Besides pilot training, safer cages will go the farthest to reducing prop injuries.
Jeff Baumgartener has designed a strong safety ring for the Skybolt v2 that could easily be retrofitted to a wide variety of paramotors and demonstrated its ability to withstand 170 pounds on a highly vulnerable spot of the netting. Here is an article showing what he built. Of course nothing is foolproof so its still always up to the pilot to exercise good judgment at all times. Safer gear just improves your odds of surviving an unexpected thrusting motor trying to chop body parts.
Animation showing several ideas to improve prop safety
The best designers will help reduce our sport’s most prevalent serious injury and much of that will come through cage improvements. The section highlights efforts to do just that. I applaud those who make gains in this area. Nothing is perfect, everything can be improved. If you know of a paramotor maker that has made improvements to cage design that will reduce the possibility for hand or leg injuries, please send it to us at contact.
The safest cages will pass the hand test: That is, prevent an open human hand from contacting the prop if holding back the paramotor at full rated thrust from anywhere on the cage or netting. They should also prevent reach-around injuries where the pilot is grabbing for brakes or falls and manages to whack a hand by going around the cage hoop.
These are examples of the inner safety ring put on at the prop’s radius. Ideally, the ring should go all the way around to the bottom. Several pilots have fallen down on launch and instinctively put their hands down to catch themselves. The hand went through to the spinning prop.
A Better Paramotor
The cage ideas in the diagram above has been added to address actual injury accidents. It’s been enhanced over the years as different causes have appeared. For example, it has become apparent that the prop should be forward of the hoop and well away from the pilots reach. Several injuries struck pilots when, during launch, they were able to get their hand around the cage. The pilot couldn’t do it while just standing there but, with the motor bobbing around, he was able to and with tragic results.
Another area that must be addressed is the frame bottom. I know of two serious injuries where the pilots calf muscle was cut when running for launch and two other accidents where the pilot was launching. One was on a forward launch where the pilot put his hands back and down, the other was during an abort where the pilot got whacked after pulling full brakes. Make sure your frame protects from this.
Cage Hand Test
A critical test for paramotor prop safety is whether it can withstand the hand test. You should be able to put your hand anywhere on the cage and, at the motor’s full rated thrust, NOT be able to touch the prop. It’s a simple test: push on the weakest part of the cage netting nearest the prop (usually its tips) and see if you can touch the blade. If you can, you’re at higher risk of a prop strike. There should also not be any large holes that would easily allow a stray hand to go through.
Here’s another test that is easier to do. See if a 3 x4″ block of wood can be pulled into the prop by pulling AGAINST the prop, through the netting, with half the rated thrust. If it can, you’re at fairly high risk.
It may seem extreme to require passing the hand test at full thrust since it will never likely be pushing only on that one point. But all it takes is a quick bounce of your hand or shoulder into the prop arc and you’re doomed. Plus, the hand test doesn’t take into account that the prop tips are arcing slightly (up to an inch) towards the cage or that the motor may flex on its mounts when you stop the cage with your hand. So the full rated thrust hand test is a minimum that motors should pass to have reasonable prop safety.
Even a machine that passes the hand test is not bullet proof. Cage pieces or lines can fail so it should never be relied on. All starting should be done with the anticipation of full power and a plan to handle it that does not include going for the cage.
There are a number of machines that can pass the basic hand test as some manufacturers have taken the initiative to pay it attention. The list of machines is growing, it seems, and hopefully more manufacturers will take this risk more seriously.
Safety Ring
Jeff Baumgartner, Skybolt designer, puts ideas into action.
He has come up with several implementations meant to address cage safety including the one pictured here, a prototype. Jeff explained that, on the next version he would decrease the open space between the hoop and motor. That would help as a pilot could get through. The intent is to show that the netting will easly pass the hand test. Reach-around clearance is provided by having an oversized cage and enclosing the prop fully. Jeff explains that clearance depends also on prop size. This cage with a 48″ prop will not have the same protection it will with a 46″ prop.
Another video showing the Safety Cage (aka Safety Ring).