both aerodynamically and intellectually, result in a straight, soft landing no matter the wind conditions.  Since going solo for the first time I have been doing solo circuits, and have really been concentrating on my landing. Unbeknown to me, my landings, though soft are actually not that great.  Once I feel the aircraft sink I have a tendency to let go of the aircraft and let it sink, instead of holding off elevator pressure as long as I can.  This is one of the things that I have really noticed since I began flying solo.

Proper landing procedure

The proper landing procedure always follows a good approach. In the Cessna 172, this is approaching at 70 knots (with zero flaps) or 60 knots (with full flaps).  We can also use different degrees of flaps, such as 10, 20 or 30 depending on the 172 model.  Once we are over the runway threshold, and 2 -3 feet above the ground, we flare – using whatever works for you for knowing when to flare!  – I use the rule of when “the ground starts to come up so fast that something must be done about it.”

Once that is accomplished, you will feel the sink. My issue has been, that once I feel the sink I ‘give up’ and assume the aircraft is ready to land, and let it sink. This can result in a hard landing.  For me, I don’t get the hard landings but  tend to let my nose wheel touch down too soon. This can be dangerous as it can result in wheelbarrowing. The key is to hold the landing attitude as long as possible and bleed off your airspeed slowly.  So once you feel the sink, pull up until you have a very nose high attitude or high angle of attack.  This will cause the aircraft to sink slowly and incrementally. It will allow the main wheels to touch down first, and the landing will be soft.

What are your landings like? Comment below