Bell 525 Has New Special
Conditions for FAA Certification
By Woodrow Bellamy III | April 19, 2018
The Bell 525 on display with Bristow livery at
Heli-Expo 2018 in Las Vegas.
The FAA has issued a final set of special
conditions that Bell Flight must satisfy toward achieving type certification on
its 525 Relentless. According to the agency, the special conditions address current 14 CFR 29 standards
that do not provide adequate standards for pilot situational awareness of
certain flight control modes while flying the 525.
Bell resumed flight testing on the 525 in July
2017, and the NTSB issued its full report on the fatal 2016 crash of the fly-by-wire utility
helicopter in January. Now, the FAA’s rotorcraft standards branch has
established new conditions that address the 525’s unique four-axis full
authority digital fly-by-wire flight control system.
The FAA is focusing on its current set of
regulations that do not entirely evaluate pilot awareness of flight control
modes while operating the 525. The helicopter’s fly-by-wire system is
configured to allow for pilot inputs and coupled flight director modes. Bell
designed the 525 so that pilot inputs are transmitted electrically to each of
the aircraft’s three flight control computers. The inputs are then processed
and transmitted to the hydraulic flight control actuators, which allow
manipulation of the main and tail rotors, according to the FAA.
“The proposed special condition will require that
suitable mode annunciation be provided to the flight crew for events that
significantly change the operating mode of the system, but do not merit the
traditional warnings, cautions and advisories,” the FAA noted in the newly
published special conditions.
By requiring a suitable mode annunciation to
flight crews for changes in flight control modes, the agency is focusing on
events that can significantly change the operating mode of the system. It is not
including the special conditions as a requirement for traditional cockpit
warnings, cautions and advisories.
The agency first proposed the special conditions
for the 525 in December 2017. A comment on the proposal from Sikorsky helped to
establish the special conditions in the final format. Sikorsky’s comment sought
to establish the special conditions so that the mode annunciation would be
placed within the pilot's immediate field of view.
The FAA’s rotorcraft standards branch also revised
the special conditions to address Sikorsky’s request to provide more
clarification in the special conditions. The Lockheed Martin subsidiary
requested that the special conditions require mode annunciation to indicate
that the operating mode is changing “in such a way as to alter the pilots
primary control strategy.”
As noted in 14 CFR 11.19 of the Federal Aviation
Regulations, special conditions issued by the FAA become a requirement of the
type-certification criteria for the aircraft type against which they're issued.
Bell will be required to achieve the special conditions on the 525 and any
future model helicopters that incorporate the same type of fly-by-wire
configuration.
“In addition to the applicable airworthiness
regulations and special conditions, the [Bell 525] helicopter must comply with
the noise certification requirements of 14 CFR part 36,” the FAA said in the
special conditions notice.
During the recent Textron quarterly earnings call,
Textron CEO Scott Donnelly told analysts that the 525 is in “full flight test
operations,” and he expects that program (along with the V-280) to lead to
increased research and development spending for Bell.
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