by Ben Fisher
Posted on July 01, 2017
Today, most of the large tech companies have drone programs, Amazon, Google and indeed Facebook. While Amazon and Google are investing in the technology to make aerial deliveries a reality, Facebook is looking to use high altitude drone platforms to connect the world with high-speed internet.
On May 22nd, 2017, the Aquila team reached a milestone with a successful flight of 1 hour and 46 minutes. The full-scale version has a wingspan wider than a Boeing 737 and is mostly carbon fiber composite so the whole thing weighs less than 1,000 pounds.
The drone was launched in Arizona as daylight broke and after the system, checks were confirmed for 'go for launch'. It used a trolly and tow vehicle to reach take off speeds. Take off climb rate measured in at 180 ft/min - which was nearly twice as fast as the first flight.
The huge wingspan and lightweight airframe are optimised to cruise in headwinds at just 10-15 mph above ground level. This is so the platform can stay airborne in the same area for long periods of time to supply internet access. It is solar powered with 4 propellers running on the power equivalent of three blow dryers. The main altitude was 3,000ft for this flight although the drone when operational will be flying at 60,000ft.
The main reason for this flight was to gather performance data and test the latest configuration. Since the initial flight the team had included the following modifications:
Adding “spoilers” to the wings, which help to increase drag and reduce lift during the landing approach
Incorporating hundreds of sensors to gather new data
Modifying the autopilot software
Integrating new radios for the communication subsystem
Applying a smoother finish on the plane
Installing a horizontal propeller stopping mechanism to support a successful landing
The flight paths were designed to fly at a constant speed, heading and altitude to measure the drone's drag parameters. This data will be used to refine their aerodynamic models, which help predict energy usage and optimise battery and solar array configuration. The added sensor data gained from hundreds of strain gauges and three-axis inertial measurement units (IMUs.) will further be used to optimise the structure performance of the airframe.
A new communications link was also tested on the day so that the drone has a primary and secondary link for redundancy and testing at different angles. Everything the drone does is designed to be slow, so after testing the landing algorithm performance while maintaining airborne the crew was confident to land the platform on a 500-foot circle gravel landing pad.
The drone is intended to be autonomous but final flight plans were uploaded during the landing sequence to compensate for the current wind conditions. The drone lands on kevlar pads below the motor mounts while the propellers are intended to lock in a horizontal formation before landing to avoid the ground.
Facebook released the below footage where you'll see the Aquilla drone gracefully reduce altitude to the point in makes contact with the gravel landing pad. However, it didn't quite go to plan with only 1 of the 4 propellers locking in the horizontal position. You can see the propellers make contact with the gravel resulting in flying debris and some damage.