Getting Helicopter TAWS Right

By John Croft
Source: Business & Commercial Aviation

The helicopter-specific obstacle database for the GTN includes 30,000 additional low-altitude threats compared to the fixed-wing version. When asked if Garmin is considering including wires in its obstacle database, Stone says “I don't know if we can comment.”

What he can comment on is the drop in HTAWS retrofits for lower-end helicopters has seen due to the FAA's move in 2012 to require STCs for all HTAWS aftermarket installations, where previously the less complicated field installation process (Form 337) was accepted. Honeywell's Ishihara has seen the change as well, noting that Mark XXI units, previously installed with a 337, now require STCs.

Stone says the aircraft downtime required to earn an STC versus Form 337 is “much greater” particularly when the FAA is understaffed and projects often go into “sequencing” for three to six months before the needed government engineers or inspectors become available. “It's a huge impact to put [the helicopter] down for months to go through the STC process,” says Stone. “It's a barrier that can prohibit, financially, getting the technology on the aircraft.”

Under the sequencing process, which the FAA started in 2005, the agency evaluates each STC project at its regional certification offices. Those that will require more than 40 man-hours of engineering or inspector time are put into sequencing, says Stone. “The initial phase is 90 days,” he says. “At the end of 90 days, the FAA reevaluates their workload to see if they can assign inspectors and engineers to work on the project. If not, application goes back into sequencing.”

“There can be significant downtime without clarity of when the resources might be available,” says Stone.

The FAA tells BCA it now requires STCs for all installations because HTAWS units meeting TSO C-194 “have an appreciable effect on the airworthiness of rotorcraft and must be accomplished via STC.”

The benefit will likely be worth the wait for operators with a genuine need for HTAWS, particularly if purchasing a system tailored to the particular environment where the helicopters do their work. “Accidents are caused by pilot distractions,” says Sandel's Block. “That's why true alerts are important. It's not about pilot skill, but about helping them out in a situation where they have other things to pay attention to.” BCA


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