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  • Writer's pictureCK Chan

Tethered UAV – Flying in “No-Fly” Zones

Singapore is a very challenging location to fly drones. Our limited airspace is shared with one of world’s busiest airport. On top of that, there are 4 military air-bases, Seletar airport, nature reserves and other high-security no-fly zones.

Aerial filming is a “must-have” for high-end video productions and large-scale construction video projects. Skyshot gets many requests for aerial filming on projects that are within 5 km from an airdrome, and we found some solutions.

The crane cam - DSLR camera capture aerial images.
The crane cam is a simple solution to hoist a DSLR camera capture aerial images.

The search for alternative aerial platforms

Several years ago, we have developed alternatives like the crane cam, which is a remote controlled DSLR camera attached to a construction crane. This method is used in several construction projects like the TPE/KJE intersection by Hwa Seng Construction and the Changi East Reclamation by Hyundai Construction & Engineering. However, crane cam has its limitations. Cranes are expensive to hire, the reach is limited and they are hard to mobilize in more challenging terrains.

Tethered drone – the better solution

So in 2017, we started developing a tethered drone solution, we called it, Skyline Tethered Drone. It solves the 2 issues that conventional drones have, limited flight times and airspace restrictions near airports. The Skyline went thru several months of development and several rounds of stringent testing. Finally, in May 2018, the Skyline was approved and certified for operations by CAAS (Civil Aviation Authorities of Singapore).

Powered from the ground up with 2 portable generators
Powered from the ground up with 2 portable generators, 1 acting as a backup.

Powered from the ground up, the Skyline has a persistent power supply. The 40-meter long tether restricts the flight path and height of the drone. This limitation is necessary for flights near airports where planes are flying at lower levels. The Skyline caters to several large-scale construction projects that we are filming near Changi Airport. The Changi East reclamation site and Pulau Tekong Infilling sites require quarterly aerial filming to document the construction progress.

How it works

Skyline is a modified DJI S900 drone with an A3 flight controller. It carries the DJI X5 pro or X5R camera that can shot 4K video and 16-megapixel still images.  Powered by 2 portable generators (1 backup) via a tethered cable, it enables the SKYLINE to operate continuously over extended time. This is much longer than most drones with a flight time of 20 minutes. It also prevents the drone from ever flying away.

The tether cable is tested to withstand more than 40 kg of tension, which is many times more than the drones thrust power. To set the drone height, the tether is measured and released from a spool. Once it has reached the ideal flight height, the spool is locked to maintain height and position.

The Skyline requires 3 men to operate. The UAV pilot controls the drone while 2 other ground crew release the tether line and perform safety checks.

The Skyline is operated by a 3 men crew.
The Skyline is operated by a 3 men crew.

Other uses for a tethered drone

Beside aerial filming, the Skyline is also well suited for aerial building inspections, security operations and other assignments where continuous operation is crucial.

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