A consortium of helicopter operators, regulators, and safety advocates is making progress on tailoring Helicopter Terrain Awareness and Warning Systems (HTAWS) for offshore operations.
Trials held in November involving pilots from CHC Helicopter and Bristow Group evaluated a modified Honeywell Mark XXII enhanced ground proximity warning system (EGPWS) in a Sikorsky S-92 simulator at Bristow’s Aberdeen, Scotland, base. The system used flight-alert envelopes developed by the UK Civil Aviation Authority and published in its CAP 1519.
Using HTAWS in offshore operations presents several challenges. Some current systems can't accurately display fixed obstacles, such as oil platforms, and mobile obstacles present a challenge in keeping a database accurate. The solution, the collaborators feel, is creating modes with alert envelopes that can be integrated into HTAWS and selected when appropriate. The modes' parameters are based flight data monitoring (FDM) data.
The protection envelopes defined in CAP 1519 came after several years of CAA-led work using FDM data provide the baseline for the enhanced envelopes. It also identified two new envelopes alerting flight crew to loss of airspeed. CHC, Bristow, and Babcock International contributed FDM data to help built a dataset of some 200,000 offshore approaches. These data were used to set the alerts for the new Offshore Envelope 7, which "provides protection against loss of airspeed on approach using input parameters of indicated airspeed (IAS) and total torque," CAA explains in guidance material. "This envelope may be inhibited below a height of 50 feet to avoid unwanted alerts during a rejected takeoff following an engine failure." CAA added that Envelope 7 "is tailored to individual helicopter types" for optimal performance.
The Aberdeen trials are part of a broader safety effort from trade association HeliOffshore, which works with OEMs, operators, and oil-and-gas companies to improve offshore rotorcraft safety.
“This trial was a great example of industry collaboration, as Honeywell was supported by CHC and Bristow pilots, some of whom had given up their time off to fly on the trials, and simulator staff who provided expert technical support during two and a half days of simulator time donated by Bristow,” said HeliOffshore consultant Mark Prior.
Honeywell is using data generated by the simulator trials to certify the company’s modified EGPWS. The association is confident that the trials will support efforts to have upgraded HTAWS available for a variety of aircraft in the near future.