The unsung performance mod
Backcountry takeoffs are probably one of the least talked about segments of operation in the backcountry, which is unfortunate as they're the most limiting and critical part of a flight. To make matters worse, primary training doesn't really address this shortcoming, and what little is covered is just enough to give a false sense of security. By practicing these as an exercise in rhythm and timing, one can build muscle memory and be cognizant of timing of the segments, and apply experience to make the shortest, safest takeoff roll.
Rarely do I have people call and ask about takeoff procedures; sure, people frequently ask what plane has the best takeoff performance, but never discuss how to get that performance. I often get questions like what airspeeds to fly for a particular plane, which plane is best for the mission, three-point or wheel landing, and a variety of other equipment and approach questions. But I don't know if anyone has ever asked a procedural takeoff question. Ironically most backcountry pilots love to brag about their airplane's takeoff performance, and it is a major consideration when picking planes for this mission, and yet no one has ever called me saying: "I want to learn to take off short."
The reality is that takeoffs, and the ensuing departure in general, are significantly more complex than the arrivals, and unless you fly some ultra STOL experimental or maybe a Carbon Cub, the reality is that you are ultimately limited by your takeoff performance and little else. Rare is the day that you can take off and depart shorter than you can approach and land; this is especially true at the high mountain altitudes where we generally fly. Furthermore, for a brief period of time you are 100% dependent on your engine. Ask any turbine driver whether they would rather lose an engine at V1 in mountainous terrain, or inside the marker on an approach to minimums. I think most would opt for the latter. Additionally, they have in hand a wealth of information and all-encompassing formulae that a those smart engineer guys have figured out well in advance that determines with reasonable certainty whether the takeoff is possible. In the backcountry, we frequently have to make decisions based on a similarly complex set of variables. First you have to ask: Is the selected takeoff area 1) long enough for your aircraft, 2) long enough for its current configuration (heavy?) and 3) long enough for today (hot?) Second, will the weather conditions cooperate with your desired direction? These could range from tailwinds and crosswinds, to downdrafts at the departure end, or high-density altitude; or it could be combination of all four. Lastly, does the departure terrain cooperate with your desired takeoff: upstream, downstream, etc?
A good example of this is the first takeoff in the video at the end of this article. The decision was very counterintuitive, as I chose to take off towards a 1500' cliff wall that is only 2600' directly in front of me. The reason that decision was made in this case was because the "runway" has a giant ditch and 20' tall speed bump in it. I don't think my Maule that day would have gotten off the ground before hitting the ditch and subsequent bump in my preferred takeoff direction, so I chose to use that same speedbump in the opposite direction as a launchpad, and didn't even have to worry about the ditch. By using ground effect and my "launchpad" I was able to get airborne before the ditch, and by staying in ground effect I was able to easily gain enough energy to climb and turn out without no drama. That being said, in my Carbon Cub the decision would have been completely different. This is a fairly typical flow of how to decide to take off. It isn't uncommon for me and my flying partners to discuss these topics at length before making what we think will be the best decision.
Unfortunately these calculations have to happen based on experience and comfort. There is no panacea, no magic bullet rule of thumb to make a complex takeoff environment simpler. And to make all of this more difficult, the bulk of these determinations have to happen before you touch down somewhere. Back when I was just getting started flying off-airport, I landed on a short sandbar in a stock Maule M7 (it had 31's but nothing else) and patted myself on the back, then turned around and realized that while that landing was fine and dandy, I wasn't going to leave that bar under those current conditions. A bit of shoveling and things turned out okay. Candidly, a more skilled pilot probably could have taken off without much ado, but I had the sense to honestly evaluate my skill and not try it. Because of that revelatory event, and the fact that short takeoffs are relatively long at our altitude, I do a lot of practice with them and recommend that to my students do as well.You might be able to land this, but you're going to need the performance and skill to get off of it.
It should be pointed out that most of these takeoffs aren't like what you see at Valdez or other STOL competitions. The reality is that in the non-competition world you're likely carrying equipment, camping gear, and hopefully a companion to make your adventure more fun, not to mention that many of the best backcountry strips are at respectably high altitudes. Even if you're at a low "play" weight you likely have more than a few gallons of fuel on board to get you home from your remote location. That said, the takeoff roll in a moderate bushplane is still under 10 seconds. In a modified Cub type you could be in the 2-5 second range from power-up to rotation. Even at our altitudes, which range from 5,000' MSL to 10,000' MSL, we rarely see takeoffs much longer than 10 seconds. While ten seconds might seem like a lot of time, the more average 6 second takeoff is still fast enough where you have a lot of information to process and react to in a short amount of time.
In primary training, takeoffs don't really get that much attention. They usually consist of the instructor saying something along the lines of: Apply power smoothly, maintain centerline, check your instruments, airspeed alive, and rotate at some predetermined speed. In fact, it's very common to let students actually perform, hands on, the very first takeoff of their training, further setting the stage that the takeoff is easy and doesn't require much skill or thought. These takeoffs are usually accomplished with plenty of margin on the airspeed, which means plenty of runway behind you. Sure, there's a brief nod to short and soft field takeoffs, but they are mostly simulated and really just a box to check on the PTS. However, in the backcountry the terrain is typically unimproved and hostile enough that you want to be light on your wheels and up in the air as quickly as possible. On a rough surface, it is critical to get your plane into ground effect as soon as possible, as it is much more efficient in ground effect than running your wheels along the ground, suffering the friction and dental-work-jarring bumps. You'll accelerate much faster once you break ground.Break the surface quickly and accelerate to a good climbout airspeed in ground effect rather than suffering the rough bumps.
Timing and rhythm and muscle memory
For the aforementioned training gap, as well as other reasons, I like to teach that the takeoff is really a matter of timing and rhythm. Most of the old tube and fabric types that a lot of us fly don't have a comprehensive flight manual with takeoff performance data, and if they do it might account for the reduced performance of grass or gravel, but not really much else. Additionally, many airframes have been modified in one way or another, making the factory takeoff and departure numbers a distant dream. To negate these factors and turn the takeoff into something of a choreographed dance, I teach counting each segment with "potatoes" as a way to judge the different steps of the takeoff, and develop them into a rhythm. This changes in every configuration, set of environmental conditions, and for each airplane, but once you get in the habit it allows you to apply it to the next similar takeoff. It's one part muscle memory and one part experience-based. And while this is certainly a taildragger biased version, the counting per segment is really applicable to any light aircraft. I like tail-up rolling takeoffs. I like to use the brakes to line up and stabilize, but not to spool the prop. I have learned over the years that statically running up the power not only sucks a ton of debris into the prop, and subsequently the tail, but it also doesn't seem to result in any noticeable decrease in takeoff distance. This doesn't mean I don't use the brakes to lineup or stabilize, in fact I usually do a quick stab after I get rolling momentum to help bring up the tail a little early if I really need to see where I am going.
This is how it works on a typical takeoff in PA-18-150 Cub at 1,320 lbs at 7,000 DA (this happens a hell of a lot faster at sea level.) This particular method is for tailwheel aircraft with Johnson Bar flaps.
- Set flaps to match full aileron travel (typically first notch.)
- Set the elevator to neutral (this changes depending on winds.)
- Throttle forward.
- Count: 1 potato... 2 potato. Shove the the stick forward (usually the requires a similar amount of right rudder.)
- Count: 1 potato... 2 potato... 3 potato. Quickly pop full flaps and positively rotate. At this point you will have broken ground at just barely at flying speed. Allow the aircraft to accelerate to a comfortable airspeed, then...
- Milk the flaps back to the original setting or retract completely depending on climb needs.
For the most part, when operating most of our aircraft out of backcountry strips you'll need to build some energy in ground effect. This is increasingly true the heavier, hotter, and higher you are. Additionally, sometimes a judgment call needs to be made to hold it on with your wheels pinned if it is really gusty. There are few feelings worse than running out of control authority while trying to milk your way over an obstacle in a narrow area, so there might be good reason to hold it on, get your speed built with the tires pinned helping you maintain directional control, then give a solid pitching rotation directly out of ground effect and away from obstacles. It won't be the shortest takeoff roll, but maybe the best idea if there is a lot of crosswind. Once again, experience is the key here.
The primary takeaway here is the underlying rhythm to your timing. It's going to change in nearly every differing configuration: weight, altitude, loading, obstacles, wind, etc. However, once you get in the habit and start to get a feel for each segment of the takeoff, the "potato" count takeoff can happen quicker than if you were staring at the airspeed indicator waiting for something to happen and then reacting.
Contingencies and conclusions
There are so many variables that contribute to what is effective in the takeoff that it would make for much too long a read, but here are the reasons this method has worked for me, and why I teach it:
First, the flap handle is positioned primarily so that I can reach it (first notch.) In some aircraft, you're going to have to lean too far to grab it from a fully stowed position (which is technically the least drag even if negligible) and I find this is very distracting to people who aren't completely comfortable in their aircraft in this environment. In most aircraft, a notch of flaps also allows you to bring the tail up sooner.
If the wind cooperates I leave the elevator at neutral until I'm ready bring the tail up. If it's windy this varies. The main reason that I bring the tail up as soon as possible is that it allows you to (once the tail is up) effect a pitching moment to induce a positive ground breaking rotation vs. taking off from the three-point attitude. An ancillary benefit to bringing the tail up is that it reduces the amount of debris that gets kicked up into the tail surfaces. If the runway isn't straight or is rough, getting it off the surface quickly reduces the possibly of the fragile tailwheel being damaged or acting as an anchor in soft dirt or sand. And last but not least, the visibility over the nose with the tail up is much better.
The reason I like the technique of counting per segment is that these takeoffs happen relatively fast even at high altitude. It may seem like forever but it's mere moments. A heavy Maule at 6,500 feet DA is still only an approximate 8 second takeoff roll where at sea level it might only be 4-5 seconds. Our Carbon Cub at average density altitude for mountainous Colorado is less than 4 seconds. I can't even imagine how fast that happens at sea level, but I assume it is quick. One really needs to have a feel for when the airplane is ready do each segment, and by getting in the habit of consciously counting (or even out loud when teaching), you put rhythm to a task that is often much more procedural (airspeed alive...rotate at X KIAS, etc) There's a lot going on in those few seconds, and many aircraft will rotate long before the airspeed registers. You can't look outside and stay on your predetermined line and keep your eye on the airspeed indicator or any other instruments. When you're off-airport, you must have your eyes focused outside the cockpit.A Maule M6 performing a shortfield takeoff during competition at the Texas STOL Round Up in Llano, Texas.
Using the rhythmic technique and focusing outside also allows you feel out your plane and determine if everything is working properly without putting too much focus on the instruments. I have aborted a handful of take offs for a variety of reasons, from too much tailwind to a failing magento to a sticky brake (hard to diagnose when you have 35 inch wheels!) In each of these scenarios, it was diagnosed the moment I attempted to lift the tail up and it was ineffective at my usual count point. That's another reason for lifting the tail-- it gives you a reference point for expected performance. If you know you have a tailwind or are heavy, or have any other reason to expect reduced performance, you can make a plan for aborting the takeoff. If my tail isn't up by the "X" potato mark, I'll abort and take a second look. There's no guessing, no arbitrary abort point; just a routine and reliable reference to help make the decision. If you don't have a plan, what happens purely by reaction or luck just isn't working banking on. If you've never aborted a takeoff, you should know that it takes a significant distance if you don't make those decisions quickly. I would say for my average student, an aborted takeoff without a plan takes much longer than either the takeoff roll or the landing roll. In many backcountry strips you might only have enough room for the roll while the rest is done over a non-"runway" segment.
It is important to point out that every take off is different, and different methods work for different aircraft and different people, but by actually putting a rhythm to each segment you can produce an accurate, reliable, and reproducable feel for your plane. After a great deal of practice you'll get an idea of what to expect at different configurations and environmental conditions, and by counting you give a rhythm to your actions and a very deliberate plan for each action. In doing so you not only extract the most performance from your plane, you also get a way to diagnose the health of the takeoff for this very critical phase of operation.