Best of Both Worlds: Precision Landings with Fixed-wing Drones

Productivity starts in the field, where acres surveyed per hour directly impacts your total project costs. Collecting reliable insights requires the right tools to do quickly, which is why drone systems have become more essential in recent years. 

When choosing an agricultural drone for mapping, finding a solution that balances coverage and efficiency serves as paramount – especially when time is of the essence. A fixed-wing solution meets both of these requirements while providing a rate of data collection that far exceeds a similarly-sized multirotor aircraft. 

Agricultural Drones: Which is Best?

Fixed-wing platforms have inherent productivity advantages in crop production. Multi-rotors are small, affordable, and nimble in tight areas. However, their efficient cruise speed is only about half of what’s possible with a fixed-wing drone like the Sentera PHX. The speed disadvantage translates to fewer acres covered per hour, which can be significant for large fields. The result? Higher hard costs are associated with labor, which can be a challenge in today’s environment. 

Since multirotors are less power-efficient, more stops for battery swaps make these platforms even less competitive in large-scale missions. For example, the PHX is capable of capturing up to 3x the number of acres per hour compared to a price-and-size-competitive multirotor.

Hybrid vertical takeoff and landing (VTOL) fixed-wing platforms aim to combine the maneuverability and takeoff/landing convenience of multirotors with the efficiency of fixed wings.  They are also a great solution for certain applications. In practice, however, compromises are necessary versus either of the component architectures. Like multirotors, for broad acre work, VTOL hybrids are less efficient than a true fixed wing drone. These systems also often carry much higher acquisition costs.

Fixed-wing Drones: What are the Challenges?

There are some challenges with a fixed-wing solution, however. Landing can be tough, specifically related to accuracy and obstacle avoidance; both of which aren’t even considerations for their multirotor cousins. 

Many environmental conditions can affect the landing performance of autonomous fixed-wing aircraft. These include:

• Variations in temperature, which may have an effect on air density and thus, impacting lift
• High crosswinds, which can push the aircraft off course
• Headwinds or tailwinds, which can cause the aircraft to overshoot or undershoot the desired landing point

In all these situations, the autopilot assesses the situation in real-time and attempts to adjust its position accordingly by changing thrust and its aerodynamic surfaces.

Fixed-wing Drones: The Sentera PHX Difference

We may be biased, but the Sentera PHX fixed-wing drone performs better than other fixed-wing drones on the market to optimize data collection in the field. 

Why? 

First of all, the PHX uses a combination of real-time estimation and control techniques that are specifically designed for the PHX airframe to accurately model and control how the PHX behaves during a landing approach. 

Because Sentera’s engineering team designs, builds, and supports this product, including the airframe and flight controller, we have the ingredients necessary to deliver best-in-class landing performance. 

For 2022, we decided to make usability even better by tuning the landing performance offered by the system.

On landing, the PHX will shut off the motor at a designated altitude and glide down to the landing point, maintaining course and stability by controlling its aerodynamic surfaces. We lowered the altitude at which motor cut-off happens, enabling the aircraft to use the thrust produced by its motor to fight gusts and winds until it is closer to the landing point. The trajectory that the aircraft follows as it descends has also been tuned to more accurately reflect the aerodynamic behavior of the PHX and take full advantage of its control authority. 

These two changes give the PHX more resilience to winds that could otherwise push it off course. To address the more aggressive approach given by our modifications, we implemented a more pronounced flare event to occur right before landing. A flare pitches the PHX up slightly to slow the aircraft down and land gently. These changes resulted in a tenacious aircraft that lands closer to the planned landing point more consistently, regardless of environmental conditions. 

These improvements were made possible without the need for mechanical changes to the PHX.  This means that anybody with a Sentera PHX can take advantage of these updates by installing PHX Firmware v180.6.2 or later from our support site.

Let’s take a look at just how dramatically performance has improved.

PHX landings are now over 3x more accurate. Its improvements result in an aircraft dramatically more resilient to all atmospheric conditions and consistently more precise, ultimately enabling pilots to fly in locations previously only viable for multirotor platforms. 

Enabling our most efficient data collection tool, the PHX, to be operational in a growing range of environmental conditions means that the best tool for the job is now even better. Be prepared to answer “yes” to the question of “wait, you can fly in that?”