Why are NASA's engineers concerned about gusts affecting the X-57?
I understand that NASA is recommending automatic torque based prop speed control to be used in flight but also in gusty conditions.
The speed of each propeller can be controlled independently, offering the ability to change the over-wing airflow pattern to cope with flying conditions, such as wind gusts.
The original airplane being used had a wing loading of about 17lbs/sq ft.
The X-57 has a wing loading of 45 lbs/sq ft with its new smaller wings.
The higher the wing loading, the less an airplane is affected by wind gusts as it needs much more wind velocity to generate lift. E.g. frontal wind gust hitting one wing, then the other on a lower wing loading would create much more roll.
High-Aspect Ratio Experimental Wing
Perhaps the most noticeable difference from the X-57’s Modification II configuration is the development and integration of an experimental, high-aspect ratio wing. Designed by Xperimental of San Luis Obispo, California, the wing features a large reduction in area, with wing loading increasing from 17 pounds per square foot to 45 pounds per square foot.
The reduction in wing area also contributes to more efficient cruise flight through decreasing friction drag. The final Modification IV effort will demonstrate that the high aspect ratio wing with the integrated high lift motor system will allow the X-57 to take off and land at the same speed as the baseline P2006T. The aircraft will also be less sensitive to gusts and turbulence, leading to a smoother flight.
If the X-57 is less sensitive to gusts, why does it need a "gust control system"?
One possible answer is that the X57 needs that flow over the wings to generate lift.
I understand that the X57:
- has 14 x 24" 5 bladed props
- props spin at about 4,500 rpm
- motors generate about 14,000W of power
- stalls at about 60mph.
Entering that into java foil, the programs generates a prop exit speed multiplier of 1.6 or roughly 100mph.
See pics below
10 mph headwind, gusting to 20 mph, increase is 10mph, which is only a 10% of 100mph airflow over the wings at a stall speed of 60mph, with wings that should be 300% less affected by wind due to 300% higher wing loading.
So why does it need a "gust control system"?