Technology and Aircraft
Bellgeo has conducted a number of investigations into the most suitable platform to mount a gradiometer. These trial platforms have included most airborne configurations including airships, single and twin engine aircraft and helicopters. While each platform has its own advantages, it quickly became clear that the Basler Turbo was the most appropriate platform for FTG acquisition for a number of reasons. Bellgeo have since invested 15 Million USD in acquiring two of these aircraft. Our most successful surveys to date have all been acquired using the Basler configuration. This survey platform has a number of benefits over alternative platforms:
- Lower noise (twin Pratt and Whitney Turbine engines with 5 bladed Hartzell propellers; more blades mean less noise)
- More stable platform (100ft wingspan is key to reducing bounce caused by turbulence)
- Slow and stable survey speed (aircraft can survey at 100knots at 80m, giving a sample rate of 55m for FTG.)
- Instrument permanently installed (no configuration or calibration issues)
- Greater production rate (8 hour endurance, maximising productivity during weather windows)
- Longer endurance (8 hours, with long range fuel tanks)
- Quieter for conservation areas (Brand new state of the art turbo prop engines with over wing exhausts)
- Manages long ferry times easily
- Full coverage LIDAR dataset, if required (High resolution)
- Bell’s oldest aircraft is 6 years old and both are equipped with market leading avionics to ensure survey specifications are strictly adhered to
The aircraft can acquire up to 1,600lkm per day, as proven in South America and Northern territories, this reduces the overall acquisition time, lessening the environmental impact of the project i.e. noise pollution and disturbance over conservation areas.
The BT67 is a converted DC-3 aircraft fitted with twin turboprop engines and state-of-the-art digital avionics (see www.baslerturbo.com). This aircraft combines excellent productivity with logistical efficiency. Our standard practice is to fly at 80m over open areas where it is safe to do so, and 300m over protected or built up areas.
As survey flights are conducted at low-level, there are two pilots and one survey technician. The equipment is sensitive to turbulence and sorties are, depending on weather conditions, generally flown in the calm of the early morning and/or late afternoon amounting to 4-8 hours per day.
(The FTG is entirely passive i.e. it does not produce any emissions apart from those associated with normal electrical power usage. The instrument is non intrusive and emits no signal, there are no harmful gases or liquids contained within it. )