Archive for category Instructional
Saying No
Posted by Colby in Instructional on May 11th, 2010
“Centralia traffic, Katana Foxtrot Echo Charlie Papa, turning final 28, touch and go, Centralia.”
I had just entered the circuit at one of the small uncontrolled fields near London. No one else was around and I had the whole place to myself to practice circuits. My instructor sat quietly to my right, letting me make all the decisions in his usual way. I would ask quesions and he would respond with: “What do you think?”
We turned final. Too high, too fast. Power to idle, flaps to LDG, start a slip to drop some altitude. It wasn’t working as planned and the runway wasn’t terribly long. I realized I had really botched the approach and had set myself up for a tricky landing.
The next decision was tough: Flaps up one notch, back pressure on the stick, full power. “Centralia traffic, Katana Fox Echo Charlie Papa, overshooting runway 28, left circuit, Centralia.” I had completely screwed up that approach in almost every way and it was the first time I ever had to overshoot during an actual approach. I knew my instructor wouldn’t be too happy and any second I was expecting him to start telling me the things I did wrong. He said, “That was awesome, good job.”
“Wait, what?” I was confused. I just made a series of mistakes which resulted in an unviable landing situation. How was any of that a good job? During the debreif after the flight, he explained what he meant by the comment. Aviation is ruled by A-type personalities: people who need to be right, who are extroverts, competitive, controlling, and impatient. To a certain extent, I possess these traits myself, but hopefully not to any extreme. My instructor explained that the hardest decision to make in aviation is the one where you admit that you screwed up. By overshooting, I admitted to myself and to him that I failed in my attempt to properly land the aircraft, but at the same time, I made the safest possible decison concerning the safety of the aircraft and all passengers onboard. Overshooting is the toughest decision you’ll make in aviation, especially if you’re an A-type personality.
Since that day back in 2007, I’ve definitely come a long way. I’m licensed, have a night rating, almost ready to flight test for my commercial license and will be starting my multi-IFR after that. I’ve forgotten many of my first training flights but that one stuck with me. It was, in my opinion, one of the most important things I’ve learned in aviation.
This is my first post in a while. I’m sorry about the absence but I’ve been busy working on getting my commercial ground school done with (all 80 hours that Transport Canada dictates). The flight school I’m with right now doesn’t currently offer CPL ground school so I’ve had to take it online with Harv’s Air in Manitoba. I wrote a post about this a while ago and I plan on doing a full review of the service they offer. Initial impressions are positive; however, there are many areas for improvement.
The event that sparked interest for this post happened on the weekend. I had planned to do my 300NM cross country which is also one of the requirements TC sets out for all CPL students, but the weather didn’t cooperate. I instead booked a regular solo slot for the afternoon and thought I would try and get up for some airwork practice. None of the flight instructors I have flown with before were at work that day so I needed one of the more senior instructors to sign me out. I’ve never flown with him either so he was a little apprehensive about signing me out. In fact, he told me he wasn’t comfortable letting me go given the current conditions (330/11G21) even though we have a runway 33 in London. The winds weren’t anything I couldn’t handle, but it comes down to liability and the person whose name goes beside yours on the sign out sheet. As an instructor, you have to make decisions that in all likelihood won’t please the student very much. I had just driven almost 30 minutes to get to the airport, did the walk-around and weight and balance and was ready to get going, only to be told (in a nice way) to go home.
Surprisingly, this was the first time this has ever happened in almost 3 years of flight training. I hope to be an instructor after I graduate university so these are situations that I had better get used to. An unhappy student is better than a dead or severely injured student.
Since I last posted, a few interesting things have happened, including getting to fly the DA40 Diamond Star. Hopefully I will have time in the not so distance future to write about it. I also ordered Peter Burkill’s book, 30 Seconds to Impact, which details the events surrounding British Airways flight 38 which experienced double engine failure on final into Heathrow. I’ve started reading it and will post a review when I’m done. Pete was nice enough to sign the inside cover for me too.
Currently, I’m focusing on my CPL written exam and preparing for the flight test. I’m sitting at just under 150 hours total time and hope to test within the next month or two.
The Sticky Note Method
Posted by Colby in Cool Stuff, Instructional, Training on November 7th, 2009
One of the first things you learn as a pilot is that a good landing stems from a good approach. In the jet world, pilots aim for a stabilized approach whereby the pilot configures the aircraft to travel at a certain airspeed and rate of descent straight down to the threshold. I recently read an article (that I can’t seem to find anymore) stating that the term “stabilize” really didn’t apply to a prop driven aircraft. The reason being that jet engines have an inherent lag between adding power in the cockpit and seeing that throttle movement translate into actual power. Jet engines need time to spool up if they are idling and pilots may not have this time if they need to execute a missed approach. Thus, power is left on during the approach to help reduce the lag time if a spool up to full power is ever needed.
In the prop world, the article suggests that the term “collected” is more appropriate. We want to configure the pitch and power settings so that we’re descending at an optimal rate, and at an optimal speed, as outlined in the aircraft’s operating handbook. So how do we know exactly what power setting to use and exactly how many degrees of nose down pitch to apply in order to touch down at a certain point on the runway which could be miles and miles ahead of us? For a lot of people, it’s simply a matter of using your gut feeling to configure the aircraft when it feels right. We have a mental picture of what things should look like at certain times and distances from our waypoint and based off these pictures, we act accordingly. This is how I’ve always set up my approaches and it’s how we usually learn. However, I recently learned of a pretty easy way to guarantee hitting your landing target that takes all of the guesswork out of approaches. Some may call it by another name, but I have dubbed it “The Sticky Note Method”.
Imagine that you’re coming to the end of a long cross country flight and you’re ten miles out. Tower clears you to a straight in – Runway 33. Using this method, you’ll be able to hit your target every time… even from ten miles away. Here’s how it works.
What you’ll need: a few sticky notes and the inside of the windshield should be nice and clean. On a day when you can take a plane up and just practice your flying, trim the airplane in straight and level flight. Reduce power so that you maintain straight and level flight, but your airspeed should be exactly the same as it is on final approach. Configure the airplane how you would normally (ie. full flap, gear down if applicable, etc). Use the minimum amount of power possible to keep the airplane at this desired speed and straight and level. Make sure you’re trimmed out.
Take a sticky note and tear off a small amount from the adhesive part (the top). Place this little dot on the windshield in front of you so that when you’re sitting normally in your seat, the dot sits right at the level of the horizon. This may take a few tries as you probably won’t get it right on the first try. Keep readjusting the dot until the stickiness wears off, or you get it right. As best you can, try and memorize this position on the windshield. For practice sake, leave the sticky there while you shoot some approaches and test this theory out.
Let’s get back to our situation. You’re on final and a ways back from the runway. Once you reduce power and start your descent, pitch the airplane in order to move this dot over the spot on the runway where you want to start your flare. Keep in mind that your touchdown point will be beyond this point, so based on your aircraft’s characteristics, place the dot however many hundred feet before your touchdown point you deem necessary. The spot on the ground that is covered by the dot represents where the aircraft would travel into the ground should you leave the aircraft in its collected state and never start your flare. The trick to keeping the aircraft on course is to never adjust your pitch and only adjust your power. Your pitch should always keep the dot over the same place on the runway that you’re aiming for. You will adjust your power to control airspeed. This is contrary to how you’re taught when you first learned to fly. Power controls altitude, pitch controls airspeed.
So assuming you keep your pitch steady with the dot over your aiming point, and you adjust power to maintain optimum approach speed, and assuming you correctly placed the sticky on the horizon when you first set this little test up, you should be starting your flare exactly where you planned.
I have to admit that I was skeptical at first. And I know I sound like I’m selling something on an infomercial, but this really does work. My instructor and I were given a 7 mile final – straight in with lots of time to test this method. We set it up exactly how I described it, and what do you know, I hit my flare point +100 feet. It wasn’t perfect, but from 7 miles away, 100 feet is pretty accurate in my mind. We did a few more circuits and confirmed that it works just as well from close in than it did from far away.
Now obviously you’re not going to fly with a sticky note on your windshield every time you go flying. This method helps you understand the principle of a collected/stabilized approach and how to fly them with greater accuracy. With practice, you’ll know exactly where that spot is on your windshield without the sticky even being there.
A cheaper way to test this out would be to do the exact same thing, but in a sim. Just place the sticky note on the computer screen’s horizon and shoot some virtual approaches. I think you’ll end up finding it’s pretty accurate there too. In fact, you may want to test this out on a computer before you even go flying.
I’m interested in finding out if other people out there have tried this, and to what avail. It’s certainly an interesting technique to try out and I want to hear some feedback if you’ve got any. Also, any other techniques/tricks that you might use regularly and want to share would be most welcome.
Diamond Katana DA20 – An Overview
Posted by Colby in Instructional, Training on August 30th, 2009
As I’ve written about before, I started my training in Diamond DA20s and later transitioned to the Cessna 172 after I switched flight schools. At the time, I had no other experience in any other aircraft so I couldn’t write a valid comparison between the two. Now however, I have about 60 hours in the DA20 and a little over 40 hours in the 172, so I feel I’m now allowed to express my opinion and provide a brief look at some of the differences. Take note that the 172s that I fly were both made in the late 1970s, so my comments are strictly related to these models and not the newer models.
The C172 is the most popular training aircraft in the world, hands down. First introduced in the mid 1950s, over 43,000 have been produced according to wikipedia. For this reason, I’m going to assume that the DA20 is the least known aircraft in this comparison, so I’ll be focusing more on it’s characteristics compared to the 172’s. So let’s get started.
The first big difference you’ll notice about the DA20 is that it’s made from carbon fibre and glass fibre, not metal. The Diamond POH (Pilot’s Operating Handbook) calls the material Carbon Fibre Reinforced Plastic (CFRP) and Glass Fibre Reinforced Plastic (GFRP). From a pilot’s perspective, I love the carbon fibre. The approximate empty weight of the DA20 is 1,153 lbs compared to the 172 which weighs in at around 1,530 lbs, depending on equipment installed. A two seater will obviously weigh less than a four seater, but the reduction in weight is definitely beneficial for a number of reasons (fuel consumption, maneuverability, etc.)
The second thing you’ll notice right away is that the DA20 is a low-wing aircraft while the 172 is a high-wing aircraft. In fact, you’ll probably notice by the end of this post that pretty much every design option is opposite between the two airplanes. There are certain advantages and disadvantages to both wing designs. Visibility is a big one. Low wing, combined with a bubble canopy on the DA20 gives you great upper visibility but seeing the ground or traffic at your 3 o’clock and 9 o’clock low positions is tough. Conversely, the same statement applies for the 172 at positions above to your left and right. It’s much easier to inspect the wing and landing gear in a high wing aircraft as well; with the DA20, you have to get down on your hands and knees to see everything. The big factor in the high vs low wing debate for me is handling characteristics. I find the DA20 to be a little more responsive and snappier than the high wing Cessna. Don’t get me wrong… the 172 is a very stable airplane, but when it comes to having a little fun or making quicker maneuverable turns, the DA20 wins.
Maneuverability usually comes with a cost though. Just as most fighters are design to be inherently unstable, the low wing is inherently a bit less stable than the high wing in this case. Where you’ll really notice the difference is on the ground during your takeoff roll. I’ve noticed the DA20 is a bit edgier throughout the yaw axis while taking off, so good rudder control is important. The 172 is a bit more relaxed and doesn’t tend to swing about as much. It’s not so much of a hindrance as it is something you have to get used to. In the air, the DA20 has a quicker roll-rate than the 172 I’ve found, but this can also be attributed to the smaller size and lighter weight. It’s the same thing you encounter in a car: lighter two seater vs a four seater sedan. The two seater will win in the turns but the sedan usually has a higher top speed. I’ll get to the speed bit later. Oh, and the DA20 is way more fun to spin than the 172!
Moving on from the wings, the empennage (tail section) is different as well. The DA20 has a high T-tail while the 172 has a conventional low tail. Again, both have their own advantages and disadvantages which I’m not going to comment on.
Let’s move from outside to inside the aircraft. Again, we’ll see that the design choices made here tend to be a little different. The DA20 uses a Continential IO-240 engine. This engine is a four cylinder, fuel injected, four stroke engine with horizontally opposed air cooled cylinders and heads producing 125 HP at 2800 RPM. The C172N uses an Lycoming O-320-H2AD engine. This engine is a four cylinder, carbureted, four stroke engine with horizontally opposed air cooled cylinders and heads producing 160 HP at 2700 RPM. Most of these characteristics are the same, but you’ll notice that the DA20 engine is fuel injected and the 172 engine is carbureted.
When it comes to fuel injected vs carbureted, I’ll take the fuel injected engine any day. It’s easier to use, gives you better performance, and is safer when it comes to icing conditions. With a carbureted engine, you have to always be conscious of icing conditions and the application of carb heat is essential. In the DA20, I don’t have to be as worried about carb icing. Of course, like any other decision, fuel injection has it draw backs. It’s harder to maintain the system; dirt in the fuel lines can adversely affect fuel flow to the cylinders. Starting the DA20 is also an art you have to master compared to starting the 172. A five year old could start the 172, but starting the DA20 is a little bit more of an experience.
Coming to the control surfaces, there isn’t too much of a difference. All three major control surfaces in the 172 are controlled by cable and pulley. In the DA20, the rudder is controlled by cables, but the ailerons and elevator are controlled by push rods. Inside the cockpit, the 172 uses a yoke control column while the DA20 uses a stick.
When it comes to stick vs yoke, I’m a stick man. There’s just something about the stick that I like more than a steering wheel. While sitting in the DA20 cockpit can be a little weird compared to the 172, I find that it’s easier to operate the aircraft in general. The throttle lever is located comfortably between the two seats whereas the 172 throttle knob is located on the dash. I’m someone who likes to keep my hand on the throttle most of the time, so having to hold my arm out in front me in the 172, just to rest my hand on the throttle, is extremely annoying. In fact, it’s the first thing I noticed when I started flying the Cessnas. I couldn’t figure out why the designers would make such an uncomfortable design decision. Having the stick sit comfortably between your legs is a plus too. To be fair to Cessna, there is much more room in the 172 cabin if you’ve got charts, clipboards, a CFS, an E6B, etc. floating around that you’ll need to access at different times throughout your flight. The DA20 cabin is a little cramped when it comes to this. In the end, I still like the design of the Diamond cockpit better.
I think I’ve gone over most of the major talking points when it comes to Diamond vs Cessna. Now let’s have a look at some of the numbers. Here is a sample of the main V Speeds between both aircraft:
Best angle (Vx) and best rate (Vy) of climb are within 5 knots of each other for both aircraft. The DA20 climbs out at a slower airspeed which makes sense due to its lower max weight and lower fuel capacity. However, maneuvering speed (Va) is higher for the DA20 meaning the control surfaces can be deflected fully at a higher airspeed should you ever need to. This brings up the issue of load factors. The DA20 can sustain G forces of -2.2 to +4.4 Gs while the 172 can sustain -1.7 to +4.4 Gs. Not much of a difference here.
The maximum flaps extended speed (Vfe) for full flaps is a bit higher in the 172 which can come in useful. The 172 is great at dropping altitude and airspeed if you’re too high on final. With flaps down to 40º (or 30º), a nice slip with make it drop like a rock. The DA20 is a bit harder to slow down and reduce altitude at the same time.
The maximum safe operating speed (Vno) is 10 knots higher in the 172 as well, giving it an edge in that category. It’s always nice to have the option of going a bit faster when you need to. To be fair, this speed can be exceeded in calm air should you ever need to. Finally, the top of top speeds to never exceed (Vne) is 4 knots higher in the DA20. This likely won’t ever affect anyone but if you’ve ever come close to Vne, then you’ve got 4 extra knots in the DA20.
Looking at the big picture, you’ll notice the speeds in general are a bit higher for the 172. The DA20 has a less powerful engine, smaller fuel tanks, and a smaller range. When given the choice of which aircraft I would take on a cross country, I’d probably take the 172. It can go further, with almost twice the fuel capacity of the DA20, and it can do so at a faster cruising speed. Now obviously there will be situations where the DA20 will be faster, but in terms of taking passengers and cargo on a cross country, the 172 is more capable in my opinion.
When all is said and done, I’m a DA20 fan. I haven’t flown them in a while but I plan to start again soon. I hope to be able to do the majority of my next 100 hours in a DA20 while working towards my commercial license. They’re a bit trickier to master, but they’re also a bit more fun to play around in. The design choices in my opinion are better in the DA20, but it’s hard to knock the most successful aircraft ever produced. To be clear, I like the 172. I think it’s good at certain things and bad at others. Same goes for the DA20. But when it comes down to which one I would choose on a regular basis for a training aircraft, I’ll take the Diamond.
Learn A System – Part 4: Flaps
Posted by Colby in Instructional, Learn A System on February 14th, 2009
The flaps on the C172 are single-slot type flaps powered by the aircraft’s electrical system. The amount of flap lowered is measured in degrees, and in the C172, the different amounts include 10º, 20º, 30º, and in some earlier models 40º.
From first hand experience, putting down 40º of flap is almost always unnecessary due to the huge amount drag that it produces.
I mentioned above that the C172 has “slot” type flaps, specifically single-slot. I’ve included a diagram below of the different types of common flap systems utilized on a wide range of aircraft.
The difference between a slot flap and plain flap is that with a slotted flap, there is room for air to flow between the leading edge of the flap and trailing edge of the wing. In other words, air can flow between the wing and flap. WIth a plain flap, the flap simply drops down and is, in essence, an extension of the wing itself.
Slats are common on larger aircraft and you’ve probably seen them on commercial airliners. Slats act to maintain laminar airflow over the wing at a high angle of attack. Check out this diagram:
In the C172, the flaps are powered by an electric flap motor located in the wing. The system is protected by a 15 amp circuit breaker, labelled “FLAP”, in the cockpit. All diagrams are taken from From The Ground Up.
Learn A System – Part 3: Carb Heat
Posted by Colby in Instructional, Learn A System on February 13th, 2009
To follow up with my last post on the carburetor, I’ll be talking a bit about the carb heat lever and what is happening inside the engine when you engage it.
Icing is a problem that can affect an aircraft in many ways: added weight, change in airfoil shape, increased drag, and reduction of airflow to the engine. While all of these effects of icing are dangerous, this post will focus primarily on the last one.
As I explained in my last post, the carburetor mixes incoming air with fuel and feeds this mixture to the engine. Icing can occur when moist air enters the carburetor and freezes to the walls and butterfly valve. The eventual build up of ice can ultimately cut off the air supply or render the butterfly valve inoperable, and it is for this reason that we use carb heat.
Carb heat works by taking unfiltered, outside air and passing it through tubes wrapped around an exhaust muffler. This effectively preheats the air before it reaches the carburetor. If ice is present in the carburetor, this air will melt the ice.
There are a few side effects of using carb heat however. The C172 POH says that carb heat will reduce engine by 100-225 RPM at full power. This is due to the fact that hot air is less dense than cold air, and with less air molecules to aid in the combustion process, power is reduced. Also, if ice is already present and carb heat is applied, it may be observed that the engine will run rougher than it was previously. As the ice melts, the resulting water enters the cylinders and causes the roughness. It is extremely important that you leave carb heat on and let the water get out of the system. Some people apply carb heat and notice that the engine is running rougher than it was – they then turn carb heat off. Ice builds up even more and engine failure becomes imminent.
The moral of this story is to leave carb heat on and let it do its job! Give it some time and engine power should return to normal, even if it runs a little rough at first.
Below are a few diagrams, courtesy of From The Ground Up that show the effects of icing, the carb heat system, and the carb icing range. Enjoy.
Learn A System – Part 2: Carburetor
Posted by Colby in Instructional, Learn A System on February 11th, 2009
In this post, I’ll be detailing the carburetor in the Cessna 172 and talking about what it does and how it works.
To start, one should know that an engine works by burning a mixture of fuel and air in a specific proportion. This miniature explosion drives a cylinder down, and then back up again, providing power. This power is used to turn the wheels on your car or the propeller on your airplane.
So what proportion is best when mixing fuel and air together? Approximately 1 unit of fuel to 12 units of air is an ideal ratio. So why aren’t planes manufactured so that there is always this 1:12 ratio of fuel to air? The answer has to do with altitude. As you fly higher, air becomes less dense, and due to this decrease in density, the 1:12 ratio on the ground may actually be closer to 1:10 or 1:8 at altitude. In order to balance this out, we need to modify the fuel-air mixture so that the ratio returns to an optimal level. This process is called “leaning” and simply decreases the amount of fuel mixed with the incoming air – this returns the ratio to normal.
All of this happens in the carburetor. In the C172, the carburetor is described as an up-draft, float-type carburetor mounted on the bottom of the engine. “Up-draft” simply means that air enters the bottom of the carburetor, then flows upwards through the system, and out the top to the intake manifold tubes. “Float-type” refers to the fact that a float system regulates the amount of fuel that sits in the float chamber of the carburetor. The float chamber is a small chamber of readily available fuel that is waiting to be mixed with incoming air.
The diagram below may provide a better visual of the process inside of a carburetor. Essentially, air flows up through a tube, called a Venturi, and is mixed with fuel coming from the float chamber. A pin inside the float chamber controls how much fuel is sent to the Venturi, and thus controls the mixture, either leaning or enriching it as necessary. When the mixture knob is moved to the idle-cutoff position, this pin fully blocks any fuel flow to the engine, which in turn starves the engine and shuts it down.
Last but not least, a butterfly valve inside the carburetor controls the amount of this fuel-air mixture that is allowed to go to the engine. This is your throttle control.
Diagram: From The Ground Up
If you have any questions, feel free to post in the comments. I hope I’ve done an adequate job explaining this system, but if there’s something I’ve left out or you feel is important, let me know and I’ll add it in.
Learn A System – Part 1: Fuel System
Posted by Colby in Instructional, Learn A System on February 3rd, 2009
I’m starting a new series called, appropriately, “Learn A System”. I’m currently coming close to my private license flight test, and in an attempt to learn all of the systems for the oral portion of my test, I plan to teach them to you.
In my mind, if I explain it to someone else, even if no one reads it, I’ll somehow magically absorb it and know it a little better than I did before. I fly the Cessna 172N, so here we go: the fuel system. (see the diagram at the bottom of post)
To begin, the C172 has the option of two different types of fuel tanks: standard and long range. Standard tanks are 21.5 gallons each totaling 43 gallons. However, 3 of these gallons are unusable (meaning 3 gallons will sit in the bottom of the tanks and can’t be sucked into the fuel lines). Therefore, standard tanks have 40 gallons of usable fuel.
Long range fuel tanks hold slightly more fuel in each tank at 27 gallons per tank. In total, both tanks can hold 54 gallons between them with 4 gallons unusable, meaning long range tanks can hold 50 gallons of usable fuel.
If you haven’t already deduced it yet, the C172 has two fuel tanks located in each wing near the root. From there, the fuel is gravity fed to the fuel selector valve, located at your feet in between the two seats in the cockpit. You can manually select to feed the fuel from the left, right, or both tanks. The off position stops the fuel feed to the engine.
From the fuel selector valve, the fuel flows to a fuel strainer which filters the fuel for any debris or foreign particles. This is also where the primer draws the fuel from where it is injected directly into the cylinder intake ports.
From the strainer, the fuel flows to the carburetor where it is mixed with air and then to the cylinders through intake manifold tubes.
So now you know how the fuel gets from fuel truck to cylinder, but the fuel system includes a few more things. There is space for air to move between fuel tanks, and in the C172N, the right fuel cap is vented to allow air to flow freely. Ventilation is essential to the fuel system as it allows fuel to flow freely.
So how is fuel measured you ask? Well the same way your toilet knows to stop filling once you’ve flushed it. A float sits in each tank and is connected to electrically operated fuel quantity indicators in the cockpit. These indicators are known to be very inaccurate, so always dip your tanks before you fly!
This sums up the basics of the fuel system. Sure, you could get into the locations of the drain valves or the proper position of the fuel selector during certain maneuvers, but I won’t bore you with things that you’ll learn in the cockpit anyways. This first lesson is supposed to be directed at the theory of it all, so I hope this helps.
Airspeeds Galore
Posted by Colby in Instructional on February 1st, 2009
I can’t take credit for the idea for this post. I started reading a fellow aviator’s blog and found an article she linked to on airspeed. I remember when I first had to swallow the idea of true airspeed, calibrated airspeed, indicated airspeed, etc. and I remember it being a little confusing. Anyways, check out this article that the non-aviating type will understand.
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