VTOL UAV

Discussion: VTOL (Vertical Take-off and Landing) Fixed Wing

The best of both worlds.

INTRODUCTION

Technological innovation is about breaking down existing barriers, being able to achieve what was not possible before. Typically, the trade-off for consumers of drones always has been

Hover time                                              or                                                  Gliding

(*Point of Interest)

Fixed wing drones have long been the preferred choice for long range mapping and surveillance purposes.

TYPICAL APPLICATIONS

Mapping

One of the most important applications of long-range drones is mapping a terrain, which can be a city, a rural area, large plants, extensive infrastructure or construction sites. Long range drones can fly really high, a considerably long distance, and for a long time. They have become the perfect devices with which to capture the various geographical features of a place.

Frequently long-range drones are used to map forests, water bodies like rivers, roads, etc. As these features are always changing, it requires regular mapping of such areas to keep the maps updated.

With the introduction of these aerial platforms, understanding geographical features has become easy as long-range drones have helped business users to employ multispectral images which in turn assist the scientists to have required knowledge of the climatological measurements of an area.

 

Surveillance

The best way to have good surveillance of an area is by doing so aerially. Long range drones are regularly used to keep an eye on people, groups, activities, infrastructure, etc.

Multirotor drones are popular with security forces because they allow them to be on a look-out for any incidents, while maintaining a safe distance, over a long period of time and hover over a POI.

Typically:

  • a multirotor drone makes sense if an application needs limited geographical coverage or has narrowly defined physical constraints.
  • a fixed wing drone is probably a better alternative, if the user application requires wider geographic coverage or needs to operate at higher altitudes.

 

A VTOL aircraft combines the ability of a rotor aircraft to take-off and land anywhere with the speed, range, endurance and payload carrying capabilities of a fixed wing.

 

VTOL Options

There are a number of approaches to VTOL configurations of UAV platforms.

 

Option1:ADD same engines for Lift to aircraft

 

One benefit of this option is that Engine 2 can be optimized for Lift, but on the downside, it adds additional drag and weight

 

 

Option2:TILT the same engines

 

The option allows for the same engine to be used for both Lift and Cruise, but on the downside the engine setup now is suboptimal for forward flight (Cruise).

 

 

Option 3: SUPPLEMENT lift engines to Tilt engines

 

In this option, which is a useful comprise of the first two, Engine 2 is smaller and intended to be supplemental to Engine 1 for Lift, lessening the drag and weight disadvantages of Option 1.

UAV PLATFORMS

Multi-Rotor (MR) Drones

Multirotor drones are better at getting into confined spaces, ie under bridges, they can hover over a specific area to capture more information and need little space for taking-off and landing.

Most multirotor drones can fly up to 15-30 minutes while some high endurance multirotor drones achieve both Beyond Visual Long of Sight (BVLOS) long range missions and the ability to hover and maintain a focus on a Point of Interest (POI) when required during such missions.

The biggest advantage of multirotor drones is the ability for take-off and land vertically. This allows the user to operate with in a smaller vicinity with little landing/take off area required. Their capacity to hover and performs agile maneuvering makes multirotor drones UAVs ideal for applications like inspections where precision maneuvering for extended periods of time is required.

The multirotor drones also involve a greater mechanical and electronic complexity which cost more and lasts longer but can become harder to maintain later. Multirotor drones have a shorter learning curve and is more responsive to pilot control.

 

Fixed Wing (FW) Drones

When it comes to mapping very large areas, fixed wing aircraft have an advantage due to endurance ability, and can fly faster and much higher, when needed. A large farm can be flown in a single flight and while still capturing data at a relatively micro level. A key advantage of a fixed wing drone is that it consists of a much simpler structure in comparison to a multirotor drone.

Another advantage of fixed wing drone is the flight characteristics due to their natural gliding capabilities being able to carry payloads for longer distances on less power.

One of the major disadvantages to a fixed wing solution is the need for a runway or launcher for take-off. Also fixed wing aircraft require air moving over their wings to generate lift, they must stay in a constant forward motion, which means they can’t stay stationary the same way a multirotor drone can. This means fixed wing solutions are not best suited for stationary applications like inspection work. The uncontrolled landings of many fixed wing designs also mean a lot of wear and tear and a shorter lifespan of the aircraft.

 

ASSESSMENT (FW vs MR) and where VTOL (colour coded) can make the biggest difference

Criteria Result Assessment
Endurance                  FW

 

Fixed wing drones can stay in the air for much longer, they get all of their lift from their wings and just use their motor for thrust. In the absence of aerodynamics afforded fixed wings, Multirotor drones, consume much more energy just to stay in the air.
Take-off Area   MR

 

A big drawback of fixed wing is that it needs a larger area for take-off and landing. Short life span: uncontrolled landings, assisted take-offs. For the multirotor drone, Vertical Take-Off and Landing (VTOL) coupled with the ability to hover allows you to fly your mission in a very tight space.
Speed                       FW

 

Fixed wings fly faster and captures data less accurately and in less detail A multirotor drone flies slower capturing data more accurately and in more detail.
Maneuverability MR A fixed wing is faster but can’t hover. A multirotor drone can fly on any axis and at any speed. This makes it ideal for filming or inspection work where space is tight like between buildings or under bridges. It is also capable of flying indoors and hover around a POI. Multirotor drones are much easier to fly for pilots.
Payload MR In the past fixed wings have had the edge when it comes to the size and amount of kit they can carry. With miniaturization of technology and improved batteries and motors, multirotor drones are catching up quickly. Multirotor drones can also handle LiDAR, which is used for three-dimensional surveying.
Size MR Fixed wing aircraft for surveying tend to be large and cumbersome to transport where multirotor drones can be folded up into much more compact and mobile cases or carry bags
Price FW Long range fixed wings often have an advantage over multirotor drones.

 

With VTOL FIXED WINGS one is able to resolve the Take-Off area constraints and improve maneuverability of Fixed Wings but is likely to sacrifice some performance (endurance/speed) as a result.

 

It does become a more complicated machine and, size remains a challenge, and the price is likely to increase.

 

CONCLUSION

 

On balance however an assessment will however tilt in favor of the VTOL combining the best of both worlds. In summary the benefits of a VTOL configuration include:”

  • A VTOL platform requires less ground based support infrastructure and physical space.
  • While a VTOL provides a little less in terms of aerodynamic performance, it is significantly superior to other rotor craft.
    • The slight sacrifice in flight performance (speed and range) is well made up with the increase in terrestrial mobility, as the it can be moved much closer to target areas and attain hover mode in a shorter space of time.
  • The slower ascent and descent of VTOL aircraft improves safety during landing and takeoff phases.