How Much Power Do I Need?

You'll notice the name of this article is not "How much power do I want?". Do what you like. However, there are other considerations besides power that need to be addressed like, quality, weight, service support and how quite the motor is. I would like to give some guidance to the new pilot who's trying to figure out want they really need.

Currently there is a contest to see who can make the biggest, most powerful motor. This is an overreaction to the bad old days of paramotoring where most the rigs were underpowered. These days most motors have all the power you need and some have a lot more.

You do need a minimum of power to safely fly. First let's look at how power is measured. Pounds of thrust is what is important to you. How big the engine is, how much horse power it has, means nothing if you can't turn that power into thrust. Here's an example, I fly a paramotor with a 210cc engine which puts out 110 pounds of thrust. There is another motor on the market that is 202cc that puts out over 160 pounds of thrust. A well engineered motor needs to balance the design of the prop, it's length, surface area and pitch to the power band of the engine.

You need an honest measurement of the motor's thrust. There is a device you can put a motor in, to measure this. The motor should be tested with the harness in place with a pilot sitting in it. There needs to be neither a head or tail wind to bias the results.

I currently fly with a 110 pound of thrust at 5000 to 6000 foot launches with wheels. I only get about 150 foot per minute climb rate. this not enough. I bought this motor when I was still foot launching, without the weight and the drag of the wheels it got around 225 fpm climb rates.

I recommend that your motor should have enough power so that, with your glider, at your weight and at your density altitude, (I'll get to density altitude in a moment.) you have a minimum climb rate of at least 200 feet per minute. I know I going to catch grief from the power mongers over over this figure, however 200 fpm will get you off the ground and you can fly around and go sight seeing. Big Fun! Let's knock off a few of the aurgements for big power,

1. That's not enough power to escape big sink. Well, nothing has enough power to escape big sink. I have been a free flight thermal pilot for for years, I've encountered sink as high as 2000 fpm. Nothing, comes even close to having that kind of climb rate. There is only one way you are going to stay safe in this sport and that is by exercising good judgment. If you are going to fly in active air you need to know how to do so. You need to know your weather, your surge control, how maintain the internal pressure of your glider and have more sense than a jellyfish. You have only one piece of safety equipment and that under your helmet and between your ears. No amount of power can save you from flying air you don't belong in. (You'll notice some pilots don't fly with helmets. That because they haven't brought the above mentioned piece of safety equipment with them.)

2. I'll have too run a long way to take off. With a 200fpm climb rate you'll take off after running around 10 to 15 steps in light winds. The glider will take off when it reaches take off speed. If you are foot launching, it's your ability to run that gets you to take off speed. Although the prop pushing you does help somewhat, it can't push you more than you can run. Most long runs come from poor launch technique. If you taught yourself to fly or had one of those three day courses, there's your problem! You never learned to launch correctly.

3. I like to twirl around with my wing tip touching the ground and I need lots of power to do that. Yeah, what ever, have fun, try not to kill yourself, OK?

Are there any good reasons for having more power? You bet!

1. You're a big dude. The bigger you are the more power you need. When you're over 200 pounds it will be more likely that you'll need more power.

2. I will normally launch from a high altitude site. High altitude is thin air, thin air needs more power. Altitude isn't too much of an issue till you get to 5 to 6 thousand feet. If your launch is above 8 thousand feet the big boy motors may be your best choice. The thickness of the air is called your density altitude. It's a big fancy word. What makes your density altitude higher, (or air thinner) high take off areas, hot days and lots of humidity. you need more power in these situations. Cool days at sea level need little power.

3. I bought a piece of junk, uncertified, mystery wing from Ebay and it has a sink rate like a ton of bricks. Alas, so many pilots get their priorities backward. After spending a lot of money on a motor they get the cheapest wing they can find. The sink rate of the wing makes a lot of difference to the climb rate of the craft. You'll need a lot more power to get a crappy old wing going. But, this is not the important part, your wing is the most important piece of equipment you will buy. ITS WHAT FLYS! You don't want to be in the air with something that flys poorly.

4. Damn it! I like power! Well, that's cool. You should get what you want.

So why wouldn't a person get as much power as they can get, after all you don't need to use it. Why get less when you can get more?

Mainly because there are other issues to consider. The most powerful motors are the heaviest. Some are close to twenty pounds heavier than a motor that would work fine for you. More weight is harder to run with and harder to land. It's harder to haul around, harder to get out of your car. If you've had any issues with your back, you should be looking for the lightest motor that you can get your 200fpm climb rate with.

This year three of my students hurt their backs with their large powerful motors and had to takes months off to rest up. All three had a history of back problems and yet did not bring this up when we were discussing which motors they should get. If you have a healthy back, chances are you will have no problems. If you don't, don't be shy, bring it up.

I have a history of back problems and eventually had to have surgery. I now fly with wheels. if I had life to do over I would have started flying with wheels. If you got a bad back do yourself a favor, fly light or fly wheels.

Another great reason to sacrifice power is, if you can make you motor quieter, do so! The greatest threat to our continued enjoyment of this sport is noise complaints from the general public. Nobody cares if we fly, but people do get annoyed by noise especially when they are outside enjoying a day off. Currently only one model has gone full out on the noise issue. Hopefully other will do so soon. We can help by asking for quite motors and rewarding those companies that respond with our business.

Happy Flying

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