Changes to Drone Rules for 2016

A new set of rules and regulations laid out by the European Aviation Safety Agency (EASA) will be implemented later this year.  In short the EASA are responsible for Aviation Safety and instruct the European Aviation Authorities, the CAA included, to administer their rulings. While these are still at ‘Prototype’ stage and are not yet enforceable, they will become law shortly.

The ‘Prototype’ Commission Regulations on Unmanned Aircraft Operations:

The changes are summarised as follows:

UAV’s will be classed on to 3 Categories – Open, Specific and Certified

1 – Open – Lowest risk that do not need permission to fly. This broadly is recreational and is further subdivided into 4 categories, A0, A1, A2 and A3. A0 category applies to home built UAVs only. There are also requirements for the Pilots of the various categories.

Drone

	Max Wight	Max Speed	Max Voltage	Max Altitude	Geofencing	Return to Home	Full Redundancy	Fitted with Transponder
A0	250g	15m/s	–	50m	No	No	No	Yes
A1	25kg		24V	50m	No	No	No	Yes
A2	25kg		48V	50m	Yes	Yes	No	Yes
A3	25kg		48V	150m	Yes	Yes	Yes	Yes

Pilot

	Max Dist	Max Alt	Min Age	Pilot Registration	Training Required	Home build
A0	100m	50m	None	No	No	Yes
A1	50m	150m	None	Yes	No	No
A2	50m	150m	None	Yes	Yes	No
A3	150m	150m	14	Yes	Yes	No

2 – Specific – This covers the use of UAVs where an operator holds a Permission for Aerial Work, and broadly will be similar to the existing rules.

3 – Certified – Covers Military use.

If you wish to see the EASA document it can be found here

https://www.easa.europa.eu/system/files/dfu/UAS%20Prototype%20Regulation%20final.pdf

and an ‘Explanatory Version’ here:

https://www.easa.europa.eu/system/files/dfu/Explanatory%20Note%20for%20the%20UAS%20Prototype%20regulation%20final.pdf

10 Reasons Drones Are Better Than MEWPs For Inspections

Keeping a close eye on the condition of a building is a key element in managing the cost of maintenance. Getting high level access to vulnerable areas is perhaps one of the main reasons why simple preventative maintenance is not identified until the problem is more serious and costly. Using an MEWP has normally been the accepted method of inspection but now there is a better way to keep an eye on things, and that is to use a drone. Here are 10 reasons why…

1. Safety – If you keep your feet firmly on the ground the risk of falling from height is almost zero. No need for MEWP or harness training. A drone, while needing a CAA approved pilot, will reduce your personal risk to a minimum.
2. Vertigo – Not everyone likes heights, so any excuse not to keep your feet firmly on the ground should be welcome!
3. Cost – On a direct comparison basis a drone is cheaper than the hire of an MEWP. If you add in the cost of your time or building professional on site then a drone survey is far more economical.
4. Speed – Given that a drone can cover a much greater area in one flight compared to the reach of a cherry picker, a survey can be carried out in a fraction of the time. A survey may be carried out within a small window of opportunity without serious disruption to normal activity.
5. Convenience – No need for cumbersome machinery to be delivered to site, road closures and diversions, ground disturbance or protection. A drone can get the data quickly and effectively minimising any inconvenience.
6. Height – A drone will legally reach 400 feet in around 10 – 15 seconds. An MEWP is limited to its physical height and reach, and the higher you need, the greater the cost of hire.
7. Access – A n MEWP is usually ‘driven’ to a point on the site and raised from there. The limited reach will require it to be moved and raised from another position. Narrow access, and unsuitable terrain limits where an MEWP can be used. A drone can be carried by one person and can take off and land almost anywhere.
8. Maneuverability – As long as the drone has a ‘line of sight’ and a direct line of radio contact it is capable of flying almost anywhere. The physical layout of the building will not restrict where it can go and there is no risk of damaging the structure with the boom or cradle.
9. Damage – An MEWP, depending on its size, can weigh up to a ¼ of a tonne (around 20m height and 18m outreach at 7m high) and if a lorry mounted access platform is needed, than the weight is considerably more. Siting an MEWP requires careful planning to minimise ground damage or disturbance. Not an issue when using a drone.
10. Ease – A drone can be carried to a suitable position and set up in a matter of minutes after having completed a Risk Assessment and if necessary logged the activity with the Police on 101. An average sized building can be completed within an hour on site.

Take a look at what we can do using drone technology http://www.helipix.org

10 Tips to Great Drone Photography

Helipix have been taking aerial shots using drones since 2008 and as professional photographers we have some very important points for you to get the stunning shots you want with your drone:

So in no particular order….

1. Plan your shot – A good photographer ‘sees’ the shot they want and then sets it up to take it. Simply flying around hoping to get the shot you want will not only be frustrating but may well get you into trouble!
2. Check the position of the sun – In nearly all situations the sun is the only source of light and will cast shadows and lens flare so make sure that the sun’s position will not spoil your photo or cover the subject is deep shadows. You will need to time your shot to make sure the light is in the right position and if necessary take the shot at a different time of the year if the low angle in winter is going to be an issue.
3. Calculate your required height – Often you may only need to go 10-20m from the ground to get the optimum shot. Depending on whether you want a plan shot, angled or oblique shot depends on what height you need.
4. Use a Field of View template – Find out the lens’ angle of view horizontally and make up a GIF file with a triangle shape that is the FOV angle. Load that into Google Earth as a layer and position it to get the best position. The apex of the triangle is where the drone needs to be. Measure the distance from the apex to the centre of the shot and this will be the height you need to be to get a 45 deg angled shot to the ground. While the distance in the air will be greater than the distance on plan, it is easier to fly the drone forward to narrow off the angle of view.
5. Take shots a differing heights – Take images as you descend, often the best images are not always the highest
6. Take Panoramas – Panoramic shots not only look good but they enable large sites to be photographed without needing to above 400 feet. Make sure that you overlap each image by at least 30% and take more images than you need.
7. Watch out for clouds – Fluffy white clouds look good as a backdrop but they have an annoying habit of creating shadows. Often where you are standing will have the sun in full view but your subject area will be obscured. Time the flight to coincide with the gaps in the clouds so that the subject is lit even though you are not.
8. Sunshine is not always best – The best light for aerial images is bright overcast. This acts like a huge ‘softbox’ and illuminates everywhere evenly and softens shadows and highlights. This means that the camera can expose the all the image. Full sun creates dark shadows and bright white areas. This makes the exposure either too bright or dark in certain areas.
9. Shoot in RAW – RAW (if your camera supports it) is like a ‘digital negative’ and will give you the best chance of post processing for colour balance, exposure, saturation etc. While the drone is in the air the camera may need to be set before take-off and so the settings will be adjusted to the best guess or automatic. RAW images will allow you to tweak the image to get the best image
10. Experiment – The drone is simply tool to hold a camera. Play around with different settings, angles and positions to see what is possible and see what works and does not. Get to know the limits and foibles of the equipment, but most of all have fun and fly responsibly!

Drones and their use in Building Conservation

The Victorians gave us grandeur and detail, the Tudors, hips and valleys and the Plantagenets gave us crumbling castles. All of which we cherish as part of our Heritage but all unfortunately give us problems, and difficult ones at that!

Take the Founders Building at Royal Holloway (above left) in Egham, Surrey (William Crossland). A splendid example how the Victorians love to create finials, dormers, parapets and a myriad of roofs, all architecturally balanced and styled as was the fashion of the day. Little thought however, as how to maintain and monitor any future works a century or more later.

Equally, Little Moreton Hall in Cheshire (above right) , a building whose shape was based on the shape of the timbers available. Its quirky twisted look add to the complex array of small roofs that have been added over the centuries. Also if we look at any medieval castle we see the evidence of hundreds of years of weathering on the huge high walls designed to keep people out. All this and more has to be monitored and looked after by specialists whose job is to make sure that these buildings are preserved for future generations. It is a huge task and one that is expensive and fraught with a delicate balance of safety, method, and cost.

The UAV has now been firmly accepted as a survey tool, capable of reaching parts of buildings that would have either necessitated expensive access equipment or worse not being surveyed at all until a major project was undertaken and the building scaffolded. But photographs of a complex building are all well and good providing you know what they are looking at. Detail of a loose parapet on the Founders Building is very useful but which parapet? The UAV can most certainly cover all the structure with images and will have a huge capacity for highly detailed shots, sometimes hundreds, even thousands. All viewing sections of the structure clearly and making it fairly easy to identify areas of concern but little regard for the surveyor having to try to work out where they are looking and perhaps from what angle.

As a consequence of the demand for UAV technology increases so does the technology to use with UAVs. In particular is the ability to create a 3D point cloud from digital images. The video above is created from UAV and ground based digital images. There are a number of programs that will create a tessellated point cloud and build a 3D model, but these are no good to a surveyor. The reason is that the 3D model does not have enough detail and is subject to flaws in the model. What a surveyor needs is a model from which to view the actual digital photos. This model is referred to as a ‘ray cloud’, each point on the model is referenced from a number of images. By selecting a point on the model all those images that have that point in the image will be selected. You will see from the video that when the camera is ‘zoomed in’ the ‘points’ are clearly visible.The surveyor can then view the images and see the ‘point’ from whatever angle the image was taken from. The software can build the model to scale and thereby enable measurements to be taken from it, distance, area and volume. Also by using GPS the model can be positioned in ‘global’ space.

No matter how complex the structure may be or how difficult the architects of yesteryear tried to make the structure for on going maintenance and monitoring, the UAV has the tools to manage the task. I bet Wren, Jones, and Crossland never saw that one coming!

Buddleia – Beauty or the Beast?

 

The Buddleia davidii has a bit of a split personality; on the one hand it is commonly known as the ‘Butterfly Bush’ as it is very fragrant and a rich source of nectar, although on the other hand it is also known and the ‘Bombsite Bush’ being often seen on WWII bombsites. Even as an invasive species, brought from China in the 1800’s, it has become a widely accepted and loved shrub, not only for its ability to attract butterflies and hover flies but as a quick and easy to grow fragrant shrub. A field of B. davidii in Hertfordshire has been registered as a “Village Green” and therefore is protected. Although it is not wholly protected as a species, it does however have many detractors who would prefer it to be classed as a prohibited weed in the UK as is the case in New Zealand and Oregon in the USA to name few.

Compared to the size of the average plant seed you would be forgiven for thinking that it would be of little consequence and concern to a strong solid building built of bricks and stone.  A small seed weighing less than 0.06 mg capable of being carried by the wind would hardly be capable of displacing a parapet coping stone or be responsible for costly building repairs.

Given the right conditions an inconsequential little seed from the B. davidii has enough destructive power to bring the strongest of structures to a crumbling ruin. However, if spotted within the first 6 months the seedling can be assigned to the compost heap well before it has chance to become a major problem.

Like most seeds, the germination is started with the presence of food, water, light and shelter. The food source can be from the lime rich mortar, which does not have a chance to dry, such as a blocked gutter. Provided that the seedling is firmly lodged in the building and is capable of receiving sunlight then the process of turning the inconsequential seed into a plant capable of crowbarring brickwork apart is inevitable. In as little as 4 weeks the seedling is tolerant to drought and the stem diameter growing at a rate as much as 5 cm per year (Watt et al., 2007) it is one of the fastest growing species in the UK. In one season these can grow to 2m and start flowering and producing seeds.

In 2 years the shrub can be 4m high and by now will have almost certainly caused some serious even structural damage to the building, the irony is that the root system may well be providing structural support to the damaged building fabric enabling the plant to inflict more damage rather than bringing the fabric down. The removal will require rebuilding and will not be localised to the area of the plant as the root system will have spread deep into the structure. A mature shrub can have a bole diameter up to 50cm and spread over 3 sq metres. If the plant is cut back flush with the structure leaving the root system it can reproduce asexually from stem and root fragments, so complete removal is the only option.

There are a number of key issues here:

1. If left to germinate and remain unseen the B. davidii can establish itself very quickly. Early detection and removal is essential.
2. While it is impossible to remove all the sites for the seeds to lodge, at 3-4mm long there are numerous areas where the seed can settle.
3. The seeds germinate in damp areas such as blocked parapet gutters or around broken downpipes so clearing drainage areas and maintaining rainwater goods is essential.
4. Invariably the plant will get firmly established in areas that cannot be seen easily, behind chimney stacks, parapet walls and areas where there is a build-up of leaf mould. Good house-keeping and simple maintenance will help.

So for now Buddleia davidiii is here to stay and will need to be managed. Careful monitoring of building structures and inaccessible areas will keep the seedlings from establishing where they are not welcome, leaving the gardeners to tend to them out of harm’s way.

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Operating Drones Commercially – 10 things you need to know

Ok, so you have obtained your Permission for Aerial Work from the CAA and are keen to get your drone business up and running. Flying a drone for fun is quite a lot different from flying your drone for business. Helipix have been operating drones commercially since 2008 and learned a number of things along the way.

Here are 10 things you need to know:

1. Batteries – Charge all your batteries the night before the flights. Always start with a fresh battery and keep the flights short. Better to recharge than to use the battery hard and risk damaging the battery. In cold weather keep the batteries warm don not leave them in your van or car overnight. Carry a small invertor generator to charge batteries on site. Often there may not be a suitable power supply or if you do have one it might be some distance away.
2. Client brief – Obtain a full understating of what the client need s from the images. Take extra and take some ‘pretty’ pictures as well. These may not be part of the brief but they might well come in useful to the client for other purposes. Making up a panoramic image is not only a simple way of giving the client ‘added value’ but it also is very useful for your website!
3. Download your images – Your whole day’s work is on a small card. If that is lost or damaged you will have to do the flight again. Download these onto a laptop as soon as possible – best to have the data twice than not at all.
4. Carry PPE – Safety boots, Hi-Vis and often a Hard Hat are required on sites. While these are often supplied especially on a building site, it looks more professional if you have your own.
5. Have a Plan B – Things are not always as simple as they may seem. Always be prepared to work around an issue to get what you need and work with the client, being adaptable is a sign of professionalism.
6. Learn to fly in awkward places – I have never been asked to work at a model flying site. You will need to work close to buildings, on difficult terrain, and in busy areas. Have your camera operator deal with people who ignore your warning signs or just want a chat.
7. Keep people informed – Letting the neighbours know what you are doing saves a lot of time explaining. Also log your activity with the Police on 101. Drones are still regarded as ‘suspicious’ and keeping the Police informed prevents an embarrassing visit from them and will not waste their time. If you do happen to have to fly close to a school it is always best to inform them first.
8. Keep everything in one box – Sunglasses, cables, leads, memory cards can easily be left on site or lost. Have the drone and all the ‘small’ bits in one easy to carry, or better still wheel, box will make life so much easier and ensure you have everything for the next job.
9. Take your time – Operating a drone in a public place often generates a lot of interest and you will often feel like you have an audience. Keep calm and concentrate on the flight, don’t try anything you are not confident in doing, no matter how much the client wants you to. Remember you are in control and as the pilot you are responsible for the safety of the flight. Your camera operator should be suitable trained to ensure that the area is clear and you are safe to land. Be firm but not rude. Once on the ground chat as much as you like but not while flying.
10. Always carry business cards – If you do happen to have an angry or concerned member of the public be as open as you can about what you are doing, quote the Police reference number and give them a business card so they might see that you are a bona-fide operator and look on your website. Equally people may have a curious interest in what you are doing – you just never know where their curiosity may lead.

Helipix vs. The Haar

Edinburgh Castle has stood as an impenetrable defence for hundreds of years sat on top of a granite dyke (the plug of a former volcano). Even though it is built from blocks of granite it is at the served mercy of the elements. If left unchecked the walls would crumble and collapse and so periodic inspection is essential to keep the structure in good sound and safe order. Indeed Historic Environment Scotland have a permanent on site presence at the castle constantly maintaining and keeping the castle in good repair. Built 150 feet from the ground the external walls are particularly difficult to inspect and the wall/rock interface is particularly vulnerable to weathering. Consequently any loose stones are a potential danger to people or property at the base of the rock face.

Recently a boulder from the bed rock itself became dislodged and fell onto a parked car, fortunately no one was injured, but the incident did raise serious concerns over public safety and the 1M tourists who visit the castle each year. The consequence was that Historic Environment Scotland have had to build a ground level defence to provide a safe area of containment for any future rock-falls. While the rock is subject to weather erosion, rain, snow creeping into cracks in the rock and freezing and spalling rock from the face, the walls need to be inspected to see if they need re-pointing, vegetation removal, and if necessary, stone replacement.

Historic Environment Scotland and Historic England have been in the fore front in using drones for high level inspections and surveys. With the castle walls at over 150 feet from the ground using a drone to provide a safe means of inspection was the obvious way forward. Helipix UAV were asked to carry out an aerial inspection of the wall/rock interface.

The survey was not without a number of problems. The large trees around the base of the rock meant that it was not possible to take off from the ground. Large outcrops of rock meant the wall was obscured from ground level. Very close the rock base was the main line to Edinburgh Waverley Station and the castle was open to the public. By carefully positioning elevated scaffolded platforms within the castle and using marshalls at ground level we were able to fly the drone below the platform level and inspect the walls using an HDMI video feed to a monitor.

With all the technical difficulties dealt with and the co-operation of Edinburgh Council and the Castle staff the one thing that caused the biggest problem was the infamous Haar. A Haar is quite simply a sea fog and Edinburgh, situated on the Firth of Forth, is particularly vulnerable to the warm moist air which meets the cold North Sea and flows in like a white curtain mist. Indeed, travel a few miles south of Edinburgh and the sun and clear blue sky will have you believe that Edinburgh would also be basking in the fresh spring sunshine. But no… the fog came and went threatening to cloak the castle in a veil of dense moist air that would have you loosing you way to the gift shop!

However, not to be beaten by a mere meteorological event Helipix managed to get the inspections carried out to the satisfaction of Historic Environment Scotland and with our help the castle will remain steadfast atop it’s volcanic plug. Helipix 1 – Haar 0.

Making an Exhibition of Ourselves!

London’s Olympia hosted the annual Listed Property Owners Club show on the 20^th and 21^st February. The show is aimed at Architects, Conservationists, Surveyors, and owners of Listed properties to demonstrate some of the many specialist services available if you own or manage an old or listed property. 

As an authorised contractor for low level aerial surveys and photography to Historic England and English Heritage we exhibited our services along with other trades and artisans. Our specialised aerial service to inspect roof-scapes was very well received and has led to a number of important leads across the South of the UK.

Traditionally to inspect a roof you would need to use a Mobile Elevating Work Platform (MEWP) commonly referred to as ‘cherry pickers’. Depending on the size, reach and articulation they can be hired with or without operator. Some are small enough to be manoeuvred around a path while the larger are mounted on the rear of a large lorry. For the purposes of an inspection their size and ground footprint can be a major limiting factor where you have formal gardens, sloping terrain, minimal access and a limited budget and time.

The drone option solves all those problems and much more besides. Not only can the drone be deployed quickly and with no ground disturbance, it can operate from almost any location. A flight can cover a large area and once a new battery is installed it can be off again getting aerial images of the roof.

During the show we demonstrated how this was used on the fire investigation at Battersea Arts Centre last March. Not only was the fire damage so devastation as to make the remaining structure dangerous it was also declared a crime scene and could not be entered. We were asked by the fire investigators to carry out a survey of the damage and from this built the 3D model of the remaining structure. This video shows how we can obtain clear high definition images and present them in an easy to use way so the visual inspection of any area is clear and identifiable.

Thankfully most of our work involves inspecting property for the purposes of maintenance and inspection. We can produce a similar 3D model of the structure using the aerial images we obtain. Here for example is a ‘flyaround’ of a 3D model of St Mark’s Church. While this is just the 3D model, it can be used in exactly the same way as the Battersea example to check on specific points.

Aerial Surveys for an Age Old Problem

Given their charm and quaint features our Listed Heritage is very desirable. From the vernacular thatched cottage to the sprawling grandeur of our palaces, our history, no matter how humble, is played out daily in them. These buildings that have withstood the ravages of time need more care and attention than the average modern dwelling. So much so that living in one and maintaining it requires specialist knowledge and skills. Every building no matter how big or small is under threat from the elements.

Nature will try to return it back to the rubble it once came from. Wind, rain, heat, insects, animals, birds, fungus, and a host of many others are all capable of slowly reducing building materials into a useless pile of debris given half a chance. The building process aims to provide a structure that will endure these attacks and remain a useful building. However, as is the most case with older buildings their design did not allow for easy access or as an ongoing additions to the property make it a myriad of roofs, gutters, and chimneys. Couple that with long forgotten building techniques and trades and it is very easy to find yourself dealing with expensive and perhaps difficult issues that require specialist knowledge and understanding.

With this in mind the Listed Property Owners Club (LPOC)provide support and advice on managing and living in a Listed Property. On the 20^th and 21^st of February one of their 2 annual shows will be held at London’s Olympia and Helipix UAV will be exhibiting there on stand F11.

So why will an aerial photography company be at a Listed Property Show, you may ask?

The issue is the inherent problems with some listed property – that of access and inspection.

Building maintenance is not rocket science; see a drain blocked with leaves at ground level and a quick piece of housekeeping will keep flooding and potential water ingress. But the same at roof level behind a parapet wall and it will go unnoticed, and when the inevitable downpour happens, the water will get in and over time will cause damage. Perhaps only cosmetic but often may lead to unseen structural damage. All because the gutter was not cleared.

All too often out of sight, is not out of mind… and neglect can cost you dearly.

With our 3D model and inspection service we can provide aerial surveys that will not only provide you with a fully referenced set of high definition images but a scaled virtual model. Take a look at this complex set of roofs and clerestory glazing. It is a fairly typical example of a building added to over the years in a piecemeal fashion. It has been repaired many times and is now listed. As a consequence it needs to be maintained without modification. Understanding the 3D relationship of the roof pitches and glazing plays a major part in the method of providing access with scaffolding, working practise, delivery of materials, and the Health and Safety requirements. With a better understanding of what technical issues the property faces will inevitably provide the client and contractor with a more accurate cost and avoid the need for Provisional Costings or day-work rates.

An aerial survey is not only quick to set up and carry out, it is also non-intrusive. Not by way of inspecting the building fabric but by getting the access to the roof. We can take off from almost anywhere and leave no trace of our being there. No scaffolding left on site, no cherry picker driven over the formal lawns or through the flower beds.

Not only will you have a detailed inspection of your roof but a scalable 3D model from which the images of the building can be referenced. Defects can now be easily identified and work methods and access requirements can be established from the model of the structure.

A further benefit of this survey is that in say, 5 years can another survey be carried out and the 2 models and images compared. Thereby the structure can be monitored by comparison of the 2 surveys over the 5 year period. Defects can be checked to see if the defect is getting worse and at what rate.  

We look forward to seeing you on our stand and discussing your requirements. Take advantage of the free tickets to the showhere and save yourself £20. If you own or know someone who owns a Listed Property then visit our stand F11 at the Listed Property Show at Olympia on February 20^th and 21^st.

Drones 10 Years On

Helipix UAV Circa 2007

While drones, UAVs, multi-rotors are now a common sight, it was around ten years ago that they first emerged as a ‘new’ technology. However the ‘new’ technology was not the concept of the multi-rotor (that is over 100 years old), it was the way the multi-rotor concept could be controlled, and that was down to some very small electronic components.

Around 10 years ago two small electronic sensors became available for commercial use; the piezo gyro and the accelerometer. The commercial applications for these small accurate components were numerous and they were exploited wherever they could. While these two sensing devices had been around for a long time, they were now available as small low cost components (SMD) and together with a simple computer system (a microcontroller) they could be used to build devices that could detect movement, change of direction and rate of change of direction. We saw mobile phones take on a new dimension of understanding orientation and games controllers that responded to physical movement. Now the actual device you held was a controller simply by moving it. Change of direction and rate of change of direction could now be used as an input and coupled to a simple program you had a system that understood where it has been and where it was going. This was just what was needed to sense and control a device that needed to keep level, and with this new technology the multi-rotor flight controller was born.

But there was a hurdle to overcome…

Piezo Gyro

Sensing change in movement and sending a signal to make another device to counteract that movement was one thing and could be computed very quickly, but the physical world takes time to respond and needs the power to make the changes. A signal to speed up a motor and provide lift with a fixed propeller can happen in a few milliseconds but the motor has to overcome momentum and use energy to enable to lift to happen before it is too late and gravity takes over. The response had to be much quicker than most components could cope with and so multirotors were limited to small payload and small physical sizes. The issue was how to control a motor to speed up and slow down fast enough to maintain steady flight or hover given that the propellers were the only flight surfaces capable of lift. The motors would need to respond very quickly and with great accuracy to be able to balance the lift at the rate of the change of direction as sensed by the gyros and accelerometer.

30A 60 V MOSFET

The early multirotors were fitted with geared prop drives, which although effective were not very sensitive and were prone to damage. What was required was a means of control that would manage rapid changes of high current via voltage control. The ‘standard’ speed controller at the time was not quick enough and was unable to respond the controller’s constant demands to change the prop speed. What was needed was a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or more to the point 6 MOSFETs, 3 controlling the acceleration and 3 used to slow down the rotation speed. These work by applying a magnetic field in a semiconductor to regulate the amount of current passing through it. The advantage is that it can control high currents with a small control current. At first the amount of voltage the MOSFETs could handle was quite small and would easily overheat. Over the next few years bigger more powerful MOSFETs became available and larger voltages could be used. That meant larger motors, larger batteries and greater lifting power. A further enhancement was the ability to use the MOSFET to ‘recover’ current from a slowing prop to recharge the battery.

Multi-rotor technology and development was closely matched to the development of the MOSFET and battery capacity. Now it was possible to control a 22V system using MOSFETs. That is not to say that a 22V system could not be controlled prior to this, it was the need to be fast enough to respond the constant subtle variations in speed of the fixed pitch propellers to keep the drone level. If you have ever seen a video of a multi-rotor in flight then you will see this constant speeding up and slowing down of the prop rotation due the stroboscopic effect of the video frame rate.

ATMEL Microcontroller Chip

In 2007 I was quoted £30,000 for a simple quadcopter fitted with GPS and a simple point and shoot 10MP camera. I am so pleased that I did not make that purchase, and for that my bank manager is eternally grateful. That specification in 2015 could be bought for well under £1,000, and while the sensing technology, battery life and operating power may have increased the one technology that remains almost in the dark ages is that of the chip that controls the whole device. Not the fact that the chip is a microcontroller similar to a Raspberry Pi or Arduino, but the fact that the programming is more often than not a 8 bit 20Mhz chipset with around 1K of RAM. This computing ’power’ is on a par with a ZX Spectrum from the 1980s albeit it is only a fraction of the size.

While the concept of multi-rotor aircraft started very early in the 20th century, it has only been now, one hundred years later, that the multi-rotor concept was able to be fully realised. These 2 small electronic components have enabled the concept of multi-rotor aircraft to become the phenomenon we see today. Both commercially and recreationally these small aircraft will become an everyday sight in an ever growing range of applications and uses. I am sure the next ten years will bear testimony to that.