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:
- Excellent: you and your passengers walk away from the airplane and the airplane is reusable.
- Good: you and your passengers walk away from the airplane.
- 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.
- 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.
- 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.
- 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.
