Common Airplane Landing Errors: Part 1, The Approach

INTRODUCTION

As a flight instructor, I get to assess the components that go into mediocre to bad landings and what it is that leads to the great, greased landings we all aspire to make, especially with friends in the cockpit.

As the old aviation saw goes there are 3 types of landings:

1. Excellent: you and your passengers walk away from the airplane and the airplane is reusable.
2. Good: you and your passengers walk away from the airplane.
3. You can guess what #3 is....

It is easier to be consistent about being in category #1 if you understand what leads to category #2 and #3 landings.

The purpose of this article is to help pilots who are having trouble landing understand the errors that you must recognize and correct to make consistently good landings. It is a good idea to maintain objectivity about your skills, but sometimes you need another set of eyes to help you identify errors that you may overlook. Try assessing errors on your own and consider hiring a CFI with the intent of receiving a report of the errors you made on your approaches and landings. The first step is to identify, the second step is to consider why the errors occurred and the third step is to fix them with help or on your own.

The earlier the errors are recognized and corrected on the approach, the better. This article only emphasizes the stable approach and its importance in setting up the pilot for an excellent landing. A bad approach will almost always result in a bad landing. A great approach may not assure a good landing, but it is a prerequisite.

A LIST OF COMMON ERRORS

• Failure to do a go-around. While this obviously ensures no landing it is important you learn to identify that yellow streak or tinge of doubt that rolls up and down your spine as you get close to the runway. It's a feeling that says I am not fully in control, the landing may not work. Respect that feeling, immediately push in the throttle, keep the airplane under control, clean up and as airspeed permits, start your climb. Try again. The go-around has proven itself to be one of the best ways to stay out of the #2 and #3 categories.
• Unstable approaches. Stability here means lateral stability, Descent or slope stability, and airspeed stability. If any one of these stability aspects is missing, you do not have a stable approach.

1. Lateral stability: failure to track the extended centerline. Not tracking the extended centerline is one of the most common errors. Often the pilot follows a line that is parallel, but to the left of the runway centerline. This leads to a destabilizing last-minute situation because the pilot identifies that the aircraft needs to be moved to the left or right and usually by several yards, a moment before the round out in order to acquire the centerline. This is destabilizing and almost always leads to a mediocre landing. Most pilots do not recognize this error. Unfortunately, I find the best way to help them recognize the error is when they are committing the lateral shuffle to attain the centerline. If you find executing large left or right corrections just before rounding out, you have to fix it. Crosswinds cause problems. An airplane tracking the centerline with its longitudinal axis pointing, say 5-15 degrees into the wind often confuses pilots. It is the vertical axis of the aircraft that tracks the centerline, not the longitudinal axis which is pointing into the wind. Before executing a side slip, an aircraft in a crosswind approach must have a proper wind correction angle to keep its vertical axis on the centerline.  Also, the aircraft must be in coordinated flight. Coordination changed close to the ground in crosswind landings when a side slip is used to make the longitudinal axes of the aircraft parallel to the centerline. It is very important that the longitudinal axis of the aircraft become parallel to the runway prior to touching down to avoid side-loading the landing gear.
2. Vertical (slope) stability: the descent on final follows a glide slope. If you want a mediocre landing, allow large fluctuations of the aircraft above and below this slope. The best way to maintain a slope is to pick a spot on the runway, the "aim point". Think of the aim point as the place where the aircraft will smash into the ground if you do not round out. Slope stability goes hand in hand with airspeed stability. In all cases, if there is visual slope guidance, stay at or above the safe slope. Above is okay providing the runway has more length than needed to safely land.
3. Airspeed stability. Letting the airspeed vary during the descent to the aim point is a good way to ensure mediocre landings. Here is where new pilots have a lot of trouble because they forget that when an aircraft is behind the power curve, it is the pitch that controls airspeed, not throttle. Throttle reduces the descent rate. The throttle in this case is an altitude control rather than a speed control. If the airplane is slow, you must reduce the pitch (drop the nose). Most novices only add power resulting in little or no airspeed change. If you were on a correct glide slope to begin with, but find you have low airspeed, the aim point will move way out in front of your reference as you reduce the pitch angle. To recap: A pitch decrease to increase airspeed usually comes with an increase in engine power to negate the altitude loss due to the reduced pitch. On the flip side, if you are too fast, you will need to hold the pitch constant to prevent a nose drop as you reduce power which will cause an increase in airspeed. The yoke and throttle often move in the same direction when making slope corrections, both in together, both out together.

Airspeed and slope stability really go hand in hand. If you keep your chosen aim point at the same relative place on your cockpit reference and you keep the indicated airspeed constant, you will traverse the chosen glide path to the aim point. So, pay attention to airspeed and the position of the aim point relative to your cockpit index. By the way, the cockpit index is whatever you want, but it usually turns out to be the top of the engine cowling or the top of the glare shield. Whatever you use, be consistent.

When I say pay attention to airspeed, I do not mean fixate on the airspeed indicator - not good! It's best to establish a pitch you think is the airspeed you want, then quickly look down, read the IAS, then get your eyes back up and look out the window at which time ask the Goldilocks question: was I too slow, too fast or just right. If too fast, look out the window and raise the nose (increase the pitch) which means the aim point may slide too close to or under your index which means you have to reduce power - recognize this quickly and react quickly. Remember it is important to notice the error and respond to the error quickly so that your corrective actions are as small as possible. Your airspeed assessment frequency should increase as you approach the ground.

REVIEW

The common errors I often see on the descent to final along with some notes on corrective action:

• The vertical axis of the aircraft is not on an extended centerline, usually several yards to the left. I find it helps if I sight the far end of the centerline then follow the line towards me extrapolating out to my aircraft. 
• Confusion executing crosswind descents to land. Many pilots have a hard time with the wind correction angle because they find it confusing having a nose point windward, away from the runway. Remember your goal is to keep the vertical axis of the aircraft on the centerline, not align the longitudinal axis with the centerline which is something that happens at the round out. This means coordinated flight up until it is time to start a side slip.
• Excessive airspeed fluctuations and not staying on the proper slope. This is due to the confusion that comes with a pilot who believes that more throttle=more airspeed. Remember, it is the pitch that controls airspeed and throttle controls the descent rate where more throttle generally slows the descent rate.
• Allowing excessive errors to occur before correcting. It is essential to learn to detect all errors (slope, airspeed, lateral) early and correct them early. Correcting large errors, especially late in the approach, is a good way to ensure mediocre landings. Don't be afraid to use a lot of flight control and power changes if necessary. Being timid during gusty crosswinds is a recipe for disaster. How much control? How much power? Answer: the right amount. What is the right amount? The amount that keeps you on the centerline, on the slope at the right airspeed, and maintains a constant aim point. Given a hefty tailwind shear, you will likely need full throttle for a few moments - use it to stabilize or go around.

THE ROAD TO IMPROVEMENT - SOME EXERCISES

At altitude do the following:

• Set power to your normal approach power settings (usually around idle to 1400 RPM for most trainers). Put in a full landing configuration, full flaps, and gear if appropriate. Trim your airplane for typical approach speeds (60-70 KIAS for most trainers). Use the pitch trim, take your hands off the yoke and see if your airplane glides down at the speed you chose. If it does not, look out the window and change the pitch accordingly by outside references. Re-trim. Once the pitch is stable, recheck your airspeed. Correct if it is not what you want. By doing this you will eventually nail the airspeed by paying attention to your pitch at a given power setting. 
• After you become good at keeping airspeed, find a fence or road leading to some ground object or your aim point, say a "T" at the end of your road. Descend using the skills above, but also keep the "T" in a constant position on your cockpit reference point with power and pitch to maintain your position over the road leading to the "T", with constant airspeed and while flying exactly over the road segment leading to the "T" and use a proper wind correction angle if there is a crosswind.

Opinion: Learning to Fly with Glass vs. 6-Pack?

INTRODUCTION AND CAVEATS

I confess up front that I find the arguments that the 6 pack is a better learning vehicle than glass to be questionable. I do not claim that one is better than the other because it depends on circumstances. For example, if you plan to rent and most of the rental fleet you plan to use consists of 6 packs or you own an aircraft that has a 6 pack and you have no intentions to switch to glass then you want to learn in a 6 pack. On the other hand, if you have access to a fleet of aircraft with both types, you may want to flip a coin if you are not sure or perhaps a rental-price differential will help with your decision. Generally glass cockpit aircraft rental rates are higher. If your future is flying to nearby airports or flying to local pattern, a 6 pack is a good choice. If your future is with the airlines, corporate flight, you appreciate modern technology, you plan to do a lot of IFR flight, etc. you may want to start with glass from day one. Personally I am biased, I lean towards going with glass.

BACKGOUND AND SOME HISTORY

There are ongoing arguments that deal with whether a beginner or the instrument pilot should do their training using a glass or a traditional 6 pack avionics set.

Glass is aviator's slang for a box with a liquid crystal display, often 2 displays, one that shows the flight instruments (PFD) and another that shows useful flight data, moving maps, engine parameters, etc. (MFD). The glass box has both a GPS and a VOR receiver. Most glass boxes display a horizontal situation indicator (HSI) and the pilot chooses which receiver drives the HSI.

Many glass installations are equipped with solid state devices that replace moving gyros and eliminate the need for a vacuum pump (One of Murphy's laws states that about 5 minutes after entering a cloud, the vacuum pump fails.)

A modern 6 pack has 6 circles cut out on the avionics panel, 2 rows, 3 columns, each cut out contains a flight instrument in the same relative position from aircraft to aircraft.

(A photo is coming here soon)

 In 1929 Jimmy Doolittle was the first to fly by using instruments without looking out the window. In 1937, the British Air Force standardized their fleet using most of the flight instruments we see today. The 6 pack has been with us several decades.

THE CURRENT STATE

The general aviation fleet is largely of the 6 pack variety, but glass cockpits are gaining in number because of retrofits to older aircraft and as standard equipment in many new production aircraft. Several companies offer retrofits which remove the classic 6 instruments and replace them with a single flat screen, Garmin and Aspen Aviation are examples of manufacturers who provide retrofit products.

THE DIFFERENCE BETWEEN THE TWO COCKPITS

Modern glass panels have fewer or no moving parts. The heading indicator and the attitude indicator operate from solid state devices which means no gyros. Data is displayed in liquid crystal rather than with mechanical "steam gauges". In the Garmin 1000 everything is solid state. There is no need for a vacuum pump on an aircraft with this unit providing the standby attitude indicator's gyro is electric. Since there are no gyros, there is no precession and no bearing surfaces to wear out which lead to inaccuracies and eventual failure.

A CASE FOR THE 6 PACK

  Some aviators are adamant that all initial training, especially at the pre-private and instrument rating level be conducted in a 6 pack. Their reasons vary. For the pre-private arguments that training should be in a 6 pack are generally of the nature that the glass presentation is too distracting and the student needs to learn to keep their eyes out the window. Glass somehow will cause a student to fixate on the glass components and keep their focus somewhere below the glare shield.

 The other argument, usually unspoken is: I learned how to fly with a 6 pack 30 years ago, so should you.

 I guess that is the best I can do for the pro-6 pack argument. Remember my confession about my bias?

A REBUTTAL TO THE CASE FOR THE 6 PACK

 Personally I find arguments regarding distractions caused by glass to be specious. As an instructor, I encounter this problem with students whether they are flying glass or a 6 pack. In both cases, the student needs a serious dose of what I call "the other function of the aviation chart" which is when I use the chart to cover the flight instruments. It is my observation that pilots of both cockpit types initially spend too much time looking at instruments. CFIs can catch this early by observing the pilot demonstrating latency errors leading to pilot induced oscillations (PIO) or jerky bank rates, excessive push and pull on the yoke and more. The beginner needs help to become aware of the substantial latency, especially with the instruments in the 6 pack.

  I have heard some say that an analog presentation is better than a digital or ribbon presentation for items like airspeed and vertical speed indications, it is somehow more human. To me, this is a religious issue. I cannot fathom why someone who is brought up reading digital time from a cell phone would be uncomfortable with digital airspeed. I can fully understand why someone who has been looking at analog gauges and 3-handed watches for decades finds it difficult to read a digital value or read a ribbon, but this means your ability to catch on depends on your own past experiences, not an "inhuman" characteristic. Also, the load of instrument interpretation is fatiguing. For example, as a pilot who learned to fly instrument on a standard VOR omnibearing selector and then switch to an HSI. The HSI is clearly a winner because it overlays heading with course and reduces a part of the interpretation load by a noticeable factor. Not only does the HSI closer to representing reality, it also reduces the amount of scan work needed by the pilot. There is nothing better than having instruments that are as close as possible to representing reality. Some argue that the 6 pack does, but this takes a lot of brain work by the pilot especially understanding position and the scan real estate is much larger than the small rectangle displaying airspeed, course and heading data, altitude, vertical speed, etc., on a PFD.

Another argument against the glass cockpit: the complexity and pretty colors are too distracting and the pre-private will fixate on the nooks and crannies of the device, being awed by pretty colors, knobs, pages, etc. and will not become a proper stick and rudder pilot. Again, this argument is pretty weak because it is up to the instructor to emphasize which features of the glass panel are relevant to the VFR student and keep the focus on those items. When the proper focus is set and enforced by the instructor, the glass panel is arguably easier because data the pilot needs to reference are in close proximity rather than spread out, sometimes over long distances in older cockpits that have undergone mystical retrofits. For example, VHF radios are often scattered over the panel (common retrofit condition on older aircraft) causing the pilot to sometimes have to lean to reach a considerable distance to tune radios or other equipment. Having all critical instruments displayed on a LCD in a few square inches of real estate is a good thing.

  Advocate for the 6 pack claim that you need to learn from that first and then learn how to use glass. I find this to be a weak argument. As an instrument instructor, I have found that in teaching for the instrument rating that the student who starts with glass has very little problem going back to a 6 pack. It does take a few hours with an instructor, but it is apparent to me that knowledge acquired from a glass panel with and HSI, etc. can easily be transferred to learning how to fly the analog gauges of a 6 pack. On the other hand, my experience has been that those who learned in a 6 pack have a much more difficult time of transitioning to a glass panel. It takes longer and leads to a lot more cussing than going the other direction. A lot of this is to do with using the various knobs and buttons. To successfully learn how to use either system, you need to a lot of repetition in the learning process. The glass system seems more complicated and in some ways it is, but remember that the comm radio, the nav radio, a CDI selector, an altimeter setting function, etc. are all in one box instead of scattered over several places on the avionics panel. A higher density of knobs and buttons exist, but not necessarily more, it's just a lot of stuff is in closer proximity. Then, add to this flight plan storage, and a host of other things one can add to an MFD (weather, airport data, etc.). No question it is a lot, but so is carrying a green AFD, the one in your pack on the back seat, and suffering through the experience of not having near real time weather at your finger tips when making long cross country flights.

Both panel types take a lot of time to learn and to use competently. If you think that you will eventually be using glass, why wait? Start early in your lessons where new things tend to stick with you.

Personally, I have heard no good reason to not use glass, but it does boil down to what is you intend to do with your learning experience after you get your ticket. IMHO, pilots who advocate against glass really do not present a strong argument. Analog gauges are not human and require a deep understanding of what it is that is producing the data that drives each gauge, how to interpret each item and how to take data from several instruments that are far removed from reality and process these between your ears to help acquire situation awareness. Much of this load is replaced by an HSI and a moving map. I am sure that the aviators of the 1930s claimed you needed to learn using low frequency radio ranging (A-N ranging) to really understand how to navigate before you used VOR when the VOR system came out in the 1940s. I am sure that many aviators lament the passing of the NDB/ADF combination, but personally I would rather take the non-precision GPS approach if available and it is getting hard to find airports without GPS approaches.

I guess if you went way back, pilots would tell you if you could not follow railroads you couldn't call yourself a pilot. I have seen the same phenomenon in blue water boating when the GPS came out and navigators using sextants would ask me what would happen if I dropped my GPS receiver in the water. My stock answer was what if you dropped your sextant into the water? I have a dry, spare GPS receiver, did you bring a spare sextant? That was when hand held GPS receivers were not cheap. Today they are a dime a dozen so to speak. There was an important advantage to using the GPS over the sextant - time. In seconds I could do what a skilled star shooter took a few hours to accomplish and I could do it even when it was cloudy and anytime time of the day. Yes, sextants are fun to learn to use for most of us, but not necessarily the best tool given today's technology.

The same is true in the cockpit. For example, using a G1000 I can immediately size up my cross and head wind components while on an instrument approach - just look at two wind vectors in the liquid crystal. I can recognize and correct approach errors much more rapidly than if I only had a CDI (near real time ground tracking data). The tools of the modern cockpit save time in assessing the external environment and this promotes a higher level of safety.

Most modern glass estimates the ETE to your next waypoint and the fuel expected to be consumed between your current point and the next waypoint and your destination. This can be calculated in one's head or by bringing along an E6B which has now fallen under your seat and is out of reach. Two of the most useful things that glass brings to the pilot is instantaneous ground track and ETE as mentioned earlier. When doing an approach with a 6 pack, at best I could sometimes get distance data to the next way point (DME or radial crossings). Distance, however, is marginally useful. I find time to the next way point a more human measure, how many more minutes do I have to do my next few things before I have to do a step down? Given distance only, I would have to estimate ground speed and then do a calculation to convert that to time. Anyone who does an approach with a 30 kt tail wind vs. a 30 kt head wind appreciates what I am getting at when I say that ETEs are much more useful than knowing indicated airspeed, guestimating ground speed, etc. Having an instantaneous track readout is wonderful because it clues the pilot to early deviations from a desired ground track, often before they show up in the deviation bar of the HSI.

A NOTE TO HELP THE INSTRUMENT STUDENT DECIDE

A general note first: Many instructors tell you need learn your IFR skills while hand flying, that is, not using any automation. I do not agree with this approach because it takes time to develop the finger skills to operate this kind of equipment just as it does for operating a modern glass panel with a flight management system. The only way you will become proficient with this equipment is to start using it from day one in your training.

Am I advocating that we never learn to hand fly? Heck no because stick and rudder is a must-have skill to possess if you want to fly safely. However, as an instrument pilot if you can hand fly an aircraft for at least an hour demonstrating good stick and rudder flight and you can do a hold and two approaches with no outside references while flying partial panel, what more do you want? No question, it is important to become a good stick and rudder pilot. Too much effort is placed on hand flying in the instrument environment even when a student is learning in an automated cockpit (glass + autopilot) producing pilots who are poor at using the automation. Many CFIs believe you need to hand fly and then at the very end of your instruction, learn to use automation. I respectfully disagree.

If you have an autopilot integral to the glass box (G1000 with a GFC700 autopilot) or even when it is not integral but nonetheless is a well integrated system (e.g., Avidyne/G430 with an S-TEC55 found in many older Cirrus aircraft) it will likely set an example for a learning instrument pilot on how to fly by instrument because of the smooth control, standard rate turns, etc.

Automation is your friend. Today automation is exceptionally reliable, but this does not mean 100% reliable (what man made apparatus is?). A modern autopilot will generally fly the airplane better than most pilots especially when the automation is obtaining digital input from reliable (no gyro) devices.

Yes, there is overhead in learning to use automation. There is also overhead in fully understanding the limitation of the automation. However, the return on investment in workload reduction and improved situational awareness pays back big time (IMHO).

If you start you instrument lessons in a glass cockpit and you have not had any glass experience, it will be difficult because you have to learn basic operations of the glass functions. For the pilot that did start with glass there are a lot of new things to learn that deal with IFR flight. Whether or not you have experience with the glass, it is best to undertake your lessons at a facility with a reasonable simulator incorporating the same equipment you plan to use in the aircraft. Also, consider purchasing a trainer-simulator that will run on your home PC/Mac so you can play and understand the features of the glass box you will be using. I like to think of trainers as a way to make sure I really understand what is going on - head work if you will rather than than use proficiency which will come with an training device or the real thing in the cockpit. Also, download either the user's manual or pilot's guide, preferably both and read it in while playing with your trainer-simulator at home.

If you are using a modern airplane with good automation, I would be wary of learning to first fly instrument by hand only leaving the automation part until later in the lessons. My approach has been to start with full automation and once the student becomes proficient, start breaking things so that they have to cope with a bad ADHRS, ADC, etc. or an autopilot that has gone south. Furthermore they must be able to operate under a heavy workload for at least an hour with these failure modes, demonstrating they can hand fly, keep on top of the workload and perform whatever approaches are available to them given the type of failure. And they have to demonstrate good stick and rudder technique at the same time using good trim and appropriate control input to keep the aircraft coordinated and flying at assigned altitude and heading or course.

Most of the glass failures will likely have to be experienced with the use of a ATD, especially when damage can result to opening circuit breakers in an aircraft and the manufacturer of the glass or the aircraft prohibit the use of breakers to simulate failures in the cockpit. Some failure can be simulated with Post-it paper while in flight, but some of these failures do not invoke various side effects, for example an inibility to display track up on an MFD when the ADHRS fails or flying an approach with a heading indicator not working on the HSI. You need to experience these failures on a simulator so that you can recognize them right away and understand how your scan will change.

SUMMARY

 Know your automation and how to use the knobs on your glass box like a concert pianist who has memorized a concerto. Later, learn how to fly with various components broken, including the autopilot. The instrument pilot must recognize each type of failure and what response is needed. It is imperative that the pilot always be in front of the automation by noting what is the next thing the automation going to do and making sure it does the next thing correctly. You still must stay on top of the gauges and monitor the automation. Even with this workload, it is much less fatiguing than hand flying, managing comms, dialing in nav frequencies, ID'ing localizers (instrument pilot), etc. all at once.

Remember that modern equipment, if used correctly is a wonderful workload reducer because it is not as fatiguing as hand flying and it gives the pilot more energy to use towards the safety of the flight. Another part of the safety aspect is due to the integration and display of information on the flight plan, aircraft systems and external parameters such as airport information, frequencies, weather and wind conditions.