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.

The Gee-Wiz Factor: Flight Without Gravity

If you ask any pilot what the four forces of flight are, you are just about guaranteed to get the right answer--Lift, Thrust, Weight, and Drag. I think most pilots have a basic understanding of how these forces work in partnership and against each other to make flight a reality. Outside of this fact though, myriads of other factors take greater precedent and the forces fall back far into our thinking. Basically, in short, most people are not flying around actively thinking about how the four forces are affecting them in the moment. 

However, from the vantage point of the right seat, I’ve had the opportunity to spend plenty of time watching students wage war with and against these forces. In doing so, I’ve gotten to see some incredible realities that I think could be of some use to the interested pilot. To dig into these forces of flight, let's take a somewhat backwards approach by imagining flight in four different ways and each time “turning off” one of the four forces. Through these absences, I think we can gain an immense amount of intuition about how each force works when it is present.

Let’s start our thought experiment by magically flipping the switch on gravity. Imagine if you will, a giant switch on top of a high mountain in the middle of the Pacific Ocean. Through this switch, gravity for the entire planet can be turned on and off. Since no one has ever managed to make it past the many flotillas of the world’s navies which guard this mountain, only astronauts and roller coaster riders have ever experienced zero-g before. The vast majority of people and governments are vehemently opposed to ever flipping the switch. All of life's infrastructure, commerce, and safety depend on gravity. Now let's say in the middle of the night, some terrorist hell-bent on causing destruction makes it through the security ring around Gravity Mountain, climbs to the top, and with the evilest of evil laughs, turns off the earth’s gravity. 

As you can probably guess, the world descends into chaos. However, we aren’t interested in all of the geopolitical, financial, or safety concerns. We are just pilots who want to go fly. The biggest question in our mind revolves around our airplanes. Can they still fly? Let’s follow along with our desperate pilot friend as he attempts a takeoff in zero-gravity.

Despite all of the obvious difficulties of floating checklists, and weightless weather reports, our friend has finally made it into the cockpit and is ready to start. To his surprise, the engine fires right up. His local airport is intent on keeping customers and has installed a magnetic tarmac and runway so that airplanes can move around on the ramp with a semblance of normalcy. Taxiing into position, he holds the brakes, guns the engine, and pulls back slightly on the yoke. The nose easily lifts and with a wave to the magnetism controller, the magnetic runway is turned off and he releases the brakes. The airplane leaps into the air without any ground roll at all since there is no gravity to oppose the upward tug of thrust.

Our pilot quickly discovers that any tugging on the yoke once airborne starts a loop. To travel in a straight line, he must neutralize the yoke so that the wing doesn’t create any lift. Since there's no gravity to oppose the wing, it is only used to bend the flight path in a new direction. Loosed from the burdens of gravity, our pilot pulls back on the yoke until the nose is pointed straight up. His old steam gauge VSI rapidly pegs out and the new digital VSI reads a staggering 8,600 feet per minute which is equal to his airspeed of 85 knots. Reaching nine thousand feet, he pushes the nose over with only his seatbelt keeping him restrained. He shoves the throttle to the firewall and is beaming with expectation. With gravity off, he should be able to go as fast as he wants, right? Sadly his Cessna, which used to be capable of 100 knots, pegs out at only 120 knots. Despite gravity being turned off, drag is still in effect. His speed boost has come from the lack of Induced Drag. Since Induced Drag is a direct by-product of lift, he doesn’t have to pay this penalty when flying a straight line because the wing isn’t lifting. However, when he decides to pitch to a new line or make a turn, the Induced Drag comes right back to bite him and slow him down.

Now, our normally stall-wary pilot decides to see what happens at stall speed. He pulls the power back and eventually shuts the engine down. The noisy rush of air over the cockpit slowly weakens as the airspeed drops. Eventually, his airplane comes to a complete standstill, high above the earth. He never had to touch the yoke and the stall warning never went off. In that moment, he got it--the stall was a result of him asking too much from the wing. When he got slow under normal gravity, he had to make up for the loss of airflow by bending the air which he did have, harder and harder until it couldn’t make the turn around the wing, and the airplane stalled. To test this, he fires back up and gets going again. He gets up to 100 knots and pulls on the yoke harder and harder. His airplane goes into a tighter and tighter loop until he gets the yoke all the way back and the wing stalls. The airplane wobbles and bobbles until he lets go just enough and the loop recomences just as before. He has learned a valuable lesson--the yoke, elevator, and wing can only be used to bend his flight path only so tight. 

Now it's time to experiment with the ailerons. With his new-found enthusiasm, he cranks the yoke all the way over to the left. The airplane starts rolling around and around the longitudinal axis without end as long as he keeps the yoke over. The farther he twists the yoke, the faster the airplane rolls. All throughout this though, the airplane keeps right on along the straight line of flight already established. After more than a few rolls, our pilot friend starts to get dizzy and stops rolling. He decides it's time to try a turn. He rolls the yoke to the left and as the airplane approaches thirty degrees of bank, he applies the opposite aileron to stop the roll. The yoke is neutral now but nothing is happening like it used to. Before, he would just roll to a bank angle and the airplane would turn itself. Not so now. He gives the yoke a tug and instead of just turning, he starts a loop thirty degrees off the vertical. His heading is changing as well as his pitch. He gets back to the level flight somehow and keeps experimenting. He finds that the only way to make a turn without changing altitude is to roll to ninety degrees and then pull. He once again makes a loop but this time it is only horizontal without changing altitude. Before, with gravity, the wing was already supporting the airplane’s weight and when banked to the side some of the lift started the turn, and the rest kept supporting the weight.

Our friend now turns his thoughts from the amazing world of gravity-free flight to getting back down to earth safe and sound. His palms start to sweat; now he wants gravity to help him get back down. Thankfully, there is no wind and the air is calm giving our pilot the best shot at returning to earth. He very carefully works his way down to traffic pattern altitude and sets up on a ten-mile final. The closer he gets, the more he throttles back until at only a mile out, his airspeed is down to a mere twenty miles per hour. Crossing over the runway fence he gently eases down to twenty feet and is down to five miles per hour. The final few feet to the runway are agonizingly slow but thankfully he finds he can very carefully get closer to the runway by gently lowering the nose, descending, and then levelling off again. Two feet off the runway at two miles per hour, the magnetism controller turns the runway back on and he gently settles to earth with a thud. He taxies back to his hangar and ties his plane down tighter than he ever has before, excited to fly another day.

The Gee-Wiz Factor: The Captain of the Ship

Today’s pilots are facing an epidemic. Thankfully, it’s not the one you are thinking of that starts with C and ends with 9. Unfortunately, this disease is much more elusive and insidious and it involves the brain. Let’s take a look back in time and see how long this bug has been around.

Going back to the early days, aviators struggled mightily against frail and ornery machines made of little more than wood, fabric, and crude cast-iron. To join the birds and return again to earth in one piece was a major accomplishment requiring fortitude and uncanny intuition. The ones who made it to old age, were the survivors. Only a few years later, military and airline men struggled against inexplicable weather patterns and cantankerously complex engines as commerce demanded airplanes be put to use in covering greater and greater distances. A lack of information both before boarding and in motion made for some “doomed if you do, doomed if you don’t” decisions. Today’s aviators are currently struggling with the exponential increase of complexity in areas of augmentation, navigation, and communication. What every pilot of every generation has struggled with though, is how to think and use the information he does have effectively. 

Let’s take a step back and consider an analogy that might help us connect a pilot to the duties he performs. Imagine you are on a destroyer steaming across the chilly cloud-strewn Atlantic in January, 1942. What positions were manned on this ship? From a bird’s eye view we might only see the Officer of the Watch, clothed in a drenched rain coat, his eyes glued to his binos searching the horizon. He is the ship's eyes. Moving into the bridge, we will find a navigator bent over a table, straining through thick glasses to figure numbers and check his course line on the chart. The helmsman stands at the ship’s wheel; his feet are throbbing in pain as he is in the sixth hour of his watch. The rolling and pitching seas are keeping him busy maintaining course. One deck below the bridge, a radio operator strains to catch the words of another ship through the stormy static bombarding his ears. Far below and aft, a greasy mechanic battles the hulking and belching diesels which turn the ship’s screws. Each of these officers and sailors play a critical role in the ship’s safe passage, but by themselves they don’t create an effective crew.

Consider though, the duty of the Captain on our ship. His career started off at the Naval Academy where he learned keys to delegation, leadership, and command. Through many tours at sea, he learned the jobs of every position onboard while also learning to lead larger and larger groups of sailors. Twenty years later, he has reached the pinnacle of his career--a ship of his own. His job now revolves entirely around crucial decisions; there is no manual labor. Most people hate to make decisions but that’s all he does now. He might ask himself, “Do I order an increase in power to get ahead of the storm which will burn extra fuel? Do I go around the north or south of the storm? Am I aware of all the contacts the Officer of the Watch has reported?” Pilots are in the same proverbial boat and we not only have to keep our Captain hat on but also switch between all of the other duties of the ship incredibly quickly. In effect, the entire crew of a sailing vessel must live within the head of a pilot.

Even though most airlines don’t use the term “Captain” anymore, the leadership, multitasking, and decision-making abilities commonly bred through military officer training are exactly what flying organizations need in pilots. If they didn’t, any monkey could do the job of a pilot. First and foremost, we need leaders who can make logical, educated decisions under pressure in the cockpit. If this is the ultimate goal of what a competent pilot is to be, we should evaluate how we train pilots from day one to ensure we are meeting that intent.

Consider the reality of the typical first lesson a student pilot faces. Before the airplane has even moved, Radio Operator’s School has begun with calls to tower. Taxiing begins and helmsman training starts in earnest just to stay on the taxiway. A minute or two after takeoff, the helmsman is saturated just keeping his nose out of the blue. He doesn’t even have a clue which direction the airplane is travelling so any navigation training on where the airplane is relative to the airport is completely lost. A few turns, and maybe a stall or two will ring out the helmsman to the point of mental exhaustion. When the nose gets too low, he must race through the bowels of the ship, put on his coveralls, and coax the engine back off the redline. Returning to port is a welcome reprieve for our new student. Sadly, the only position not covered was that of Captain. Applying the Law of Primacy to our first lesson, shows we have reinforced important yet lesser duties over the few that matter most--situational awareness, decision-making, and resource management. In short, through the sin of omission, we have downplayed the importance of the most critical skills a pilot will ever use.

So, the next time you take a student out for their first flight, take on all of the extra duties and start with the student learning to be a Captain. Before starting engines, have the student ask you about completion of the flight plan, fuel planning, weight & balance, and risk analysis. While you taxi the airplane, talk about ensuring the proper taxiroute. Pose the question of what to do in a brake failure or collision situation. As you enter the runway, discuss wind awareness and crosswind inputs. As you switch frequencies to departure, make sure they know how important it is to be on the correct frequency. Before making a turn, ask your student what they should look for before dropping the wing. As you head for the practice area, discuss how important it is to be heading the right direction and the consequences of going the wrong way near restricted airspace. As you gently maneuver, discuss the importance of mentally keeping track of nearby traffic and obstructions. In preparation for slow flight, share the minimum maneuvering speed, and have the student warn you if you get too slow. Once it’s time to head back, give the student the choice of what airspeed to fly. Do they have enough gas to maintain high-cruise? Do they have enough time to listen to the weather and complete the checklist before arrival? As you get closer to the airport, discuss the importance of entering the pattern correctly and the dangers of improper entries. After the flight, quiz your student on what hazards were encountered and how they were avoided. Discuss the decisions they made and the factors that governed them. 

Consider now, your subsequent flights. Keep the overarching focus of each lesson on the primary duties of the Captain. Decision making, situational awareness, and risk management should be the first topics discussed in a debrief. When it’s time to learn a new skill, discuss how you will relieve the student of certain duties so that they can focus on building that one skill. Once the laboratory for that skill is complete, hand duties back over to them. For example, when it's time to do airwork, make sure you both know who is looking for traffic and obstructions, who is aware of the practice area boundaries, and who is handling the radios. Next time, we will discuss which duty is the second-most important onboard your ship and how to teach it.

As your student progresses, analyze their behavior to ensure the Cranial Captain is at his post and all of his crew are working together properly. If not, it's time to take the controls, let your student relax, and maybe crack a joke that the Watch-Officer needs to be court-martialed.

Clear Skies and Tailwinds,

David

The Gee-Wiz Factor: Life of Air

Imagine having a front-row seat at a debate on some hot-button political issue. Words are flowing and emotions are getting heated. Interruptions abound and tempers flare. You are trying to keep up with the conversation but it's all just happening too fast! What can you do to get a grasp of the crux of the argument? Unfortunately, my brain just isn't quick enough to keep up with this kind of discussion. I like to go back and rewatch the debate several times if I can. 

Take for example a debate on kitchen cleanliness. The first time I go back to watch it, I might focus on one person and ask, ”What is the pro-dish-soap advocate thinking and saying?” Then I go examine what the anti-dish-soap advocate is thinking and saying. Finally, I see how these two are interacting with each other. 

This is what we have done so far in examining our airplane in-flight. We first looked only at how the airplane bent and groaned when forces acted on it. We then looked at how air and airplanes interact with each other through Angle of Attack. Today, let's just look at how air responds to the airplane acting on it.

You might be surprised to know that as far back as Archimedes in 250 BC, we have known that fluids are made up of individual particles. The size and interaction of these particles, however, remained a mystery until much more recent times. Today we know that fluids are made up of an ever changing conglomeration of either atoms, molecules, or a mixture of the two. These particles are in constant motion relative to each other and are not stuck together like solids are. In fact, they spend their days playing a constant game of bumper cars.

Let’s follow along with Ollie the Oxygen Atom as he carries out his normal existence up at eight-thousand feet. The clock strikes midnight and Ollie is currently zooming straight up at 1000 mph. In only 50 nanometers he collides head-on with another oxygen atom travelling straight down at 500 mph. Now Ollie starts travelling straight down at 500 mph and his collision buddie is travelling straight up at 1000 mph. What just happened is known as an Elastic Collision and since it was head-on and both colliders weighed the same, they exactly traded speeds with each other. This is, however, relatively rare. As Ollie starts travelling straight down at 500 mph he makes it about 60 nanometers before a nitrogen atom only going 50 mph collides with him at an angle. They both glance off at angles and at speeds only a nerdy physics student could calculate. 

All of this collision business has been going on for as long as Ollie has existed. He has been over the north pole at 60,000 feet, bounced off the wings of butterflies deep within the Amazon rainforest, and even had a fly-on-the-wall spot for the signing of the Magna Carta. Millions of creatures have breathed him in and exhaled him out. He has collided off of his fellow oxygen and nitrogen atoms more times than you could tally using all the pieces of paper on earth. At Ollie’s scale though, temperature, sound, and friction don't really exist, among many other properties we are familiar with at our scale of observation. In fact, between Ollie and his nearest neighbors vast areas of empty space exist relative to their size. In fact, Ollie is only 346 trillionths of a meter in diameter. To put that in perspective, you would need almost 500 million oxygen atoms lined up side by side to make it across the dot of an i on this page. All Ollie has ever known is this constant game of collisions. At this scale, what seems to only be chaos rules.

Today Ollie is in for a treat. He has stood nearly still for some moments and has also gone well over 1500 mph during others. As the dawn breaks, Ollie notes a slight increase in the umph of the collisions he's experienced. He still slows down some, but on average he noted he's been moving faster. To us humans, we would sense this increase in atomic motion to be temperature; the air hitting our skin would be moving faster and we would recognize it as heat. 

At 7:00 am, Ollie starts to sense something strange is happening--he's still getting hit from all sides but he has noticed he's had fewer neighbors and fewer collisions off his right side. He notices he is starting to drift ever so slowly to the right since he is getting the normal punches on his left but fewer off his right. At about 7:04 he notices this drift is starting to get stronger. He has moved an extra inch or so to the right. At 7:06 things get really crazy as this slow crawl to the right rapidly turns into a crowded stampede. Three seconds later things have gotten really violent and Ollie gets a front-row seat to the madness as all of a sudden a blade swings violently toward him. A hard aluminum molecule makes contact and yet another collision is added to Ollie’s list. He surges even harder to the right as the aluminum molecule gets a shove to the left thanks to the swinging follow-through of the prop. They part ways never to encounter each other again.

Through many more random collisions with other oxygen and nitrogen atoms in the ensuing milliseconds, Ollie quickly shares his experience of the blade by giving away some of the energy he received. He still bounces up and down, left and right, and side to side, but overall, he's moving to the right. 

Despite having had a one-in-a-billion chance among his neighbors for a direct collision with what was the propeller of our airplane, only a split-second later Ollie is directed through the never-ending motion of his friends towards the bottom of the wing. He strikes a paint molecule just below the leading edge and gets a kick downward and forward, yet the billions of molecules near Ollie drag him along under the wing like an unwilling country music hater in a Willie Nelson flash mob. Ollie's downward collision from the wing is definitely not unique. In fact, a billion of his closest neighbors also struck the wing, crowding them all closer together to allow a path for the wing to pass through. Being closer together caused even more collisions among themselves. We would recognize this at our scale as a slightly higher pressure. This experience with the wing has forever changed Ollie’s path in life. In fact, he will pass along the presence of the wing in every collision he ever makes after this event. He will band along with trillions of other oxygen and nitrogen atoms that have also encountered the wing and will pass along this information far upstream for other atoms to prepare a path that will allow the wing to pass. This communication is the essence of what allows fluids to create beautiful streamline paths around wings.

To sit back and examine such a scenario seems mind bogglingly complex. Through the chaotic motions and collisions of seemingly innumerable atoms and molecules, a beautiful and consistent flow pattern is created. We have reached the heart of aerodynamics, an incredibly complex study of how airflow can be harnessed to create useful forces like thrust and lift. No human or computer has ever been, or will likely ever be, able to fully predict exactly how these rambunctious particles will behave around a certain shape like a fuselage or a wing. That is what is so incredible about aerodynamics; no full understanding has ever been found and if I can wager a guess I highly doubt one ever will be. 

We must, however, ask ourselves what we have learned from this example.

1. Motion of air is incredibly complex and chaotic on small scales, yet it can be incredibly uniform and orderly on large scales.

2. By means of roundabout communication through elastic collisions, individual atoms share their local understanding of other particles and objects like wings and propellers with other fluid particles at a distance. 

3. Fluid particles always order themselves in a way that is in complete harmony with the laws of nature. 

4. Fluid particles and the greater flow of fluids are never aware of the simplifications humans use to understand or explain aerodynamics. 

If all of these observations are correct, we have to wonder what all of the fuss is about in aerodynamics textbooks. There certainly are some fundamental facts of nature that we use to understand aerodynamics but they aren't the answers to our problems themselves. Historic figures like Bernoulli and Newton gave us some amazing insights, but each of them is just a dim glance at something that is so incredibly beautiful and complex that humans just aren't capable of fully grasping it. So, the next time you hear terms like "Bernoulli's Equation", vorticity, circulation, and Navier-Stokes, know that these are only approximations or parts of something so incredibly complex and amazing that lets us fly and see the world in a way few in all of history have ever been able to witness.

If you haven't been bored to tears yet about fluid motion, take a look at this cool gas simulator by Paul Falstad.

Clear skies and tailwinds,

David

The Gee-Wiz Factor: The Wing and the Wind

In the last article, we discussed how the structure of an airplane behaves and responds to outside forces. These forces included the upward pressure from the pavement on the landing gear and airflow over the fuselage and flying surfaces. We looked more at what the forces did to the airplane internally, instead of how the airplane interacted externally with the forces themselves. Today, let's look at the airplane's interaction with the air through which it travels.

Imagine if you will, what it must be like to be a bird in flight. These flying creatures seem to have an innate understanding of how to maneuver in the air from the moment they first leave the nest. They know what they can and can't get away with when using the air to provide their path. Our winged friends know a whole lot more about aerial maneuvering than even the best of pilots.

Consider though, a poor bird caught out of the roost at night and in the clouds. The poor fellow has no idea where or how high he is or which way he’s pointed. He decides to just keep flying until morning and then hope to see well enough to land safely. In the meantime, all he can do is flap his wings. About the only sense our poor friend can rely on is the rushing of air straight over his beak and back to his tail feathers. Sadly, this is no guarantee that he is flying straight and level and slowly, something in his bird brain senses that he is descending. This is not a concrete sense like his vision could have given him on a clear day--it’s just an inkling. He lowers his tail feathers, and he feels the air shift from hitting him on the beak down to hitting him on the neck. The air flows past him at an angle now instead of from beak to caboose. Our friend has just changed his Angle of Attack (AoA). Unfortunately, this is the only thing he can know for sure.

Now, let's wish our poor feathered friend the best and for the sake of a happy ending we’ll say he made it till morning and broke out of the clouds to find his nest nearby. What we need to take from this story though, is the pure and isolated idea that any heavier-than-air flying machine is governed and limited by its AoA. Try to put away every single property that you might want to see or control. This includes pitch, bank, airspeed, and so on. No matter which direction you are going, whether straight and level, turning, straight up, or slightly down, you will have some AoA. You can be pointed in any direction and have any AoA. In short, only think about the wind and the wing. 

Now we must consider how we control this relationship and the inherent realities and limits behind it. Know that the stick in your hand is purely an aerodynamic control. It is not an up and down control. It definitely is not an airspeed or an altitude control. The stick in your hand controls AoA and that's it. If you need more AoA pull the stick back; if you need less, push it forward. You should have a good idea from your early training that pulling on the stick has its limits. Pull it back so far and you keep getting more AoA. Pull it back too far and the wing now meets the wind at too steep of an angle to get useful lift out of the wing. Remember this can and has happened to many aviators in all sorts of attitudes, not just with the nose being up. Most aviators have never performed anything other than benign straight-ahead stalls at shallow pitch attitudes. It is ingrained in us from early on to not let the nose get too high. The nose gets high and we start to get timid of pulling on the stick in a serious way. Sadly, all of this creates a fallacious link between pitch and AoA. Then, when you start doing aerobatics, or heaven-forbid end up in an inverted unusual attitude emergency all our faulty intuition falls out the window vent. The timidity to pull that came from a nose-up attitude is unconsciously lost. We then haul back on the stick hoping for a miracle. The wing stalls, and what we may have bet our lives on isn't there to save us.

Imagine now you and your airplane replacing our poor bird in our previous example. All you have in the panel is an AoA gauge, nothing else. This, of course, would be a horrible and deadly situation to be in but just imagine for now it's a harmless lab experiment. You are flying along and you pull back hard on the stick for a good thirty seconds. The AoA gauge goes up while you hold it back. Did you pitch straight up? Did you do a loop or a turn? Did you nose up and then pitch forward again? Is up even up anymore? There is no way to know. All you know is that for thirty seconds, the wind met the wing at a steeper angle than it had before you pulled back. Now you push forward on the stick and hold it. The needle on the AoA drops to zero. The air rushes right over the nose of your plane--straight from spinner to tail, leading edge to trailing edge. You push even harder forward, the needle plummets below zero. The air now rushes at the upper camber of the wing and parts the trailing edge heading for beacon light on top of the rudder. Have you done an inside loop? Plummeted straight toward Mother Earth? Pointed straight up? There really is no way to tell.

The moral of this story is that the wing can never meet the wind at more than the critical angle of attack. You could be completely upside down and turning but if the AoA isn't critical yet, you will have control relative to the air. In essence, the air can still be used to bend and shape your flight path. What we need then is a consistent way to know when we are near or at the stall.

The avionics guy's answer to this problem might be an AoA gauge. These are nice to have but are incredibly expensive and rare in GA so they are off the table as a blanket option. Some might say you could rely on an airspeed indicator for this. Sadly, airspeed indicators are pretty lousy at universal stall prediction. Do you know the stalling speed of your airplane inverted at sixty degrees of bank? Good luck calculating that one. We need something else and sadly money can't just purchase it new out-of-the-box.

Let's shift our thinking to the loose nut who is death-gripping the stick. You would be amazed how many pilots get busy and don't even realize they are pulling the stick back dangerously far. Their brain is on autopilot and just trying to keep the attitude "right". This pilot is only thinking about his relationship to the horizon, not the air he is journeying through. Believe me, it happens and more frequently than we might like to admit. In a car, it's incredibly easy to stay on the road, you just keep your eyes forward and turn the wheel as the curves come and go. Try to think about the air as a road, not the land beneath you or the horizon ahead of you. This invisible road can only have turns so tight, and the grades only so steep.

Thankfully, there is an answer to our problem. We need to get our brain into the feedback loop with our arm and hand as they are pulling on the stick. In short, you need something telling you how far back you can pull the stick without stalling out. This is what replaces the needs for instruments or numbers in our head. Start trying to feel for cues in your arm and hand muscles as you are pulling; learn to recognize when you are asking for more from the wing. Know what your arm feels like along your side or on your leg when you've got it back at or near the stall. You may or may not get buffeting cues depending on the airplane. Know what they feel like at 50 knots and 100 knots; in other words, mushiness in the controls is not a guarantee you are near stall. Practicing with many different attitudes and airspeeds will let you build this universal awareness of how much is enough and how much is too much. 

One of my favorite ways to practice is to go up and do high-speed turning stalls. Climb to a healthy altitude, bank steeply, and then pull as hard and as quickly as you dare to enter a turn. It's kind of like the Price is Right for Pilots. The person who pulls the most without going over, wins. Keep in mind this is all about how far back you have the stick. You don't need to measure it with a ruler or find the magical amount of pull to induce a stall. That's the wrong way to approach this. You just need to know how much you've been pulling on the stick and if it's back or not. Then, when you are in the pattern and trying too hard to crank it around the base to final turn, a little voice will travel up your arm to your noggin and say, "Woe is you if you pull back anymore". 

Now for a few side-notes. It amazes me how basic and limited the Private Pilot standards are for stalls. Advanced stalls, the ones that will get you in serious trouble, only have to be demonstrated to the student once. They don't have to practice them and most don't want to! The average new private ticket holder probably only has twenty or thirty stalls to their name. That's hardly an introduction, let alone mastery. Go out and do twenty or thirty stalls in one flight. Your confidence, awareness, and familiarity will vastly improve. Keep track in your logbook and set a lofty goal of say a thousand stalls. Track them like you track your flying time; you will want more. Also, if you don't have a g-meter stay below maneuvering speed. If you do have one put the airframe to the test and venture out beyond the false security of one-g and maneuvering speed. You will be amazed what these flying machines can really do. The same principle applies to AoA gauges; they let you know right away how much you've used and how much is left. You'll be pleasantly surprised at how aggressive you can get and yet stay within limits. Finally, keep in mind that not every airplane can be flown by feel like we are used to in GA. Here again, consciously knowing you are bringing the stick back can be a help in addition to AoA gauges and stick shakers.

Clear skies and tailwinds,

David

The Gee-Wiz Factor: Airplanes Don't Have Eyes

Series Introduction

Over the past four years of flight instruction, I have witnessed many students struggle mightily, at least at some point in their training, with understanding how to control the flying machine they are trying to master. Having also flown with many seasoned pilots, I have found no shortage of backwards, inefficient, puke-inducing, and sometimes downright dangerous, control behaviors. At the core of this problem lies a mixture of some simple physics and applied aerodynamics known as the mechanics of flight.

From my first week in the right seat until now, I have wrestled with how to teach the mechanics of flight to my students. What rules of thumb should I use? What information is fact versus fiction? What level of depth is too much and what is not enough? Why teach aerodynamics if we don't apply the information? The answers and implications to these questions are, in my opinion, monumental. 

What we teach and reinforce in the cockpit, lays the groundwork for what will hopefully be many decades of flying whether for personal enjoyment or professional application. As flight instructors, we have an immense responsibility for the future safety of our students. Some of this responsibility shifts to the newly-minted private pilot to continue self-study and maintain proficiency however, the majority of it still lies in the first lessons we provide as educators.

It is my opinion that we should teach the facts of the mechanics of flight for all they are worth. They should be recognized as complex topics requiring careful study. They should not be ignored or simplified to the point of irrelevance. 

Unfortunately, the facts governing the mechanics of flight can seem unreachable, complex and unintuitive; on top of that they are often buried in the stilted and awkward language of academic writing. Take a glance into books with titles like Fundamentals of Aerodynamics and Aircraft Performance and Control and you will be met with dense paragraphs of mathematical minutia and few, if any, helpful diagrams or pictures. Theory is presented instead of application. Anyone interested in this meeting of the practical with the theoretical must understand both worlds well enough to play a "Where's Waldo?" in the textbooks.

Back in the old days of flying, the flying community knew a whole lot less about many factors governing flying than we know today. This included weather, aerodynamics, weight and balance, radio communications, etc. What I like about the old literature from those days is that when facts were well understood, pilots were expected to read, understand, and apply that knowledge to good effect. My favorite example of this is the Pilots' Powerplant Manual published by the Civil Aeronautics Administration in 1940. This book has more useful information in it about engines than what most A&P mechanic students are coming out of school with these days. If a pilot of that era were to have ingested and comprehended that book, they would have been a one-man army of engine comprehension. That is the kind of guy I would want up front in a DC-3 over some patch of inhospitable terrain at night and in the clouds with an engine issue.

Sadly, even though our collective knowledge of aerodynamics, performance, and control accelerated exponentially through the 20th century in the engineering world, the pilot community has remained in the dark on what is actually happening when we as humans interact with flying machines. There is a little-known, yet beautiful world of understanding that exists between the flying and aerospace engineering communities and is within easy mental reach of anyone smart enough to solo an airplane or pass a college aerodynamics class. 

The purpose of this series of articles is to share the amazing insight a pilot can have about how their airplane flies and will find this information can entirely change the way they control their airplane. Some of the information may or may not have practical use, but that's the cool thing about something free -- you can take or leave it at no charge! That's why I have entitled the series; The Gee-Wiz Factor.

Airplanes Don't Have Eyes

Imagine with me for a moment what it must be like to be born blind. With no ability to sense light, the beauty and detail we are all familiar with would be only a mere concept. Small objects could certainly be felt and maybe some sort of mental "picture" could be built. However, descriptions of larger structures and landscapes would likely have very little meaning. How close would your idea of the horizon, the sky, and land be to reality? I can imagine that if someone born this way were to gain sight, the larger world would be of entirely different proportion than they might have expected. Houses may seem smaller than anticipated, and skyscrapers enormously larger than expected.

The world the blind do live in however, is richly full of touch and sensation. Without a sense of sight to get in the way, these people must have an incredibly refined sense of force and pressure. The slightest air draft, brush of a book's page, or change in seat pressure when going around turns in a car is likely much more noticed and analyzed. 

If you will permit me, let's personify our airplane and imagine what it must be like to experience flight from it's blind perspective. Resting on the ramp, the tarmac presses up into our airplane's wheels as the force of gravity maintains it's ever-present pull upon every molecule of our plane. This pressure on the tires bulges them slightly, transmits this force to the axles, and up through the landing gear which bends slightly to provide the necessary resistance. This bend of the gear slightly twists against the fuselage mounts and stretches the bolts holding the two together. From here, the loads transmit into the aluminum structure and spread like a drop of food coloring in a glass of hot water to the entire airplane. Some parts experience enormous compressions, stretches, twists, and bends. Others feel only a slight reaction. You can be assured though that every part feels something. Our airplane is at rest and only it feels its own aches and pains. The cloud drifting overhead, the sun setting in the distance and even which direction is "up", are all unknown to our airplane.

All of a sudden, a door opens and in a moment extra forces have been added. Pressures run in an instant, down through the seats, across the floor, around in circles within the bulkheads, and down through the gear and tires to the tarmac which now bows ever slightly more into the earth beneath. Our airplane lets out a slight metallic groan; maybe it's only a maintenance technician checking the tach time. Suddenly, electricity flows from the battery, through some circuitry, and into the starter. The engine gallantly resists but is no match for the starter as the prop starts to swing. The conditions are just right in the engine which fires right off. Waves of vibration jump from the engine case, through the rubber mounts, to the engine mount, and finally into the airframe. Every single part of the airplane is now in rhythmic vibratory motion; every rivet and fastener is under constant assault to let go. Our airplane sighs and mutters to itself, "Here we go again."

The throttle cable feels a shove, and transmits the push to the engine which responds with more rapid rotation of the prop. Gooey wax particles on the surface of our airplane feel an increase in collisions and the slipping of tiny air molecules passing over that had just gotten kicked in the pants by the prop. The wax passes off these forces to the paint beneath, which passes it off to the primer, which passes it off to the aluminum below which then shares it with the rest of the structure. By kicking these air molecules backwards, the prop gets an equal and opposite reaction forward which strains against the crankshaft, which passes it off to the case of the engine. The same path taken by the engine's vibration is also taken by this forward tug and over a short time every molecule in the airplane is made aware of the need to move forward. Suddenly, the wings start to feel the collisions of billions of air molecules over and under their outer skins and transmit the message to the landing gear far beneath which no longer have to wage the constant fight against gravity. The rush of air over the entire plane surges faster and faster. More and more reaction is felt through the skin, which transmits to the rest of the structure, which after a while is exactly balancing out the forward tug from the propeller. Our airplane has no idea how fast it is going, which way is up, or how high it is above the ground. All it knows is that the tug-of-war on it's bone structure has stabilized and it only has to worry about the constant ache of vibration.

This is all that mechanical devices like airplanes understand; forces and their accompanying stresses. These are the only commands an airplane's bones and flesh can reply to. A force is enacted, internal stress is created, and in the absence of an opposing force, the airplane surges through acceleration in the direction of that force. Sadly, we as visual humans, have little natural capability to grasp this dark world devoid of everything except mechanical forces. Someday, I would love to put on a magical pair of glasses which would let me see into this mysterious world of actions and reactions. Yet, for the moment, diagrams and drawings in textbooks must suffice. 

In the meantime, start thinking of the airplane's controls as force controllers. The elevator doesn't merely raise and lower the nose like a grocery store grapple game stick moves the grapple from one position to another, it adds and subtracts from the forces at play upon the airplane. If this tug-of-war of forces is dominated by the force you have introduced, changes will happen. More about this battle next time.