Microlines - Safety issues?  

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Unsheathed lines on the Advance Iota

About this article
Various pilots share their experiences of unsheathed lines and Rick Livingstone starts the thread. There are links to a related BHPA safety advisory and other articles on microlines.

Pilot profiles
Intermediates - Rick Livingstone, Dave Horne
Experts - Ed Cleasby, Kitt Rudd, Mike Cavanagh (Managing director of Ozone)

May 2011
Original post
- CSC forum

Nov 2015
Added to Knowledge Base with kind permission from the authors

Related articles
BHPA safety advisory - Unsheathed upper cascade lines
Unsheathed lines fragility - Free.Aero article
Discussion on unsheathed lines at Paragliding Forum.com
Paraglider line materials and why they matter to you


Rick Livingstone

I suggest this is valuable reading for anyone considering, or already owning, a glider with Microlines......

I've separated this info and put it here as a new topic. (All quotes below have been taken from 'Accident on Clough 24-4-11' - which is all well worth reading.)

After my Hike experience (see below) I bought a Rush2 rather than a Swift. More or less the same glider apart from the Rush2 is made of more substantial (if heavier) material, has a little less performance and it has NO MICROLINES !!!

Ed Cleasby

On the subject of lessons. I'm (and this may well be only me) finding microlines a real sod on some days. I've now flown three times to discover a loop through knot. Once in a inner B cascade and twice in tip or brake cascades. On a calm day you have the time to check them but on strong, breezy days they are a pain to check out fully. Twice I've had to undo a line from the maillon to remove a twist that encourages a loop through. The upper tip casades are really hard to see just from building a wall and damn near invisible on the ground. I mentioned in an earlier post that I'd lost a Langdale day through having to fly down to the valley to take a B line loop out, plus a second day when I tripped over a brake line and it just ...... snapped! (I hardly touched it).

The lesson may be when you're eager to take off ..... you must not forget all those line checks; especially with the new dental floss lines.

Dave Horne

I also found unsheathed lines a right devil at times (flew an Ozone Swift), it's so easy to not notice a knot during pre-launch and I once launched off the side of Skiddaw lower man only to discover a knot causing a smallish cravat on one wingtip. Fortunately I managed to tease it out once I had a bit of height on.

But the real wake up call for me was bracken! On my old wing (sheathed lines) I found I could usually get small pieces to tease out whilst building a wall and never had any problems. On Catbells I was shuffling about in a strongish breeze and managed to drop the wing on some of it's well-known bracken. I unstrapped and got out of my harness and cleared it all - so I thought - after moving back on to the grass.

Was building a wall after the breeze had dropped back a bit and noticed two REALLY SMALL pieces of bracken still in the lines. Decided I could tease them out without getting out of my harness, just as a gust came through. This lifted the wing which rose up with lines astonishingly well glued together courtesy of the bracken and whirled around like a dervish above me. Well you can imagine I was thinking "If I can't get this thing down and it lifts me off I'm a gonner". It was ceratinly one of those adrenaline moments. Fortunately I managed to collapse it and spent a good 5 mins thinking about the meaning of life etc afterwards

So my unsheathed lines message is - KEEP CLEAR OF BRACKEN AT ALL COSTS. And I would imagine heather isn't too clever either!

microlines on the Advance Iota
Inside the Cousin Trestec lines factory

Rick Livingstone

Here are my experiences with microlines, just to re-inforce what Dave Horne and Ed are saying: I had an Advance Alpha Hike - all lines unsheathed, top ones like dental floss! All the lines were particularly vulnerable not just to knotting but also to abrasion & damage.

Certainly for Lakes flying, with heather and bracken and the odd bit of sharp rock at take off, I would now only consider having micro lines on the upper cascades. i.e. They would be lying on the wing's lower surface when it was laid out for launch and would not normally contact the ground.

I suggest anyone considering a fully microlined glider ought ask themselves - 'Do I really want to sacrifice line safety for performance?' and 'Am I really flying the glider so near it's maximum performance that the microline improvement will really make that much difference to my flights?' i.e. Should I be concentrating on becoming a better pilot rather than on flying a higher performance, but less safe, microlined glider?'

Mike Cav please note: If certification allowed, I would like to see part sheathed line sets offered as an option on microlined gliders.

Ed Cleasby

Totally endorse Rick's option idea of sheathed lower (main) lines .... I'm already seeing too much abrasion damage for my liking. Nice grassy take off areas are fine but too often we also have to contend with heather, bracken and rock and it's so easy to get some damage.

Rick Livingstone

Ed, it's my belief that every fibre of a microline needs to be taut and loaded to give the claimed breaking strain. If there is any visible 'fluffing' on the line it is, imo, dangerously damaged and weakened and needs replaced ASAP.

On my Hike I knew there was some fluffing on several lines but decided it was minor & safe to use; then during a windyish launch, a line snapped on me.

When I carefully inspected all the lines I ended up replacing over half a dozen that I hadn't realised were actually DANGEROUSLY DAMAGED.....
You live n learn - with luck!

Kitt Rudd

Welcome to my world guys! - Having flown with unsheathed lines for most of the last 20 years. I can say you learn to adapt. In the early days I would occasionally break lines, generally through heavy handedness and lack of finesse. But with a bit of practise I am generally happy launching from most surfaces. My top tip is learn to pick your glider up - sometimes it is necessary to start your launch using only one side of your wing to avoid snagging lines - it all comes down to practise practise.

Watch me now after stating this I will now go and break a line on my next launch.

Mike Cavanagh

Hi Guys, these would be my thoughts on this (as CSC Safety Officer)...

Firstly and most importantly is that by focussing on unsheathed lines you risk hiding the true causes of the incident that we all must learn from.
And secondly micro lines are not a safety issue, just a care issue.

On the first thought...
Main cause...
The incident highlights the importance of doing proper pre-flight checks on your lines before taking off. On a nice grassy, gentle take off like Threlkeld Knotts/Clough Head there is no real excuse to get that wrong. It was not particularly windy either so that check should have been pretty easy to do.

Line material does not make this check any more or less important!
Any line material can tangle, some types of sheathing can make it harder to undo tangles than others, and some unsheathed line is easier to untangle because it does not have the more abrasive sheath to lock it in place. Thinner line can get tighter knots than thicker line. Swings and roundabouts - they all tangle.

Whatever the line material you should always check it is clear before launching and if you think the ground you are on can still cause problems due to bracken or heather getting caught then, when you pull up the wing, you should be checking for that too.

On the ground, checking lines is easy to do, once a glider is laid out. My technique, after shaking out any obvious tangles (shaking them, with just a bit of pull on some bits, is usually sufficient (and I always have them due to the way I pack my wing), is to then start with each riser, put a finger between the A, B, C Ds etc and then run them up towards the canopy, until I can see they are all lines are clear all the way to the canopy. It takes seconds to do and I can't remember when I last had a tangle in the air - and certainly never anything major.

Secondary cause...
If you have failed on your pre-flight checks and find yourself in the air with a tangle that won't come out with an easy pull of one of your lines (that will often frees twigs and things) then you should land in the easiest/safest place possible as quickly as possible. Landing somewhere that would normally involve some tricky brake work should be avoided if possible. If a tangle is on one side then remember that the brake input on that side may not behave normally. If the tangle has already resulted in an unexplained collapse you have to be doubly cautious.

Although it is easy to say in retrospect, landing on top of Threlkeld Knotts on a thermic day was probably not the best place. Aiming for somewhere soft and boggy was a good plan, and it sounds like the pilot was very unlucky with that. Basically you want to be as gentle as possible, unless you have ascertained the tangle allows your wing to still behave well.

Second thought...
Largely covered in what I say above. Thin lines, like all lines, are not a safety issue unless you have abused them. Tangles are a safety issue and tangles are down to care, not the material.

For sure like all materials you have to look after them and not abuse them. Damaged lines should be changed. And don't think that just because you have a sheath the lines don't get damaged easily - sometimes the sheath hides the damage.

And answering some of the questions that have been raised on this thread...

Slippy lines...
Unsheathed lines are already slippier than sheathed lines. It is more the fact that they can make tighter bends that means they can get difficult to untangle. However, as they are slippy they actually shake out more easily than braided sheathed line. I'm not sure that any of us want to get any type of grease on any of our gear! Some do have a silicon coating to help with the UV.

Lightweight gliders are designed to be lightweight - adding sheathing increases weight and you could be surprised how that can add up. Using different line (or any material) to what was certified would normally invalidate the certification. Even if going to a stronger line a load test at least would be needed for a test house to extend the certification. May also need a flight test on at least one size to check it has not changed anything there too. So no, you cannot easily change the lines.

Unsheathed lines reduce drag and for a lot of pilots it is important to maximise their performance (more speed, better glide etc.)

Putting my Ozone head on...
putting sheathed MAIN lines on an M4 would theoretically reduce glide by about 0.5 (area goes from .29 to .34m2) and adds about 100grms to the weight.
Changing ALL lines on an M4 would theoretically reduce glide by about 0.75 (area goes from .29 to .36m2) and adds about 200grms to the weight.

In summary - micro-lines are not a safety issue. They just need good care, but you should be doing that good care whatever type of line is on your wing.

Mike Cavanagh

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