DEFENCE
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Sensor fusion updates
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Defence P24INQUIRY GARRETT REIM LOS ANGELES
Osprey crash linked to rotor downwash
Report on fatal collision with USS Green Bay points to sudden loss of lift encountered amid recirculation off ship’s hull
Accident involving Marine tiltrotor transport resulted in three deathsUS Marine CorpsA
n investigation into the fatal
crash of a US Marine Corps
Bell Boeing MV-22B Osprey
tiltrotor into an amphibious
transport ship in August 2017
has found that the rotorcraft suf-
fered no mechanical or electrical
problems, and that its flightcrew
was not at fault.
A paragraph containing the
service’s “most probable” expla-
nation of the mishap was redact-
ed in the investigators’ report, al-
though engineers with the US
Naval Air Systems Command
(NAVAIR) noted problems with
the aircraft’s rotor downwash in a
non-redacted section.
The report offers few other
clues as to what caused the tiltro-
tor to strike the side of the USS
Green Bay while participating in
a training mission off the eastern
coast of Australia. The aircraft
rapidly lost altitude on its ap-
proach for landing on the ship’s
deck, hit the vessel’s side and fell
into the Pacific Ocean, resulting
in three deaths and injuries to 23
others on board.
While withholding an official
explanation for the mishap, engi-
neers with NAVAIR “discovered
the presence of recirculated
downwash reflecting off the hull
of the ship and back into the rotor
arc”. This appears to have caused
a thrust deficit, prompting a 200-
300ft/min rate of descent before
the MV-22B’s left engine nacelle
hit the flight deck. The mishap
occurred in daytime and with
light wind.
In 2015, another MV-22B
crashlanded onto the deck of the
amphibious transport ship USS
New Orleans. Both aircraft had
similar gross weights and experi-enced recirculating downwash,
the investigation reveals.
The USMC placed no blame or
pointed to any cause in the most
recent mishap.
“The mission was complex,
challenging, and included flying
into and out of a highly congested
operational area. Executing thismission required a detailed plan
and superior technical perfor-
mance,” notes Maj Gen Thomas
Weidley, 1st Marine Aircraft
Wing commanding general. “The
Marines were mission-capable,
fully trained and qualified. The
mishap aircraft was mechanically
sound.” ■DEVELOPMENT
GARRETT REIM LOS ANGELESUSAF targeting
offers for A-10
rewinging deal
UK’s Commando Helicopter Force will employ 25 adapted AW101s
Leonardo HelicoptersT
he UK Royal Navy has taken
delivery of the first of an even-
tual 25 Leonardo Helicopters
AW101 Merlin HC4 heavy-lift
transports, but future upgrade pri-
orities for the type are already
being outlined.
To be operated by the RN’s
Commando Helicopter Force
MODERNISATION DOMINIC PERRY PRAGUE
Upgraded Merlin HC4 enters service
as navy outlines refuelling ambitions
(CHF), the former Royal Air
Force Merlins are being upgraded
and marinised under a £388 mil-
lion ($517 million) contract. De-
liveries of the rotorcraft, which
are being raised from the HC3/3A
standard, are to run until 2023,
but the CHF is already consider-
ing its next upgrade require-ments, with in-flight refuelling
topping the list.
“We would really like that ca-
pability – it would really be a
force multiplier,” Lt Cdr Aaron
Cross, operations officer for 846
NAS, one of the two units that
will operate the rotorcraft, told
SMi’s Helicopter Technology Cen-
tral and Eastern Europe confer-
ence in Prague.
“[In-flight refuelling] is not part
of the Mk4 [programme], but add-
ing it clearly multiplies most of
the Merlin’s capabilities,” says
Cross. “That is clearly where we
are looking beyond the Mk4, so in
five years’ time that will be the
drum we are beating.”
As part of the current modifica-
tion work, the Merlin receives a
folding tail and main rotor blades,
a new glass cockpit and an im-
proved defensive aids suite. ■P
otential contractors have
been given until 22 June to
respond to a request for proposals
to replace the wings on up to 112
Fairchild Republic A-10 ground-
attack aircraft for the US Air
Force.
Released on 25 May, the re-
quest seeks first deliveries no later
than April 2019, with the activity
to be covered by an initial five-
year contract, plus two optional
one-year extensions.
The USAF launched a re-wing-
ing programme for its A-10 fleet in
2006, with a contract award to
Boeing. The company completed
upgrades on aircraft assigned to
six of the service’s nine operation-
al squadrons in January 2018, but
made a business decision to not
continue working on the pro-
gramme. ■