The HeliNav TrackMaster sensing system from Sensor Technology enables Heli-Lift Services to provide a unique helicopter-based extraction service in forests where the ground is wet or boggy, or in environmentally sensitive expanses and areas of special interest, ensuring minimal disruption to the environment. With these services, the company is meeting the tree extraction requirements of everything from thinning and commercial timber supply, to the plucking of Christmas trees for delivery to towns and cities around the country. The technology incorporates a strain gauge into the cargo hook that carries the helicopter’s under-slung load.
The wireless Load Sensor is a strain gauge based stainless steel tension type sensor. It has the capability of wirelessly transmitting its data to a readout where it both displays live readings and records them to build up an exact profile of each operation. Integrated 32MBit memory can hold up to 280 hours of data which can then be downloaded to a PC via its USB cable. The Load Sensor transmits using the worldwide licence-free frequency of 2.4GHz using two built in antennae.
The readouts can be cockpit mounted for the pilot’s use or handheld by an assistant on the ground (in fact, signals can even be transmitted to multiple control units simultaneously). The complete system is entirely autonomous, making it independent of the helicopter’s control systems, while being wireless means it does not require additional certification of the electrical systems. It also means it can be swapped from one helicopter to another, allowing a small number of systems to be shared around a fleet of helicopters.
This is a challenging operation for the helicopter pilot. The tree is suspended on a 100ft line, and the pilot has to hover over the tree while the harness is attached, and then lift it straight up without risk of damage to other trees. Time is also of the essence, as the helicopter has to set down for refuelling every 40 minutes.
At the same time, it is important for the operator to keep a track on the total weight lifted and to monitor the strain on the harness cables – not simply to ensure the weight of the tree does not exceed the capacity of the lifting rig and the helicopter, but also so that the aggregate strain over time is known so that maintenance can be scheduled and cables can be replaced before their operational duty limits are reached.
There are commercial considerations, too. Billing is based on the weight of the load and the distance travelled, so the helicopter operator needs to provide the client with accurate work reports and precise billing. In the cockpit, the HeliNav TrackMaster controller accurately logs the weight of the load and also the distance travelled. The controller also uses an on-board GPS (global positioning system), inclinometer and accelerometer to help plot flight paths, flight times, fuel requirements, etc.
Sensor Technology Ltd is located in Oxfordshire, UK. Vist their website or call +44 (0)1869 238400 for more info.