Just once dawn on could twenty two, Facebook reached another exciting and necessary milestone for the Aquila program — finishing the made second complete check flight of the craft. The craft flew for one hour and forty six minutes, and landed dead on our ready landing website.
In order to launch right once sunrise, that was at 5:15 am, we tend to showed up at the gate to Yuma work in Arizona at 12:30 am. whereas some members of the team began to open the structure and carry the heavier-than-air craft onto its takeoff dolly, the remainder folks ready the bottom management station and engineering station. And just about everyone studied the wind forecast.
Aquila’s second check flight took under consideration the teachings we tend to learned from our 1st flight. beforehand of the second flight, we tend to incorporated variety of modifications to Aquila, including:
Adding “spoilers” to the wings, that facilitate to extend drag and cut back carry throughout the approaching
Incorporating many sensors to assemble new knowledge
Modifying the autopilot code
group action new radios for the communication scheme
Applying a electric sander end on the plane
putting in a horizontal propellor stopping mechanism to support a made landing
At 5:27 am, the sun was simply higher than the horizon, and also the craft had passed all our preflight checks. The radio links (redundant uplinks and downlinks square measure put in each for additional information measure and for redundancy) were purposeful, the management surfaces and spoilers were free and proper, and every one four motors more established commands properly.
After finishing our pre-takeoff list, our temporary wait was rewarded with low measured winds in addition as low forecast winds. a fast poll of the pilots and engineers resulted in an exceedingly “go for launch” decision. The launch speed was calculated at twenty seven mph and this was passed to the operators of the tow vehicle. The crew closely watched the displays, awaiting the signals that the autopilot had commanded unleash which the heavier-than-air craft was ascent removed from the dolly.
Takeoff was traditional. It additionally quickly became apparent that every one the systems were functioning normally: The motor current, the velocity chase, the heading chase, the radio links, and also the differential GPS all showed nominal behavior. the sole surprise was a contented one: The climb rate – at one hundred eighty ft/min – was nearly double as quick as on our 1st flight. we tend to attribute this to the various refinements to Aquila — particularly a electric sander end — that were supported learnings from our 1st flight.
We continuing the climb to three,000 feet, searching for signs of a healthy craft before the plane got higher than our planned flight envelope. With all measurement “in the inexperienced,” we tend to continuing the climb. By design, Aquila will nothing fast: It climbs slowly, descends even slower, and once flying upwind moves solely at 10-15 mph over the bottom. we tend to designed Aquila this manner as a result of it’s meant to remain within the same space for long periods of your time to provide net access. Aquila is solar-powered and intensely power-efficient —- running on the facility equivalent of 3 blow dryers.
This second flight was all concerning knowledge. we tend to flew prolonged check points at constant speed, heading, and altitude to live the airplane’s drag. the info from these “trim shots,” as they’re referred to as, are accustomed refine our mechanics models, that facilitate U.S. predict the energy usage and therefore optimize for battery and electrical device size. we tend to additionally undertook in depth instrumentation of the airplane’s structure, adding many sensors to the craft to grasp however Aquila’s form responds to flight in time period. These enclosed many strain gauges and three-axis mechanical phenomenon activity units (IMUs.) These tools serve to verify and refine our structural model, that predicts each the static form of the heavier-than-air craft — designed to be terribly versatile to reply to wind gusts and maneuvers.
Throughout the flight, we tend to additionally continuing to verify the drag created by new “spoilers” that we tend to additional to Aquila at numerous angles. Spoilers square measure movable surfaces on the wing of AN craft that facilitate produce drag to scale back speed and reduce carry. we tend to additionally tested the 2 radio links’ signal strength from numerous side angles.
After testing the landing algorithmic rule with AN elevated landing, we tend to committed the heavier-than-air craft to a whole, made landing on the selected website.
The Aquila craft has no undercarriage within the ancient sense. It lands on Kevlar pads guaranteed to very cheap of the motor pods. The explanation is twofold: 1) we tend to land at terribly low speed and descent rates, therefore we are able to save the burden and drag of struts and wheels, and 2) abundant of the aircraft’s mass is focused within the motor pods, since this is often wherever the batteries square measure installed; once the batteries land, stopping the descent of the remainder of the craft imposes very little load on the structure.
For the landing pad, we tend to created a five hundred foot circle of level gravel, concerning half-dozen inches deep and with the consistency of rough sand. Aquila flies autonomously, with the exception of manual interventions in cases akin to lining up with the wind. Therefore, shortly before landing, the flight crew uploads a landing arrange supported the wind direction such the heavier-than-air craft lands upwind, therefore respecting the wind limit.
When landing, the Aquila craft follows a three degree path — the glideslope — that starts some hundred feet within the air and ends on the bottom. A feature of this category of heavier-than-air craft is low drag — it’s the sole thanks to wing the restricted power daylight will give. however whereas drag is that the archenemy of flight, it’s the staunch ally of landing. The spoilers that we tend to additional to the craft square measure controlled by the autopilot. once the autopilot senses that the craft is higher than the glideslope, it opens the spoilers a lot of, and once it senses that the craft is below the glideslope, it closes them. Meanwhile, because it will throughout the flight, the autopilot lowers or raises the nose exploitation elevons, that facilitate to extend or decrease velocity.
A few seconds before landing, the autopilot stopped the propellers as planned so as to lock them horizontally. The propellers square measure meant to lock within the horizontal position to avoid damaging them once touching down. during this flight, the motors all stopped, however just one propellor secured horizontally. The craft settled onto the landing surface terribly gently and came to a stop in concerning ten meters. it had been was} absolutely excellent. like driving a automobile on a gravel surface, landing a plane on gravel causes some minor, easily-repairable dings, however otherwise, Aquila landed in nice form.
From our near engineering station, our Aquila team watched a video stream displaying the air-to-air read from our chase eggbeater. we tend to had a ringside because the craft swimmingly softened to a stop in an exceedingly cloud of dirt — and also the engineering station erupted in cheers. once Aquila’s landing, the employees at YPG informally christened this landing space “Aquila Beach” — a reputation that the whole team was proud to adopt!
Needless to mention, the whole team was excited with these results. Connecting individuals through high-altitude solar-powered craft is AN audacious goal, however milestones like this flight build the months of exertions worthwhile. And what’s significantly gratifying is that the enhancements we tend to enforced supported Aquila’s performance throughout its 1st check flight created a big distinction during this flight. within the returning months, we’re excited to require the teachings from our made second flight to continue the Aquila program’s attain facilitate bring the globe nearer along through property.