NAVY IGNORED REQUIREMENT TO CUT HAZARDOUS NOISE IN JET DESIGNS

Inside the Navy - 1/12/2009 -
Service seeks to quiet F/A-18E/F, EA-18G
NAVY IGNORED REQUIREMENT TO CUT HAZARDOUS NOISE IN JET DESIGNS

The Navy’s F/A-18E/F Super Hornet fighters and new EA-18G Growlers
built to fly electronic warfare missions emit very loud noise that is
hazardous to sailors’ hearing, but the problem might have been less
severe had the service not ignored requirements to design quieter
jets, according to an internal naval audit.

Navy, Marine Corps and Air Force high-performance jets produce 130 to
150 decibels of noise, well above the 84 decibel level deemed
hazardous to hearing. The F/A-18E/F and EA-18G emit as much as 150
decibels. Jet maintainers’ earplugs and earmuffs only provide limited
protection against such noise. When developing new aircraft, the
military is required to try to mitigate the problem through better
design.

But the previously undisclosed report reveals Navy officials tasked
with acquiring the Super Hornet and the Growler -- which are based on
a common Boeing design with GE engines -- ignored requirements to
actively address the hazardous noise problem early on. The ears of
countless sailors on carrier flight decks could be suffering the
consequences, according to the Naval Audit Service’s Oct. 31, 2008,
interim report. Sister publication Inside the Pentagon obtained a copy
through the Freedom of Information Act.

The F/A-18E/F, which was developed in the 1990s, achieved initial
operational capability in 2001. By 2002, the Navy committed to
creating a Super Hornet variant, later dubbed the EA-18G, to replace
aging EA-6B Prowler electronic warfare planes. The Navy’s online “fact
file” about the F/A-18 E/F trumpets the Super Hornet acquisition
program as “an unparalleled success.” But auditors found that was not
the case when it came to the hazardous noise problem.

Super Hornet program officials at Naval Air Systems Command in
Patuxent River, MD, made no initial attempts to mitigate the flight-
line/deck jet noise hazard through design selection, the report says.
This defied a key military standard and the Navy’s own system safety
program plan for the aircraft. Both documents include a “system safety
design order of precedence” urging the elimination of hazards through
better designs.

Auditors found there was no mention of noise limitations in the F/
A-18E/F and EA-18G acquisition strategy and contract statement of
work. The Navy also ignored guidance relating to risk levels and risk
acceptance authority levels and failed to track the noise hazard and
its residual mishap risk, the report says.

“These conditions may contribute to a hazardous environment of high
noise exposure associated with jet aircraft that, according to the
Naval Safety Center, increases the likelihood of permanent hearing
loss to sailors and Marines,” the report states. Hearing loss is
costly for warfighters but also for the Navy at large, which faces
lost time and lower productivity, loss of qualified workers, military
disability settlements, retraining and medical bills.

Super Hornet and Growler program officials did not first try to
mitigate the noise hazard through design selection because they lacked
internal controls to ensure compliance with the system safety design
order of precedence, the report says. The program did not pursue
minimizing noise generated by the F/A-18E/F engines through design
because warfare sponsors did not identify noise requirements as key
performance parameters (KPPs) in the operational requirements document
(ORD), according to the report.

Program officials also told auditors that the emphasis on reducing
current personnel noise exposures did not exist at the time the ORD
was issued, and therefore, funding was not allocated to mitigate the
noise hazard. Further, program officials “stated that noise was always
part of the ship and aircraft environment and no viable technologies
were available at the time the engines were designed,” the report
says.

Test results indicate that new high-tech hearing protection devices
will reduce noise exposure on the flight deck by at least 43 decibels,
but that is not enough, the report says. The resulting noise will
still exceed the level considered hazardous to hearing, auditors found
after consulting a professional audiologist.

But the Navy is now focusing more attention on the challenge of
quieting Super Hornets and Growlers. In a statement released to ITP
through a spokeswoman, Capt. Mark Darrah, the Navy’s F/A-18 and EA-18G
program officer, said his office is committed to reducing the noise
levels.

“Our top priorities include the health and safety of our aircrews and
maintenance personnel as well as the environmental impact on the
surrounding communities,” Darrah said.

Because of this, Darrah’s office has formed a joint government and
industry team to research all proposed options for noise level
reduction. Current research indicates that placing chevrons on
variable exhaust nozzle seals of the F414 engine is the most viable
option for reducing noise levels, he said. Darrah’s office and the
Office of Naval Research have jointly committed almost $6 million to
complete engineering and manufacturing development for this project.

“A contract is in place with General Electric Aircraft Engines on this
project and work is expected to begin shortly,” he said. “While we
will continue to examine other options and technologies as they
mature, the solutions we put in place must be deployable and
affordable without degrading aircraft performance.”

Boeing spokesman Philip Carder said the company is “consistently
looking for new and innovative technologies that can reduce the effect
of its operations, products and services on the environment” and that
noise reduction is a key part of that effort. Boeing is on Darrah’s
government/industry team, he said.

GE Aviation spokesman Gregory Haas said a full scale test to
demonstrate and validate mechanical chevrons for noise reduction was
conducted by GE and the Navy on an F404 static engine. Test results
indicated the potential for 2.5-3.0 decibel noise reduction, roughly
equivalent to a 50 percent cut in noise energy level, he said.
Industry is continuing to work with the Navy to design, test, and
field mechanical chevrons for the F414 engine, he added.

The report says the Navy agreed to establish a formal process to
actively seek new, and document prior, ongoing and future efforts to
identify potential design solutions to fix identified hazards, and
pursue additional ways -- whether in design, devices, or other methods
-- to quiet Super Hornets and Growlers. The Navy also agreed to track
the noise hazard. But Navy officials are still sorting out how to
address a recommendation to re-establish risk levels and risk
acceptance authority levels in policies and procedures.