The "D" Point by Brian S. Germain
Although there are many ways to improve one’s accuracy in parachuting, I have found no better way than flying a consistent pattern. By connecting a series of invisible points in the sky, “Altitude-Location-Checkpoints” as I call them, we can create a consistent flight path that makes us more predictable in the air, as well as significantly increasing our chances of landing on target. The typical pattern, made up of three distinct turn points, I will now argue is not quite enough to get to the target with the consistency we are looking for.
The standard flight pattern for a ram air parachute involves a downwind leg, a cross wind leg, and an into-the wind leg, also know as the final approach. This pattern is defined by three distinct turn points, “A” (Base to Final), “B” (Downwind to Base), and “C” (pattern entry point). It is true that if we are prepared to modify our approach in light of new information along the way, we can hit the target. But wouldn’t it be nice to get there without needing to modify our flight path, to just sail along and turn when the altitude is right? That is exactly what the inclusion of a fourth turn point does.
The trouble with the standard pattern is that there is a good deal of guesswork when it comes to the length of the Base leg. Depending on the glide ratio of the parachute, the location of the turn to Base leg will vary widely. The better the relative glide ratio, the farther the turn to Base needs to be from the target. Our ability to adapt to this changing environment is spotty at best, and often requires substantial correction along the way. This creates traffic conflicts, as well as varying airspeed and decent rate, making life far more difficult for us, and for the canopies behind us. In most cases, the length of the Base Leg needs to be longer than we think.
This becomes an even more important issue for swoopers setting themselves up for a high speed approach. If the length of the Base Leg is incorrect, the pilot is forced to either float in the brakes or “S-Turn” prior to the initiation of the dive. This has consequences to the approach, even if they manage to reach the Initiation Point at the correct altitude. If they are flying significantly faster than usual when they arrive at the initiation point, they may lose much less altitude in the turn due to the increased front riser pressure upon initiation. If they are flying significantly slower than usual, they may lose a much greater amount of altitude in the turn, and find themselves hooking into the ground. It is my experience that, aside from the altitude of the Initiation, the selection of the “B” point is the most important aspect of a high speed approach.
If we simply add another checkpoint prior to the entry into the Downwind Leg, we can take the guessing out of the process. Assuming that the turn points are equidistant in altitude (300, 600 and 900 feet), we can simply add another unit above the original pattern entry to create a fourth, or “D” point, precisely on the wind-line, upwind of the target. What this does is, it creates a Pre-Base Leg, which shows us exactly how long the Base Leg needs to be. In other words, if the altitude between the points is 300 feet, the “D” point is at 1200 feet.
The beauty of the data that this “D” point brings us is, we discover the exact length of the base leg without choosing the precise location of the “B” point prior to exit. This means that we can fly this pattern at a new drop zone, or when we are landing off, and learn where the altitude-location-checkpoints are for that specific landing area. It doesn’t help us with the “depth” of the pattern points, but it puts us in the ballpark, assuming that we have a rough idea of our canopy’s glide ratio.
When the winds pick up, this method still works perfectly well. The crab angle on the Pre-Base Leg is equivalent to the angle of crab on the Base Leg. Note that the horizontal distance of the offset from the target on the downwind leg on a windy day is exactly the same as it would be on a no wind day (A to B = Anw to Bnw). This is only true if we do not compensate for the side-slip of our ground track due to the crosswind legs.
However, even when we do choose to compensate for diagonal crabbing on the base leg and create a “Holding Crab”, if we create the same crab angle on the Pre-Base Leg, we end up on the perfect final approach despite the complex situation. This is easily accomplished by simply making our goal to fly a box pattern on the ground, flying our Pre-Base and Base Legs perpendicular to the wind-line.
Also note that the length of the base leg is longer on the No Wind condition than it is on a windy day on which we perform a Holding Crab on the crosswind legs. This is due to the reduced groundspeed when in a Holding Crab, and the diminished glide ratio that comes as a result of it. If you aren’t pointed where you are going, you will not move there quite as quickly.
This method assumes something that many canopy pilots do not have: a trustworthy altimeter. A standard dial-type, analog altimeter is not sufficient to give us the kind of accuracy we are looking for. Even the digital dial-type is not usually graded in such a way that we can distinguish units of one hundred feet or less. These are freefall altimeters. For the precise data required by today’s canopy pilots, we need digital altimeters with digital read-outs. Even better, many of us have found, is the heads-up advantage of an audible altimeter designed for canopy flight such as the Optima and Neptune. If you have an audible alert telling you where you are, it is far easier to keep your eyes looking outside the cockpit and on the action that may require your instantaneous reactions. All that being said, your eyes have ultimate veto power. If things do not look right, your instruments must be ignored. Too many skydivers have hit the ground due to complete faith in their instruments that let them down due to mechanical problems, battery issues or some unconsidered technical malfunction.
Assuming that you use this accuracy technique the way it was intended, and you notice what is happening as it is happening, you can take a huge step forward in consistently hitting your target runway. It will take a while to dial-in your approach so that you actually hit the target, but the target is always a secondary goal to hitting the centerline of the runway and turning to final at a reasonable altitude. If you plan your pattern well, using four distinct points along the way, you can change what you are capable of handling as a canopy pilot. Not only will you feel better about yourself, you will increase the likelihood that you will live a long, healthy life. That, of course, is the mark of a great skydiver.
In addition to being a highly experienced skydiver with over 14,000 jumps, Brian Germain is the author of several books including The Parachute and Its Pilot, Transcending Fear, Vertical Journey, and Green Light. He is currently designing canopies for Aerodyne Research, and offers canopy flight courses worldwide. For more about Brian’s Books, Seminars and Parachutes, visit his websites: www.BigAirSportz.com and www.TranscendingFear.com
Landing Pattern – Landing Approach Simulation
Landing Pattern is an interactive computer simulation program for ram-air parachutes. It is similar to flight simulators, such as Microsoft Flight Simulator. One can fly a landing approach of a parachute in different wind conditions. Currently only Skydive New England is available in
the simulation as a virtual drop zone, but more will be added in the future.
Usually the landing pattern is shown to the students on top of an aerial picture or a satellite image. The pattern has an entry point around 1000ft, then the turn to the base leg around 500ft, and then the turn to the final around 300ft. The altitudes for these points are kept constant, while the position of the canopy
relative to the landing target changes depending on the wind conditions and canopy parameters. Static Line Interactive released a free online service Landing Pattern Estimator that shows you the landing pattern above the satellite image from google maps. Landing Pattern allows you to fly a landing approach. Landing Pattern comes with tutorials that explain each leg of the landing approach.
You can pick the wind direction, wind strength, starting altitude, position for the
jumper, and the type of the altimeter to use (digital or analog). You control the
left toggle by pressing the left mouse button and moving the mouse up and
down, and holding down the right mouse button allows you to control the right
toggle. If you hold both mouse buttons together you control both toggles at the
same time to flare the canopy. You can experiment with normal and flat turns. It is possible to switch between top view, side view, first person view, and free camera. You can show or hide the landing approach guides.
Top view allows you to see the the movement of the jumper from above, which is useful to see the
general shape of the pattern that you are flying. It is easy to see when to turn to
the base leg or to the final leg.
Side view allows to see the difference in altitude between the jumper position
and the proposed landing approach. It is also useful to see the changes in the
canopy pitch as the flare is performed.
After understanding how to fly the approach using the top and side camera views you can use the first person view. This is how you would fly a canopy in real life. You can look at the analog or digital altimeter mounted on your chest. You can also see the proposed landing approach to follow. Use the mouse to look around and locate the target. Free camera allows you to fly the camera around so you can find the perspective that helps you the best.
At the end of the jump you can flare the canopy for landing. After touchdown,
you will see the speed of your landing as well as other statistics about your jump.
You can review the trajectory of the jump and compare the current trajectory
with trajectories from previous jumps.
Author Information:
Alexander Shyrokov is the founder of Static Line Interactive, Inc.
Big Canopies in Turbulence
I have spent much of my life studying parachute stability. It has become an obsession of sorts, spurred by a fairly sizable stint in a wheel chair- funny how that works. I have designed and built many, many canopies with the goal of creating collapse-proof canopy. I have failed. It is impossible.
This is the case because, despite the best efforts of the designer to increase internal pressurization and dynamic stability, the canopy can still be flown badly and become unstable. This will always be so. The job then, falls on the educators, and on the pilots themselves to learn and rehearse the essential survival skills that increase the chances that the correct action will be taken in the spur of the moment.
I stated in my original article on turbulence, entitled “Collapses and Turbulence”, that the key is to maintain lots and lots of airspeed and line tension. I still hold that this is generally the truth. However, upon re-examining the situation, I have realized that my perspective on the situation is based on my frame of reference. I fly sub-100 square foot cross-braced speed machine that falls out of the sky like a homesick bowling ball. I do not really represent the whole. The average-size parachute is 150-170 square feet in the civilian world, and much larger for students and military jumpers. In further exploring the issue from the perspective of lighter wing loading and larger parachutes, I have discovered that this is not necessarily best way to fly a larger canopy in chaotic air. Here is why this is so:
If the parachute has a great deal of drag, i.e. a light wing-loading, thick airfoil or is a large parachute in general, the rules change. Such canopies are less capable of maintaining high speeds unless flown very aggressively. Due to the high drag variable at the canopy end of the drag equation (“Rag Drag”, as I call it) the excess airspeed makes the canopy itself want to retreat behind the jumper far enough to reduce the airspeed far below the unadulterated full flight speed. This momentarily increases the likelihood of a collapse. The parachute levels off in mid air, slows down, and for a brief moment, becomes vulnerable to collapse.
Therefore, when flying a canopy with a short, powerful recover arc, aiming to increase the speed beyond full flight becomes a double-edged sword. If the timing is wrong, such as when leveling out high (prematurely), the situation can become very dangerous. The truth is, leveling off well above the ground is dangerous for any wing-loading, and can happen with any parachute due to an incomplete plan or an imperfect execution.
Parachutes flown below one G, at speeds less than full flight speed tend to be more susceptible to collapse. So, if the pilot is quick with their "Surge-Prevention Input", (what paraglider pilots call "flying actively", the risk of collapse is significantly reduced as the negative pitch oscillations will be minimized, thereby diminishing the likelihood that the wing will reach a low enough angle of attack to actually achieve negative lift and dive toward the jumper (i.e. collapse and scare the daylights out of you).
Given the fact that the only preventative or corrective response to a collapse is to stab the brakes as quickly as possible, the sooner the pilot responds to the forward surge, the less the input necessary to avoid or correct a collapse. Therefore, a canopy with a great deal of slack in the brake lines will require more motion on the part of the pilot to create any appreciable effect. This means that a canopy that is in full glide, with the toggles all the way up in the keepers and three inches of excess brake line trailing behind will take longer to see an increase in the angle of attack due to the control input than one with no slack in the brakes at all.
So then the question is posed: “Do we shorten the brake lines on larger canopies to help the pilot prevent collapses?” The answer to this is no, we cannot. This will result in serious bucking during front riser input. It will also mean that following a few hundred jumps, the canopy will be in significant brakes when they think they are in full flight, due to their “lazy arms” pulling the tail down when they should be flying arms up. This will result in lower average airspeeds that will reduce the parachute’s flare power, as well as it’s penetration into the wind. This will also result in more oscillation and distortion in turbulence.
The answer comes to us from our sisters and brothers in the paragliding world. They teach their students to hold a touch of tension on the brakes when flying through turbulence. The goal here is not to put on the brakes and deform the tail, but to simply take up the slack on the brake lines, in preparation for a 12-24 inch strike on the toggles to prevent a collapse. Some teach their students to hold about 5 lbs of pressure on the brakes, while others teach that we should hold no more than two inches below the “Feel Point”. Either way, taking the slack out of the brakes is like standing ready in the door, even when you can't see the count.
So, on larger canopies, it appears that a light touch on the brakes may help prevent collapses. However, it is not because the canopy is more stable in this configuration, but simply that the pilot is more prepared to prevent the wing from surging forward in the pitch window. Once the wing has passed through that parcel of turbulent air, however, the job remains to regain the full flight airspeed, while maintaining positive G's. Letting the wing surge back into full flight too quickly can send the wing out of the frying pan and into the fire. Get it back to speed gently, but get back there as quickly as possible. These are opposing goals, so the actions of the pilot once again become pivotal, calling upon trained skills and acute attention to sensation.
Ultimately, the best way to handle turbulence is to deny it battle. Despite what your ego is telling you, you already have enough jumps. I know you want more, but sometimes the best way to go is to sit on the ground and watch the inexperienced jumpers get experienced.
Live to fly another day.
Brian Germain Big Air Sportz www.bigairsportz.com
Canopy Control - A DVD Review
When I started skydiving more than 25 years ago,
the leading cause of skydiving deaths was the failure to pull on time, or at
all. Skydivers just failed to do the one thing every one of us knew we _must_
do: pull.
Education, regulation specifically addressing
this issue, and not least the development by Helmut Cloth of the first AAD
widely accepted by experienced skydivers in the 90's helped to control this
problem… only to show the emergence of another, more insidious: skydivers were
dying in increasing numbers under perfectly good parachutes, hitting the ground
at unsurvivable speeds sometimes after colliding at low altitude with other
perfectly good parachutes. And this happened not only to hot shots under
handkerchief-sized canopies, it also affected jumpers flying conservatively
under big canopies.
Once more, the response adopted by the skydiving
community has been to put an increased emphasis on the education of skydivers,
their instructors, safety officers and DZ operators.
It is here where “Canopy Control: Core
Essentials” fits right in. Produced by VASST.com and authored by Chris Gay and
Chris Warnock, it is aimed primarily to new skydivers. To them, it will be an
invaluable tool to complement and clarify what they are learning in the first
jump course. But while reviewing it I found it is also extremely useful for
experienced skydivers as a refresher of basic concepts that may or may not have
been adequately acquired, and sometimes forgotten, years ago.
The DVD is divided in several sections totaling
55 minutes, with another 12 minutes of bonus material plus a couple of printable
charts. In the beginning the host Chris Gay introduces a key concept: “the
person most responsible for your safety, is you”, and it is with this in mind
that one should view this DVD, regardless of experience level. Throughout the
DVD the importance of different aspect of flying our canopies in relation to
others is constantly reminded and related to, as a way to increase our awareness
of other canopies in the air and to reduce the chances of a collision. It is
also constantly reminded to seek advice from an instructor or canopy pilot
coach.
In the “Terminology” section, Chris Gay
introduces and proceeds to explain basic terminology and concepts related to
canopy flying. As through DVD, well conceived and executed graphics, both static
and animated, are used to clarify the point being made. This, in addition to the
even more prevalent footage of canopy pilots executing the maneuvers being
discussed or explained.
In “Planning and Landing Pattern”, this process
is thoroughly explained. While more experienced skydivers jumping at their local
DZ may not be conscious of doing it, it is a skill that must be acquired and
developed. And when we are on a new DZ… well, then we all are “new” skydivers.
In this regard, great importance is given to acquiring local knowledge on the
peculiarities of any given DZ we may be visiting regarding local regulation,
obstacles, landing areas, not to land zones (a.k.a. Farmer McNasty’s fields),
wind indicators, etc. Also, it is explained how to explore the landing area and
what to watch out for.
The section “Flying the Pattern” follows, in
which great emphasis is given to adapting the landing pattern to changing
conditions. There is an extensive treatment on how to modify the landing pattern
according to different wind conditions, and what to do if they change after take
off. Similar treatment is given to the effect canopy traffic on the landing
pattern and how to adjust accordingly, or what to do is you find yourself in the
landing pattern at altitudes different than planned. And what to do if, in spite
of all our planning and best efforts, we find we are not going to land where
intended? That is also explained in this section.
“Canopy Controls” is the most technical of the
sections, in which a in-depth explanation of the diverse methods of controlling
the parachute is given, as well as in what situation every kind of input is
appropriate, always relating it to the aerodynamic forces involved.
“Getting Back From Long Spots” deals with how to
recognize the probably landing site and how to adjust the flight of our canopy
to correct it in order to land in the intended site in different wind
situations. It also explains the ever important how to plan and what to watch
out for if we end up having to land out.
“Flaring” advices on how to improve our
landings. Explains how the canopy reacts while flaring for landing, different
flaring techniques, and how to learn more efficiently this aspect of canopy
control.
The main section of the DVD finalizes with a
“How to Learn More” section, in which different training aids and techniques are
advised.
In the Bonus section a variety of complementary
topics are discussed: wing loading, technical aspects of canopies (7 vs. 9
cells, elliptical vs. “square”, cross braced vs. standard, flight
characteristics of small vs. large canopies), on heading openings, packing for
better openings, when to learn swooping, and finally a safety review Q & A. As a
bonus of the bonus, if I may call it that, there is footage of the Canopy
Formation 4-way world champion team Clean Air demonstrating what it is meant for
“canopy control”.
In summary, as stated by Chris Gay, “Our goal to
make this DVD is to help to make you a safer skydiver”. I believe that reviewing
and following the advice in this DVD, both by beginners and experienced
skydivers, will certainly be a big step in that direction.
Canopy Formation Part II
CANOPY FORMATION PARACHUTING
- CF (Part 2)
Part 1
may be read here
Packing the Canopy
You will want to pack your canopy for a CF jump in a way
which will ensure that:
it opens fast and reliably
it opens on heading
all canopies involved open with identical timing
A good way to achieve this is to pack the main similar to a reserve canopy, as the requirements for a reserve opening are about the same.
Indeed, many CF teams do so. Since there are different methods of reserve packing, it is recommended that all jumpers involved in a team or group should use the same packing method for safety reasons. Doing so reduces the probability
of collisions and unintended different opening levels to make sure that each team member has an optimal set up for his way to the formation.
Type of Exit and Exit Order
A good exit speed is 70 to 80 knots with little prop blast.
Newcomers to CF will enjoy greater success if the jumpers exit one after another
in the same way students perform “hop and pops” and remain stable. It is
essential to remain in a symmetrical body position until the canopy is
completely inflated to assure that the canopy opens on heading and continues
flying straight until you want to fly your pattern towards the docking position.
With experience comes a tighter exit timing, and this practice becomes even more
important.
If your canopy does not open on heading you can easily end
up in a dangerous collision or at least in a bad position during the approach to
the formation. Also, other jumpers can be disturbed as they try to avoid the
errant canopy.
In general you will exit in the order of your position in
the formation. Competition teams might use different techniques to speed up the
build of their first formation.
Timing
Teams with more experience will eventually develop an exit
with two or three jumpers standing in the door, jumping with only very little
delay, and pulling in sequence to create a perfect set up for the build of their
first point. In this type of exit, the last jumper leaving the plane (front
person in the door) deploys first. The next jumper deploys when he can see the
beginning deployment of the jumper above. This leads to a set up with the lower
canopy slightly in front, which creates a perfect set up for a final approach.
Set-Up for Building the Formation
In most cases it makes sense if the person flying the Base
sets up on heading, flying with a little brakes and slightly lower than the
jumpers that will dock next. That gives the next jumpers the potential to fly to
their docking position because altitude is our fuel.
A good position for the final approach of a single canopy
is slightly higher and to the side (perhaps slightly behind) of the canopy to
dock, onflying parallel with it.
The optimum setup of course depends on the flight
characteristics of the formation to dock on.
For docking on a fast sinking formation, it’s probable that
the setup will be lower than for docking on a floaty formation. The necessary
experience to estimate the perfect set up will only come with the jumper and
quality of your jumps
Body Position
Fig2.1
To keep your canopy flying straight with even controls, body position must be symmetrical. Shoulders should be square and arms in a “box position” with legs slightly spread and bent as shown in the sketch of a stack. If you lift one leg from that position while stretching the other one your canopy will start to turn towards the stretched leg. If done with intention, this can be a useful tool. For example, a stair step formation might benefit from stretched-leg control. Bent legs also provide the potential to compensate for tension in a formation and to dampen oscillations.
Reducing Altitude
When getting into the setup position for your final
approach to the formation you may find yourself higher than desired (if your are
too low or far behind you won’t be able to get into the formation).
There are different ways to lose extra altitude without
using much space. It always makes sense to stay in a small area because long
distance movements take much more time. Additionally you may interfere with the
waiting position of another jumper.
Furthermore, you might have difficulties estimating your
exact position. Below, you’ll find methods of losing altitude.
Cross Controls
If it is important to use very little space, you can easily
lose altitude by using cross controls. That means you’ll pull down one front
riser, then compensate the move your canopy would now make by applying the
toggle on the opposite side. Because the canopy is being distorted it sinks and
will pick up speed to the distorted side. The toggle action evens out this
momentum so that the canopy ends up sinking in place, assuming that the right
balance is applied. Doing so you can get into the desired set up position for
your final approach without disturbing another jumper in his set up position
close to the formation.
Rear Riser Stall
A similar result can be achieved by performing a rear riser
stall. To do so, you grab the connector links on your rear risers and pull them
down carefully. This is not very hard to do. Because the main part of the lift
is being created in the first third of the profile where the A- and B-lines are
attached to the front risers, this is a fairly light pull..
At first, the canopy will begin glide flatter without losing much speed. This range can be useful if you find yourself far away from the drop zone on a down wind flight pattern and want to get as close to the DZ as possible. If l the risers are pulled down a little further, the canopy will smoothly begin to stall and sink very fast. This technique can help to lose a
lot of altitude. However, it should be practiced with only two jumpers involved before being used in a big way jump. It is not recommended in a tight echelon as the canopy may come out of the stall bailing out to the side, and interfering with others in the lineup.
Rear Riser
If you are too low and need to gain altitude on the way to
your waiting position, or if you’ve gotten behind the formation, you can use
very light pressure on both rear risers to fly a fatter path without
losing much forward speed. This has to be done very carefully because it you
pull them down too much you will lose speed and only millimeters further, end up
in the rear riser stall previously mentioned.
About the oldest technique to lose altitude is the “sashay.” The sashay begins with a radical toggle turn away from the formation and then a reverse movement as soon as the canopy has tilted to the side; this movement is stopped out with both toggles. It is not very efficient, utilizing a lot of area and you may lose track of your position relative to the formation. It takes a lot of practice to get good results with this radical maneuver.
Over the Top
Also from rotations comes the “rotation over the top“. The move begins with going to deep brakes quickly. As soon as the canopy rocks back grab both front risers and quickly pull them down without letting go of your toggles. It takes less force than you might expect because if done at the right moment, the front riser pull will coincide with the canopy having almost no lift and no tension on the lines. Next, you riser down little further than your final
destination, release the risers, and swoop into your docking position by using
the toggles.
Today some successful teams are using a combination of the
two techniques mentioned above. However, these should be considered advanced
skills, to be discussed in another article.
Techniques for Approaches
The most challenging part of a CF jump is the build of the
initial two-way formation or the dock on a single canopy. Remember, a formation
will usually not perform as well as a single parachute. Docking on a larger
formation always gives you a little extra performance relative to the formation
since you have a single canopy with all of its lift potential. Good technique(s)
is/are required to dock with a single parachute of similar performance.
That means you’ll need to gain some momentum when
attempting to dock on a canopy flying by itself. The only way to do so is by
setting up higher and not too far behind the canopy you’ll be docking with.
The canopy to be docked upon should slightly hold brakes
to make things easier.
The docking jumper begins his approach setting from a
position with his feet approximately at the level of the canopy he’s docking on;
slightly behind or a little to the side. The approach is initiated by using
front risers to pick up speed and controlling the direction of flight. Now pilot
the canopy to a position slightly lower and slightly behind the final docking
point. The final move is performed via toggles (reducing speed), swooping up to
the desired level, and aiming the docking cell to the desired position (center
cell for a stack or end cell for a stair step). It is essential not to have too
much energy left when docking and also not to end up too low. If you end up too
low the dock will fail. If you find yourself having too much left-over energy,
you should abort the dock for safety reasons and use the potential energy to fly
to a good position for a new setup and another attempt.
Building the Formations
In principle, there are only two or three ways of making
approaches.
Building a Stack
To build a stack, the jumper who is docking sets up
slightly behind and above the canopy he’s docking on while the jumper to be
docked upon flies straight holding a little brakes. The lower canopy stays in
brakes until the docking center cell has touched his back. If the dock is
perfect and he has some experience, he can take foot grips hooking his feet
behind the center lines. If not, he can release his toggles and grab the docking
canopies nose get it into the right position and then take the foot
grips. Having done so, the lower canopy pilot gets back on the toggles to
control the formation. Never release the toggles before the docking canopy has
actually touched you because if you do, your own canopy picks up speed and flies
away from the canopy trying to dock.
In any case it is important that he releases both toggles
evenly to prevent the formation from spiraling.
It is also very important that the docking pilot can see at
least the lower legs of the jumper he’s docking on. Should the legs become
shorter and shorter you need to add more brakes. It an absolute NO to pass under
a jumper you intended to dock on. If you have the impression that this is about
to happen you must abort the attempted approach by either stalling radically or
turn away with one front riser pulled down. It can be extremely dangerous to fly
underneath and in front of a formation because your burbles can cause canopies
in the formation to collapse. Also you could lift up with the middle of your
canopy under the jumper you wanted to dock on ending up in a wrap. That means if
you perform any kind of dock on a formation you have to be in full control of
your canopy at all times and able to abort if not. Otherwise you are not
qualified to do CF jumps.
Fig
2.2
If
the docking canopy ends up higher than wanted, it’s not necessarily a
problem. The docking jumper can park his canopy with his nose in the center
against the lines of the top canopy and slide it down by moderately using his front
risers until the top jumper is able to reach for his grips.
Approaches to lower positions in a stack or plane will need a lower set up
than for high positions because the formation begins to sink more with its
size - especially the “plane” formation.
Speed teams may still want to dock positions three and four from a higher
position and perform a riser dock by aiming their slider to the jumpers feet instead of the center cell.
Building a Plane
A plane formation begins with a stack. Next, the top jumper
climbs down the center A-lines and once the slider has been reached, he now
hooks his feet behind the front risers of the lower jumper. The lower jumper
helps by putting on some brakes to increase the lift of his canopy. If the top
jumper needs to pull himself down on the A-lines, it must be done with
uniformity to prevent the formation from oscillating sideways.
Building a Stairstep
The Stairstep is the second basic type of formation. The technique for building a stairstep dock is similar to the techniques explained previously but because the Stairstep is far less solid than a stack or plane, everything has to be done with lighter input and greater precision.
The set up for the final approach is slightly to the side
of the formation. To make a clean straight and precise dock you’ll want to keep
it relatively short with not too much potential. You may start with one canopy
width to the side of your target canopy and your canopy slightly lower than the
canopy to dock. The approach should be from the side rather than from behind so
that the jumper to be docked upon has a good view of the line he wants to catch
as well as remaining in the clean air to the side of the docking canopy. Also in
this type of dock you should never get too low or lose sight of the target. The
docking end cell should end up at the hip to the shoulder of the docked body.
The docked jumper can now hook his outside foot behind the outside A-line of the
docking canopy with his body staying outside the docking cell. If the grip taker
should need to use a hand grip to guide the docking canopy to a good position
for taking ther foot grip he has to be well aware to maintain his body position
in the harness to prevent unwanted influence on the flight of his own canopy.
The docking pilot puts on some outside front riser trim as soon as the top
jumper has taken his grip to prevent his canopy from coming up on the opposite
side. After having set his canopy by doing so he may release some of that trim
or maybe even all of it. Sometimes it gives you enough trim to stretch the
outside leg to keep the bottom canopy flying nicely. Sometimes no further trim
is needed any more but still you should keep your hand on the outside front
riser ready to apply trim again if needed.
The set up for stairstep docks in lower positions may be
somewhat lower. None-the-less be aware that a stairstep formation flies fast and
flat compared to other formation types. If your setup is too low your docking
time may become very long.
The build of the stairstep, stack, or plane can of course
also be done in reverse order with the lower canopy flying in little brakes and
being the target and the top canopy flying the approach. The technique is
referred to as the Top-Dock and will be explained with techniques of
sequential CF later on.
Flying in the Formation
As in free fall skydiving you have to keep on flying after
you docked. In a stack for instance, especially in the bottom position, you need
to make sure that your canopy does not get too light and floats up. All canopies
should have slight tension on the center A-line to make the formation healthy.
In a plane it is important that all cells of all canopies
are inflated. If not the jumper in question can reinflate his closed cells by
putting on some brakes. Perhaps he will also have to maintain some toggle trim
to keep his canopy’s nose open. Also a jumper next to a closed cell can help by
pulling the nose open.
Good awareness is needed in formations with stairstep grips
like stairsteps, diamonds or boxes. Especially jumpers in lower positions need
to always keep their canopies from coming up or around. Possible techniques are:
outside front riser trim asymmetrical leg position and inside toggle.
Signals within the Formation
To signal information to other jumpers in the formation
there are two ways. You can either shout a command by addressing the jumper with
his name or use certain signs. In bigger formations it is more convenient in
most cases to use signals instead of vocal communication to avoid noise and
confusion. The signs and commands to use must be known well to everybody. In
case of vocal information you must never use negative commands. If for instance
you shout “don’t cut away!” and the other jumper misunderstands he will cut
away. In this case you should have said “hold on!” for example.
In large formations there are two very useful signals to
the jumper below you: Twisting your foot sideways means the jumper whose canopy
is on that foot needs to get lighter for example by putting on some brakes or
easing the front riser pressure if possible.
Shaking the foot vertically means get heavy which means put
on some front riser pressure or signal further down if the jumper(s) below is
(are) light on you as well.
Piloting a Formation
Stack and plane formations always follow the top canopy and
are controlled by the top jumper also called the pilot. The stair step needs
more caution than the stack because it is connected less stable. Diamond
formations act similar but in bigger formations the pilot might need some
assistance by all the out side wing people to help keep the formation flying
straight or to help turn the formation. Bigger diamonds are fairly inert. It
takes some time to make a big diamond turn.
The most attention is needed in stair steps. In a turning
stair step the bottom jumper always needs to compensate the change in the flight
characteristic of the turning stair step versus the straight flying one. If the
formation is turning away from him he needs to release some of his outside front
riser trim and if the formation turns towards him he needs to increase the trim
on his outside riser. Because the links in a stairstep formation are similar to
pivot points these formations need to be turned very carefully.
Separating a Formation
Separating a formation needs at least as much attention as building one, especially for safety reasons. Also should it be done high enough. Bigger formations should be separated at 1.500m (5.000ft) and smaller ones at 900m (3.000ft).
Small formations can be split in reverse order of building letting go one jumper after another. The jumper whose turn it is to go shouts the names of the ones holding him and they drop him. Then he clears the proximity of the formation immediately to give room for the next
jumper to leave it.
Larger formations in the shape of a diamond of up to 36 jumpers can be split by using a technique called STARBURST. The starburst is being started by the designated person calling “starburst! - starburst!” which is to be echoed through the formation. Then one person starts
a count down calling “ok – ten, nine…..two, one, break!“ Everybody else joins the count loudly to make sure that everybody is able to hear it. On “one” everybody get his hands on the controls and on break lets go of the grips to fly out of the formation radially away from the center.
Peter A. Pfalzgraf
Rheingaustr. 24
12161 Berlin
[email protected]
Canopy Formation Parachuting
By Peter Pfalzgraf
In the early days of CReW (as canopy formation skydiving used to be called) I wrote and published a little booklet for those who were interested in learning the new sport. Things have changed a lot since then. So, I found it necessary to publish something new to make general information on our sport available to everybody interested. This essay combines techniques and hints from Europe and America. The latest input came from the training camps for the new canopy formation world record attempts aiming for a 100-way formation.
Canopy and Harness (Figure 1)
The times are gone where they had all-around canopies that could be used fairly well for any kind of skydive. Such canopies as the Cruisair, ¬U¬nit, Pegasus, Cruislite and Fury were once very common.
Today, the best parachutes for canopy formation parachuting (briefly known as “CF”, in the old days) are 7-cell canopies. These parachutes are the safest concerning deployment and stability in flight, especially in turbulent conditions. It is no coincidence that reserve parachutes and canopies for BASE jumping are mostly 7-cell canopies. Triathlons and Spectres with Dacron lines can be used for casual CF jumps, although Lightnings are the CF canopies of choice. If you intend to do a CF jump today you are well advised to use a canopy that has been designed for this kind of activity.
As a compromise for your first attempts, you may use a 7-cell canopy with a thick profile (for instance a student or accuracy canopy). Never attempt CF jumps with elliptical canopies, canopies with wide wing spans (in comparison with the depth of the profile/length in direction of flight) and/or a low profile.
Today’s CF canopies are available in different sizes for different weight classes. It is important that people intending to join a CF jump use the same type of canopy with the same line length and trim. Furthermore, the wing loading (weight under canopy per square foot) should be reasonably identical to guarantee similar flight characteristics.
The container of your harness should be big enough for the packing volume of the canopy to make sure it can be closed properly (safety!). There should be no handles, container flaps, pop-top pilot chutes or anything else sticking out that could get caught in another jumper’s lines. Those things could result in unintentional reserve openings or problems on separation. The bridle should be short or even better, self retracting to prevent your pilot chute from being caught in the other jumper’s lines while you are in a formation. You can imagine that separating a plane formation with one jumper’s pilot chute entangled in the other jumper’s lines will most certainly result in serious problems.
Additional Equipment
The altimeter should be worn in a way that makes sure it does not get snagged and can always be seen while you have your hands in the toggles.
The helmet should provide not only head protection but also allow good hearing. It should not cause wind noise that might affect your hearing.
Every CF jumper should carry a hook knife that can be used in case of an entanglement or wrap. Sometimes it only takes one line to be cut to get free and save a reserve ride.
The hook knife of course should also be worn in a way that prevents it from being caught or ripped away.
Your shoes must not have any hooks. They should fit loose enough that you can get rid of them if need be in order to get free.
It is very useful to wear long socks to protect your legs against bruises and line burns.
Aerodynamics of the Airfoil
Lift is the force that keeps a canopy in the air. Opposite to a round canopy that only creates a big air resistance to slow down your descent using a large area of fabric, the square parachute, or airfoil, really produces lift like the wing of a glider for instance. The square footage of an airfoil is approximately one-sixth to one-quarter of a round canopy, and yet has a far lower rate of descent.
The lift of the airfoil consists of 1/3 high pressure under the profile (similar to the round canopy) and 2/3 low pressure on the top surface created by the undisturbed airflow. This effect is the important matter for us.
The physical reasons for this effect aren’t pertinent to this particular discussion. What is most important is to know that the main part of the lift depends on the undisturbed airflow on the top surface of the square canopy, forward speed and the shape of the profile. The lift increases with forward speed and grows with the thickness of the profile. The air resistance of the canopy slows the forward speed down.
Due to the different pressure at the upper and lower surface of the profile air will flow around the sides of the canopy from the bottom to the top following the pressure difference. This effect reduces the lift and is called induced resistance. As a consequence of this, the maximum lift is in the centre of the airfoil. The stabilizers on either side of the profile are designed to reduce the loss of lift by hindering the airflow from the bottom to the top surface. Another way to reduce the loss of lift is to make the airfoil very wide so that the percentage of wing area being affected becomes comparably small. A good sample for this solution is the paraglider. This shape of airfoil is, of course, not good for CF activities.
Because of the airflow around the sides and also around the tail, a parachute gliding through the air leaves a track of turbulence. The side turbulence creates a zone of turbulent air on either side beginning at the trailing corners of the airfoil. The turbulence of the tail creates a turbulent zone rising from the trailing edge of the canopy.
It is clear that a parachute or canopy formation flying into such a turbulent zone will be affected by losing lift. Even aircraft flying through the turbulence of a canopy formation will lose considerable altitude.
Figures 2 and 3 show the shape and position of the zones of turbulence.
In a formation these phenomenon cause effects that can be noticed clearly. Just the top canopy in a formation gets only undisturbed airflow and has the maximum possible lift. All canopies having a body in front or on a front corner will lose lift due to the turbulence caused by the body out in front.
Aerodynamics of the basic Formation Types
Knowing the things mentioned above, we can predict that any type of formation cannot perform as well as a single canopy. That is useful for building formations as it gives the single canopy the potential to approach and dock on a formation due to its extra lift and forward speed.
In principle all formations consist of a few basic types. Let’s look at the conditions in these.
The Stack
The stack (Figure 4) is the most basic formation. To build a stack one jumper sits on top the other jumper’s center cell and hooks his feet behind the center A-lines of the lower canopy similar to sitting on a chair. There will be some tension on the lines because the lower canopy in this type of formation will have a little less lift. In a stack the body of the top jumper is in front of the center cell of the lower canopy. The turbulence of that body meets the airflow of the lower canopy exactly at the point where the main lift is created and leads to a considerable loss of lift. This means that a stack will sink far more than a single canopy.
The Plane
The plane (Figure 5) is created out of the stack. The top jumper climbs down the center A-lines and hooks his feet behind the front risers of the lower jumper underneath the slider. The lower jumper supports him by putting on some brakes to increase the lift of his canopy. For this formation type one or two cross connectors are required, which either connect the front connector links (one line) or two lines that connect the front and rear connector link on either side. Otherwise the top jumper might slide back up due to his plus of lift and pull up the slider, which would result in a collapsed lower canopy.
In a plane formation, the turbulence/loss of lift effect is not as strong. As the top jumper’s body is beneath the two canopies, one might think there is no loss of lift at all, yet the line contact causes deformation in the lower canopy and additionally forces both canopies into a new aspect ratio. This leads to a loss of performance. A single canopy will perform better than a biplane.
If a plane becomes bigger there will of course, be canopies with bodies in front of them. Planes with more than four canopies will sink faster as the plane formation grows larger.
The Stairstep
In a stairstep formation (Figure 6) the top jumper is positioned outside of the lower canopies end cell. He takes a foot grip on the outside A-line. Flying the stair step requires much more experience than flying a stack or plane formation because the link is not as stable. It is more of a pivot point than a stable connection. The lower jumper has to compensate for the influence of the upper jumper’s body to the flight of his canopy. To prevent the lower canopy from coming up and around you can put some tension on the outside front riser of the lower canopy or the lower jumper can stretch the outside leg while lifting the inside leg.
The stair-step is far less turbulent than the stack and plane. The body of the top jumper only causes turbulence on the outside corner of the lower canopy and that is a part of the airfoil that contributes only a minor amount of lift. That means that a stair step formation is only slightly less efficient than a single canopy.
Because only one side of the lower canopy is affected, the other side will perform better and cause the canopy to rise and drive forward. If the lower jumper does not compensate for this, his canopy might come up and around, leading to a wrap. To prevent that the lower jumper will start to compensate for the difference as soon as the top jumper has taken his grip. Possible ways to compensate include putting tension on the outside front riser and stretching the outside leg while lifting the inside leg. One might also apply some slight inside brake.
You can determine how much trim is needed by easing up on the risers or brakes after the canopy is set. Sometimes the formation will fly well with only slight trim or none at all. Nevertheless, the lower jumper should keep a watchful eye on his canopy to immediately compensate, if necessary.
That wraps up part one. Join Peter in a week or so for Part 2, when we'll dive deep into building and controlling these formations.
Canopy Flight Simulation for Education
Skydiving requires an action to survive. Freeze, fight or flight are natural reactions to stress but they do not work for skydivers. There is very little time to think about what to do next when the ground is approaching fast. Hence, our response must be quick. We can separate a human reaction into three process: perception, assessment, and execution. These processes happen consecutively. The faster we complete them, the quicker our response is to the changing environment. Let's examine how education and training affects these processes.
Perception is the process during which we become aware of information: we look at the altimeter to know the altitude, we look around to see if no other canopies are moving to collide with us, etc. Education and past experiences play a major role in a person's perception. We are not necessarily aware of what we look at. Education trains us to look for the right information in the right places. For example, if we do not look around after our canopy opens to see where the drop zone is, we will not turn to fly toward it. On the other hand, even if we see where the landing area is, we may not know how to detect if we can reach it. As a result, we may not make a turn to fly toward the landing area in time.
Books and instructors tell students where to look and what to see, while videos show us examples. However, once students are in the air, they must make a conscious effort to look in the correct direction and focus on the right information: "It's landing time. The ground is moving very quickly. It should not move so quickly. Ohh... I must look at the horizon, I must not look directly underneath." The goal is to make proper perception a habit, because conscious effort is slow. Habits develop with practice, and practice takes time. A student has not yet developed habits and may forget to think about what to pay attention to, but help comes from the instructor over the radio: "Prepare for landing flare. Eyes on the horizon..." One does not develop a habit by taking a class, reading a book or watching a video. Instead, these sources supply knowledge that can be used during practice, which eventually leads to habit. Simulation of a situation, on the other hand, does help to develop a habit, in a safe environment.
The emergency procedures that every jumper practices before every jump (you do, right?) is the example of a "simulation". In such "simulation" we create situations and responses ourselves. Another example of a "simulation" is hanging in a harness during a safety day. In this circumstance, an instructor creates an emergency situation for us. Dirt-dive is an example of a non-emergency "simulation". Airplane pilots take the concept of "simulation" further by using flight simulators (http://en.wikipedia.org/wiki/Flight_simulation). The military have used skydiving computer simulators (these are similar to flight simulators) for some time. Nowadays, computer parachute simulation software is available for everyone.
The second process in our reaction sequence is assessment - making a decision about what the acquired facts mean. We look at the altimeter and it's 2000 feet. Nothing to be done just yet, or maybe we still have a problem with the canopy, or maybe we see that we are not making it to the landing area, etc. Education has the largest impact on the process of assessment. We are taught what actions are required in different situations. At the very beginning, all we need to do is to pick the right action from the proffered set of actions.
Speed of the recall is important. Repetition is key for a quick recall. Taking a class, reading a book, or watching a video are good ways to refresh our memory (safety days help us do exactly that). The disadvantage of these methods is that they cover very limited number of situations and conditions. For example, we are told that to get back from a long spot we can use rear riser input, but that's only true for a certain ratio of your canopy forward speed and the speed of the wind. In some situations, we may have to use front risers or brakes. Now instead of a simple memory retrieval task, we have to do some reasoning. We may have all the knowledge to do the reasoning properly, but it's slow and error prone (time pressure and adrenalin rush do not help rational reasoning). Simulations offer an efficient way to condition memory by repetition. A computer simulation also allows for an infinite amount of situations with different conditions. It's easier to make a decision when we have already seen such a situation before.
Execution is the process of acting on the chosen response. Muscle memory allows us to speed up this process. Instructors, books, or videos can not help this process. Muscle memory is developed by repeating an action... but we already know that simulation is good for that! Pulling the cut away and reserve handles while hanging in a training harness or before your reserve is due for a repack are good examples of muscle memory training: we feel how hard we need to pull the handles, what the proper motion of the hands are, etc. Computer simulation can help as well, but it is most effective with a special hardware, which is not yet available at a reasonable price.
We have covered three processes that contribute to our reaction: perception, assessment, and execution. We repeat them over and over again. Every time we do something, a new set of conditions manifests itself. There is a dynamic and complex relationship between the situation and our responses to it. Instructors, books, and videos can only mention a very small set of examples. Traditional simulation methods (use of the imaginations or/and an instructor) are also quite limited. A computer simulation, however, provides real time feedback for all possible actions that we can exercise in the simulation. We can judge the correctness of our actions based on what happens next.
Simulation has always been an essential part of skydiving education and training. Computer simulation takes this concept further and allows for even better results. We have seen how it can help us when other means of education and training are less efficient or can not help at all. One may ask: "How good must a "computer simulation" be to be used for training?". A similar question would be "How good must a picture be in a text book?" The answer is "As long as it (simulation or picture) reasonably illustrates the required concepts." No educational tool can or should be used by itself. The purpose of the tools is to make a student think, ask the right questions, and develop the correct responses.
Given our limited attention span, it's always a compromise between focus on safety and focus on other things, especially for novice jumpers. The faster we get our habits and muscle memory developed, the safer our jumps become. This is why it's important to understand what tools are available to us, and what their limitations, advantages, and disadvantages are. In his book "The Parachute and its Pilot" Brian Germain phrased it this way "When we can acquire the right information, and access this data at the right time, we have a pretty good chance of walking away from sketchy situations." Our goal is "to acquire the right information." We can do this most efficiently when we understand what educational and training tools we have in our disposal: classes, book, videos, simulations, etc. The newest tool in the skydiver's toolbox is computer simulation software. This software greatly complements the other means of education and training. Which, in turn, will result in a safer and more enjoyable sport.
Author Information:
Alexander Shyrokov is the founder of Static Line Interactive, Inc.
Clean Up Your Turns
"Turn coordination" is a topic that, until recently, has been mostly unapplied to ram-air parachute aerodynamics. In simplest terms, this refers to the degree to which a flight vehicle is aligned to the relative wind during a turn. Another way to look at this is the degree to which a turning aircraft is pointed at the relative wind with regards to the yaw axis.
A "clean turn", from an aerodynamic perspective, is one that keeps the nose of the aircraft pointed at the relative wind throughout the turn. When flying airplanes, this prevents the passengers from spilling their drinks, as well as saving fuel and preserving airspeed. In parachutes however, this aspect of turning has mostly been ignored. As parachutes become faster and faster, the time has come to begin thinking about this aspect of our canopy flight for several very important reasons.
The first has to do with the ability of the pilot to level off at any point during the turn. Lets face it, sometimes the ground creeps up on us. Flying an aerodynamically sound turn increases the likelihood that you will be able to convert your airspeed into lift in a timely manner. If you are sliding sideways through the sky because you are simply jamming a toggle down, you are not prepared to interface with the planet. The relative wind is jumping across the bumps on your parachute, creating turbulent flow, while the suspension line load is getting shifted to one side of your canopy. When you attempt to stab out of an uncoordinated turn, there is a hesitation before the parachute begins to change direction and level off. If the ground gets to you before this happens you may find yourself watching Oprah in your hospital bed for a while (not that I have anything against Oprah).
The second reason for flying a coordinated turn has to do with overall parachute stability. In an uncoordinated turn, the nose of your parachute is not pointed at the oncoming relative wind. It is sliding sideways. This means that the pressure in your wing is being compromised, in addition to the wingtip on the outside of the turn being presented to the relative wind. If you hit turbulence during this kind of "sloppy" turn, you are much more likely to experience a collapse of this side of the parachute. In other words, if you are turning right, your left wing more likely to fold under. Interestingly, when an aggressive, uncoordinated toggle turn is released, the opposite tends to happen. When the right toggle is released, the right wing surges forward as the drag is released and it is presented to the relative wind, opening the door for a collapse on right side of the parachute. Either way, this can result in way too much daytime TV.
A fundamental problem...
There is a fundamental problem with the way in which most of us were taught how to turn our parachutes. They said: "if you want to turn right, pull down the right toggle." Simply pulling on a toggle increases the drag on the right side of the parachute, retreating that wing tip. At the beginning of the turn, it is purely "yaw" energy. It is like the pilot of an airplane stepping on the rudder pedal. As a discrete action, steering toggles are an incomplete input. We need some "roll" energy.
The harness is more than a way to attach the jumper to the parachute. It is also a way to manipulate the canopy itself. If the right leg reaches for the earth as the left hip reaches for the sky, the parachute will turn to the right. It is true that smaller parachutes will respond quicker to such inputs than larger ones, with elliptical canopies responding the quickest, but harness input will have an affect all parachutes. Most importantly, when used at the initiation of a turn, harness steering converts a toggle turn into a coordinated maneuver. This is true if you are under a Lotus 190 or a Samurai 95.
When flying an airplane, all turns begin by initiating roll energy with the ailerons, (rotating the yolk), followed by an application of the rudder to coordinate the turn. The old airplanes had a string on the cowling (hood) to show the direction of the wind-flow, while newer ones have slip indicators on the instrument panel. If only we had such information while we were flying our canopies. Ah, but we do…
Trailing behind your wing is all the yaw axis coordination data you will ever need. It is called your pilot-chute. If you are flying a coordinated turn, your bridle will remain parallel to the ribs of your canopy throughout the turn. If at any point it goes slack, whips around like a snake or drifts off to one side, you are not flying a clean turn. You are not carving your wing through the sky; you are skidding out of control. The relative wind is not following the valleys of your ribs; it is hopping over the bumps, tumbling into chaos.
Try this on your next jump. Look up at your canopy while you are flying straight and simply yank a steering toggle down to the ½ brake position. You will immediately see what I am talking about as your pilot-chute swings off to one side. Next, lean in your harness, lifting one leg-strap to yield direct roll axis input. It may turn and it may not, depending on the wing. This is not important. Then, while holding the harness input, pull the steering toggle to turn toward the direction of your harness input. You will notice that the pilot-chute is trailing straight back, even in a sharp turn.
Once you have experienced your first real coordinated parachute turn, it is time to develop new habits. This takes time. I find that when learning a new skill like this, it is best to have a simple way to remember the process. In this case, try using the following sequence for every turn you make: 1) LOOK, 2) LEAN and 3) TURN. This is mnemonic was taught to me by a great paragliding instructor and skydiver, J.C. Brown. Rather than thoughtlessly jamming a toggle down, look where you are about to go, lean in the harness to establish the roll, and finally, pull the toggle down to flow deeper into the maneuver.
When you play with this kind of turn, you will find that the parachute simply feels better; that you feel more in control over the wing. You will also find that you can better bump both brakes down during the turn in order to reduce your decent rate, or even level off completely. While practice is necessary to perfect the technique, all parachute have the ability to transition from a descending turn into a level flight turn, into a soft beautiful landing. If you know how to carve your way out of a low turn, there will never be a reason to hook into the ground, ever.
Although many skydivers still think of their parachute simply as a means to get back down to the ground after a skydive, learning how to use the system the way it was meant to be used will increase the chances that you will get back down to the ground safely. Gravity pulls equally on those who love canopy flight as those who abhor it. From twenty years of teaching parachute flight I have learned this: you can only become great at something that you love. The more you understand, the more you will explore. The more you explore, the more you will feel control. The more in control you feel, the more you will love it. And that, ladies and gentlemen, is what it is all about.
BSG
Brian Germain is a parachute designer, test pilot, advanced canopy flight instructor and author. Brian's book The Parachute and its Pilot has become the worldwide source for canopy flight information and is available at a gear store near you, or through Brian's website: www.BigAirSportZ.com
Another Look at No-Wind Landings
The advice Brian Germain provides in his article titled "Surviving the No Wind Landing" might help you achieve consistent, comfortable landings on days when the winds are calm. Unfortunately, other jumpers might not be as successful when trying to follow that same advice.
Some of the techniques described in "Surviving the No Wind Landing" are slightly advanced, and jumpers who are just trying to perfect basic flaring skills might find those techniques difficult to use. Other information in that article might be helpful to people flying certain specific sizes and types of canopies, but we might discover that this information does not actually apply to a significant number of canopies in common use.
The first piece of advice Brian offers is to "make sure you level off within touching distance from the ground." This can certainly lead to softer landings, particularly in calm winds. There is only one problem: if many jumpers fear no-wind landings, there are probably even more who are afraid of flaring too high. For some people the game is over at the instant they realize they have made that mistake: they expect the worst, stop flying, and start panicking.
In an effort to always level off within touching distance from the ground some jumpers develop a habit of consistently flaring too low. Another common problem occurs when people reach for the ground with their feet, believing they are within touching distance when they are actually a few feet high. People who suffer from these habits are often pleasantly surprised, and see a remarkable improvement in their landings, when they learn that it is not actually necessary to level off with your feet right at ground level. Many modern canopies are actually very forgiving of a high flare.
Understanding the Stall
A very common concern is that a canopy will stall if it is flared too high. Brian reinforces this concern when he mentions the importance of arriving at the ground "before the stall breaks." To understand why flaring slightly high is not necessarily a problem we need to take a closer look at the concept of a stall.
"Stall" has a very specific meaning in aviation. It is a significant decrease in lift caused by a separation of airflow that occurs when a wing reaches its critical angle of attack. Understand? No? Okay, then imagine a car driving down the highway, heading toward a curve in the road. Most highways have gentle curves, for good reason, because cars tend to fly off the road if a curve is too sharp.
Now think about the relative wind blowing in your face under canopy. Your canopy bends that relative wind to create lift. Pulling down on both toggles pulls the tail of the canopy down and bends the relative wind even more, creating even more lift. The further you pull the toggles down the more lift is created, up to a certain point.
The "critical angle of attack" is the point where the curve becomes too sharp and the relative wind separates from the canopy like a car flying off of the road. This separation results in a sudden and dramatic loss of lift. The term "stall" refers specifically to the sudden loss of lift that occurs in this particular situation.
Image 1 shows a canopy being intentionally stalled. In frame "A" the brave and handsome test jumper is putting the canopy into brakes, pulling the tail down and increasing the curve that the relative wind must follow. In frame "B" we see the canopy in very deep brakes, but not yet in a stall. The canopy is curving the relative wind sharply and creating a lot of lift. In this flight mode it is flying slowly through the air with a very low rate of descent.
In frame "C" the canopy has reached the critical angle of attack. The lift is rapidly decreasing as the canopy begins to stall. In frame "D" the canopy has entered a full stall.
When flaring it is obviously important to have your feet on the ground before your canopy stalls. But let's think about a student canopy. Student canopies are traditionally not supposed to stall when the toggles are held all the way down in a full flare. They are either specifically designed that way or are rigged with extra slack in the brake lines.
What about a slightly smaller canopy, such as one that might be used by a novice or intermediate jumper? If the brake lines are set to the correct length specified by the manufacturer, many canopies in this category also will not stall when the toggles are held all the way down in a full flare. They will simply maintain a slow forward speed and low rate of descent, just like frame "B" in image 1. Even if they do stall it might not occur until the toggles have been held all the way down for a number of seconds: sometimes five or six seconds, maybe even more. Jumpers who fly these types of canopies don't really need to be too concerned about an accidental stall.
You may be surprised to learn that some small, "high-performance elliptical" canopies also will not stall with the toggles held all the way down, or at least not until they've been held there for a few seconds. Whether or not a particular canopy will stall when it is held in a full flare depends on several factors, including the model and size of the canopy, the length of the brake lines, the length of the risers, and length of the jumper's arms.
When held in a full flare a significant number of canopies will simply maintain a relatively low airspeed and rate of descent, at least for several seconds. This knowledge can be very helpful when we talk about flaring high. Look at image 2. In frame "A" we see a jumper reaching level flight with his toes about six feet above the ground. Tragedy? Not really. There are only three things he needs to do: 1) wait wait wait; 2) keep it straight; and 3) FINISH!
"Wait" means stop pulling the toggles down as soon as you realize you've started flaring too high. Save the rest of the flare for later. "Keep it straight" is important, too. You want to look at a point on the ground out in front of you and keep the canopy flying straight toward that point, just like driving your car down a straight road. And when the canopy starts to drop you back toward the ground, just before your feet touch down, push the toggles down and FINISH your flare, as we see in frame "B." In most cases doing this will result in a reasonably soft, stand-up landing as we see from the last two frames. Even if you don't land softly, look at frames "B" and "C" again. What body position are you in when you finish your flare properly? Looks like you're ready for a PLF, doesn't it?
Granted, you will achieve softer landings on calm-wind days if you level off right above the ground, but that is a skill that needs to be developed through practice. An important step in that process is learning to relax and stay focused if you do flare high. This will allow you to keep flying the canopy and finish the flare properly, which will improve your landings in all conditions.
Practice at Altitude
We can see the importance of knowing whether or not your canopy will stall when held in a full flare. How can you find this out? Yep, you guessed it. Under canopy, in your holding area, above 2000', after checking thoroughly for other canopies, push those toggles all the way down and see if that baby stalls. If you've never stalled a canopy before you may want to get some advice from an instructor or coach before trying it.
So try it. Did your canopy stall? No? Makes flaring seem a bit less intimidating, doesn't it? Or was the canopy easier to stall than you expected? If so, you may want to have it checked out by a rigger.
Some canopies are relatively easy to stall, even with the brake lines set to the correct length. If you are jumping one of these canopies then hopefully you've already perfected your landing technique under something more forgiving.
If you can't stall your canopy just by holding the toggles down, does that mean you won't be able to get enough stopping power at the end of your flare? Some people believe so, and Brian touches on this point in his article when he stresses the importance of making sure your brake lines are "short enough:"
Brake Line Settings
"Most manufacturers set the brake lines to allow for a certain amount of slack so that when the front risers are applied with the toggles in the hands, there is no tail input. This, coupled with shorter risers... will prevent you from reaching your parachute's slowest flying speed."
In reality, many popular canopies do not come from the factory with this much slack in the brake lines. For example, people who jump a Sabre2 from Performance Designs or a Triathlon from Aerodyne Research might prefer to have the brake lines lengthened a few inches beyond the factory setting if they use their front risers a lot. Even then, they might not lengthen them to the point where there will be no tail input all when the front risers are used. Even canopies specifically designed for swooping won't necessarily have the brake lines set that long.
Is there really anything wrong if your canopy does have a bit of extra slack in the brake lines? Usually not. Even with the brake lines "detuned" on a student canopy, we still expect students to learn how to stand up their landings. In fact, many popular canopies used by experienced jumpers will also slow down enough for a comfortable landing even if you cannot reach the canopy's absolute slowest flying speed: plenty of people achieve soft stand-up landings in calm winds under canopies that will not stall when the toggles are held in a full flare. Even jumpers who have intentionally lengthened their brake lines for swooping can still achieve comfortable landings in calm winds.
Is there anything wrong with shortening your brake lines? In some cases, yes! Especially if they are shortened so much that they pull the tail down when your toggles are in the full glide position. As an example, look closely at the tail of the canopy in image 3. It seems like the jumper is pulling the toggles down slightly, but a closer inspection reveals that his hands are all the way up.
Having a canopy's brake lines set too short like this can significantly reduce the flare power on some canopies and make them noticeably more difficult to land, particularly on calm-wind days. Excessively short brake lines are more common than many people realize and frequently go unnoticed. It is a common mistake for someone to shorten a canopy's brake lines because it appears that the canopy "doesn't have enough flare at the bottom end," when the real problem is that the brake lines are already too short!
If you're really convinced that your brake lines are too long there are a few steps you should take before having them shortened. On your next jump, after you've released your brakes, put your toggles all the way up against the guide rings and look up at the tail of your canopy. Don't forget to watch where you're going and look out for other canopies. If your canopy looks like the one in image 3 then forget about having the brake lines shortened. They probably need to be lengthened instead.
If your canopy seems difficult to land you can also have a rigger measure the suspension lines and compare them to the manufacturer's specifications. It's possible that your canopy has simply gone out of trim and is due for a reline.
Once these steps have been completed then get some of your landings videotaped and see if you are finishing your flare properly. Look at the jumper in image 4, just as he is touching down. Does he need shorter brake lines to get a better flare? No, he needs to push his toggles all the way down and FINISH flaring before he touches down. Most jumpers finish their flares at least slightly better than the jumper in image 4, but not finishing completely is one of the most common flaring problems. Brian makes a very good point about this: "the brake lines can only work if they are pulled."
If you are still absolutely convinced that you need shorter brake lines then follow another good piece of advice Brian gives and only shorten them an inch at a time. Make several jumps, preferably in different wind conditions, before shortening them any more. And remember that you can significantly reduce a canopy's flare power by shortening the brake lines too much.
There is usually some excess brake line left over when the toggles are tied onto a canopy, and there are front row seats in purgatory for people who cut this excess brake line off. That excess line should be finger-trapped back into the brake line or secured in a similar fashion in case the brake lines need to be lengthened later on. A qualified rigger should know how to do this correctly.
What else might affect your landing on a calm-wind day? Brian discusses the importance of keeping the canopy flying straight during the flare, and not allowing it to bank or turn. He emphasizes this by stating that "any tilt in the roll axis will result in a premature stall of the parachute…. due to an effect known as 'load factor.'"
Load Factor
If we are going to introduce "load factor" into our discussion then let's do the math. At a bank angle of 30 degrees load factor will increase stall speed by approximately 8%. A bank angle of 45 degrees will increase stall speed by 20%.
The exact stall speed of a ram-air canopy will depend on several factors, but let's use 5 mph (8 km/h) as an example. In that case, a 30-degree bank angle while flaring will only increase your stall speed by 0.4 mph (0.64 km/h). To increase stall speed by 1 mph (1.6 km/h) you will need a bank angle of 45 degrees while flaring, which is a pretty sporty maneuver by most people's standards.
While load factor might sound important, is a 0.4 mph increase in stall speed a significant consideration when landing your canopy? Probably not. Nonetheless, is it important to keep the canopy flying straight while you flare? Absolutely. Even without a stall occurring, banking or turning while you flare can cause you to touch down at a higher speed. You will probably also land with your body off balance, and fall over sideways.
A bank or turn during the flare is most commonly caused by reaching for the ground with one foot. You can usually see yourself doing this on video, and might even feel yourself doing it while it's happening. This problem can easily be avoided if you focus on looking straight ahead, keeping your body straight, and flaring evenly.
What should your feet be doing? Do you need one foot below you and one out in front as you prepare to touch down? That probably will happen naturally just as you stand up at the end of your flare without putting any extra effort into making it happen. And putting extra effort into making it happen could cause you to reach for the ground with one foot.
If you need to think about anything while you're flaring, think about keeping your feet together as you get into level flight, and continue keeping them together while you fly the canopy in a straight line across the ground as far as possible. If everything is going smoothly then as the canopy sets you down you can just stand up as if you were getting out of a chair. Your feet know what to do.
Look at image 5 below. We see a jumper flaring his canopy with his feet and knees together, knees slightly bent. Looks like he's simply maintaining a good PLF position, doesn't it? As he finishes his flare and the canopy sets him down, his feet come apart slightly to accept his weight.
Harness Body Position
What about leaning forward in the harness? Is "freeing your body from the pitch of the system" a crucial part of flaring? Look at image 5 again. A pitch change does occur when the nose of your canopy tilts up at the beginning of the flare. This pitch change is what puts the canopy into level flight, and the pitch change is actually created by the movement of your body under the canopy. In fact, it can be extremely helpful to view your body as an integral part of the parachute system instead of separating yourself from it. Feeling your body swing in conjunction with the canopy's movement is an important part of doing effective practice flares.
If you like to lean forward in the harness and it seems to help your landings, that's fantastic. It feels nice and looks cool. But it's also not a problem if you simply sit still in the harness and let your feet swing out slightly in front of you as you flare. Your body will rock up onto your feet as your feet touch down and accept your weight. You can either "lean forward into the experience," as Brian suggests, or maintain a more laid-back pose if you prefer. Whichever one feels more comfortable is the best one for you.
The technique Brian calls the "Seagull Landing," where you dip down below standing height then rise up again at the end of the flare, also feels good and looks cool if you do it correctly. You'll do it correctly if you develop the technique naturally while you practice good basic flaring skills. Putting too much conscious effort into achieving a "Seagull Landing" is similar to the belief that you must level off right at ground level every time: it can result in the same problems and bad habits. Most canopies will slow down just fine if you level off a comfortable distance above the ground and simply maintain level flight through the remainder of the flare.
In general, it might help to stop thinking about a "no-wind landing" as being significantly different from a "normal" landing. The basic skills that you use to land in stronger winds will also help you land softly in calm winds. Any bad habits you develop might not hurt your landings too much when there is some wind to slow you down, but those habits are usually still present and affecting your flare to some degree, and can be eliminated by practicing proper techniques.
Eliminating those bad habits by keeping things simple, letting yourself relax, and focusing on good basic flaring techniques will go a long way to improving your landings in all conditions. Soon you'll be just as confident landing on calm day as you are on windier ones, and you may even start to prefer calm-wind landings.
Experienced skydiving instructors and coaches, like those in any other sport, develop their own opinions, philosophies, and teaching methods. The advice you get from one person may be quite different from what someone else tells you. This can actually be a good thing sometimes, because the advice that helps one person may not be equally helpful to others.
The most basic, fundamental principles of aerodynamics can be used to describe the flight of any wing, so some of the things you learn about one canopy will certainly apply to others. However, specific performance characteristics can vary greatly from one aircraft to another: a 210 sq. ft. canopy does not perform exactly the same way as a 107, and a Triathlon does not perform exactly like a Sabre2. A Sabre2 does not perform exactly like a Lotus, and a Lotus does not perform exactly like a Twin Otter.
When discussing canopy performance and flying techniques the most important piece of advice I give my students is this: don't passively accept anything anyone says, including anything that I tell you. Think about it, and if it doesn't make sense keep asking questions until it does. More importantly, experiment in the air and see for yourself if it's really true.
Also, remember to breathe.
Scott Miller
References:
Direction of Commander, Naval Air Systems Command, United States Navy. Aerodynamics for Naval Aviators. Washington: Naval Air Systems Command, 1960. Revised 1965.
Germain, Brian. "Surviving the No Wind Landing." Dropzone.com. Sep 05 2007. (accessed October 13, 2007)
Surviving the No Wind Landing
One of the most dreaded conditions of all is the no wind scenario. This fear is so profound that many jumpers in fact avoid jumping in no wind conditions. Although landing with the benefit of a headwind is unarguably easier, there are specific methods that markedly improve the chances of standing up your landing. Here are a few tips that will help you to land softer and safer when the wind goes away:
1) Make sure you level off within touching distance from the ground. If you finish the flight with some space between you and the earth, you will have more than just forward speed to deal with at the end of the landing. All parachutes stall above zero airspeed, which means that as soon as the extreme slow flight capability of your parachute is attained, it will drop you into the ground with both forward and vertical movement. The best way to deal with this is to be sure that you have already arrived at standing height when the stall breaks. That way, the only remaining kinetic energy is forward movement, which can be diminished by taking a few controlled steps.
2) Make sure your brakes are short enough. Most manufacturers set the brake lines to allow for a certain amount of slack so that when the front risers are applied with the toggles in the hands, there is no tail input. This, coupled with shorter risers (most parachutes are set up for 21 inch risers), will prevent you from reaching your parachute's slowest flying speed. With the help of your rigger, shortening the brake lines is an easy task. Take out not more than one inch at a time and give it a few jumps before taking more out.
3) Keep the parachute over your head. Any tilt in the roll axis will result in a premature stall of the parachute, which will drop you into the ground while you still have ground speed. This is due to an effect known as "load factor". When a wing is in a bank, it requires a bit of increased angle of attack to keep it flying at the same height or descent rate. This results in an increased relative weight, which in turn increases the stall speed. Keep your eyes looking down the "runway" and you will be able to notice variance in your bank angle easier. Making smooth corrections to the bank angle all the way to the end of the landing will result in a softer touch-down and less forward velocity at the end of the ride.
4) Be sure that you are finishing the flare. Keep smoothly adding brakes until you run out of arms, or ground-speed, whichever comes first. In other words, if you are flying into a significant head-wind, flaring all the way down will make you go backwards, as the speed of your parachute will be less than the speed of the wind. Flaring straight down is the only way to accomplish a complete flare, as stylish outward sweeping of the arms out to the sides or to the back will only result in a stylishly ineffective flare. The brake lines can only work if they are pulled.
5) Assuming that a PLF is not necessary, put one foot under your spine, as the "main landing gear", and the other out in front as the "nose gear". That way you will not plant both feet at the same time and pivot onto your face. Slide your main gear along the ground as long as you can, and then when the friction finally grabs your foot, take that first step onto the front foot.
6) Loosen your chest strap and lean forward in the harness. This will allow you to get your weight over your "landing gear", rather than back on your heels. The parachute will increase its pitch angle as you progress through the landing, but your body doesn't have to tilt in accordance. Freeing your body from the pitch of the system will allow you to feel more comfortable finishing the flare, as you will not feel the urge to let up on the toggles as you put your feet down to get to a more balanced pitch angle.
7) Let the wing sink down below standing height during the second half of the swoop, and then use the canopy's lift to bring you back up to standing height. Referred to as the "Seagull Landing", this allows you to arrest any excess forward speed, as you will be in a climb at the last part of the landing. Be sure not to climb above standing height as you do this, as that will result in a drop at the end that will put you on your face.
8) Practice slow flight up high. The more comfortable you are with the low-end range of your canopy's performance envelope, the longer you will be willing too keep your toggles down at the end. Fear of the stall results in incomplete flares, as well as letting up the toggles at the end of the landing. Keep the canopy in brakes for at least 30 seconds (up high), and perform smooth turns right and left. This will help you fly your way out of any bank angle created by an asymmetrical level off during the flare.
9) Believe it is possible to land perfectly. It is. Only when a pilot thinks: "I am going to crash" is the crash inevitable.
10) Get video! There is no greater tool than actually seeing yourself land. The best way to get filmed, I have found, is to film other people.
Landing in no wind can be great fun. Ultimately, this is how we counter the fear of landing our parachutes. If you lean forward into the experience, your positive body language results in more fluid, appropriate actions that actually improve your situation. When you are comfortable with landing in no winds, you begin to actually look forward to those zero-wind sunset loads. Scooting across the ground with maximum forward speed can be incredibly enjoyable when you know you have the skills to handle the situation.
In the end, the only way to achieve this is to jump on a regular basis, and enjoying the learning process is how this is reinforced. Find something about every landing that you can smile about, even your crashes. Everything that is not the path shows us where the path is not.
Happy Landings!
Bryan Germain
www.CanopyFlightInstructor.com
Editors Note: Also see - Another Look at No-Wind Landings by Scott Miller