Bell Geo owns and operates three Basler BT-67 aircraft that provide an unparalleled ability to survey in any environment.
In the early days of airborne gravity gradiometry surveying, the single engine Grand Caravan was the aircraft of choice for most all survey companies. This is a good aircraft but had some limitations on gravity gradiometry surveying.
Bell Geospace wanted a plane that had:
- Two engines for added safety.
- Low sensitivity to turbulence for improved data quality.
- A strong track record of reliability.
- Good endurance for increased international reach.
The Basler Turbo retrofitted DC-3 (BT-67) checked all of the boxes, and then some.
The BT-67 is a converted DC-3 aircraft fitted with twin turboprop engines and state-of-the-art digital avionics. It combines excellent productivity with logistical efficiency.
We own three BT-67s and 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, including:
- Better stability: a 100ft wingspan is key to reducing bounce caused by turbulence.
- Slow and stable survey speed: the aircraft can survey at 100knots at 80m, giving a sample spacing of 55m for FTG.
- Instrument permanently installed: no configuration or calibration issues.
- Longer endurance: 8 hours, with long-range fuel tanks to maximise productivity during weather windows.
- Lower environmental impact: less noise pollution and disturbance over conservation areas thanks to state-of-the-art turboprop engines with over wing exhausts.
- Manages long ferry times easily.
Standard flying practice
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.
The aircraft is capable of acquiring 1,600 line kilometres a day and has achieved more than 1,200 km a day on many occasions. The limiting factor on acquisition endurance is turbulant air at low altitudes caused by midday heat. Compared to other platforms the BT-67 handles turbulence very well, this reduces overall survey acquisition time.
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 or the late afternoon, amounting to 4-8 hours per day.