By Mark Murray, EAA 394554
This piece originally ran in the April 2024 issue of EAA Sport Aviation magazine.
Well, that didn’t go to plan. You departed point A with the expectation of arriving at point B. But, because of an engine failure, you arrived at point C, a narrow access road leading to a cotton field. It’s a pretty field, and the road is long and smooth. It’s not where you wanted to be, but you are safe and healthy and the airplane will fly again eventually. Like the old joke goes, it wasn’t just a good landing, it was a great landing.
What really irks me is when someone says, “Wow, you were lucky that field was there.” While it’s true that the flight didn’t go as planned, the landing did. Luck had nothing to do with it. Some of the planning was done well beforehand, and some was done in the moment. All of it was successful because of initial training, continued practice, and planning for the inevitable.
In previous articles, we discussed planning for engine failure on takeoff and in the airport pattern. Now, let’s look at how we can plan for that emergency in cruise.
Glide Ratio vs. Sink Rate?
Just like most things in aviation, you’ll fall down a deep rabbit hole of information when you study engine-off airplane performance. Nothing wrong with that. Details are great. But most of us need some basic how-to pointers when thinking this through. And the thrust of this article is attempting to glide in simple, draggy ultralights and light-sport aircraft. So, we’re gonna keep it simple.
Glide ratio and sink rate are two terms you’ll come across often when evaluating an airplane’s engine-off performance. Glide ratio is defined as “the ratio of speed divided by descent rate.” A more understandable definition is “the distance of forward travel divided by the altitude lost in that distance.” Obviously, an airplane that glides forward 10 miles for every 1 mile of altitude loss is a better glider than one that glides at 5-to-1. Sink rate is defined as how much altitude you lose over time. For example, an airplane that loses 500 feet per minute is gliding much better than one that loses 1,000 feet per minute.
I recently got caught up in a “vigorous discussion” online about which value was more useful to a pilot who has just experienced an engine failure — glide ratio or sink rate. I was leaning heavily toward sink rate when I realized that it’s not a smart question.
After the engine failure, knowledge of neither really help if you haven’t done your homework beforehand. True, I find a lot of comfort gliding an airplane that’s going to give me twice as long to set it down from 1,000 feet AGL, thus the reason I’m a fan of known sink rates. But, if I’m not aware of my glide ratio, that time isn’t going to necessarily get me to a safe landing zone.
Glide ratio is great for airplane glide comparisons. But in the heat of the moment of an actual engine failure, it’s highly unlikely you’re gonna whip out your trusty E-6B flight calculator at 1,000 feet in your Aerolite and calculate how far that ratio will get you. But, do you realize you are already running a mental E-6B program every time you fly?
Every time you set up a descent rate for a normal landing, you’re mentally calculating how much descent is needed over a given amount of distance and time to arrive at a certain spot on the runway. True, you rely on numbers such as airspeed and engine rpm to get you there, but you also use a visual glide slope, the sight picture of the airplane in relationship to the horizon, which is actually no more than a reference point for your actual angle of attack. That is then transmitted visually back to you as a numerical representation of air pressure on an indicator (airspeed). Your brain is doing all of that automatically. And yes, it becomes much more natural through practice.
Years ago, an experienced flight instructor told me that a good landing is nothing more than rolling up to a stop sign in a three-dimensional world. When he got the deer in the headlights look from me, he explained that within time, it becomes natural to spot the stop sign well ahead, know when to let off the gas pedal, know how long to coast, when to apply brake pressure, and how much. And you do all that without numbers.
I was reminded recently of how this skill has to be learned while teaching my son how to drive. I’m glad to say he smoothly rolls up to stop signs now, but it took some time to hone those skills. (By the way, I will never be a driving instructor. Flight instruction only for me, thank you very much.)
With that in mind, think back to my recommendation to practice airport pattern engine-idle spot landings (“Engine Failures Happen: Just own it,” August 2023). In some ways, removing power from the landing equation makes the maneuver easier, and practicing it gives you a lot of confidence in the pattern. Now, let’s transfer that knowledge to cruise flight. Assuming your landing zone is straight ahead, the maneuver is even easier now as no turns are necessary (in reality, it hardly ever works out way, but stay with me for a moment).
So, let’s practice it. This is actually an easy and fun learning technique. Spot a potential landing zone straight ahead, pull power to idle, maintain whichever airspeed seems to work, and see if you can make that field. You won’t land but have a predetermined “wave-off” altitude where you apply power and climb back out. Try again, starting at the same altitude and position, and try a different speed. I usually start with my normal approach speed and decrease on every try while keeping safely above stall speed.
You’ll learn several things, such as which speed gives you the best distance or time. With ultralights and draggy light-sport aircraft, you may find there isn’t much difference in time and distance between a few selected speeds. Or maybe you will. It depends on the airplane. Most importantly, you’ll start to learn just how far you can “coast to the stop sign,” and it’ll start to become second nature.
Disclaimer: All of this is to be done taking necessary precautions such as maintaining safe speeds, altitudes, and distances from obstructions, maintaining appropriate engine temperatures, etc.
But, in the real world, you have more options. When practicing this with students, with nothing but trees straight ahead, I’ll surprise the students by pulling the power to idle (Yes, every CFI relishes this “pop quiz.” Don’t let any of them tell you different.) I watch their reactions. After dropping the nose and establishing the glide speed, I ask, “Where are we going to land?” Usually, students start frantically looking straight ahead, trying to find that little “goat path” that might work.
I say, “Yeah, maybe. But what about beside or behind us?” Then, they start looking around and realize landing zones are all around us, maybe even directly below us. This is where the previous practice with spot landings combined with straight-ahead glides start to pay off. You are starting to create the mental version of a glide ratio calculator.
At any given time during cruise, if the engine was to fail, all around you in every direction, you are looking at your possible landing sites. Go back to the definition of glide ratio: “the distance of forward travel divided by the altitude lost in that distance.” At altitude, have you ever tried to guess the distance of a landmark? Try it sometime.
Spot a distant airport, guess how far you are, and then pull it up on GPS. It’s surprising how difficult it is to judge distance in flight. So, just knowing you have a 10-to-1 glide ratio isn’t going to help. But by practicing gliding, you will. Knowing intuitively how far out you can land is your mental E-6B. I call this the “cone of possibilities.” Or, in other words, looking out in all directions, you should start to get a sense of how far you can glide.
Interestingly, it’s not uncommon for my students to ask, “Okay, if it was to quit right now, could we make that field, or that one behind us?” Most of the time I know. Sometimes, if I’m uncertain, we’ll cut to idle and try. It’s good practice for us both.
This also brings up another interesting point. Sometimes the best option is the one directly below you, especially if your airplane is very draggy. Gliding practice will make all the difference.
Going Mental
So, again, the point is that practice makes perfect. We have lots of awesome information and gadgets available nowadays, many much more sophisticated than the trusty old E-6B. But, as we become more “gadget dependent,” it seems we’re losing some of the basic skills that differentiate a pilot from an aviator. This practice, even if you never experience an engine failure, makes you a better aviator.
Next time, in Part 2, and the final of this series discussing engine failures, we’ll discuss setting up that final glide to the cotton patch.
Mark Murray, EAA 394554, of Georgetown, Georgia, was always fascinated by airplanes, and then discovered ultralights thanks to an article published in National Geographic in 1983. In 2008, he earned his light-sport repairman maintenance rating and turned his hobby into a business, eventually becoming a CFI and an A&P mechanic.