How much engine power is enough?

Basic considerations

Many paramotor pilots already know exactly what they want in terms of engine choice and power. However, if you are relatively new to paramotoring and uncertain of how much power you really need, then this section aims to provide you with some rules of thumb.

Your power requirements also depend on your style of flying; if you plan to do aerobatics, then you will need a lot more power than someone who is into cross country flying for example. If you are just starting out in the world of paramotoring, your power requirements will be moderate.

The engine produces thrust via the propeller to move a paramotor forward in order to launch and fly. It is important to select an engine with the optimal amount of thrust for your specific level of experience and style of flying. Having an underpowered paramotor could be dangerous during launch or in situations where a steep climb is essential. Likewise, having too much power in the hands of an inexperienced pilot could also be dangerous.

Apart from the aforementioned points, your body mass and physical strength are the primary determining factors. You will need a certain amount of thrust to launch safely and effectively, and you need to be strong enough to comfortably carry and run with the paramotor on your back during launch. Other factors such as the altitude of your launch site and the size of your glider are also important. At higher altitudes, the air density is lower and therefore you may experience a higher launch speed. At the same time, the engine thrust will be less at higher altitudes, so a marginal engine at sea level will be underpowered at a higher altitude. Smaller, sport-oriented gliders will also need a higher launch speed than a training glider for example, requiring more output from the engine.

Another consideration is fuel consumption. Bigger, more powerful engines will have higher fuel consumption. If endurance is important to you, then bigger is not always better. Also, bigger engines are heavier, and you have to be comfortable with the weight of the paramotor.

The following section presents two rules of thumb that have been developed and used in paramotoring communities and may assist you with your decisions.

Method One:

The first method is based on your body mass and works as follows. Allow 15 hp for the first 70 kg of your total body mass, then add 1 hp for every 5 kilos above 70 kg to determine the engine power requirement. For tandem applications, both occupants’ body mass should be used. For example, the required engine power for a 90 kg pilot is 15 hp + 4 hp = 19 hp. For such a pilot, the Atom 80 will be marginal even at sea level. Using this calculation method, the engine options are as follows:

Method Two:

The second method is more informative as it indicates the required thrust and the maximum paramotor mass (foot launch) that should be comfortable for the pilot to carry. It is based on the so-called 30/70 percent rule. According to this method, the paramotor should not weigh more than 30% of your body mass, while its thrust should be at least 70% of your body mass. For the same 90 kg example pilot, the paramotor should weigh less than 27 kg (dry mass, without fuel) while its thrust should be at least 63 kg. Therefore, the smallest engine option for this pilot is the Safari 125 or the Polini Thor 130, which agrees with the engine selected using the first method. For the available engine options, the thrust produced by the engines are roughly as follows (thrust ranges are due to different propeller sizes available):

The following graph plots actual paramotor static thrust (thrust when stationary) as a function of engine power. Data were obtained from manufacturer’s official documentation as far as possible. Engines included in the analysis are from Air Conception, Cors-Air, EOS, HE, Minari, Nirvana, Per Il Volo, Polini, Ros, Simonini, Sky and Vittorazi - a total of 37 engines. When fitted with a larger propeller, some engines produce significantly more thrust. For example, the 27 hp engine producing 93 kg of thrust is the Vittorazi Moster Factory R with a 140 cm propeller, which is quite large for the size of the engine. Similarly, when fitted with the smallest propeller in the range, less thrust is produced. The blue line represents the best average fit through all the data. Over this small power range, the relationship is practically linear as shown.

Figure: Test Results of Actual Paramotor Engine Thrust vs Power

Manual pull or electric start?

The primary consideration when deciding whether to opt for an electric start is the additional mass of 1.5-2.0 kg that this option will add to the paramotor. Furthermore, there is the hassle of having to keep the battery charged. Consideration must also be given to your flying style. A manual starter makes more sense if you are into cross-country flying and want to trade mass for extra fuel. On the other hand, if you are a strong person who doesn’t need extra flight endurance, or your flying style requires stopping and restarting the engine during the flight, then an electric start option might be for you.