In recent months Makani has met two critical flight milestones in first-of-kind demonstrations as per the requirements of the ARPA-E sponsored Wing 7 project. Both of these flights occurred at Makani’s test site on the Alameda Naval Air Station.

Milestone 4 stipulated autonomous transition from crosswind flight to hover mode. In this demonstration, the wing moves rapidly from high-speed, circular flight back into stationary hover flight and remains stationary for over a minute before landing. This demonstration shows the wing’s ability to regain stationary hover flight before landing to a perch.

Makani first met Milestone 4 on September 1st. During the short flight, the wing transitioned autonomously from hover into crosswind flight, performed six loops and, at a command from our controls team, autonomously transitioned back into hover. While hovering, the wing remained stationary, supporting the fully extended tether for over a minute under full autonomous control.

The Wing 7 program is an 18-month project with quarterly milestones. This flight marks the completion of Makani’s third milestone and the halfway point of the project. Makani plans to demonstrate launching and landing to a perch and a full power curve compliant with IEC standards.

The Makani team has achieved a significant milestone in the pursuit of inexpensive renewable energy during this flight of its latest prototype, Wing 7. Wing 7 has a wing span of 8 meters, weighs 58.4 kg and has a rated power of 30 kW.

This was the first flight of its kind to demonstrate both power generation and the autonomous flight modes needed for launching, landing and crosswind flight.

More info about flights and the project can be see in the News section of our website.

In the push to complete a power generation flight within the development timeline, the team conducted 60 tests of Wing 7 during 16 test days. This required a number of sleepless nights, including one in the field. On the day of the milestone flight, the team woke before dawn, set up the wing and waited for the high wind that was forecast for 6 am, but the air remained calm. Later that afternoon, after moving to a slightly windier spot, wind arrived and the rest is history.

The graph below shows the flight path of the wing from launch to transition and into circular flight. Once in circular flight, the path is repeatable, demonstrating the effectiveness of Makani’s controller in minimizing the effect of gusts and changes in wind direction.

Test goal: Demonstrate flight transitions: transition from hover to crosswind flight, fly in crosswind and transition from crosswind back into hover.

While these transitions have been demonstrated in Makani’s six degrees of freedom (6-dof) model, transitions like these have never been demonstrated with a tethered wing.

On September 17, Makani’s team demonstrated that these transitions are indeed possible with the Wing 6 prototype. The success of this test proves that the same planform can be used for tethered hover, crosswind flight and the difficult transitions between these modes. Wing 6 is built with the same aerodynamic configuration as the proposed Makani 1MW system and confirms that this is an effective design.

This footage was first shown at the Airborne Wind Energy Conference at Stanford on September 29, 2010.

May 28th, 2010: Wing 4, Makani’s 10 kW scale prototype is shown here generating power while under fully autonomous control. The purpose of this test is a single point verification of the power curve according to IEC standards. Wing 4 met expectations by generating an average of 5 kW in 8 m/s of wind.

A close-up of the power generation graph, which shows power variation during a loop. The starboard turbine generates significantly more power because it travels faster as it is on the outside of the loop.