Untangling lineplans

Read about lineplans and line codes. Discover how to fit a replacement line to your glider.

If you damage or break a line, the quickest and cheapest way to get in the air again is to order a replacement line to be sent through the post. It’s something we’re happy to do, but there are some things to bear in mind to make sure that it all goes to plan.

Of course, that’s exactly the right place to start – the lineplan. Identifying the correct code for the line that you’ve broken is pretty important to ensure that the replacement provided is the right one. If you ring up and ask for “the second one off the innermost red line” or a similar description, there’s a significant chance of ending up with the wrong line.

Identifying the right line would be simpler if there was an industry-wide standard way of referring to lines, but there isn’t. There’s a broad consensus over some elements. For example, the lowest lines are the main lines, the ones connected directly to the wing are the uppers, and anything in between is a mid, perhaps a lower-mid or upper-mid if there are more than one mid levels. And everyone refers to the lines closest to the leading edge as the A lines, with progressively higher letters towards the trailing edge. It’s also normal to number from the centre of the wing towards the tips, but there are other approaches.

Ozone have a labelling convention that follows these simple principles. You can see this from the lineplan for the Delta 3 (Figure 1). As an example, trace back from the upper line A6, which is the sixth upper counting outwards from the centre, closest to the leading edge. You can see it’s connected to AM3 (that’s the third mid line counting outwards from the centre) which joins AM4 at the top of AR2 – that’s the second main A line, which Ozone abbreviate as R for riser rather than M for main, to avoid confusion with M for mids.

Ozone refer to the brakes using the letter K. Have a look at K9: it’s connected to the brake main, KRL1, (braKe Riser Lower 1) through three other lines (an upper riser line, a mid‑lower line and a mid-upper line).

Most manufacturers’ approach is logical, and makes sense once you understand it. Advance, for example, use an additional number to identify the level in the cascade, starting from the wing. Both Advance and Ozone would refer to the same line as A6, but then they would diverge. So translating Ozone speak to Advance speak means the mid AM3 becomes 2A3, and main AR2 becomes 3A2. This works for most cases with Advance although there are exceptions, and the Advance use a completely different convention for their brake lines.

Even after you refer to the lineplan, there’s still scope for mistakes and confusion. So for example, on a Skywalk lineplan, the following three lines, CII, C2 and c2, refer to a main, a mid and an upper respectively. Obviously.

So, armed with your lineplan, you know precisely which line you need. It’s worth noting the colour of the existing line because some manufacturers don’t detail that in their specification sheets, and others change the colours during the production run. Before you order, also make sure you know your glider and size. I know it sounds obvious, but we regularly have to make a second order after the pilot realises he got the size wrong the first time around. And last week we had to remake four lines when the owner realised he had the original Speedster, and not the Speedster 2.

Fitting a line is straightforward enough, and the notes below outline the steps to take. Given the scope for error in identifying the line right when ordering, do make sure you check that the line looks a reasonable match for length with the one on the other side before you start fitting.

Finally, you may remember from earlier articles that lines shrink over time. When a replacement line is made to specification, it may well be longer than the line it replaced. For us in the workshop, it’s simple to make appropriate adjustment, but that can be more difficult at home. If you discover your lines have shrunk, it’s worth being aware that attaching the new line with a double loop at the maillon will reduce its effective length, typically by 9mm.

How to fit a replacement line yourself

If you find one of your lines is damaged, you can get a replacement through the post and fit it yourself.

  • Give yourself plenty of space to reduce the risk of tangling the lines and make sure you have time to avoid being rushed.
  • Lay out the wing and lines.
  • Identify the main line that is connected to the line you need to replace.
  • So far as you reasonably can, try to separate this main line from the others.
  • Before starting to remove lines, check the length of the new line against the corresponding one on the other side.
  • Open the maillon, removing the O ring or maillon insert as necessary.
  • Remove the main line that’s connected to the line you want to replace. If it’s not the first one off the maillon, to get at it, first move the other lines across to the other side of the maillon, rather than removing them (Figure 2).
  • Work your way up the cascade, unlooping from the bottom (Figure 3).
  • Replace the damaged line: put the upper line/line tab through the upper loop of the new line, and then feed the other end of the new line through the loop(s) of the upper line/line tab (Figures 4 and 5).
  • Repeat the process back down the cascade to the maillon (Figure 6).
  • Refit the main line, O ring or maillon insert and firmly close the maillon.
  • Check that all the lines are attached and untangled.

And most importantly, on your daily inspection before you next fly, check again carefully that you have not tangled any of the lines.

If you want to chat anything through, we’re always happy to offer help and advice over the phone (01433 627195) or by email (info@aerofix.com).

2018-12-23T12:41:47+00:00Replacement line|