Last reviewed: 06 April 2004
Hang Glider Maintenance by
Mark Dale and Angus Pinkerton
from the Auckland Hang
I have been reading the accident report in the February issue of Hang
Gliding and it is horrifying to find
that approximately 20% of fatalities last year could have been avoided
by a little thought before takeoff.
I am referring of course to accidents which occurred as a direct result
of (a) not checking the glider
before takeoff and (b) not checking the harness before takeoff. Let
us start with the first cause - that of
not checking the glider. The reason that this check is carried
out is to determine if the glider has been
assembled properly and if it is damaged in any way. The sort
of things that we are looking for are: torn
sail, worn sail attachment straps, dents or gouges in tubes, bent tubes,
kinked wires, thimbles wrapped
round tangs, sail pinching on saddles, bolts loose, safety pins missing,
incorrect wire tensions, battens
not correctly in sail, etc. Take care to ensure that all
bolts show threads past the nut and that ny-lock
nuts are not recycled.
It is recommended, indeed mandatory, that you have another pilot check
your glider before takeoff.
I suggest that it is best to set up a routine for pre-flight checks
similar to that described below in order
to try and ensure that no stupid mistakes are made:
- Start at the nose of the glider and run your hand
down one leading edge to the cross tube,
checking for: dents, scratches and tears in the sail and batten pockets.
- Check leading edge bolts, tangs, wires and ensure
sail is clear of saddles
- Run hand along leading edge to wingtip, checking as before
and then ensure the sail
attachment is OK
- Run hand along trailing edge to keel, checking
for loose threads, proper fixing of battens
and tension of the sail
- Check rear of keel sail attachment, center batten, tangs, wires
- Carry out the same procedure running along the other
trailing edge and up the leading edge
to arrive again at the nose.
- Check nose plate bolts, tangs,
wires and sail attachment.
- Sight along keel and check reflex.
- Visually inspect the kingpost and ensure the wires are clear.
- Move to the crossbar and run your hands along its complete
length, checking for damage.
Yes- even if this means climbing inside the sail if you suspect damage
(do the leading edge while
you are in there).
- Check that wire tensions are even on both
sides (on level ground) Deflexors as well if
yours has them.
- Move to the "A" frame and check the heart bolts and top
A frame bolts. Inspect both
down tubes for damage and for "work hardened" metal from restraightened
- Check both bolts at the bottom of the A frame and ensure
the wires are securely attached
and not tangled.
- Run handkerchief along flying wires to test for any kinks
or broken strands.
- If there is anything you are not happy about, make sure the
pilot knows about it.
- Inspect the Harness straps for wear and tear and that the
knots are tight and secure.
- Check the Parachute Bridle for wear and then ensure the chute
is securely contained and
that the safety pins are in place.
- Inspect the Hang straps for
wear and the height the pilot hangs off the bar.
- 19) Ensure their legs are inside the leg straps and that the harness
lines are not tangled.
- Tell the pilot your conclusion
As for the frequency that these checks should be carried out, the answer
- After first rigging up.
- After any hard landings, crashes, alterations or even laying
the glider on the ground.
- Always before a soaring flight because that is of greater
duration (usually) than gliding
Now then, having completed that, having a sound glider with you does
nothing if you
forget to hook up. There are several things you may not be aware
- It's difficult to hold onto an A frame if taken by
- A glider dives at about 45o if you fly hanging from
the A frame.
- If you don't pull yourself into the A frame within
30 seconds, you never will.
- You can't hang by your hands for more than about 1.5
So lets get another routine going which you as pilot always go through
- Move the glider to the takeoff site.
- Hook up and lie in your harness (if prone) and
ask your nose launcher to see if all lines
and straps are clear and check the carabiner is properly locked shut.
- Check your helmet
- Stand up and look left and right - just a quick
visual check of the glider.
- Ask your launcher to ascertain and tell you what
other gliders are around and what they are
doing - nothing is worse than to takeoff in the path of another glider.
- Confirm with your nose launcher what your takeoff
procedure will be - ascertain which way
he intends to duck, tell him what you are going to say - and be explicit
- "Ready, Go:" or
"One two three, go" but TELL HIM. The nose launcher is doing
you a favor, he has no glider
to stop him falling down the cliff - its only fair to keep him in the
picture - TELL HIM. And
when you say Go!, Go for heavens sake. Don't wait around for
winter to fall. If you don't
need a wire launch you don't need one from the start.
As a last point, don't forget to check out the launch site thoroughly
and (hopefully) you will
also know something of the landing area.
After all, we hope to minimized danger. Everybody respects the
safety conscious pilot - that
should be you. And don't forget, if it doesn't feel right, don't fly,
there'll be other times.
(Once you have rigged and inspected your own glider seek out someone
else in the same position.
This way two gliders can have their second pre-flight check at the
same time - an added advantage
is that the pilot doesn't stamp around impatiently waiting for you
With some of the more sophisticated supergliders it would pay to have
someone familiar with the
machine to do the second pre-flight
check. Otherwise the would be checker suffers form visual
overkill inspecting all the wires,
tubes, tangs, bolts, etc. which festoon these machines.
Inspection efficiency is reduced
and some vital fault could be missed.
Thanks are due to Mark Dale and Angus
Pinkerton for their help in the preparation of this article.
Hang gliders are very simple machines.
So simple, easy to rig, and fly that sometimes we lose sight
of the fact they fly on the same
principles as much larger and more complicated aircraft and that
the failure of any of their many
parts will result in a frightening experience ending in a reserve ride
or at the worst extreme, death.
Two of the important tools for glider
maintenance are not spanners or screwdrivers but pieces of paper,
or to be more precise the manufacturers
handbook or instruction manual and the batten profile.
It is vital to have these in your
possession, as many of the queries you may have about your glider
can be answered by referring to
these documents. Follow the instructions and stick to the placarded
limits for your glider detailed
Some of the maintenance that a lot
of pilots overlook is maintenance of a preventative nature.
For example, most of the wear on
a hang glider takes place not when it is being flown, but being
transported. Using two very thin
roof bars to which the glider is very tightly strapped means all
the weight is being taken by two
very small areas, and this will result in wear on the sail in a very
small area and even dents in the
main tubes if the glider is "dumped" onto the roof rack too hard.
Using a ladder or similar to transport
the glider on a roof rack will spread the load and avoid the
risk of sail damage. Overloading
the roof rack results in damage to rack, car roof and the risk of
the roof rack coming off the car
resulting in serious damage to the glider. An incident
several years ago led to three cars
being damaged and four gliders being trashed.
Glider storage is another issue that
not too many pilots seem worried about. Leaving a glider out
in the rain means that the sail
will eventually start to develop mildew, with the discolouration and
damage to sail fabric that will
inevitably shorten a glider's life. Far worse though with aluminium
alloy is the risk of unseen corrosion
to the insides of the tubes, as the glider in its bag experiences
first the extreme damp and cold
of an English winter, then the humidity as the water trapped in
the bag when it last rained evaporates
but can't escape from the bag. Add to this the fact that the
glider was landed on a beach and
the salt and sand allowed to get inside the sail and you can see
how a glider can be reduced to unsafe
and valueless quite quickly.
Rigging wires are very easy to kink
whilst packing away, and doing so will reduce their life quite
considerably as well as risk in
flight failure. Some gliders do not have a very good fitting where
the side wire leaves the bottom
of the upright, and rigging gliders with this type of side wire on
the keel like pilots do on the continent
will kink them within a few flights.
Battens, especially those made of
softer alloy will flatten quite quickly. This has two
consequences generally, the flattened
aerofoil section does not have as good a minimum sink
as the higher cambered original
section, and the pitch stability of the flatter section is often worse.
Additionally, if the battens have
been flattened differently on each side, the glider will develop
a turn. This, along with a leading
edge bent in a careless landing is probably the most common
cause of turns in gliders. Check
your batten profile often, both the safety and performance of
your glider are at stake!
So, we've discussed glider maintenance,
and the word strip down hasn't yet been used. Treating
your glider gently, packing it away
carefully (both sail and wires), and finding a dry place to store
it can do a lot towards delaying
the inevitable aging process.
The pre-flight check is the next
stage of preventative maintenance ,any gradual changes in the glider
may be monitored over a period of
time. If you find anything you're not sure about, ask! In one fatal
accident, a glider that had been
ground looped was flown subsequently without a serious check.
The keel failed in flight and the
glider folded up. Any thing that's bent in the tube department
should be replaced, straightening
tubes is very foolhardy. All nuts and bolts should be checked,
recently a pilot had an upright
fall off a glider whilst preparing it for flight. The bolt that held
the upright in place had dropped
out, because the nut that retained it had gone missing!
However gliders, like all other aircraft
need periodic maintenance. Most of it is of a check nature.
Despite the simple nature of a hang
glider, after all they're easy to take apart and reassemble,
there are a number of pitfalls for
the unwary. Accidents and incidents have occurred due to
incorrect assembly after a DIY stripdown.
One glider had the string used in the early stages of
tensioning the pull back bridle
attached to the wrong part of the bridle. The force used to tension
the bridle was incorrectly applied
to the stitching, peeling the seams apart and resulting in failure
of the bridle!
Over tightening bolts
is a very common mistake. Any parts left over at the end of a
rebuild point to a serious error
on your part. Manufacturers don't fit parts that aren't necessary,
and if you can't see what it does,
don't make the mistake of thinking you can do without it!!
Certain components will wear and
One of the most fundamental things to hang glider
safety is pitch stability, an area
not many pilots understand or have enough respect for. One of
the main components of pitch stability
is the luff lines. So you need to check your luff lines haven't
stretched, and the lengths are still
correct? WRONG!! Luff lines are not specified in terms of length,
but of luff heights above a fixed
datum. Sail stretch means that as a glider ages, if the sail stretches,
the luff line lengths will need
to be shortened to retain the correct luff line heights. This is definitely
a job for the manufacturer. One
pilot who had his glider checked found the luff heights at best on the
very bottom end of the safety envelope.
In fact of the six critical measurements on the glider four
were below the acceptable safety
standard. Luff lines only work at radical pitch angles, so having
them longer will not make a glider
go faster. A slight change in height will radically affect a gliders
Leading edges will
also acquire a slight set, which is a gradual bend over their
complete length. Clouting the leading
edge results in a sharp but very small bend. Again, how
much set is acceptable in a tube?
Without knowing the proper tolerances on these components
it is not possible to make an informed
decision as to whether to replace them or not. For this reason
gliders are best sent back to the
manufacturers at the interval specified in the manual for a strip down.
All bolts will then be replaced
again with aircraft quality ones to the original specification and
all wires and tubes checked.
of warning for the purchaser of the cheap glider: a glider that
is more than five years old with
no documented maintenance history may be expensive to make safe.
The Germans have a mandatory glider "MOT" at five years and every two years after that.
This does protect the second hand
market and second glider values in Germany are much higher
than the rest of Europe. Most manufacturers
run a strip down service during the winter when the
weather is bad and glider manufacture
enters a natural doldrum. It's a very good idea to take
advantage of this to get your glider
serviced. The cost is nominal to cover labour unless any parts
require replacement, in which case
they will have to paid for at standard retail prices. Components
like wing wires will need to be
replaced very two years or 100 hours, the precise details will be
found in your manual. Side wires
are not expensive, but if one fails the results will be catastrophic.
You may not get much time to consider
whether the $323.50 would have been a good investment
as you plummet earthwards.
about it now, with both feet on the ground!