Paramotor Harness: High/Low Hook-in, Weight Shift?
Jan 15, 2007 | Section
II, Chapter 12
Suspension Systems |
>Understanding Paramotor Torque
better, high or low hook-ins? A nearly
religious fervor surrounds proponents of each yet I find that most pilots stick with what they
learned on and enjoy it happily thereafter. Of those who do
switch, just as many go from high to low as vice versa.
So what's the difference? Why choose one over another? Marketing hype
can overwhelm the shopper and it's almost always just that—hype. I've
now flown both types enough to know that's it's really more a case of
preference. There are obviously differences, and each has benefits but,
like most aspects of aviation, there
are tradeoffs. I will analyze three types of systems: High,
low without weight shift and low with weight shift. There's also the hybrid Mantis which goes from high
launch to low attachment in flight.
It may be helpful to check out
Understanding Harness Terminology.
are some important concepts. The pivot point is where the
wing/risers/carabiners pivot on the harness or frame. It's frequently the bottom of
the carabiner but not always. If the carabiner is attached to
a short piece of webbing that is free to move on the frame, then that
point of motion is
the pivot point. This is a critical concept because whether the thrust
line pushes above, on or below this point affects behavior.
Machines with a very low pivot point wobble around more because
their center of gravity is barely below the pivot point. The farther the
thrust line is from the pivot point, the more changing thrust will
move the machine.
Center of Gravity (CG)
Where the pilot/motor combination balances, both vertically and
horizontally, is the center of gravity. It will usually be located
somewhere inside the pilot near his back. The center of gravity is most
important as it relates to the pivot point. If the CG is well below the
pivot point then the machines will resist changes in tilt. If the CG is
on or near the pivot point, the pilot will tend to wobble in pitch
(fore/aft tilt back) and roll.
CG is a summation of all the weights involved. It's like a
barbell—two masses on each end sum together to result in a CG at the
center. On a paramotor the weight of the engine, frame and fuel tank all
sum together for a paramotor CG then that combines with the pilot
to create a pilot/motor CG. Pilots prefer the CG of their
paramotor to be up high on their back and close. It's hard to wield a
machine that sits low and aft. In almost all cases, the height on your
back is a matter of adjustment but the motor's rearward distance from
the frame is a design element.
Regardless of paramotor design, the pilot/paramotor CG is almost
always going to be near the same point because it's always beneficial to
have it high and close.
The biggest difference in flight will be hand position. The lower the
hook-in, the lower your hands will be on the brakes. Soaring pilots may
like this because they can fly their soaring wings without any changes
to the brakes and brake positions will be similar. Of course you can
adjust your brakes to be at that same position even on a high hook-in
machine just by letting them be a bit longer.
Note that wings intended for motoring frequently come with shorter
risers to accommodate high hook-in machines. Be careful if you fly motor
risers on a low hook-in machine, the brakes may well be much
lower than you expect. The greatest risk is that the wing will overfly
you and you'll use too little brake to damp it. Also, you could end up
needing more brake (or taking wraps) to flare.
There are two basic types of low hook-ins: those intended for weight shift and those
that are not.
There is precious little difference in the launching techniques or
difficulty between high and low hook-ins. Launching technique for me is identical except for hand position which
will be slightly lower on low attachment machines. Also, be ready to
have the brakes at a lower hand position when damping the wing's
New pilots do seem to learn a bit easier on high hook-ins. The Mantis
designers sure felt so—their hybrid machine lets you launch and land
with high hook-in points but fly with low through a mechanical
You really can get used to anything. I've spent some effort trying to determine the
difference in launching difficulty with little success. A properly adjusted paramotor, and
that's key, will present nearly the same ease regardless of low or high
One factor that can hurt your launch effort is cage size and relative
position. If the cage pushes out on the D lines during inflation, then
your wing will struggle to come up. It's like trying to inflate a wing
with the D's pulled—you'll want to figure out a way around that. One
technique is to do the initial inflation leaned way forward so
the cage is above the lines. Then try to get the lines up past the cage
quickly. That isn't always possible on every motor but is something to
try for large cages. Also, the lines catching anything on
the cage will torpedo the effort.
Several categories listed below include one with a launch.
All low hook-in machines share certain characteristics.
- Connecting the risers down low requires also connecting them
closer to your arms. You can clip the risers to a more forward
attachment point but will then risk leaning back too much. Excessive
lean-back can cause riser twist on launch or in flight or other
- In flight, the pivot point is near the CG which makes for a
"busier" ride since bumps transfer more motion through the wing. Free
fliers appreciate this feedback when looking for thermals, but many
motor pilots prefer to minimize it.
- Full power, especially before the pilot gets seated, tends to lean
the top part of the cage forward. This can put your brakes very close
to the cage such that letting go of a brake can let it go into the
prop, a potentially catastrophic event. This has happened about 5
times that I'm aware of although, fortunately for the pilots, the
brake got cut off before it could wrap up in the prop.
Low Hook-in without Weight Shift (Mid Low)
Examples: 1) Bailey 4-stroke, 2) Walkerjet, 3) Inflation tests
using the Bailey
These machines are characterized by having attachment points slightly
higher than their weight shift counterparts and have no pivoting bars.
They can have the hook-in points as low as those with pivoting
bars but usually don't because they're actually trying to minimize the
turbulence transferred to the pilot.
This type of machine gives up weight shift in exchange for a less
wobbly ride in bumps. Even so, with the CG still very close to the pivot
point, there is a lot more wing motion transferred to the pilot so it
will be a busier ride than a high hook-in machine but less than a low
weight-shift machine. Plus, not having the pivoting bar further reduces
the business in flight.
Low Hook-in with Weight Shift
Examples: 1) Airfer, 2) Pap (photo by Jamie Beckett), 3) Free
Spirit being launched by Robert Kitilla. Other examples not shown: Fly
Products (only one model), Parajet,
The majority of all low-attachment machines are of this type. They
have the lowest attachment points and use pivoting bars to further
increase weight shift. The intent is to mimic free flight as much as
possible while still accommodating the weight of a motor.
With the CG is very near the pivot point and the pivot bar action,
the machine feels very "loose" in turbulence. It wobbles around both
left/right and fore/aft. It takes several flights but you most certainly
get used to. After having been loaned the Fly, Airfer and HE versions
for different events, I've become comfortable with the wobbling but a
new or transitioning pilot will find it distracting at first.
These machines lean back the most. Even with the risers on their most
aft setting there is a fair amount of lean back at my weight. That means
more torque although that is also easily reduced to acceptable levels on
a well designed and properly adjusted machine.
High Hook-In Attributes
Examples: 1) Pivoting J-bars on SD. 2) Launching the SD. 3) Fresh
Breeze with harness-attachment above, Blackhawk also with harness
attachments. 4) Fly Products with sliding webbing on a harness
The original paramotors used overhead J-bars and high hook-in points to
better balance the heavy motors in use at the time. Technology has
evolved both in harness/frame design and decreased motor weight.
Nearly all high hook-in machines have the same geometry although they
take different approaches. Look at
suspension systems to understand the differences. Here are the
- The CG is well below the pivot point (hang point) so the motor has
less tendency to move around in response to turbulence. Full power
tends to angle the pilot back instead of tilt him forward.
- All high attachment systems allow the hang angle to be adjusted
completely vertical, so the propeller plane is straight up and down.
That's not as comfortable in flight but is generally easier to launch
and minimizes torque effects. On soft mount systems, where the
carabiners attach to harness webbing, the tilt-back angle can be
adjusted to keep the motor anywhere from completely vertical to
significantly leaned back, even to a dangerous degree.
- If the seat-to-carabiner height is too great (a maladjustment), it
can be difficult or impossible to reach the brakes on wings with long
risers (some soaring wings). This must be checked because pilots have
launched their soaring paraglider on a high hook-in motor without
checking and then been unable to reach the brakes.
- Several experienced paramotor instructors who have taught on both
low and high hook-in types have concluded that high hook-in paramotors
have a slight edge for new pilots to learn quickly.
Adjustment is critical on all harness systems. I've flown machines
that were nearly unairworthy until changes were made, both high and
low hook-ins. In one memorable case, Alan Chuculate and I were asked
to give a demo for some USHPA (then USHGA) folks when they were
considering adopting power. We borrowed a motor brand that we were
familiar with but had never flown this particular example. On the way
there, we decided it would be best to give this machine a test flight.
We could barely launch it the torque turn was so bad as the wing
lifted. I looked at the harness and noticed that it was attached on
the the wrong side of the engine—an arrangement that allowed the motor
to move to my right shoulder and cause a severe torque twist. Putting
the harness/frame attachments on the other side of the motor
completely solved the problem. The demo, it went off without a
motor shown far left is an example of a high hook-in machine that left
the risers excessively high. It used an early weight shift system that
allowed the pivoting arms (comfort bars) to float upward and the pilot's
body to sink deep into the seat. This same motor was later modified with
a geared weight shift system that kept the pivoting arms lower therefore
lowering the risers by a good 4 inches. This is why it's important to
deal with someone who understands the dynamics of different harnesses
and be suspicious of those who denigrate one system or another too much.
They may have little experience with both.