What you need to know about drone landings

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What you need to know about drone landings

It has been a few weeks since my latest blog post, on “Drones and energy efficiency”, so let me first start by thanking everyone for the overwhelming response. It is obvious that the professional drone user is starting to recognize the need for endurance to achieve better ROI. I’m surprised to find that so many of you have had similar considerations, contrary to the ongoing multirotor hype. As one gentleman so eloquently put it, “It was very interesting to refresh the basics and also to understand again that multi-copter vs fixed-wings energy efficiency differences come from the basic foundations how each fly. I did not pay attention previously that electric motors in multirotors do not work on nominal rpm most of the time – and in the engineering, the efficiency comes when a device works in nominal, at best unchanging conditions most of the time….. It is like accelerating and braking at high rates in a car and expecting low fuel consumption.”. Again, thank you for the many emails and sharing.

All landings start with a take-off

As a fixed wing manufacturer of a small hand launched platform with a fairly steep climb angle I have found that arguments like “but a multirotor can do a vertical take-off” to mean very little. Sure, there are companies out there building fixed wings that need all kinds of launch contraptions to function, and yes it has hurt the fixed wing’s credibility as a very versatile solution, but in all honesty, – when I launch our fixed wing, throwing it at an angle upwards, it is only a matter of seconds before it’s way above the treetops or most any obstacles, and the choice comes down to endurance (as it should).

Why is the landing important?

Well, what goes up must come down. Joke aside, when landing you are faced with a few problem statements:

  • The safety of people, livestock and property
  • The durability of your drone
  • Protecting your data
  • Space required to enable a controlled landing

Here is where a multirotor excels, for natural reasons, being capable of Vertical Take Off and Landing (VTOL), but what if you can find a suitable solution that does not suffer from the inefficiency, that proven beyond doubt is what multirotors suffer the most from among all flying platforms?

Multirotor

VTOL capable, extremely steady in the wind and requires the smallest of landing surfaces. The multirotor’s capability of utilizing quick acceleration and stopping or even reversing all its rotors is what enables it to be very steady in strong winds, with the downside of consuming a lot of energy.

VTOL fixed wing hybrids

A similar idea to the multirotor, but with fixed wings carrying it during its mission. Logic states that yes you do, from an energy perspective, perform better than a multirotor during missions and similar during landings. However, it is a compromise, and as all compromises there are a few problems. Most of the solutions will land as well as a multirotor in none to very moderate winds, but let’s face it, when the wind is a bit stronger you are literally trying to land an upright sail. This can have two consequences, wind drift and tipping over once it touches down, making it largely unsuitable for windy conditions, where it stands a good chance of breaking as well as being nowhere near as capable as the multirotor in hitting the right spot, thus demanding a lot more space.

Fixed wing

Fixed wing drones do a lot of different type of landings and require different type of landing space and terrain. The upside to all fixed wings is of course the superior energy efficiency.

Parachute

The parachute solution is of course a good way to safely bring down a drone that may not be built with durability in mind. That said, it takes very little imagination to figure out what wind will do to landing precision, wind drift being significant.

Net

There are some that suggest landing into a net. Apart from the fact that it would probably work, it makes it a hassle to bring and set a net up. That said, consider a scenario where you are on a vessel out at sea and wish to do recognizance or data collection missions out to 80km away, requiring endurance and being limited by a small landing area. For such specific situations, the idea of a net has a certain appeal.

Belly (skid) landing

The most common type of landing, and the type that a professional user would benefit the most from, with no extra equipment required. Here it is essential that the fixed wing is built with durability as a consideration. Another prerequisite is that the drone is capable of good wind estimation and exact ground distance sensing. Again, there are companies out there building fixed wings that need large open spaces and flat surfaces to function, or even survive the landing, and yes it has also damaged the fixed wing’s credibility as a very versatile solution.

There are mainly four types of landing approach:

  •        Linear precision approach
  •        Circular approach
  •        Assisted approach (Autopilot stabilized manual landing)
  •        Hitting an obstacle (not joking)

The linear approach requiring a bit more space gives control over the landing spot while the circular should be possible within a 60×60 meter area. An assisted approach, should you care to learn (this is optional), is very precise, as it is pilot controlled, and is doable in most situations.

Hitting an obstacle might actually be a good choice when wanting to limit the space required for the landing approach, although I wouldn’t suggest doing this with any other drone than the SmartPlanes Freya (lest someone decides to sue me for suggesting such). Suitable obstacles would be bushes or small trees (the high ones might include some difficult climbing, – been there done that). What I wouldn’t recommend is what an Australian customer of ours wrote, “FYI your SmartPlane is one of the most incredible items I have ever seen; I still can’t believe that it flies after a 90 km/h collision with a rock levee… the Ricoh camera is btw incredible strong as well.”, – rock levees are after all made out of,…..rocks.

Summing up

We built the Freya to last through all sorts of impact scenarios because of the abundance of trees in the forestry industry and coarse blast gravel in the mining industry. Our value proposition “Operational availability” (you could potentially read it as system durability) permeates our R&D. The follow-on effect is that not only can we land almost anywhere, – we are less limited to having need for larger areas to do so. Or as our engineer answered the project team, while participating in NASA’s BVLOS UTM TCL-2 in Reno Nevada, when asked about landing requirements, “- show me a bush and I can land in it.”

Thanks for reading, it makes writing all the more fun!

Roger Öhlund CMO SmartPlanes

 

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