For Those Who Are Serious About Mastering the Power-Off 180° Accuracy Landing
Introduction
Picture this, you just got your private pilot’s license and a friend of yours invites you out to fly gliders. You like having the engine up front but decide to go anyway and give it a try. After a nice flight soaring in the thermals you find yourself in the landing pattern and are surprised to see the pilot moving a handle on your left side forward and backward as you come down the approach. Every time you seem to be low the handle goes forward, the glider surges forward and the glide gets better. When you sense that you are too high the handle comes back, the glider slows, and the glide steepens. You’re perplexed that a glider could have a control just like the throttle on an airplane that seemed to accomplish the same task yet didn’t have an engine. You wish you had something like this magical handle when the examiner failed your engine and you almost didn’t make it into the field you chose for your emergency approach and landing simulation.
The Difficulty
Fast forward a few years, and you are preparing for your commercial checkride. The Power-Off 180° Accuracy Approach and Landing has been giving you fits. You’ve had a few nice days when the winds were calm, you were the only plane in the pattern, and you were hitting your point almost every time. However, you’ve also had a few days when it's been windy, gusty, bumpy, and busy; and it's been a mess. You are worried that if the checkride is anything like one of those days, chance and luck will decide your fate.
Thankfully though, with the right knowledge and practice you can learn to be incredibly consistent with your power-off approaches. Let's start by making a quick review of the commercial requirements and the real-world needs for the power-off approach. The Commercial Pilot Airman Certification Standards (ACS) CA.IV.M.S8 states,
This may sound like a tall order to fill. Not only does the airplane have to touch down in a narrow window but also has to be in a flare attitude over the centerline in a proper sideslip as needed to fight the wind. You may wonder why the FAA would ever require this and unfortunately they don't elaborate much in either the ACS or the Airplane Flying Handbook (AFH). The AFH vaguely attempts to give an answer in stating,
In my opinion, the FAA is beating around the bush here and is trying to say that a pilot needs to be able to put an airplane anywhere he chooses with great accuracy under the stress of an emergency engine failure. Let’s face it, the vast majority of runways are relatively long, and the landings pilots will make on them are almost never made as spot landings. However, I can speak from personal experience that the majority of possible emergency landing spots are smaller and more confined than most pilots would prefer. I had to put a Grob 102 glider in a 1,200 ft cow pasture with a cell tower and pine trees on one end and a barbed wire fence on the other. Thankfully, lots of previous power-off approach practice in my airplane, and lots of glider training helped me safely get that sailplane down in the first four hundred feet of the field and stopped three hundred feet short of a fence. Unfortunately, bad decision-making put me in a place where it was literally either the tops of pine trees or the field I ended up using. Hopefully, you will never find yourself in this kind of situation, but unfortunately we can’t hope away the possibilities of tough emergency situations. The best course for you to follow is to prepare and practice for power-off approaches like your life depends on it. It may very well someday.
Now let's take a look at how patterns and approaches are typically taught to see if these methods help or hurt learning the power-off approach. As a new pilot, I was taught to use landmarks on the ground to lay out my approach. At one airport in particular I remember being taught, fly down this railroad track on downwind, be at 800 feet over the pond and turn base, head towards the red barn, be over it at 500 ft and turn final. In short, I was taught to use these kinds of external ground references to make their patterns more consistent. In transitioning to the Cessna 172 as a new pilot I was also taught a by-the-numbers approach procedure. On downwind, trim for 90 knots, at the numbers pull carburetor heat, reduce power to 1500 rpm, add 10° of flaps and slow to 85 knots. Turn base and add 20° of flaps and slow to 75 knots. Turn final, add 30° of flaps, and slow to 65 knots. You most likely learned something very similar. I don’t know about you, but I was also taught to use the PAPI/VASI lights to fly my final approach. Too many red lights and you are low so add power. Too many white lights and you are too high so reduce power. Flying the lights really was simple and I was glad to have them there.
Unfortunately, all of the paradigms we just mentioned completely remove or complicate the underlying skills behind repeatedly successful power-off approaches. These critiques aren’t directed at any instructor or school in particular and are more a critique of the whole community. All too often a new pilot learns these techniques and procedures and then comes to rely on them. He needs his landmarks to make it around the patch. If you take him to a new field, his patterns will be a mess until he finds new landmarks and that normally takes several laps. He also relies on the configuration procedure to arrive on final at the right airspeed and altitude to make an approach. Unfortunately, at the same time, the added complexity of the procedure burns brain cells and limits his situational awareness and judgment. In short, he is mentally buried in making the airplane behave like the pattern diagram demands. Finally, if the PAPI lights are out of service, our friend struggles to keep the airplane on the right glide. His glide problems have to get pretty bad before he realizes he is off the right path.
Please don’t think that I am entirely against landmarks, multi-step pattern procedures, or PAPI lights. They all have their place but I think we have come to over-rely on them to make good approaches and landings, especially the power-off variety. In this primer, we will discuss the underlying knowledge and skills that seem to have been forgotten over time, and I think you will realize that you don’t need many of the crutches we have just discussed.
What Makes a Good Landing?
If you have perused aviation websites, aviation books, and YouTube enough, I’m sure you have come across articles and videos that claim to have the magic sauce to making better landings. Every self-proclaimed expert has their own opinion of “if everybody did this one thing their landings would be amazing”. Unfortunately, approaches and landings are so complex that one technique or trick will never help you be consistently good in every situation. Many of these techniques help people somewhat in that they help fix blatant mistakes, like not focusing down the length of the runway in the flare. Sadly, there is no one magic solution to making good landings. Instead, a very complicated yet correct solution lies in one simple statement.
A pilot must be able to consistently account for every internal and external factor affecting his airplane in the landing environment.
This is far easier said than done, but in this primer we will discuss the many factors in detail that war against your attempts at good power-off accuracy landings. To put it another way, we are going to go do some serious intelligence and reconnaissance against our atmospheric enemies to know how to fight them when the battle comes.
Digging Into Factors
Internal Factors
Glide Angle
The first issue we need to address is a matter of terminology. We need to get rid of the idea of being “too high” or “too low” on approach. Instead, we need to replace them with the steepness and the shallowness of the approach. What really matters on approach is the angle at which the airplane is gliding, not if you are at 500 ft when you should be at 550 ft at that exact moment. When you are approaching you are always getting lower, so to speak of high and low is relative. Just call it what it is, glide angle.
Now we need to sit back and do some theorizing. Believe it or not, it is up to you to decide at what glide angle you fly your approach. Now I’m not talking about doing a bunch of equations so that you can say that you approach at exactly 6.24864°. However, you should be able to weigh some basic factors to decide upon a configuration that gives a good angle of approach. What is a good angle of approach you ask? Well, it is my opinion that your approach angle should be as steep as is reasonably possible and here’s why.
Picture if you will, somebody shooting a rifle at a paper target, however, the weird thing is that the target is mounted on a door. When the door is closed, the target is fully in view and perpendicular to the path of the bullet. However, when the door is opened, the target stands at an angle to the shooter. With the door wide open at 90° the target disappears. What good is this you may ask. Well it's a matter of error. When the door is closed, and our shooter shoots yet makes a little error, maybe due to the natural sway of his hands, his shot will be off slightly on the target. However, if the door is opened almost all the way open, just barely enough so that he sees the target warped, yet misses by the same amount, his shot will completely miss the target.
To put it another way, imagine two warplanes tasked with sinking an enemy warship at sea. One airplane is a dive-bomber and the other is a fighter which strafes the target low across the water. Both release their bomb at the same distance to target, however, the dive-bomber dives from 80° above the horizontal while the fighter plane approaches at a very shallow 5°. If both pilots make identical mistakes in aiming at the moment of release, the dive-bomber may only miss by 10 ft while the fighter will miss by over 110 ft. This is a huge difference and only because the dive bomber approached from a steeper angle.
We can’t dive-bomb our point like a dive-bomber could since the best glide angles for typical light airplanes live in the 5° to 10° range. However, steepening the angle from just 5° to 7° will in theory reduce potential aimpoint errors by over a third. Also, the steeper the angle, the shorter the approach. The shorter you can make your approach, the less time and distance external factors like wind and thermals have to disrupt your glide. Now the shorter the approach, the tighter and closer your approach has to be. The absolute limit for this is the 180° turning radius of your airplane. Basically, in this case you would have no base leg or straight final. You would be turning the entire approach, and I can speak from personal experience that these 180° turning steep approaches are the most accurate if you have the mental capability to keep up with them. It’s like dropping a rock into a bucket instead of tossing in a rock from 50 ft. Now if you’ve never done one of these before, or you’re an instructor and you don’t think your students could hack these approaches, you are wrong. If a pilot can’t be trained to do one of these safely, he shouldn’t be flying. The reason being that strong winds can put you in a position where this tight, turning, steep approach is required.
Let’s shift gears now and think about how the airspeed we choose affects our glide angle. If you do the math, you will find that airspeed correlates with drag through the drag polar, and that drag directly correlates with glide angle. In short, you choose an airspeed that matches a certain drag on the drag polar, and the higher that drag is, the steeper the approach will be. The shallowest you can be, of course, is at Best Glide Speed. Now most people think that Best Glide is obviously the best speed. However, this isn’t the case for numerous reasons. First of all, it goes against our steepness argument. Second, it's a bad place to be because glide performance gets worse if your speed changes either faster or slower. If you get faster, drag goes up, and you come down steeper. If you get slower, drag goes up and you come down steeper. That’s not a good place to be.
What about airspeeds farther away from Best Glide? Very slow speeds, like ten knots or more below Best Glide, are not good for numerous reasons. We all know getting slow in the pattern is dangerous in regards to loss of control, stall, and spin. You also end up with high sink rates which can only be recovered by lowering the nose. This momentarily increases the sink rate until drag is reduced and better glide performance is achieved. Flying in the Region of Reverse Command also has a downside in that airspeed is more inherently unstable. If, say, windshear slows you down, the higher drag from going slower makes the airplane want to slow even more. If you get an uncommanded airspeed increase, the decrease in drag helps allow the airspeed to creep up even more. High airspeeds, like ten knots or more above best glide, are also tempting but they have their own downfalls. High speed approaches are steep, which is good, but they also bring more airspeed to the table when it’s time for roundout and flare. More airspeed means a longer roundout and flare which adds to the uncertainty of your touchdown point since there's more room to screw up or be screwed by something like a gust or runway thermal. In anything with more wing-loading and weight than a Cessna 172 you also get into sink rate recovery issues where you may run into stall before you get the vertical speed under control.
You may be befuddled at this point. If Best Glide Speed isn’t good, and neither are excessively slow or fast airspeeds, what is left? In my opinion, Best Glide Speed plus five knots is the closest thing to a universal best approach speed. In a Cessna 172, that's 70 knots or 80 mph. At this airspeed, you have a steepness advantage over Best Glide Speed. You also have options in that if you start to come up short, you can slow to Best Glide and get better performance.
Speaking of flaps, let's shift our discussion to how they can help get a steeper approach angle. Of course, flaps do modify the wing’s lift in weird ways, but we don’t care about that. Flaps always add drag and more drag means a steeper approach. Since we want a steeper approach and options to regulate it, a medium to medium-high flap setting is, in my opinion, ideal right from the power reduction. In a 172, that's 20° of flaps. If you need to steepen the approach you still have one more notch to go. If you’re coming up short right from the get go and still have several hundred feet of altitude, a careful flap retraction can increase the glide. You may or may not get away with this on a checkride since the AFH specifically says to never retract flaps on approach. However, if you are in a real emergency and are coming up short and don’t have any other options, a flap retraction might save your bacon. One of my favorite approaches in older 172’s is to apply full 40° flaps at the numbers and then immediately turn and try to make it to the runway. About the only thing steeper is the Space Shuttle on final for the Cape.
Airspeed Consistency
Now we need to settle on how consistent we need to be in our approach when it comes to airspeed and approach angle. We talked earlier about how lots of students learn methods where airspeed and flap settings change on each leg of the approach. From what we know now let’s think about how these approaches would affect glide consistency. How does the glide at 85 knots and 10° of flaps compare to 75 knots and 20° of flaps? Unfortunately, there is no easy answer to these problems. Your glide could be changing on every leg and that makes it very difficult to judge and rely on your glide. I think the military has gotten it right here. Both the Navy and Air Force pilot training procedures call for making just one configuration change at the numbers and then students just have to focus on keeping the approach consistent all the way around.
Now we also need to decide how precise we need to be in holding our desired airspeed. I’ve found from personal experience and after some digging into drag polars, airspeed needs to stay within two knots to ensure sufficient consistency in the approach. That’s a tough order for many students to attain and is well within any airspeed tolerance in the Commercial ACS. Anything more than two knots variance from your chosen approach speed changes drag, and the resulting glide angle change is enough to cause trouble in judging the approach.
Reserve Energy
Every good flight plan includes a fuel reserve. We are all very aware of the day and night requirements for carrying extra fuel to have options in case things don’t go as planned. Nobody likes having to use the reserve and in actuality it is quite a scary event if you do. However, a fuel reserve is really just an energy reserve. We can apply the same principle to any phase of flight and the power-off approach is no exception. With power at idle, we are only left with two options for a reserve, glide angle and excess airspeed. It should be pretty obvious that carrying extra airspeed is not a good option. We are left with glide angle and that means to have an energy reserve, we need to fly an even steeper approach than we have talked ourselves into at this point.
By flying an even steeper approach than we need, we are flying above the path we would normally be on. Then when we encounter some external factor that starts trying to kill our glide, we have some buffer before we have no way of making it to our point. If we carry the reserve down to the aimpoint, that extra energy will turn into extra distance in the roundout and flare which we definitely don’t want. We need a reliable way to get rid of this reserve. The only reliable way I know to efficiently dump energy is the forward slip. I’ve found an approach that doesn't need to burn any of the energy reserve requires about a three second full rudder forward slip. This is why I tell my students,
The Roundout and Flare
As we’ve already alluded to, we want the shortest possible roundout and flare possible. Of course, the slower we are, the shorter the distance it will take to decelerate to our touchdown speed. Also, the more flaps, and drag we have, the shorter the distance our deceleration will take. If your energy budget will spare, full flaps on short final will help in this regard. The shorter we keep this transition both in terms of time and distance, will help minimize the detrimental weather gremlins that are out there trying to keep us from making our point.
Ballooning can also be a major issue in landings and especially in high stakes spot landings. Most people are unaware though, that airplanes lose their capability to balloon as they start to encounter significant induced drag at low speeds. The theory behind this is rather complicated and has to do with a peculiar airspeed known as Minimum Sink Speed, flap drag, and ground effect. When these factors are combined and analyzed they reveal an airspeed that lays the threshold for flaring. Above this speed the airplane is very likely to balloon. Below this airspeed, pulling back to flare induces so much drag that any attempt from the airplane to climb is firmly stopped and countered with an almost unconquerable descent. I’ve found that this airspeed lies around 45 KTAS or 50 KTAS in a typical Cessna 172. In short, patience, height, and a smooth steady rearward pull on the yoke is needed to slow the airplane sufficiently before it’s time to really haul the nose up in the final flare for touchdown.
One of my granddad’s favorite flying stories involved a little Aeronca Champ taildragger that he was flying solo on a blustery coastal California day. My granddad was using all of the money that he was earning as a radio operator in the Navy to put himself through flight school. As he came in to land on the last pattern of the day, the wheels touched down before he had gotten the stick all the way back to settle all three wheels on the runway. Then a stiff gust swept across the runway and infused the wood and fabric wing of the Champ with more lift. According to his telling of the story, he was ten feet in the air before he knew what was going on, but thankfully he slammed the throttle wide open. The 65 horses up front jumped into action and hauled the little plane back into the air before the gust had a chance to die and drop the plane back onto the runway ungracefully. Thankfully his next landing was better and he lived to tell the tale to all of us grandkids. The moral of this story was that an airplane is not done flying until it is on the ground and the wing is stalled. Any contact with the runway before the stall-warning sounds and the nose comes up is a dangerous flat landing.
One of my most fiendish impulses is to haul the yoke back on a poor sweaty student who has landed fast. The airplane then leaps a foot or two back into the air and settles in a full-stall nose high landing. Most are bewildered that I would dare steal a second landing for the logbook from their first attempt. However, it goes to show that an airplane is not done flying until the wing has given up the ghost of lift by way of an aerodynamic stall. Make sure you aren’t letting your airplane touch down until it is completely out of flying potential. If you are picking your aimpoint and touchdown point well, the last three seconds before touchdown should feel like a Hail Mary Pass as the airplane skims just above the surface before settling into the touchdown zone.
External Factors
Up till now, we’ve been looking at factors we can control. It’s time once again to shift gears; we now need to look at outside factors that we have no power to control. We can, however, look at how to recognize and account for these outside factors in a way that still lets us make consistent approaches.
Wind
If a student and I are on downwind and I ask them what the wind is I usually get a recitation of wind speed and direction from the last AWOS they scribbled down. Sadly, this isn’t enough information to be aware of the full wind pattern in the vicinity of the airport. Let’s start by nailing down what we can know. First, keep in mind that every wind value has an accompanying height or altitude at which it was taken or forecasted. The first and easiest value to find is the local wind from the AWOS/ASOS or ATIS. Most weather reporting systems read the wind off a tower or pole which is usually thirty to forty feet off the ground. We can also check the wind forecast at altitude, the lowest of which is usually 3,000 ft AGL. Theories from fluid mechanics tell us that the wind speed of any fluid in contact with a solid surface is zero at the surface. You might think this sounds ridiculous but keep in mind that the oxygen and nitrogen atoms that make up air are crazy small.
We now have three wind values. Zero at the surface, some speed and direction from the local weather reporting system at some height off the ground, and a speed and direction at 3,000 ft AGL. If we had a full understanding of the wind from the surface to 3,000 ft AGL we would find a pattern that looks something like the following diagram.
This pattern of change from the surface up to a higher altitude is known as the Boundary Layer. The boundary layer is a result of the friction of the earth’s surface interacting with the winds aloft. The entire traffic pattern, approach, and landing happens within this ever-changing pattern of wind. Since the wind will likely be stronger at altitude, the descent portion of the downwind past the numbers will happen quickly and if the pilot isn’t careful they will get carried farther than they like before turning base. I call this the Downwind Double Whammy since you can get carried on downwind and then have to fight your way back on final. Even just a few extra seconds wasted on downwind before turning base can waste any chance of making it to your point.
Of course, a headwind on final also has its own double effect in that the headwind requires a steeper approach to keep the aimpoint and that point must also be shifted closer to the desired landing point since the headwind shortens the roundout and flare distance.
I’ve found from experience that the boundary layer really kicks pilots the hardest on final approach from about 500 ft down to about 100 ft. Wind speed in this window can change by as much as ten knots and most pilot’s never realize the accompanying airspeed loss being caused by the boundary layer. The boundary layer’s loss of headwind is basically a constantly changing wind shear. As the airplane descends through it, it is constantly losing airflow and the airspeed drops unless the pilot anticipates it and continually pushes forward to keep the airspeed on the mark. Even if the pilot can keep the speed, the boundary layer will cause a loss in glide angle, yet another factor we need to account for. I’ve found that the steeper I can fly through the boundary layer, the less it affects airspeed and performance loss. If you take the angle to the extreme, a vertical dive would not be affected at all by the boundary layer. We certainly can’t do that but obviously the steeper the better. Yet another reason to fly a steep approach.
We now need to take a look at crosswinds and how they affect base and final. A stiff crosswind, especially one stronger at pattern altitude can really mess with the base leg. A tailwind on base certainly helps from bleeding too much energy trying to get to the runway, however, being too steep also has its own problems. More than once I have seen students get really steep because of the tailwind, get behind the airplane mentally because the approach starts happening fast, and overshoot final. A headwind on base can bleed energy so quickly that a typical student won't catch it in time and end up short.
Gusts and their accompanying letoffs also have a way of messing with students. Unfortunately, we don’t have magical glasses that let us look into the invisible world of airflow. If we did it would be as easy as seeing a wave crash onto a beach. Since we don't, we are left to handle gusts and their accompanying letoffs as they come. Be ready to fix airspeed and glide issues quickly if you are expecting gusty conditions. Think of handling gusts like swimming out to sea with waves in your face. You are in a calm patch of water and swimming at a normal pace. As a wave approaches, you have to swim faster to not lose ground and also have to raise your head to not get inundated by the wave. As the wave passes you can go back to your normal swimming. In an airplane, when a gust hits you dead on the nose, the airflow and airspeed rapidly increase. As we pass into the body of the gust, the newfound headwind steepens our glide and reduces our performance. While this is happening, the trim stability of the airplane tries to find its way back to the original airspeed. As the gust passes the airplane is spit out back into a slower headwind which causes an airspeed loss and changes the glide yet again. The best you can do in gusty conditions is to keep the airspeed on the mark with smooth yet aggressive inputs. Account for the glide as you normally would with timely changes, but be decisive enough to get the glide back on track while assuming the gust is here to stay. If it doesn’t start all over and reestablish the glide in the new conditions.
We also need to account for upslope and downslope wind. Whenever wind flows over rolling terrain, the air must follow the contour of the earth. If, for example, there is a dropoff short of the runway you are landing on, picture the wind flowing over the runway and then down the dropoff. This airflow down the hill at the surface encourages the air above it to descend as well. Then, on final, you can expect sinking air which is yet another negative effect. Vice versa for upslope wind, expect rising air which will be harder to descend through.Upslope wind is rather rare on final since it's not good to have higher terrain in the vicinity of a takeoff and landing corridor. You might experience it on downwind or base sometime though. At my local airport, with a wind out of the northeast and landing on our northerly runway it's not uncommon to get some upslope wind on a left base and downslope wind on final.
In summary, a full understanding of the local wind pattern explains why the tailwind on downwind is usually stronger than the headwind on final, how the headwind on base is running the energy bank dangerously low, and why the boundary layer is causing airspeed decay and performance loss on final. Before jumping into the pattern, make sure you have done your research and have built a mental picture of the wind pattern all the way around the patch.
Atmospheric Stability
We have already seen how wind, the horizontal motion of air, greatly affects the power-off approach. In this section, let's take a look at how the vertical motion of air affects this maneuver. Most pilots are very aware of what the wind is doing, but very few have any idea of how air moves up and down in the atmosphere. Once we have an idea of how that happens we can apply it to the problem at hand.
To understand the vertical motion of the atmosphere, we first need to get comfortable with the idea of Atmospheric Stability. This is the tendency of the atmosphere to suppress or encourage vertical motion of air. When atmospheric stability is high, air tends to stay at its existing altitude. If it tries to change altitudes the atmosphere resists against it, thus keeping it close to where it started. If atmospheric stability is low, air is encouraged to move vertically. As you might guess, atmospheric stability is a good thing if we are trying to make power-off approaches. We will have a smooth, steady, and consistent atmosphere to descend through. When the atmosphere is unstable, the atmosphere is willing and able to help stir vertical motion. If a parcel of air starts ascending, the atmosphere will help it ascend even quicker. The tricky part about this is that we have almost no way of knowing exactly where the lift and sink will be or how strong it might be. This adds uncertainty to the approach and must be accounted for by adding to our energy reserve. Let’s take a look at how to characterize atmospheric stability next.
The first big clue we can look at is the pressure pattern in our region by way of a Prognostic Chart. Pressure patterns tell us a lot about the vertical flow of air on a very big scale. If you remember from your early study of weather, air flows downward and outward in a high and inward and upward in a low. These two patterns from high and low pressure systems don’t exist in isolation. They exist in a form of symbiosis where air in a low flows inward and upward then moves laterally from the low to the high at great altitudes, usually well above 50,000 ft, where it by then has cooled and dried and then flows downward and outward in a high. Cool dry air gently descending within a high creates atmospheric stability that results in generally smooth air, hazy conditions, uniform clouds, and showery rain. Warm, moist, rising air associated with low pressure systems creates plenty of turbulence, thermal activity, cotton ball clouds, and thunderstorms.
When making approaches in a stable atmosphere you know what to expect. The bottom isn’t going to fall out from underneath you in sink. However, in unstable air, you have no way of knowing if there are two lifting thermals, or a wide area of weak sink in front of you. Keep in mind that thermal activity usually sets itself up with small strong columns of rising air that then trade off their air to large patches of weak sink. If, for example, one thermal is trading off air to one area of sink that is fifty times larger; the air in the area of sink can descend fifty times slower than that it was rising in the thermal. This is why thermals are so much more noticeable than an area of sink. As you enter a thermal the airplane will rapidly change its vertical path. In our case, a thermal can be strong enough to turn a 500 ft/min descent into level flight. Conversely, in a large area of sink, the descent rate might only increase slightly but since this area of sink is so much larger it can have just as much of an effect, albeit in the opposite direction, of a thermal. Since thermals are relatively small in size, there's always a chance that you might never hit one in an approach. You might have just barely missed three of them and never knew it.
My plan when flying an approach in thermal conditions is to prepare for my entire approach path being in sink. Since sink is draining the energy bank, I fly a steeper approach angle as already discussed. If I happen to encounter a thermal, I only have seconds to start bleeding energy so that I don’t find myself so steep I can’t possibly make my landing point. If I didn’t do this I would be dependent on the conditions to even out the loss and gain from sink and thermals, respectively. I’ve seen this exact scenario play out with students who had no idea what the thermals and sink were doing to them. I remember one student in particular, who made no account whatsoever for lift and sink and was dangerously low on base and wasn’t making any attempt to fix it. Then as he turned final, he caught a huge thermal which brought him back perfectly on glide. The student made a great spot landing right on his point. He then proceeded to make three more landing attempts and missed the point every time because he never recognized the thermals and sink.
Wake Turbulence
Another enemy to the power-off approach are the air currents created by wake turbulence. Most of us are aware of the dangers caused by landing behind large and heavy aircraft, however we also need to look at how wake turbulence from any aircraft affects airflow down near the runway. Since a wing generating lift displaces air downwards and outwards, we need to visualize this flow pattern coming from the airplane’s landing before us. If for example a Cessna 172 lands in front of us and is on the typical three degree glideslope they will land somewhere past the 1000 ft marks which are usually well beyond where your touchdown point will be. This means that our glide path will pass through and below the flight-path of the aircraft in front of us. In that case if we are landing within two to three minutes of that airplane we can expect the bottom to fall out from underneath us when we pass through their path. If you are expecting it and have added a little to your energy reserve, you will be ready. Otherwise you will likely be short and in need of more money for a reexamination.
Combined Examples
Let’s now combine all of the atmospheric effects we have looked at individually to see what you might be up against whenever it comes time to make your approach. We will look at a best and a worst case example to get an idea of what you could experience.
The best case is simple. The wind is calm meaning we don’t have to worry about a headwind on final, or carrying wind on base and downwind. There will also be no boundary layer or geometric lift to worry about. The atmosphere is stable so we don’t have to worry about thermal activity. The pattern is empty so nobody is going to cut us off or stir the air on short final to drop us in short of our point. As long as we are consistent in our procedure and pay a little bit of attention to our glide on final, we can make our touchdown point every time with ease. If you are ever lucky enough to get these kinds of conditions, use your practice to get a good feel for what your airplane’s glide and flare capabilities are. Knowing what the ideal is here, will help you recognize when adverse factors are diminishing your glide.
Now for the worst-case scenario. The wind is a 45° right crosswind blowing at fifteen gusting twenty knots. It is even stronger at pattern altitude thanks to the boundary layer so the tailwind on downwind is trying to carry you perilously far before you realize it's time to turn base. That right crosswind on final is a headwind on left base so you will have a fight there as well. On final, the boundary layer airspeed loss will be stiff so be ready to hang onto airspeed with forward pressure on the yoke, and lose even more glide angle. The field topography includes a downslope short of the runway so you are expecting the air to stick to that contour and be pulling the air at your altitude down with it. The local altimeter is pretty low at 29.75 inHg, puffy clouds are building off in the distance, vultures are circling in thermals, and the little Cub that you just watched land was getting tossed around pretty hard. From all of these observations you are expecting turbulence to be causing its usual trouble along with severe thermals and sink that could either try to lift you to the moon or drop you into the dirt. You may need every ounce of energy you have so your best bet on this one is to keep close on downwind, turn hard as soon as you cut the power, and keep the flaps up until you are sure you can make it.
Putting It Into Practice
Procedure Consistency
Growing up, I worked and learned with my granddad in his machine shop, building and shooting competition target rifles. I was amazed at the level of precision it took to make parts for these paper punchers. My granddad was an engineer and he had used his technical smarts to better understand how to make rifles hit their targets with precision. In short, he taught me that for a gun barrel to throw its bullets at a target consistently the barrel had to be well supported by the stock of the rifle and the shooter had to interact with the gun exactly the same way every shot. Even just a slight change in gripping the rifle, or how you pulled the trigger, or how you looked through the sights all affected how consistently you would hit the target.
As I got farther into flying, I found that the same kind of precision and consistency from competition shooting was also important in making good approaches and landings, especially the power-off accuracy landing. This consistency started first and foremost with procedure. I found that I needed to time my procedure down to the second to have the best chance of making my touchdown point. Pulling the power a second early, turning base a second late, starting the round-out a second early, all made a difference. Putting some numbers to those single seconds, at 85 knots on downwind, pulling the power a second late, translates to 150 feet past the touchdown point. That can make a big difference when we are trying to hit a 200-foot-long window.
What I am getting at here, is that your procedure must be incredibly consistent in terms of order and timing. In training, I’ve seen many students be inconsistent with the order of procedure. For example, on some laps, they may pull the carburetor heat and then pull power and on others they pull the power and then the carburetor heat. They may bank at twenty degrees on some base turns and thirty degrees on others. Instead, we need to know the exact procedure we are going to use and the exact cues we will use to enact that procedure. Flaps should not just be added “on base”. Instead, they should be added at a definite point that can be hit every single time. From personal experience, I’ve found the only definite point to be within one second of rolling out on base.
If you are having trouble hitting your landing point consistently in steady conditions, procedure is the first place to start troubleshooting. Take an instructor along or video yourself and analyze the order and timing of what you are doing.
Accounting for Factors
Every pilot knows a safe flight starts with good preflight planning; but what about planning for the power-off approach itself? Outside of basic wind considerations on final approach, I have never witnessed a student pilot plan ahead for nonideal factors on approach. Maybe some pilots do but the overwhelming number of botched power-off attempts I have seen, seem to confirm my theory.
Instead, before we even leave the ground, we need to be thinking about all of the atmospheric factors we have already discussed and come up with game plans ahead of time. Am I going to have a headwind on base? What do I expect for thermals and downdrafts in the descent? Once we have these kinds of questions figured out then we need to mentally modify our pattern to follow through on our preparation. If you are expecting a headwind on base, that would also imply that we will have a tailwind on crosswind. Therefore, we probably need to make a continuous turn from upwind to a crab on downwind to have a fighting chance at making the runway. If we are expecting thermal activity, we should prepare ourselves to be hyper-focused on the altitude on downwind, and then also keep it in tighter on the approach in case we encounter sink and conversely also be ready to slip aggressively if we catch a thermal.
I like to weigh all of these factors against each other to see how much I am being helped or hurt on making it to the runway. For example, a left quartering headwind on final will hurt, but the tailwind on left base will help. A downslope under my approach path might neutralize thermals. Sink from the downwash of a plane landing before me will make for a double-whammy with boundary layer on final. This is a good mental exercise that gets you thinking of the tug-of-war happening against your energy budget.
If you can do what we just discussed, you will be well out in front of the crowd when it comes to the thinking side of the problem. However, one other aspect of accounting for factors still needs to be covered and that’s real-time accounting. I have beat up the pattern with many students and am always amazed that a consistent negative factor will affect them on one lap and the student never accounts for it on subsequent laps. After three laps of a headwind killing the glide on base, I will point it out to the student. Some are so mentally saturated that they never noticed. Others see the problem but are too nervous or uncertain in their abilities to apply a fix. I would rather see a student try to fix the problem on the next lap with a major overcorrection rather than not trying at all or a minor correction more built on hope than decisiveness. When flying in dynamic conditions try to learn on every lap. Every lap should be better than the last and what may have been a mess on the first attempt should be nice and clean by the last.
Seeing the Glide
Every pilot knows, at least in theory, how to control the glide on final approach. If the aimpoint moves up in the windscreen, the airplane is descending short of the point. If the aimpoint moves down in the windscreen, the airplane is heading for a point beyond the desired aimpoint and will land long. If the point stays steady, you are on path to your aimpoint. This technique, however, says nothing about the approach angle itself, a factor we have discussed at length and are keen to control.
Most pilots are also familiar with runway shape effects for determining glide angle. The steeper the approach angle, the longer and skinnier the runway appears. Conversely, the shallower the approach, the shorter and fatter the runway appears. Since power-off approaches are always steeper than the three degree glide slope displayed by the PAPI or VASI lights, these lighting systems are completely useless to us. When we aren’t on a known glideslope, we really have no way to know exactly what glideslope angle we have on approach. However, with enough practice you will develop a keen intuition of your glide angle. You may not be able to spout off a number but you will know if it is right or wrong. You’ll know what “somewhat steep” looks like and what “really steep” looks like.
Knowing the glide on final, as we have just discussed, is only about a third of the battle. We also need to be able to judge it on base, and from initial descent at the numbers on downwind. Picture a string connected to the nose of your airplane that is strung out in front of you, around the base and final turns, and finally tacked down at your aimpoint. You should be able to see the wideness of each turn and the steepness of each path. With practice you will be able to see this invisible path out in front of you and around your approach. It will tell you when are too steep, too wide, or too shallow in your turn. This visualization is what you then rely upon to make it down to an on-profile final approach; not a red barn on the ground or your altimeter.
The Thinking Rate
I remember the first time I used a quality autopilot. It amazed me how well the device kept us on course and on altitude. Excursions due to turbulence were swiftly corrected. This helped me realize that an autopilot can think faster and see smaller problems than a human pilot. We will likely never have autopilots for power-off approaches but we as pilots can learn from the quick-thinking of an autopilot.
On approach, the quicker we can think through and process airspeed and glide angle issues, the more consistent and smooth our approaches will be. Unfortunately, most students are so busy just keeping up with procedure and basic control that they can’t think through issues quickly enough to fix them before they become big problems. Then they have to rush from fire to fire. My favorite example is the classic airspeed loss on final. The student doesn’t notice the nose fall which five seconds later causes a tiny flick on the airspeed indicator. Ten seconds after that, the airspeed is over five knots fast and the student finally catches the problem. If they had kept their problems small, and the corrections to their problems small they would have had more time and mental energy to keep the juggling act going without big issues popping up.
From my own experience, I’ve found that to be consistent on approach, a pilot needs to be on a two-second thinking rate. That means for the entire approach, turns and all, every two seconds the pilot needs to be recognizing and correcting for airspeed and glide issues. We’ve already seen how one second can make a huge difference when it comes to procedural timing. I think two seconds is a reasonable ask in terms of judging problems.
The other issue here is how quickly we judge the sufficiency of our corrections. I’ve seen it so many times; the student recognizes a problem and they attempt a fix. They then go on their way assuming that the correction they have made will fix the problem. Unfortunately, the vast majority of corrections I see on approaches are insufficient to fix the problem at hand. We pilots also need to be looking for the results of our corrections and if they aren’t happening on that same two second rate, we need to speed up our brain’s autopilot processor speed.
Also in regard to thinking, we need to ensure that we are multitasking efficiently as well. I remember one commercial student in particular who, on one lap, was turning base while also making the base radio call. I could already tell that we were rather slow which had shallowed the glide and had made us rather steep. As soon as they let the push-to-talk go I started correcting their speed problem which would then require a glide correction. The student got visibly mad with me and proceeded to tell me I was asking too much from his multitasking ability. I think he liked hearing himself on the radio…
Multitasking Melvin on the other hand, uses all of his senses and limbs to good use simultaneously. While turning base he is controlling the yoke with his left hand, moving his right hand to the flap handle, masterfully working the rudders with his feet, and pushing the PTT with his left thumb. His ears are listening to the whistle of the slipstream to ensure the airspeed is steady, and also to the sidetone in his headset to ensure the radio is transmitting. His eyes are hard at work ensuring visual pitch and bank are correct for the turn while also straining to see the runway to ensure the glide is right. Melvin’s suspendered posterior is sensing coordination and also waiting for the kick and lightness of thermal and sink. Let’s just say he is busy but effective.
Looking Inside vs. Outside
When I start a new private pilot student, I cover almost every gauge in the panel. This is how it stays almost all of the way through pre-solo maneuvers and landing training. Every now and then a cover might come off for a specific maneuver or lesson but approaches and landings are entirely without instruments. Believe it or not these students develop an uncanny ability to judge height, speed, and glide angle. They can hold 90 knots and 1,000 ft on downwind and 65 knots over the fence better than many commercial students. This is because these students have mastered all of their senses, not just the visual. They have learned the core techniques of precision visual pitch control, trim by feel, coordination by rump, and airspeed by ear, the same skills aviators of old used to coax cantankerous rudimentary biplanes into the air.
This training and experimentation with my private students has proven to me that most of us over-rely on our instruments. If I could only uncover one gauge in the pattern, it would be airspeed. Sometimes the slipstream sound just isn’t giving enough information and thermals and sink can mess with pitch picture, therefore requiring a glance at airspeed. If I got one more option the ball would be my choice since coordination is important in making clean and safe turns. Other than that everything else is basically useless. The altimeter is effectively worthless since we should be judging our glide angle visually. The heading indicator and compass tell us directional information that is available right out the window. The attitude indicator and turn coordinator repeat bank that is plainly visible to the eye in relation to the horizon. Finally, the VSI lags so badly that in VMC it might as well not even be installed so as to save weight. Learn to use your own senses instead of the mechanical and archaic senses of your instrument panel and your flying will get much smoother and more precise.
The Weak Link of Pitch and Airspeed
Everyone knows that pitch and airspeed are linked. Since we don’t have to worry about power here, because we are at idle, we have a very repeatable and consistent relationship between the two. Lower the nose, and you’ll settle into a higher airspeed. Raise the nose, and the airspeed will drop accordingly. Thankfully, if you work hard on your eye’s outside flying skills, you should be able to hold your airspeed within a knot or two consistently. Your eye is just that good at judging the airplane’s pitch between the horizon and the cowling.
There are, however, times and places when the pitch and airspeed relationship gets upset. Flaps of course increase the incidence of the wing and thus more flaps means a lower pitch to maintain the same airspeed. If you are putting in more flaps, expect the nose to need to drop ahead of time, so get ahead of the curve and add some forward pressure as you lower the flaps. I see so many students go to put in flaps and they don’t lower their pitch and then they wonder why the airspeed waffled indecisively. Help you airplane out by helping it figure out where it needs to settle.
Also, the boundary layer, which we have already discussed at length, affects pitch. If you are anticipating it, just go ahead and do the same as you did with flaps and push into it. The nose will need to sit lower as you penetrate the boundary layer to keep the airspeed. Since boundary layer effects usually kick in in earnest around 500 ft and go all the way down to the surface, just expect a lower pitch on final all the way down to the roundout. Once again, I see so many students on final blindly trying to hold the pitch they held in the downwind descent and on base and then wonder why they lost airspeed.
Finally, thermal activity also messes with pitch. The moment you enter a thermal, rising air will start to try to bend your flight path up higher than before in stable air. If you keep the pitch stable by pushing forward on the yoke, expect your airspeed to climb, drag to climb, and expect your flight path to stay about the same. If you let the pitch come up to match airspeed, expect the thermal to shallow your glide, likely making you steep. My strategy when encountering a thermal is to keep the airspeed constant but also increase drag to avoid the thermal’s lifting effect. That means I either slip, which I prefer, or add flaps. Going from calm air into sinking air carries its own problems. When you enter sink, expect to lower the nose to keep airspeed. The sink will then steepen your glide and likely bring you up short. If you have been carrying a sufficient energy reserve by maintaining a steeper glide, you should be fine. If you get desperate, hopefully you can cut the corner on a turn. Things get really messy when you transition from thermal to sink or vice versa. You should be able now to figure out what would happen in those kinds of situations.
Clean Slips
Flying a nice clean slip is definitely a challenge. It’s one of those techniques you can practice and practice and just when you think you’ve got it down, you’ll disappoint yourself. I know I have many times. We all know that airspeed indicators are just about useless in a slip. A steady pitch attitude is usually “pitched” as an alternate means of airspeed control in a slip, but I’ve rarely seen this done well. Instead, the audible pitch and volume of the slipstream seems to be the most reliable airspeed indicator as long as your ears are tuned in. Try it the next time you slip.
Every airplane I’ve ever slipped always seemed to have a mind of its own in terms of what actually happens to airspeed in a slip. Cessna 172s like to slow down in a slip, while Diamond DA-20s like to rapidly accelerate in a slip. No matter what happens be ready for either case when you get ready to hammer on the rudder.
Last Ditch Drag Reductions
Pattern geometry is the greatest tool you have when it comes to controlling your glide. Turn from downwind to base a second early and you could be screaming high. Turn base a second late and sometimes, you might not even make the runway. That’s only a two second difference. Coming up short on base is one case where geometry can help immensely. Learning when to cut the corner by starting your turn to final early can help scrape away hundreds of feet of ground you would otherwise have to cover. Make sure though that you are not using this tool too late or too low. If you are crossing the threshold in a turn or still turning below 300 ft AGL your cutting of the corner was too little too late and is unsafe, in my opinion. Use it earlier rather than later.
Another controversial drag reduction technique is raising flaps. About the only time I will allow my students to raise flaps is when they went to full deflection to try to come down super steep and are still relatively high. Above 600 ft AGl going from 30° to 20° flaps on a 172 can definitely be done safely and will help the glide. Every time flaps are removed in the air, some lift will be momentarily lost causing serious sink, before the airplane can recover it’s glide. This is why low altitude flap restrictions are a definite no-no. You don’t want to be losing glide angle and airspeed at low altitude.
Finally, if you are lucky enough to be flying an aircraft equipped with a constant speed propeller, you have one final option to try to stretch your glide. At idle, the propeller rpm control can usually be pulled safely to low rpm thus feathering the propeller. You will be amazed how effective this drag reduction can be at giving you just a little more glide. Just make sure you put it back to high rpm before advancing the throttle to avoid having to buy a new engine worth more than your car.
Transition and Flare
Hopefully, up till now, you have done everything you can do to arrive above your aimpoint on speed and on height. From here there is very little you can really do to affect your touchdown point. Hoping for a big change here is like asking a missile that has been on the wrong path for a thousand miles to wildly change its path at the last moment to strike it’s target. Once again the ACS states,
The beginning of this requirement basically forces you into making a full stall nose-high landing for your power-off approach to count. If you try to drop the airplane in or attempt to land flat, the examiner has every right to fail you even if you make the point. This basically requires that you make a full deceleration and flare to just above stalling speed which will give you the longest possible distance between your aimpoint and where you touch down. Learn to really run the airspeed out and only let the airplane touch down once all available airspeed is gone.
Conclusion
I hope you have enjoyed drinking from the power-off approach firehose. As you well know, this maneuver and landing is one of the most difficult maneuvers pilots face in their training and is also one of the most serious when it comes to emergency preparedness. Hopefully that reality will encourage you to master it. The intent of this primer hasn’t been to make you an expert overnight, but hopefully it will give you a good bag of tools when it comes to diagnosing any difficulties you might be having. Keep practicing and evaluating yourself through the lense of this primer until you can nail a point like a sharpshooter taking the wings off a fly at fifty paces.
Clear Skies and Tailwinds
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