By David Kaminski-Morrow in London

Helicopter operator Bristow Group is preparing to embark on a trial to establish whether airborne collision-avoidance systems (ACAS) could be used for civil helicopter operations.

It is planning to install a Rockwell Collins TCAS II system on a Eurocopter AS332 Super Puma – the first time, claims the operator, that such a modification has been attempted. The plan parallels safety studies, detailed at a Eurocontrol seminar on 30 May, indicating that the use of TCAS II could potentially reduce helicopter mid-air collision risk by a factor of two.

Bristow’s plan is still in its early stages. The company is seeking initial regulatory approval and supplementary type certification for the modified helicopter, which will operate from the company’s Aberdeen base in Scotland.

“We don’t know if it’s going to work,” admits Bristow flight safety officer Derek Whatling. While he says that “conventional wisdom” suggests TCAS is only effective for fixed-wing aircraft, he believes that there are “serious flaws” in this reasoning – and that technical discussions have convinced him that tests are “worth a try”.

While helicopters typically operate a lower altitudes, around 4,000-7,000ft (1,220-2,140m), there is still a collision risk from other helicopters and fast military jets, says Whatling: “The numbers are different, but the hazard is the same.”

Bristow is being supported by Shell Aircraft, which is funding and assisting the design work to fit TCAS to the aircraft. Whatling hopes that the trial, which will cover a range of operational environments, could begin as early as this year.

TCAS resolution advisories typically require an aircraft to climb or descend at 1,500ft/min (7.62m/s) or, if necessary, at 2,500ft/min. Whatling says that there is “no reason” why a large helicopter cannot respond to such requirements, but adds that performance assessment will be part of the test regime.

TCAS II algorithms are designed for fixed-wing airframes and the equipment is not certificated on rotary-wing aircraft. But Eurocontrol ACAS programme manager John Law says: “Perhaps this could be challenged. There has been a significant number of nasty airprox incidents in recent years. We know ACAS reduces mid-air collisions. On that basis, maybe it’s reasonable to assume a benefit for helicopters.”

Law says that installation is “not a trivial exercise”, but that the safety study on potential use of ACAS on helicopters has proven “more encouraging than might have been expected”.

Source: Flight International