Julian Moxon/PARIS
French avionics specialist Sfim has developed a new low cost system to replace the optical equipment used for tracking aircraft flying runway approaches when calibrating runway landing equipment.
Its Traki trajectography kit uses the satellite global positioning system (GPS) instead of a ground- based theodolite to locate the aircraft in space while calibration measurements of instrument landing systems and other landing aids are carried out.
At present, optical trackers have to be aligned extremely accurately with the aircraft by a skilled engineer using an infrared beam. Optics are also hit by bad weather.
The Traki can be installed in an aircraft without any modifications to the host system and provides trajectography data in real time as well as being lighter and more reliable than optical equipment, says Franck Buffon, flight inspection sales manager at Sfim. He adds that using the GPS also means that landing systems can be calibrated in conditions up to Category III, and at night. Tracking accuracy is 100-150mm, against 3m using a theodolite.
Sfim and the STNA, the French navigation standards authority, have already developed a complete GPS-based flight inspection system, the Carnac 21, which is claimed to be the first such equipment in the world. The system is being used by the STNA in an ATR 42, although a smaller version has recently been installed on a Beech 200 and is claimed to demonstrate operational cost reductions of more than half those of the larger aircraft.
The Traki ground-based unit consists of a GPS receiver from US company Ashtec, a 5W UHF transmitter, power supply and back-up battery. Similar equipment is mounted on the aircraft, with a UHF receiver. For instrument landing system checks, the Traki is claimed to be accurate to 0.1m, and 15m for a routine VHF omni directional radar check.
Source: Flight International
