Line tangled in prop and broken during takeoff - not sure what went wrong

[forecaster]

Hi, I am new to paramotor and not so new to paragliding itself (100+ hours of airtime). My last takeoff in the complete windless conditions has gone wrong, luckily only the paraglider line broken, no other issues.

It was a classic/front launch but from the beginning I couldn't make all the risers and lines cleared up although they were good - I was not sure A's are on the top of the other lines so I was trying to clean it up while having the glider at the back of me. Evening, mosquitos started to bite, I started getting impatient as the sun was setting and very likely did not check everything. Because it was absolutely windless, right when I started pulling the A risers I added thrust to add myself more energy and then felt slight tension on the left brake and heard a broken line. Turned out that the main A line. the one closer to the center of the glider got rolled on the propeller hub and - luckily for me - very quickly burnt as it was rolling really tight one scroll next to each other.

Now, I am absolutely sure I should have not launched in that state of mind, it was irresponsible. But what am trying to figure out now is what actually happened. Is that possible that the A line, the one that I'm pulling when launching gets hooked by the propeller with the propeller's diameter being smaller than the cage? Well, I'd expect more C or brake lines to get loose and being hooked, but not the A ones which are tight. Really confused here....

Maybe I've hooked the A line when trying to clear it up before the start, but still, when pulling it during the start it should have leant over the cage and tighten making the room for the propeller. I strongly believe the line was not tangled 360 over the propeller's hub before I added throttle because right before I started to run, with my lines still loose I gave the engine some throttle and then released.

Below are the photos of my paramotor. What do you think? Any hint will probably be helpful

 

Edited September 24, 2020 by forecaster

[AndyB]

You did not run fast enough. In nil wind especially you have to psyche yourself up to run and run as fast and hard as you can. Many people have a tendency, at the point the wing comes up, to then not be running as fast and hard. Because the wing pulls back and stops you running for a moment, then you likely did not keep trying to push as hard as you can. Adding power makes the wing flip up even quicker (I do power launches) and as the wing hits the top of it's arc, you have to be moving really fast and using lots of brake to keep the wing from over-flying you.

[Steve]

If you are very new to paramotors then power launches need to be approached carefully otherwise you may create other issues for yourself. Try adding some airflow from the prop, then reduce the throttle and move forward, then apply power again once the wing is overhead but keep moving forward all the time. Not all wings will need lots of brake to stop overshooting, some are easier to control than others. 

[kiwi k]

Only a video of event would give anybody a clue of what you may or did do wrong, if you have local fellow fliers that might observe your take off or even capture it on phone or camera, then there might be a simple explanation or something your doing wrong.

Are you trained or self taught ?

[forecaster]

21 hours ago, kiwi k said:

Only a video of event would give anybody a clue of what you may or did do wrong, if you have local fellow fliers that might observe your take off or even capture it on phone or camera, then there might be a simple explanation or something your doing wrong.

Are you trained or self taught ?

Yeah, I know it's hard to tell not seeing the incident, the question was more to get your opinion whether there is any chance that the lines tensed during the launch may get caught by the propeller or not.

I have 10 years experience in free-flying in the mountains, completely new to powered paragliding though but I can tell the training I got was a decent one. I assume I may have not checked that the line was already in contact with the prop before I applied throttle, and then it would be clear to me what I done wrong.

[AndyB]

If you launch the wing, get it overhead and in control (taxi it without power), then apply power you will be fine. Applying power earlier, like I do because I am disabled, means you have to run like a gazelle...all the time, no pause, anywhere. If you catch a line in the prop then you have allowed the lines to go slack enough to get there. Most people I see start their run, then the wing pulls back and then they stop pushing as hard as they can ie pause.

When using power the wing flips up more quickly and so you have to be moving even faster at that critical moment it reaches the top of it's curve, otherwise lines go slack. It took me dozens of take-offs to perfect using the right amount power - not too much. Too much does 2 things. It can flex your arms back into the cage and then the cage into the prop. It also pulls the wing up quicker, which retards your run/pulls you back more, meaning you have to be ready to move forward even quicker than before. With a lot power the wing pulls up with so much force that for a moment it is trying to pull you over backwards, then a split second later you can fall flat on your face as the pull disappears and you need to be in Gazelle mode.

[forecaster]

Thanks @AndyB, it makes a lot of sense. I will put more attention to keeping the pressure on the glider and have the lines tight all the time. Also, I will apply throttle only when the wing is over my head or close to that point.

[adamjedgar]

I power launch all my paramotors...i was forced to learn this way because i wasnt strong enough to forward launch without power.

 

I have a little tip for you (pardon the pun)...

 

When power launching its vital that you only use a small amount of power initially whilst pulling wing up. Over throttling causes the risers to squeeze against the cage deforming it (unless you have a really strong cage). This deformation results in one of two outcomes..

1. prop hits the cage

2. lines are caught by propellor tips.

 

in your case, because you have a single ring cage, and a rather large prop, i am almost certain that number 2 above is exactly what has happened to you.

 

I have a youtube video where i overthrottled power launching with a brand spanking new 3 blade propellor (a long time ago but i think it cost something like $800 AUD).

In my case the result of overthrottling was number 1 above...prop hit cage (i have dual ring cages on my units)

 Took 25mm off all three tips on first attempt at launching with it. In my case it was just a muscle memory issue with throttle setting...the two blade prop i had before didnt respond as well and so my automatic throttle input was the same with the 3 blade prop. the engine revved up really quickly and bam!!!

 

see short youtube video here...

out

 

Next time you power launch, make sure that you do not use much throttle initially whilst wing is coming up off the ground. Your cage unfortunately i do not believe is a good type of cage for power launching...its only a single ring and the propellor is very exposed.

 

Second, its also vital when power launching that you DO NOT LEAN FORWARD during launch!!! I cannot stress this highly enough, you must stand very upright and move forward with the push of the engine. Standing upright helps allow the lines to clear the cage very early on in the glider pull up. Its not that you should be jamming legs into the ground in front of you against the thrust of the engine...just make sure you stand very upright as soon as you can.

 

hope this helps

Edited September 29, 2020 by adamjedgar

[AndyB]

I have the same issue about what power to use and muscle memory. I have a NItro and a Tornado. One 2 bladed and one 3 blade. Both the throttle position and the noise made and different for each. I find the only way to retrain my head when switching between them is to bend forward and apply the power gently until I get to the right amount, Then hold it, start running and straighten up.

[forecaster]

20 hours ago, adamjedgar said:

Over throttling causes the risers to squeeze against the cage deforming it (unless you have a really strong cage). This deformation results in one of two outcomes..

1. prop hits the cage

While I totally buy the 2nd outcome (commented below), I must admit I hardly comprehend this phenomena. I can't imagine how the thrust could pull the loose raisers at such a power that those raisers bend the cage and make the propeller catch the cage... Or I misunderstood it completely

I think you are right that what happened to me was that the A line got sucked in by the propeller just when I let the lines get loose (did not pull the canopy strong enough after the first pull backwards). I will postpone my power launches by the time I get confident and hands on with the paramotor on my back.

[AndyB]

You can simulate cage flex easily. Thrust is say 80 kg. so on the ground sit someone in the machine and try pushing 40 kg on one side, just at one point. It will flex a lot. Also, the prop flexes a little forward. On my AC machine there are velcro straps holding the cage quarters together. I have actually cut them with the prop....without breaking anything! 

[forecaster]

19 minutes ago, AndyB said:

You can simulate cage flex easily. Thrust is say 80 kg. so on the ground sit someone in the machine and try pushing 40 kg on one side, just at one point. It will flex a lot.

Ok, I think I got what @adamjedgar meant - the cage pushed backwards by the tight lines/raisers leaning against it when I added thrust.

[adamjedgar]

You would be suprised at how much force the wing and therefore risers are capable of exerting on the cage ring...its a really big amount that most cages simply cannot resist.

If you look at tandem trikes, they have added cables between trike and cage to help this issue as well as hooks high up on cage for risers to sit on.

 

If your lines were so slack they got sucked into the propellor i find that difficult to see happening when you are moving forward pulling wing up unless you were turned somewhat sideways before you added power.

To be honest, if you can forward launch without power, you can power launch...its pretty easy. As i and others have said, the trick is not over throttling early on in the pull up. this part just takes practise and a committment to the early part of  launch. If you dont committ and the wing starts to loose it rising momentum, it will want to fall back to the ground. If you try to force it to fly at this point by continuing with even more power, it will quickly go parachutal, at this point you're stuffed and very likely to compress cage.

 

When i first started motoring i was always worried about how to get the wing to launch straight ..i worried so much i stuffed my launches repeatedly. The thing is, forget about any of that and just pull the damn thing up...it wants to fly straight, the only reason a wing doesnt is because the pilot over thinks starts concentrating more on steering doesnt maintain the initial launch momentum and tries too hard to fail. They start giving up on the launch before the wing has even got 4 feet off the ground. The wing immediately starts to loose its launch momentum just as the pilot realises something has gone wrong (but isnt really sure what or why), the wing starts to go offline because its no longer flying, pilot starts to pull now whilst also throttling up further, only its too late and wing is rapidly starting to go parachutal...

 

Most lower end wings require very little pull to get them to come up off the ground, however, once that process is initiated, pilot must keep it going, keep the momentum happening.

 

Btw, dont be hard on yourself when you blow a launch...it happens all the time in nil wind for a lot of reasons.

 

Another thing to keep in mind (i forgot to mention this before), quite often nil wind isnt nil wind. You may actually have tried to launch in a moment where the faintest tail wind was blowing. This is very common on light days where winds tend to be variable direction or when flying just before sunset when catabatic conditions are very common.

I recently had a launch where wind well above tree line was clearly east, however after failing 3 launches...wing just had zero pressure and refused to fly, i decided to go to opposite end of the park, face west and launch in what i was sure was a tail wind...perfect launch straight away... i couldnt believe it unless id seen it with my own eyes...the catabatic from west was coming in underneath the easterly above and sinking down over the front of the tree line to the west of me. Once i was well above tree line i flew straight into the easterly again...i thought this kind of thing only happened in really hilly terrain (like around mountains) but clearly i was wrong!

 

Edited September 30, 2020 by adamjedgar