Originally Posted on FreeFlightAdvice.com: February 21, 2015
Q: I have been hang gliding for 3 year, and i would like start learning how to make a loop… But in my country there is no one who knows how to do it…
I am have a lot of doubts… what speed must i have…? what should be the amount of VG…? What do i need to practice first…? So my email to you has two questions…
First if you can descrive in details all the process for a perfect loop…?
And the second is if you can give me one or two exercises to practice… and i will film them and send them to you…. and you could give correction and instruct me so that when i go for it i know exactly what i am doing…
This is my dream… possible know only on Photoshop…
Thank for your attention and let me know your thoughts and if you can help me…
A: This is a fun question and I’m surprised it’s taken someone so long to ask it! I have to predictably preface my response by saying aerobatics are dangerous, and hang gliders are not practical aircraft for such activities. There is also a big difference between doing “wingovers” (which are really just high-banked turns) and doing what I like to call “BIG aero” which is the large climbing maneuvers like loops. If you can live without looping your glider, I suggest you do that. But if you MUST… read onward…
You might want to start with our previously published article about how to get into aerobatics by building a solid foundation first, and progressively working up to the bigger/riskier maneuvers: http://freeflightadvice.com/aerobatics/
Since that article already exists, this one will be entirely dedicated specifically to LOOPING.
At first glance loops are beautifully simple. In physics terms it’s the transfer of energy from potential to kinetic, and back again. In layman’s terms, we take altitude turn it into airspeed by diving… then we cash in that airspeed for altitude as we climb up and over the top of the loop. In this simplistic view, we can identify some key things to focus on.
Altitude- lots of it! Entry speed- the faster you go, the less likely you are to run out of speed at the top (but there are other risks associated with going TOO fast, which I’ll get into below). And the last key is efficiency- when transferring energy we want to preserve it as much as possible (so to answer one of your questions, that means full VG).
Let’s look at each of those key things a little bit closer, starting with altitude. It seems kind of obvious we want lots of altitude if we’re going to loop. But what I’d like to touch on is how that altitude is achieved. One of the risks in doing aerobatics is the extreme loads we can create on our wings if we are not careful… or if we hit turbulence at high speed. So thermic conditions might be great for getting really high… but it’s very high risk for looping, and I can’t discourage it enough. We want very calm, smooth air. There are a select few ridge soaring sites that offer such conditions, but usually this means flying either very early in the morning or very late in the day… from a really high mountain. Or towing.
Another key we identified is entry speed. I really can’t give you a specific airspeed you need to achieve in order to accomplish a loop. There are WAY too many variables… and you shouldn’t be looking at your airspeed indicator as you’re entering a loop anyways! But what I can tell you is that the dive, or entry of the maneuver, is an art in itself. Check outJohn Heiney’s article “The Ups and Downs of Freestyle Hang Gliding”for a great write up on “learning to love the dive”. Do not be fooled into thinking it’s so simple as “pull in to go fast”. There’s a lot more, like how slow you are going before you pull in, and how quickly you pull the bar back, both of which can get you a more nose-down attitude and therefore help you build more speed. But there’s such a thing as too much here, too… because if you reach top speed when you are still pointed straight down, now you need to let the bar out a little to begin pitching around… by the time you reach keel-level with the horizon, you have used up some of that speed you built up.
I also like to think of bar position as “pitch in reserve” when talking about aerobatics. Usually we associate a given bar position with a given airspeed, but that’s not exactly accurate. The fact is, the farther back the base tube is when you enter a loop, the more pitch you have available to you to create direction change and maintain positive load around the top. More on this later…
The other key thing we identified is efficiency. This applies in two places- First, our equipment. The higher performance the glider, the better it holds energy (and I mentioned earlier, always VG full tight for looping). The other place efficiency applies is in your inputs. Even if you get your glider going super screaming fast, you are not likely to do a successful loop if you let the bar out very quickly because you will lose all that energy you built up. On the other hand, if you let the pitch out too slowly, you will do a HUGE arc and probably run out of energy before completing it. The most efficient pitch rate is something best learned through experience- another reason to start with small wingovers and very gradually build the skills to loop.
My process is this: I like to start by getting the glider into a steep nose-down dive to build lots of speed. Because a true loop requires that we enter and exit on the exact same heading, I focus on keeping the wings level and doing my best to prevent any kind of yaw oscillations as I begin my dive (lowering the nosetooquickly seems to lead to yaw or roll issues). I feel strongly about only using appropriate equipment for aerobatics, and one such tool is a cocoon harness. I mention that now because, as
Balled Up and Going Fast on a U2 160
I’m sure you’ve seen in my videos, I like to “ball up” and really get by weight forward. Back in the olden days of looping- before my time- such acrobatics were required to get the lower performing gliders up to the necessary speeds to loop. Modern topless gliders are very different- we need to be careful of going TOO fast. I like balling up because A) it feels F***ing cool, and B) because then I can straighten out my body to move some weight aft and begin the pitch up entry of the loop, WITHOUT bending my elbows are changing the bar position at all. Keeping my elbows straight helps with the bar pressure at the entry as the glider begins to load up, and keeping the bar position way back gives me maximum “pitch in reserve”. If you are going to use the balling up technique, it’s important you don’t hold it too long! With that much weight moved that far forward, holding it is about guaranteed to overspeed your glider. I once achieved 117 mph doing this, and I’m very lucky my wing didn’t disintegrate around me at that speed. Our gliders are not built or tested for such abuse… and we should not expect them to withstand it!
Once I’ve straighten my body and the glider begins pitching up toward keel level, I am monitoring my pitch rate by watching the horizon. Speed + pitch rate determine the size of your loop, and at this point our speed is what it is and it’s too late to do anything about that… bigger loops need more speed, and the more speed you have the faster your pitch rate probably is as you’re entering. So if my pitch rate seems a little slow, I’m going to let the bar out a teeny bit more to tighten my loop so it’s a little smaller so I have enough energy to go all the way around. This takes a lot of practice and experience to feel and analyze and make split second adjustments like this… I recently wrote about my first two loops where I was not ready because I couldn’t keep up mentally as the glider went around. Do not short yourself my rushing into loops- build your foundation so your mind is ready!
Head Up and Looking Where I Want to Go
As I continue climbing into a nose-up attitude, I’m really focusing on keeping the wings straight, level, and balanced. I know I’m going to lose visual reference of my heading (the horizon ahead) as I keep pitching up, so I’m doing my best to make my loop as straight as I can here. Once I’m maybe 15-20 degrees nose-up relative to the horizon, I look straight up toward my nosecone. At looping speeds the glider is VERY sensitive to even tiny roll inputs, and if you turn your head to look out to one side you are very likely going to roll that way just a little bit, and your loop won’t be on heading (so technically just a climb-over, and no longer a loop at all).
Once I’ve given up the horizon I’m basically looking at blank sky. I could be climbing straight up like a rocket or I could be close to upside down at this point… and with only looking ahead, I track my placement in the maneuver through G loading…
Climbing Into a Loop at Cowboy Up Hang Gliding in WY
The only G load that keeps us hanging in our harness (and having any weight shift control over the glider) comes from the centripetal force of the pitch direction change. What I do here depends on the situation; if I’m trying to do the biggest, roundest, best loops I can- then I’m trying to maintain a very light G loading all the way over. I’m letting the pitch out justenough to keep me positively loaded… but I’m well less than 1G of load…light, but not weightless. But if I’m not so much focused in HUGE loops, or I’m nervous about slightly variable conditions, or not having tons of altitude, I will let the pitch out a bit faster to spend less time upside down… and monitor that still by trying to maintain a constant G load over the top, but the smaller, faster, tighter maneuver produces more G’s. Again, it takes a lot of practice and training to mentally prepare to truly fly the glider THROUGH the loop… it took me around 15 years of being absolutely obsessed with it!
As the horizon comes into view (inverted) beyond my nose cone, I’ll at the very least
One of My Loops Where I Should Have Pulled In More In the Exit
stop letting the pitch out at this point- and may even pull in very slowly. Because we lose speed as we climb into a loop, if we maintain a constant G load throughout the loop the shape of the maneuver tends to look like a #9, where it gets tighter and tighter as we slow down. Nothing wrong with that, except aesthetics really… but to “fix” this I’ll try to stretch the back side of the loop a little. Again, this is really situationally dependent, and I don’t always do it. But the principle is that pulling in lowers the angle of attack, reduces the pitch rate, and flattens out the back of the loop a bit. As long as I’m past the apex (keel level with the horizon, inverted) I’m not too worried about stopping upside down, because I know the physics work for me. A glider with airspeed and a forward CG (because I’m pulling in) will want to point the nose down toward the ground. If anyone reading is going to try this bit, it’s important to note how smooth that pull-in needs to be… because our
David Gibson Shows Us Pulling In Through the Exit
bodies + harness weigh so much more than our wings, the laws of inertia mean if you stuff the bar too fast you’re more likely to rotate the glider opposite of the desired pitch curve… and then you’ll experience negative G’s, and you’ll probably slam in to your glider, and… well it’s all bad after that…
So maybe you’ve read this far and thought to yourself “Ok, now I know how to loop”…
And maybe you do? But knowing it, and executing it are very different. The thing with looping is that it has very narrow margins for error… and the consequence of a mistake- even small- can be SEVERE. I would not be so bold as to say there is NO safety margin… and I wouldn’t say you have to be PERFECT if you are going to do a loop… but that’s pretty close to the truth. The margins are made larger by YOU- training, practice, study, and understanding. By managing the situations you create- what equipment you use, how well maintained it is, what site or conditions you are doing this in. There’s very little we can do to mitigate the consequences of an error… so do all you can to prevent an error in the first place.
Enter going fast, but not too fast. Pitch smoothly and efficiently, without overloading the glider, but not so slow you run out of speed before you’re past the apex. And maintain as much “pitch in reserve” as possible. Starting out, you can spend as little time upside down as possible by continuing to pitch out through the maneuver- some call these “safety loops” (funny name, considering). And if you get slow, get your weight FORWARD and HOLD ON! I hate even saying this, but pushing out is kind of ok- IF YOU HAVE AIRSPEED- because it increases the pitch rotation and completes the loop faster, with more positive G load (more weight shift control). But having your CG aft while inverted is EXTREMELY risky as your airspeed decreases… and if you’re already pushed out, and getting slow, the motion of pulling in might very well initiate a tuck. It’s kind of a bad place to be all around, so avoid it by doing it right from the start… which is done by working up to looping very progressively (did I say that already?!)
Don’t rush it… you can get here with practice and patience!
The last thing I’d like to say is the VERY valuable lesson my father taught me about aerobatics: Do not EVER do anything that you aren’t sure of the outcome. If you’re not sure how your loop will end up, don’t even try it because you’re clearly not ready yet. When you’re ready, if you devote the time and effort for many years, there will be no doubt how it will turn out because it’s just what you’ve been doing already, only very slightly different (no roll as you climb).
Be careful, be prepared, and if you MUST do it- do it as safely as possible! Oh, and get it on video (to learn from, of course) haha