#### Tench745

##### Master member

As many know, wing loading is a terrible way to compare how aircraft of different sizes will fly. To compare models of different size we use cubic wing loading, which gives us a number we can compare pretty universally across all sizes of aircraft. They fall somewhere in the following categories:

**Slow-flyers and Gliders**: under 4

**Trainers and Parkflyers**: 5 to 7

**Aerobatics**: 7 to 10

**Scale**: 10 to 15

**Warbirds and Racers**: 15 and over

When sizing motors we have compare watts/pound depending on the type of flying you want to do. The categories are something like the following, depending on who you ask:

**50 -70W/lb**. …....Trainers and slow flyers

**70-100 W/lb**. .....Basic aero/sport flying

**125 W/lb**. …........Precision aerobatics

**150+ W/lb**. …...…Extreme 3D performance

My current line of thinking is: why do we compare power to weight directly? Would there be any benefit to comparing power to cubic wing load?

I crunched a few numbers to start a comparison. All data for the given aircraft are from Wikipedia based on rated power and maximum weights, so they don't necessarily reflect actual use cases of a given aircraft.

- A full scale Cessna 172R has about 160hp(119312W) and a gross weight of 2450lbs, for a power to weight of ~49W/lb. At gross weight a 172R would have a cubing wing loading(WCL) of 17.1.

- A Zivko Edge 540 has 310hp(231167W)and a max aerobatic weight of 1550lbs, for a power to weight of 149 W/lb. At its aerobatic weight the Zivko Edge 540 has a WCL of 22.7.

- A J-3 Cub has 65hp (48470.5W) and a max weight if 1220lbs for a power to weight of 39.7W/lb. Its WCL at max gross is 8.2.