The Wing to Parachute Conversion

If you’re like me, the first time you went out to stall an airplane was probably a stressful experience. The reality of that experience has rung true in some form or another for me as I look back on ten consistent years in the cockpit. After getting my private, I remember only a few hesitant attempts at stalling an airplane until I received more training at the commercial and CFI levels. Then, as a new CFI, I can remember the pit in my stomach the first few times I had to go up with students to stall airplanes. From there, the fear slowly left me but was still present in my students. I was then surprised to find this same concern and trepidation among my fellow professional pilots at my day job. In short, I have come to find that fear of stalls is a universal reality among pilots. Where does this fear come from? I hope to get at a small aspect of it in the paragraphs below.

When I sit down with a new student pilot on day one, the topic of stalls is hot on my lips. However, I first ask them an unlikely question. “Can monkeys fly airplanes?” I ask. To this, I usually get an odd look and a hesitant answer. The correct answer to this question is a resounding “No”. However, the “why” to this question is far more important than a simple answer. I then explain that monkeys can’t fly airplanes for one important reason. That reason is their lack of comprehension and application of knowledge. Besides the fur and love for bananas, monkeys can’t read a book or listen to a talk on flying and then go try it out. We humans, on the other hand, can do this. We learn theory first, and then we apply that theory to reality, shaping our understanding and skill. So, you might ask, what knowledge do we need to get to the bottom of adequately understanding and applying stalls? Read on to find out.

When pilots stall an airplane, we need to know what is happening to our wing and the forces acting on it. For example, if you read NASA’s educational pages on aerodynamics, you will find the figure on the left at the top of this article. This figure is the classic Angle of Attack versus Coefficient of Lift graph with which we are all familiar. In short, this graph says that as AoA increases, lift increases proportionally. Then as we approach the critical AoA, lift peaks and then decreases to the end of the curve. The problem with this graph is the “drop into the abyss” past the point of peak lift. Without saying so, this graph would have you believe lift drops to zero once an airplane stalls. Whoever made these graphs likely didn’t intend for that message to get out and was just done graphing useful data. Unfortunately, this miscomprehension of the data on our part as pilots is just flat-out wrong. Look at the figure in the top right of this article. Believe it or not, lift doesn’t drop to zero post-stall. As seen in the second figure, it can do quite the opposite, increasing beyond the lift achieved just prior to the stall. The problem, though, is that this increase in lift post-stall comes at a considerable drag penalty.

So how do we reconsider our understanding of stall with this information? I like to explain the stall to my students as the “Wing to Parachute Conversion Point.” When we stall an airplane, we go from efficiently creating lift with our streamlined wing to making some lift and lots of drag. This isn’t all bad because sometimes drag can be a good thing. Drag is the force that makes a parachute descend gently to earth. Drag does something similar for us: it sets up a steady descent that keeps us from falling to earth like Wile E. Coyote. This is why the bottom doesn’t fall out from underneath you when you do a stall, in contrast to what you may feel on one of those vertical drop amusement rides. If you closed your eyes while someone else did a stall, you probably wouldn’t feel much at all besides the usual gentle buffet. Now, will drag lower us to earth as light as a feather? Absolutely not, but it’s not the drop off the edge of a cliff many of us think it is. In fact, it sets up a nice nose-low descent, allowing us to ease the stick forward and get the airplane flying efficiently again.

So, in conclusion, if you approach your stall practice with this newfound fact, you will eventually find a few nice-to-know realities.

1. Properly designed and loaded airplanes only stall when pilots pull the stick back to the stalling point.
2. Properly designed and loaded airplanes come nicely out of the stall when we let the stick forward again.
3. You must be aware of your control inputs to know if you are pulling back on the stick.
4. Flying in trim is the easiest way to tell if you are headed for aft stick and an accompanying stall.
5. A proper aerodynamic recovery from a sufficient altitude with sufficient power makes for a nonevent.

Happy stalling!

 

References

https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/incline.html

https://ascelibrary.org/doi/10.1061/%28ASCE%29AS.1943-5525.0000607 

Glider Training

Several years ago, I had the opportunity to take an introductory glider flight with the late Phillip LaBerge, an icon in the soaring community. I knew then I wanted to learn how to soar but didn’t have the time thanks to college and the flying club. A few months after graduation, I had scheduled my training but the Air Force had other plans and I had to cancel as I was moving to Keesler AFB in Biloxi, Mississippi.

After settling in Biloxi, the glider bug bit again and I was pleased to find the Coastal Soaring Association online. Emailing the President, Emmett, I set up my first lesson for the following Saturday, two weekends before Christmas, 2017. Arriving early, only Emmett was around and he quickly put me to work helping to prepare for a small fly-in pancake breakfast. A few airplanes and some pilots showed up soon after and I was already enjoying the camaraderie of the soaring community.

Shortly after breakfast, I was taught how to pre-flight the club’s Grob 103 glider and helped tow it out to Elsanor Gliderport’s Runway 09. The day was filled with training flights for several students but Emmett had enough time to take eight flights with me! Before each flight, he would brief in detail what we would be doing from the back seat of the 103.

Emmett gave me the controls shortly after takeoff on our first tow. He trusted me more than I trusted myself and I was definitely having doubts as we went weaving up, down, and all around behind the powerful Pawnee tow plane. Releasing at 3,000 ft the air was smooth without a sign of thermal generated lift. It was December in the south so this wasn’t much of a surprise. The high overcast didn’t help any either.

As soon as we were off tow, I tried to get a handle on the glider. We went slipping back and forth across the sky as I struggled to coordinate the ailerons with the rudders. With such long wings, gliders have quite the adverse yaw, way more than the Luscombe, and require significant rudder application for only a little aileron.

Gliders, in contrast to airplanes, don’t have a ball or turn coordinator. Instead they have yaw strings which are pieces of yarn taped directly in front of the pilot on the outside of the canopy. The problem with a yaw string is that it goes in the opposite direction in which the ball travels for the same sideslip. It took over three flights to rewire my brain to use a yaw string. Now that I’ve learned both its not difficult at all going back and forth between the two.

After only practicing turns and some closed-spoiler stalls on my first flight or two, Emmett upped the ante on the next flight. Instead of just sticking right behind the tow plane, we practiced boxing the wake--a maneuver where the glider is flown down through the tow plane’s wake and then flies a rectangular pattern around the wake which is quite a challenge when flying in tethered formation with a big old Pawnee.

For the last flight of my first day, we did a simulated rope break, where we actually released at 200 ft AGL from the tow plane. This is an everyday training event for a glider and we made a normal right turn back and landed on runway 27 without incident. By this point, the sun was heading west and it was time to call it a day. I asked Emmett the age-old student pilot question, "When will I be ready to solo?" I got a noncommittal answer and an invitation to come out the Saturday after Christmas.

Thankfully, some of the issues I worried about in flying gliders turned out to be non-events. Emmett warned me against flaring a glider which is a big no-no for an airplane that sits in the level flight attitude with both wheels on the ground. Somehow I was able to quickly break a power-pilot instinct and get nice and comfy with the ground without pulling--something I attribute to learning wheel landings in the Luscombe. 

I was also concerned about misjudging my glide and possibly descending too low to make it to the field on arrival or coming up short on approach. Most power pilots will quickly grow accustomed to the seemingly astonishing glide capabilities of a modern sailplane. Emmett also taught how to approach at half-spoilers which sets you up for a nice tight approach, similar to approaching power off in a typical piston single. The spoiler handle then effectively becomes a throttle on approaching, pushing it forward to reduce spoiler and get more glide while pulling back would open the spoilers and increase the descent. In effect, a half-spoiler approach gives margin in both direction. You can get too steep or too shallow, within reason of course, and still correct for it.

Chomping at the bit to solo, I made the drive out on the appointed day to fly with Roger, another great CFI-G. We flew three flights and then went inside to do the pre-solo quiz and endorsements. Just like my first solo eight years prior, I could feel the difference in the glider with only one soul aboard. Lift off was sooner and I got a little more float, which was promptly killed by a little extra spoiler, on landing. It was a uneventful flight and I got in a few more solo hops before the others were ready to pack up and head home.

Over the ensuing two months, I kept flying to get in my twenty solo flights required for the Glider Commercial Certificate. Bad weather worked against the examiner planning to travel out to give several of us aspiring soarers our check rides so we just kept flying. With each flight, I was learning more and more from the Grob 103. I was getting a little aggressive with my maneuvering, especially enjoying lazy eights and sixty degree wing overs.

Also checking out in the Schweizer 2-33 with Rus, another club CFI-G, I learned some tricks for steep turns and emergency descents. Rus is very intense with his training and holds your feet to the fire both in terms of knowledge and skill. I learned how to use opposing screws on the instrument panel to maintain a perfectly banked steep turn sans attitude indicator. Rus also demonstrated a high speed full spoiler descent. With the spoilers fully open and the nose pushed down to 90 mph, it felt like we were dropping like the Space Shuttle on approach to Kennedy.

Weather and calendars finally cooperated and we prepared for our check rides on the second weekend of February, 2018. Heading early out to Elsanor that Saturday, we met Piet, a glider examiner who travelled from Pennsylvania just to fill the gap for Glider Examiners in our area. An overcast hung above the field but was expected to lift. Jumping right in, we began my oral portion of the check ride which was less than stellar but certainly still passing.

Walking outside, we found the ceiling starting to break apart. Piet put the go-no-go decision firmly in my lap. Not wanting to bust a check ride for illegal operations around clouds or reckless decision-making, I elected to hold. I got a weird vibe from him and the more senior glider pilots around. I wasn't sure if they liked my decision or if they thought I was being too cautious. Piet provided some hinting and commented that the "rope break might happen first." This was the hint I was looking for so I organized the launch party to make the long trek to Runway 27 which was the one farthest from the club office.

I made sure to cover all of my bases and brief Piet in detail on the glider and all safety procedures. I briefed our emergency return plan and got it in my head that we would be turning back for Runway 09 if the rope broke at or above the turn-back altitude. Launching into a stiff headwind, the Pawnee pulled us eagerly skyward. Pulling the handle at a generous 400 ft AGL, I made a right turn but didn't like our closeness and the necessary tight turn to get back to 09.

Going out on a limb, I announced a change of plans to land on the crossing runway with my previous turn putting me on a tight low base. The turn to final couldn't have been at more than 50 ft AGL but Piet never said a word as we got out and set up for the next flight.

By the time we were staged for our second tow, the sky had cleared enough for me to be comfortable with the flight. We talked over what we would do on this tow and I mentioned we would do "power-off stalls" Piet and the other old glider hands each gave a disappointed chuckle. Reaching 2,000 ft, we hit the local ceiling but several large holes were around and we took one nearby.

Only having a few thousand feet of room to maneuver in, we quickly ran through each of the maneuvers. Lift was nonexistent and we were back on terra firma in a matter of minutes. A final tow took us back up to the same hole and we finished our maneuvers just as we caught a small dose of sustaining lift. I played around for a few minutes applying my very limited thermalling skills.

As we approached the field for the final time, I was instructed to fly a no-spoiler approach. On very short final I was given my spoilers back and made a final safe landing. Heading back into the club house we filled out the necessary paperwork and I was an official commercial glider pilot!

My next goal after passing the commercial was to complete the CFI-Glider, CFIG, postehaste. The FAA had different plans thanks to their rule which requires 15 hours PIC in category and class to be eligible for a CFI certificate. This is usually no problem in powered airplanes but in gliders short flights are the norm unless the weather is really cooperating. I needed another twleve hours of PIC and that was going to take some time. Thankfully, soaring is an addictive past time and I spent the next several months having a ball.

Only a month after passing the commercial in February, the Gulf Coast was blessed with a bout of beautiful soaring weather. Cool nights and mildly warm days provide ideal soaring conditions since the earth's surface gets a chance to make drastic temperature changes which means tall thermals in abundance. In addition the coast also experiences sea breezes in the afternoon which brings in cool moist air from the ocean, heats it over the coast which then causes it to rise quickly making cumulus clouds. On one such afternoon in March my little buddy Jefferson and I got to experience both of these conditions in abundance. 

As usual, I signed up to tow gliders in the Pawnee all day that Saturday. Flying the Pawnee never gets old and since the weather was so good the glider guys were out in force. Reports started coming in from exuberant pilots as they were getting lift up above 5,000 ft, a rarity on the Gulf Coast. For once, I wanted to be in a glider instead of the Pawnee. I waited impatiently until my reservation came up in the Grob 103 and also convinced somebody to pull us in the Pawnee. It was nearly 3:00 pm before we were on tow and ready to go. 

Heading south from Elsanor, we passed over a small forest which are usually areas of sink instead of lift. Passing over farmland we felt the pushes in the seat and the lifting of wingtips which hint at the nearby presence of thermals. We took all the altitude we could get from the Pawnee and then Jefferson pulled the release. We started hunting and quickly found a strong thermal which took us from 3,000 to 5,000!

With plenty of altitude we started heading for the coast; only fifteen miles distant. We new that if we made it to the coast their would be no way to return unless the thermals kept up, but we weren't too worried about that. Besides, Jack Edwards Airport and several outlying Navy strips would be available to us if need be.

We passed through more thermals as we made our way but passed them up. For once we didn't need them. Within about a mile of the coast were down to 3,500 ft and searching for a thermal. A small cloud was forming above us and it seemed like a good sign. We headed for it and wow what a thermal! As soon as we centered it we were doing over 800 ft/min and it was staying steady! We took it all the way up into the base of the cloud where we could see vapor actively converting from a light haze into stringy swaths, and then finally join the base of the cloud. We were over 9,600 ft MSL, which turned out to be the clubs altitude record for the year and it took hardly any unusual skill on our part!

We circled in the base of that cloud for over ten minutes watching it form. We couldn't get any higher than where the water was turning into cotton. Several birds had also found the lucky thermal and were enjoying our pirch with us.

We slowly made our way back towards Elsanor, the altitude just gently melting away with barely a care. After some formation with some other gliders we finally pulled the boards out and dropped into Elsanor. It was the end to a perfect soaring day.

The Gee-Wiz Factor: Going Nowhere Quickly

“Pawn to E4.” I can remember back to when I was first learning the game of chess. Lots of discussion was had about how each piece could and couldn’t move. That first day I was overwhelmed with the rules I had to follow, procedure was the only matter on my mind. As far as I knew, you just moved your pieces around the board looking and hoping for an opening to take a shot at your opponent. As you can probably guess, I lost my first several matches that day. In fact, I can’t remember ever winning a match of chess. My lack of practice combined with a complete ignorance of chess strategy has surely led to this string of defeats. Most of us know though, that strategy is a huge part of chess, in fact the strategies behind chess are probably more of what makes chess chess than the pieces and squares on the board.

This relation between procedure and strategy also holds true when it comes to navigation. I can remember back to my first cross country planning lesson and the automatic headache I received. True courses, true headings, calibrated airspeed, outside air temperature, variation, deviation, and the list went on. I was so weighed down with terms and numbers that all I could do was try to follow the procedures and processes I was being taught to fill a navigation log with scribbles. My first cross country flight was a debacle of botched radio calls, missed checkpoints, and chicken scratch addition. On my first solo cross country flight I was terrified of missing my one and only destination that was within spitting of the interstate I had followed to get there. Lets just say it took many many hours of cross country experience to wean myself off of the GPS and finally be comfortable just sitting back and watching the scenery go by waiting for the next landmark to appear over the horizon.

Before we even cover the multitude of factors and procedures involved in cross country planning and flying, we need to first talk about strategy. This is a lost subject in our modern era of the “Magenta Line”. In this and future articles I hope to share some strategies I’ve stumbled upon while out stooging around over the last few years. I think you will find that these concepts will give you some added confidence while out and about on the sky streets.

We recreational pilots are always looking for excuses to go fly. The “exactly 50 nautical mile” airport is of course one of the most sought after destinations, especially if there is food on the other end. We pilots spend a lot of time and effort flying to places that we immediately return from; we don’t leave the home nest empty for long. It’s easy to have the tanks topped off on the rental 172 on a nice day and pop out to some place for a $100 burger. Not much thought required. However, in flying older and smaller airplanes on longer trips, I’ve found more consideration is required before just jumping in and going.

For example, a little problem slapped me in the face two separate times before I finally sat down with pen and paper and figured it out. I used to go out to my glider club all the time in my Luscombe. My tiny fuel tank held just enough gas to legally make it round trip without having to stop for gas. Then one day I had quite the tailwind going out and without much more than a second thought I assumed that boost going out would help get me back even-Steven even with a homebound headwind. It didn’t, and I had to divert for fuel fifty miles short of home. Here’s an explanation of what was happening.

Picture two airports exactly 100 nautical miles apart. Your airplane travels at exactly 100 knots and you need to make a round robin trip for the aforementioned burger. If the winds are calm it’s pretty easy to see that the ground speed both ways is 100 knots and that each leg should take exactly one hour for a total trip time of two hours.

Now imagine you have a ten knot tailwind going out. Groundspeed would be 110 knots and 90 knots on the return. Of course it will take less than an hour going out and more than an hour coming back but how long is the total trip? The first time I looked at this I assumed it would average out and be exactly two hours. So has everyone else I’ve ever posed the question to but in fact this isn’t the case. You may be shocked to find that it actually takes a little longer, two hours, one minute, and thirteen seconds.

To see what I’m getting at here, spool those winds aloft up to fifty knots. Now our outbound groundspeed is 150 knots and fifty knots coming home. At those rates it takes forty minutes going out and two hours coming back for a grand total of two hours and forty minutes. At this point you are probably thinking I’ve broken math or am playing some evil trick with the calculator. Hang in there for two more examples and we will get to the explanation you probably want.

Now consider a ninety nine knot wind for ground speeds of 199 and 1 knot, respectively. Going out takes thirty minutes and nine seconds while the trip home takes one hundred hours. That’s a roundtrip time of one hundred hours, thirty minutes, and nine seconds. That's a long trip for one burger.

Finally, think about the implications of a 100 knot wind. That gives us a ground speed of two hundred knots going out but zero for a return. In pure mathematical terms that means our trip would take an infinite amount of time. None of us have time for that.

What you might notice first from this example, is that a steady wind on an “out and back” cross country never helps, it only hurts. Strangely enough that means the best wind conditions for this type of trip are calm winds. It’s better to have no wind both ways than a steady wind that is a tailwind on one leg and a headwind coming back.

This alludes to the surprising fact that headwinds hurt worse than tailwinds help. To get a grasp on this you have to “start slow”. Imagine your car is having serious issues and can only go one mile per hour. It’s going to take a whole hour to go one mile. Now double your speed to two miles per hour. You just cut your trip time to go one mile down to thirty minutes.

Now let’s take this example from one extreme to another, think of a jet going 500 mph. Push the power up to get 501 mph. You’ve added one mph but that one mph is pretty insignificant to the other 500 mph you already have. On a 500 mile trip that extra mph will save you eight seconds. Basically what I’m trying to say here is that each extra knot you add to your speed gets less and and less significant. Start taking speed away and each knot you lose results in a significantly slower speed.

In summary, we’ve arrived at the first of many important little strategies to keep in mind when out and about. Never assume all things to be equal on a round-robin trip when wind is at play. At the least, on a typical student cross country you may be five minutes late. Unfortunately, when the stakes are higher the outcome could be much worse. In short, always be sure of how much time a potential trip is going to take. Next time we will dig deeper into some more peculiarities of time, speed, and wind.

The Gee-Wiz Factor: Flight Without Lift

For those of us who are air-minded, I think we could all agree that lift, and the devices that create this still mysterious force, are truly remarkable. Without the modern development that led to aircraft and the lift they create, today’s aviators would be like the many generations who came before-- dreaming of being in the air, but left standing on the ground. Thankfully, though, we are surrounded by innumerable inventions which harness the power of moving air. From airplanes and helicopters to windmills, compressors, vacuums, and desk fans, we humans are quite well equipped. 

Hidden at the core of each of these devices is a curious little shape known as an airfoil. These little 2-D profiles are rarely seen as they are the inner cross-section figures of the wings, propellers, and blades we rely upon to power our planes and and invigorate our vacuums. You may wonder what is so special about these streamlined teardrop-like shapes. Some think these shapes are integral to the existence of lift. However, as one of my college professors said, “Even a barn door will fly if you bolt a big enough engine to it.” The answer lies in efficiency. Aerodynamicists have spent over a century investigating which airfoils are best for any given situation. Which are best for slow speed flight and which are best for high speed flight? Which are best when the wings are dirty; which are best when wings are clean? Which are best for the stubby wings of the Space Shuttle and which are best for a skinny winged sailplane? Which are best in the confined housing of a jet engine, and which are best at the tip of a spinning windmill on the plains of Kansas?

Sadly, nobody has definitively answered any of these questions. Nature is far too complex and elusive to give us a confident 100% rating on what shape is best for any particular airplane or situation. The curvature of the bird’s wing gave the curious their first clue as to how to shape a wing. However, from there we have determined where some shapes do better than others. If you took the airfoil shape of a Piper Cub and bent an F-16’s wings to match, it would never be able to break the sound barrier and outspeed its enemies. If you took the airfoil shape of an intercontinental passenger liner and tried to force it upon a Short Take Off and Landing (STOL) airplane it would never lift a fisherman and his gear off a sandbar marooned out in the middle of a desolate river. 

As has been the theme of this series, however, we must ask ourselves how flight would be different with one of the four fundamental forces “turned off” and the other three left to fend for themselves. I can’t even begin to imagine what would be different about air’s behavior if it couldn’t partner with a wing to create lift. However, let’s just assume for the sake of this case that we humans had never stumbled across the idea of airfoils. Would the possibility of flight be completely skunked? To answer this question, we have to go back to the basic physics of what an airfoil accomplishes.

On the first day of one of my last classes in college, Jet and Rocket Propulsion, our professor made a bold claim--in the first five minutes of class, he would teach us all the theory we would need to succeed in his class. “Picture this,” he said. “You’re floating in a rowboat in the middle of a perfectly calm lake. You don’t have any paddles, and you need to get to shore. However, you do have a 50 pound box of rocks aboard. The concept of equal and opposite reaction from school comes floating back and you decide to throw a rock astern. You notice your boat develops a slight forward drift so you keep chucking rocks to the rear. Before long you’ve built up and can keep up enough speed to get to the dock.” He then explained how this story is analogous to how a rocket engine works. It takes fuel and oxygen already on board, burns it, and kicks it out the tailpipe in the opposite direction the rocket needs to go.

Since our class was about both rockets and jet engines, he went on to extend the analogy. “Imagine now you're in the same boat but without any rocks aboard. You still need to get to the dock but this time your rocks are on the dock. You convince your friend to toss you a rock from the pile so that you can use the same trick as the last time. However, you notice that when you catch the rock, the boat drifts slightly backwards, farther from the dock. You turn around and throw the rock back even faster than it was going when you caught it. Your progress is much slower this time. Your friend decides to mess with you a bit and starts chucking the rocks to you harder and harder. His throwing arm is just as good as yours and as long as he keeps this up you won't be making any progress at all.” This analogy connected with how airbreathing jets and propellers work. They take air coming right at the airplane and chuck it backwards harder than it was received. 

Through this roundabout analogy, we’ve arrived at the crux of what an airfoil does. It deflects and influences air to travel in the opposite direction that lift is needed, thus providing the required reaction. Hopefully, you can now see that when speaking of wings, propellers, and blades, the idea of lift and thrust are interchangeable. However, for our purpose of imagining flight without lift, hopefully you can see we still have options. Even if airfoils don’t work, rocket engines are still available to us. Another viable candidate for a lifting force is buoyancy, the same kind of buoyancy used by blimps, party balloons, and boat keels. 

So, with enough imagination, I think we can see a path back to powered human flight. A rocket powered airship would be quite the sight to behold but since both of these technologies exist in their own right, the coupling of them is not too far fetched. In fact, if you go back in history before the Second World War the bright optimism of the day held airships, helicopters, and airplanes in equal esteem. No one was sure which technology would win out.

Sadly, the explosion of the Hindenburg airship in May 1937, and the proverbial explosion of airplane technology in the early days of World War Two, ensconced our world with the domination of airplanes as we know them today. Without the need to trap lifting gasses inside a bag or expel rocket fuel with fury, the wing had found its place in the subduing of air. Alternative forms of air travel have still continued on and have found their own niche markets but the airplane, with the force of ever outstretched wings, will continue lifting us into the future.

The Gee-Wiz Factor: Flight Without Thrust

The nightmare of a B-rated 50’s horror movie has come true. A multitude of King Kong’s cousins have subdued the earth and killed off the entire human race. Since all of the fighting and bloodshed is over, a few of the Kongs have settled in Daytona Beach, Florida. With nothing else to do they head over to the airport and find all of Embry Riddle's Cessna 172s sitting on the ramp. Since they are too big to climb in, they decide to have a paper airplane throwing contest of sorts.

A few planes are picked up and tossed. To their frustration some nose dive over and crash at their feet. Others pitch up steeply and slowly waft down to a point not much farther away. A few glide well and head south for New Smyrna Beach. The Kongs are frustrated with their gliders’ consistency so they head off across the peninsula in search of other entertainment. You can probably guess why some 172s did well and others didn’t. Obviously, the Riddle students who flew the planes last didn’t follow the "After Landing" checklists and left the trim wheels in wildly different positions. Some were left full nose up, others full down, while a few were reset to the takeoff position.

In similarity to our previous articles, the Riddle 172s only had three forces acting on them. In this case the three are Lift, Weight, and Drag. We have found a scenario where one force is noticeably missing--Thrust. This situation brings up a key point in our understanding of the physics and realities of flight: every airplane, no matter how many engines it has, with a pilot in it or not, can be a glider. Some glide well and others don’t.

In the primary training world we hear so often about the “Four Forces of Flight” and “Steady Level Flight.” Yes, it is true that in steady and level flight the four forces oppose each other nicely. Thrust takes care of drag and lift takes care of weight. This, however, is just one of a multitude of situations we will find an airplane in. The Riddle planes that happened to be trimmed just right so as to glide at the toss of King Kong, are also in steady flight. In short, all of the forces on these planes have figured out a way to oppose each other. These airplanes though are in steady and descending flight.

We have two ways to look at the forces acting here, both in the “normal to us” vertical and horizontal way and also parallel and perpendicular to the flight path. Even though the second method is tilted, the two tilted directions are still perpendicular to each other so its a valid way of looking at the problem. Both cases are interesting and yield different insights.

In the vertical and horizontal case, we see that part of both lift and drag work together to oppose weight. We can see that in the middle diagram below with the large blue arrow showing the purely vertical part of lift and the tiny red arrow showing the portion of drag acting upwards. It’s interesting to think that drag is actually pointing upwards here which is a good thing; it's keeping us from speeding up and heading down towards Mother Earth faster than we may like. This is analogous to how a parachute works where the drag from the canopy points straight up. Shifting gears to the horizontal, we see that a sliver of the lift balances out the majority of the drag. This stands in contrast to steady level flight where thrust and drag balances each other out. Lift takes the place of thrust here.

Now from our other perspective we can look at the forces from our tilted viewpoint that is parallel and perpendicular to the descending glide path. We see that all of the lift (blue arrow) is opposed by most of the weight (middle diagram) and that drag is opposed by a sliver of the weight. In short, our “weight thrust” keeps the drag at bay.

Let’s shift gears now to the powerless plane itself. What about the airplane makes it go through the air at a certain speed and at a certain glide angle? As we said in the King Kong example, the position of the trim had a big effect on how well each airplane could glide. Let’s simplify the elevator trim system to a simple stabilator like Pipers have. Instead of a horizontal stabilizer with a hinged elevator and added trim tab, a stabilator is just a single wing pivoted by the yoke and trim system. In this case, we will take three Pipers and glue their stabilators in different positions. The first is full down, the second neutral, and the third full up.

If the Kongs took each of these three airplanes separately and just dropped them from a great height, each airplane would eventually stabilize at a certain Angle of Attack (AoA). Just like a weathervane is turned into the wind so will each airplane hunt for and find the angle of attack at which it can steadily pass through the air. They may waffle around for a bit finding this angle but eventually they will settle out. This AoA has nothing to do with how heavy the airplane is or how slick or rough the surface of the wings and fuselage are. In short, the AoA rules the day.

With the AoA of our three Pipers determined, let's see if we can figure out some more information about how each will glide. Think for a moment about the eventual path of every leaf that has ever changed colors in the fall and been separated from its tree. The moment that bond in the stem is broken, a slow descent for the ground begins. Since leaves are rather large for their weight, this fall through the air is usually a gentle one because each little bit of the leaf’s “wing” is only having to support a little bit of weight. A gliding airplane is very similar. The lifting surfaces of the airplane determine its AoA, as we’ve already discussed, and its weight combines with this AoA to determine how quickly the airplane will pass through the air. Of course, if the airplane weighed nothing it would have no desire to head for the earth’s surface and wouldn’t have any airspeed. If it weighed as much for its size as a leaf does, it would take a similarly gentle and slow downward journey. However, since airplanes are rather heavy for their size compared to leaves, they assume much quicker airspeeds.

We know from our intuition of slow flight here that the greater the AoA the slower the airspeed can be. This is because the airspeed and the AoA combine in symbiosis to generate lift, the opposing force to gravity. Wings have to deflect air to generate lift and the higher the airspeed the more air that gets deflected. The greater the AoA the easier it is for the wing to actually do the deflecting. This works out nicely so that the higher the AoA the less airspeed we need to do the deflecting and so we come up with a nice relationship between the two where we can trade off between airspeed and AoA and still get the same lift.

Now you may be wondering about the glide path at this point and for good reason. This is after all that oh-so-important number in the emergency section of every POH which shows how well your airplane will glide in the event of an engine-out. A crappy glide ratio like 5 to 1 and you’ll be lucky to make it farther than a five-year-old can chuck a rock. An amazing glide ratio like 40 to 1 could win you a spot at the winner’s table of a soaring event. Somewhere in between at 10 to 1 and you’ll have enough glide to pick a decent enough spot to put your Cessna down in the event of a hiccup.

At this point, the airplane can’t help but fly at a certain AoA due to the geometry of the wing and the tail. This AoA combines with weight to pick our airspeed. Drag, as you probably well know, depends on airspeed. The faster we go and the more parasite drag we get; it’s just like holding your hand out the car window. The faster you go the more the wind fights you. The slower we go the more deflecting the wing has to do through AoA to balance out gravity. That AoA works in concert with the wingtips to make wingtip vortices which create Induced Drag. So basically, our airspeed dictates how much drag we will have and the higher the drag, the worse our glide ratio gets.

So, now we have come full circle. We can finally answer the question of why one Riddle Cessna nosedived into the ground right at Kee-Kee Kong’s feet. The trim was set for a low AoA which required the airplane to accelerate to high speed to balance gravity. This high speed put the drag through the roof which gave it a glide ratio worse than a lawn dart. Another Cessna had it’s trim set at full nose-up which demanded the airplane to fly at a high AoA. It didn’t take much airspeed to help out the large AoA to make the necessary lift so it gently wafted down at low speed. However, since it was flying really slow, induced drag dominated and brought this Cessna down just as steep as the last bird we talked about. At least it didn’t hurt Ko-Ko Kong's toes when it finally made it down to earth. And finally, our last Cessna’s trim was set just right so that the AoA partnered perfectly with the best glide speed to overcome weight with lift. Since the airspeed was just right, parasite and induced drag both played nicely, with neither dominating the other. This allowed our final Cessna to glide off into the sunset and crash right into the downtown of New Smyrna Beach, ensuring King Kong would be the honest winner of the official Kong Family Embry-Riddle Sponsored Paper Metal Airplane Throwing Contest.

The Gee-Wiz Factor: The Tale of Talk

“Talk” If this isn’t the most important word in a flight instructor’s vocabulary, it's definitely in the top 10. I am increasingly amazed by the mighty muscle of this little word. From students to newly minted private pilots to flight instructors, the power of the spoken word proves itself over and over again. In this article, I share good and bad speech practices in the cockpit. This may seem like a weird topic at first but I think you’ll find it fascinating in the end.

Picture this: a student and his instructor are beating up the pattern shortly after the crack of dawn. Tension courses through the veins of the moment. Our student has been getting better and better at landings on each lesson. The word “solo” has been mentioned a time or two and the student has even completed his pre-solo quiz and all the required docs are onboard to make a potential solo legal. The instructor is rooting hard for his student; he wants him to solo TODAY! However, once graceful landings have turned to shambles. Our poor instructor just can’t believe his student is messing up so badly; everything was so consistent on recent flights. Reminders for altitudes, airspeeds, and flap settings abound.

Finally, out of frustration, the instructor sits back and utters one word to his student, “Talk.” Our frazzled flyer picks up the proverbial ball and starts talking through what he is doing. Magically, patterns and landings improve. Before long the instructor has been left on the ramp, radio in-hand and a new solo aviator is born! Some amazing events happened the moment the communication baton was passed from the instructor to the student. For one, the instructor stopped stating obvious facts that the student knew existed but didn’t have the mental capacity to fix. Our instructor realized the student was only three seconds behind his order of business, a mere moment in the grand scheme of things that really didn’t matter. When a distraction or case of tunnel vision presented itself, the brain didn’t accept repetitive words but urged the eyes to move back to a continuous scan. In short, our student pilot proved to his instructor that he did know what to look for and more importantly, he found an almost fool-proof way to avoid fixation.

Now, let’s look forward to a few years in time. Our former student now enjoys taking friends up to experience the wonders of flight. He has carried his talking commentary forward from that great first day of solo flight to the present. Onboard the packed Skyhawk are three passengers: one friend who really enjoys flying and two of his reluctant friends. Before they even boarded the airplane, our conscientious aviator took the time to carefully and methodically talk through every facet of riding in a little airplane. Some corny jokes, detailed explanations, and a soothing voice have put our passengers at ease. A ripple of excitement runs through the cabin as seats and belts are clicked into place and checklists are voiced out. Words like “mixture” and “magneto” don’t mean much to our new sky-voyagers but hearing them spoken in a professional calm voice gives them the confidence to know that their pilot knows his stuff.

After the engine fires up and everyone checks in on intercom, our pilot slightly lowers his voice and makes a call for taxi on par with any captain who flies the line for a major. The sights, sounds, and senses of each upcoming event are talked through with a detail and confidence that keeps our passengers in the loop. Before runup they know it will get noisy and drafty for a moment. What would have seemed like a needless and intimidating engine blast to an uninformed backseater is now an essential and understood part of the pre-takeoff checklist. By talking through the procedures, expectations, and senses of flight, our aviation ambassador has won a few more friends for air travel.

Time zips forward again and in the meantime, our student turned private pilot has gone on to earn his instrument rating and commercial certificate. He’s finally ready to prepare for the daunting flight instructor initial checkride. Based on the advice of many other instructors, our soon-to-be teacher of the skies has taken his talking to a whole new level. From his new vantage point in the right seat, our CFI candidate can talk through every detail of every commercial maneuver in minutia and is bound to impress the examiner. On the last practice flight before the checkride, his instructor assures him he will be ready because he talked through every maneuver all in one breath all while maintaining commercial standards. The checkride nerves build, the day approaches, and the new paper certificate is taken in hand. A new CFI is born!

The day finally comes; an intro flight sparks an ember of interest and our new CFI has his first private student. Before he realizes it, they are in the practice area standing a 172 on its tail in power-on stalls. For the first time, our instructor is no longer in direct control of the airplane. In effect, he is flying by voice command. So many little things are going wrong. Corrections are needed here and corrections needed there. The student barely gets a word in edgewise. Postflight discussions aren’t much better since feedback is given to the sweaty student but questions are rarely, if ever, posed in return. In a way, our instructor is all alone in his words.

Just as a craftsman slowly builds and refines his collection of tools over the span of a career, so does our flight instructor as he crafts his toolbox of words. What seemed like simple explanations are broken down and rebuilt as students give their own understanding of what they thought they heard. Elegant analogies, as fine as the chisel of the engraver, are slowly collected and employed. Jokes once shared during taxi are now saved for the walk back from the plane. One of only five needed corrections during a steep turn is carefully chosen and shared. Our flight instructor has gradually learned the power of focused, considerate, and carefully chosen speech. Words are selected for their greatest desired effect on the student. Gone are the days of the firehose.

Despite great strides forward in the tale of talk, our instructor still forgets his lessons learned from time to time. Words fly from his mouth and pass swiftly through his students’ ears but not to the controls. In his mind, things just need to be right and a bundle of words attempts to make it so. However, sometimes all that needs to be said is the word “talk.” The talking stick, so proudly accepted, enthusiastically applied, and refined, is handed from one pilot to the next, its many benefits helping all who apply it.

The Gee-Wiz Factor - Flight Without Drag

How much does wind resistance slow a runner? How hard is it to drag a sled up a muddy hill? How much gas does a rocket burn going through the atmosphere on its way to the moon? What do all of these questions have in common? They all involve a struggle against friction. You may think friction and aerodynamic drag are a total nuisance and life would be better without them but let's take a look at how the elimination of drag would change flight as we know it. Through its absence, you might just catch a glimpse of how influential it is both in good and bad ways. Furthermore, you should also get a glimpse into the world of energy management and how airplanes trade energy back and forth between potential and kinetic energy.

In high school physics I remember the teacher saying things like, “let’s ignore friction here” or “assume the angle is small” or “neglect wind resistance in this case.” I couldn’t understand how you could just disregard things like friction and wind resistance when solving a problem. It seemed that doing so would mess everything up and change the problem. Early in college, I learned that this approach made problems understandable and solvable at our novice levels. We just accepted that we weren’t getting the whole picture yet. In later years, we added these factors back and although we could get more accurate answers, wow! it really complicated things! After solving problems the simple ways and the hard ways, I learned that cancelling factors was an art that required careful intuition. Cancel the wrong factor and you get an unsolvable problem or make-believe scenario. Cancel the right factor and the math would get easier and the result would be close enough to reality to be useful.

Today though, we do want to wildly change the problem from reality. We want to get a glimpse into a world where normal aerodynamic drag doesn’t exist. Let’s be clear though, we are only getting rid of drag. If we got rid of every other kind of friction, our problem would turn into a never-ending slip-and-slide of uselessness. Basically, what I mean is we aren’t going to get rid of the friction keeping our pilot’s shorts on, or the friction that slows the tires down after takeoff, or the friction in the engine. Just to be clear, lift, thrust, and weight are still in play here. So let’s follow along with Cheapskate Chester as he boards his Cessna 150 bugsmasher in the middle of a hypothetical hot summer Drag Drought.

Chester finally has a free Saturday to fly so he wakes up early and checks the Forcecast and sees the Drag Drought is still going strong. No storms with torrential drag drops are on the horizon. Nothing seems out of the ordinary as Chester climbs in and cranks up. His engine idles a little faster than normal since it doesn’t have to overcome any induced or parasitic drag like it used to. He just pulls the throttle back to full idle and doesn’t have any problem. Taxiing out for takeoff is no different than normal. Runup is routine. After making a half-hearted radio call on his cruddy communicator (don’t forget he’s a cheapskate), Chester takes the runway and pushes the RPM up to redline. Expecting a violent neck-snapping acceleration experience, he is disappointed at the usual slow lumbering of the 150 on takeoff. You might think that without drag, the takeoff run would be greatly reduced. However, since parasite drag only builds with speed and Chester is still relatively slow, the total lack of drag isn’t much different than having small amount of drag. Normally, Chester rotates and is in the air by the 1,500 ft marks. Today, he is airborne a hundred feet or so short of them. Not much of a boost.

Despite the abnormally normal takeoff, Chester is really surprised by how high he must lift the nose to maintain his normal climb speed. The vertical speed jumps up to a healthy 1,800 ft/min versus the usual 400 ft/min. Now this is more like it! Since the engine doesn’t have to constantly overcome drag it can devote 100% of its effort to climb.

Even though there is no drag, there is still a limit to how quickly this little plane will climb. Imagine an elevator with two motors that normally pull it upward. Lose one motor and your trip to the top floor will take longer. The usual drop in climb capability still slows his ascent since the engine has less air to breath for making power the higher he goes.

Reaching 6,000 ft in a hurry, Chester decides it’s time to level off and see how fast he can go. He pushes the nose down and keeps the rpm up on the redline. Up at this altitude on a summer day, our friend is usually happy to get 100 mph. The airspeed steadily builds. He blows past 100 mph and into the yellow arc. As the needle makes the last sprint for the redline, Chester reaches over and yanks the mixture back to cutoff and the engine quits. The airspeed settles at 160 mph, just under Never Exceed Speed. With the engine off, we are now just down to lift and weight. Thrust and drag have departed the picture.

Now Chester has never liked being up near redline. His instinct tells him to pull back on the yoke and slow down. He can’t think of any other way to try slowing down so he gives it a careful tug. Everything seems normal as he pulls back; the nose comes up, the altitude starts winding up, and the airspeed drops off. Also being afraid of stall, Chester decides to level off at 60 mph, six mph over the Cessna’s 54 mph stall speed. He checks the altimeter and finds he is at 6,730 ft. He pushes the nose down, the speed builds, and the altitude unwinds. Out of a sense of curiosity he decides to get cozy with redline again and is amazed to find himself back at exactly 6,000 ft with an airspeed of 160 mph. He repeats his climb and descent pattern ending back up at exactly the same ending altitudes and airspeeds as before. He is amazed! This is the first time Chester has ever witnessed the true one-for-one trade of airspeed for altitude!

Despite his amazement, Chester slowly realizes a horrifying fact. He can’t think of a way to get below 6,000 ft without going over redline. If he were to push the nose down, the airspeed would immediately go out of limits. From our vantage point, we can do the math to find out what his airspeed would be back down at sea level and it comes out at a whopping 452 mph. Chester knows his airplane could definitely not take that kind of airspeed structurally, and a landing at that speed would be foolhardy. Thankfully, since he isn’t burning gas, his trusty fuel gauges aren’t imposing a time limit on his flight.

He tries lowering his flaps, slipping, and even cracks his door but finds that none of these tricks help bleed the speed. The distant words of his flight instructor slowly start to creep back into his cranium. “Confess Climb Conserve Communicate Comply” The 5 Cs from lost procedures come back to his memory and so he starts to act them out. He has already admitted to himself that he has a problem. He climbs to slow down a bit and thankfully doesn’t have to worry about conserving fuel. He flips on his cruddy communicator, dials it to 121.5, and lets out a wailing cry for help. Thankfully, nearby air traffic control hears his plea and asks for his position and altitude. They inform him to circle and to wait for help.

After about an hour, Chester notices a large white vehicle off in the distance headed his way. A gargantuan rigid airship similar to those of days gone by climbs to meet him. The radio operator onboard this monstrosity asks him to climb until he reaches minimum airspeed and take up a northerly heading. He passes along his final airspeed and altitude and the airship maneuvers out in front of him. To Chester’s amazement, the airship carefully starts slowing down and the radio operator tells Chester to aim for the large hangar door open on the back of the airship. His 150 is slowly eaten by the airship and wing walkers gently guide his airplane onto the deck.

Overcome with curiosity, Chester immediately asks how the airship is able to slow down and finds that the engines onboard have reversible thrust. This lets the airship speed up, slow down, and also go down without overspeeding. Before long, the airship gently settles to earth at Chester’s home airport, and his Cessna is rolled off the back onto the tarmac. As the behemoth gasbag sails away, Chester’s friend stops by and in conversation asks if he has complied with the latest Airworthiness Directive for the Cessna 150 fleet: the installation of a reversible pitch propeller. Chester shakes his head in dismay as he recounts his recent saga of being stuck at 6,000 ft without a way to get down. If Chester ever gets around to prying his padlocked pocketbook open, he will be able to fly his 150 again without needing a rescue.