T
HIS PAST SUMMER, OUR INDUSTRY welcomed back an old friend, one that hadn’t been seen in the US market since 1999: the single-engine helicopter certificated for flight under IFR conditions (SE-IFR). In July 2019,
Leonardo received an FAA supplemental type certificate (STC) for the first SE-IFR helicopter in more than two decades, the TH-119. Less than a month later, Bell received an STC for its 407 GXi to operate under instrument flight rules. It’s no coincidence that both of these exciting new entrants
arrived so recently. Tese first certifications are the culmi- nation of decades of work behind the scenes, in both tech- nology and regulation. Te paths the two manufacturers took to certification, however, are vastly different.
SE-IFR: A History To truly understand the SE-IFR issue, it’s important to understand how we got here. Helicopter flight rules for instrument conditions made
their first appearance in the 1970s. At the time, single-engine rotorcraft conducted IFR flights regularly, well before the advent of GPS, glass cockpits, and digital autopilot systems. Te rules these helicopters were certificated under, found in Appendix B of 14 CFR Part 27, Airworthiness Standards: Normal Category Rotorcraft, hadn’t changed significantly since the early 1980s. In 1999, the FAA issued AC 27-1B,
operating in instrument conditions. Industry interpretation of this change was that triple-redundant systems would now be required. At the same time the 2003 AC was issued, Part 23 single-
engine airplane manufacturers received relief from these new requirements: SE-IFR airplanes were required to meet a probability of one in 1 million before being subject to duplicate systems. In response, new aircraft came on the scene, like the Cirrus SR-series, that deployed the latest GPS, glass cockpits, and autopilot technology. Tis relief wasn’t extended to the helicopter industry, however, in part because the latter was still a long way off from meeting even this lower probability requirement. “Tere are several reasons why regulation changes for small light airplanes couldn’t be extended to helicopters at the time,” says Harold Summers, director of flight operations and technical services at HAI. “Helicopters aren’t inherently stable like airplanes. Tere also was a great deal of work needed to prove that the aircraft could be safely flown in IFR conditions without all the redundancies. Te advanced, lighter technology for helicopters hadn’t yet caught up.”
More accidents (194), and resulting fatalities (326), occurred from 2001 to 2013 from pilots being ill-equipped for MVFR and IIMC conditions than would have occurred from the expected failure rates of SE-IFR helicopter systems.
Certification of Normal Category Rotorcraft. Tis document, which was a total revision of AC 27-1A, issued in 1997, dictated the extinction of SE-IFR rotorcraft. AC 27-1B in essence incorporated into Part 27 numerical
safety analysis methods as a way of determining OEM com- pliance in meeting safety standards. Te advisory circular (AC) required helicopter manufacturers to prove that critical aircraft systems had an “extremely improbable” failure rate of one in 1 billion. In other words, OEMs had to demonstrate that these systems would incur only one failure in 1 billion hours of runtime. Any critical onboard system that couldn’t meet this failure rate was required to be duplicated, with redundancy providing an additional safety margin. Overnight, single-engine IFR helicopters became cost and
weight prohibitive. In 2003, AC-1B was revised again, raising the bar even
higher. Tis time, the AC defined loss of function of attitude, airspeed, or barometric altitude instruments, or conditions that would cause those instruments to issue hazardously misleading readings, as individually “catastrophic” when
Industry Asks for Change In 2015, with support from partner associations, the helicopter industry petitioned the FAA to consider reducing certification barriers for SE-IFR helicopters. In the 16 years since the publication of AC 27-1B, a number of important technologies, including WAAS (wide area augmentation systems), GPS, cell phones, tablets, and flight planning apps, had been introduced, all available in affordable, lightweight, consumer- friendly packages. Te industry was finally in a position to meet the same one in 1 million standard as light airplanes. In the summer of 2015, HAI, AHS International (rebranded in 2018 as the Vertical Flight Society, or VFS), the General Aviation Manufacturers Association, and the Aircraft Electronics Association published the 14 CFR 27 Single- Engine IFR Certification Proposal, an association and industry white paper (
bit.ly/SE-IFR). Te proposal explicitly linked improving helicopter safety to facilitating an economically viable certification plan for SE-IFR helicopters and expanding IFR operations. Te paper referenced worldwide helicopter accidents
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