increase in the aircraft’s maximum gross
weight and speed.
In July 1995, the US Navy launched the
H-1 upgrades programme which was intended
to increase the commonality between two
new attack and utility helicopters. It replaced
separate planned UH-1N and AH-1W midlife
and avionics upgrades. Development of
the new models formally began when Bell
Helicopter received a $310m engineering and
manufacturing development (EMD) contract
for the AH-1W/4BW project on November
14, 1996. It was followed on January 2,
1997 when a $134m option for UH-1N/4BN
development was exercised.
A critical design review (CDR) for the
redesignated AH-1Z and UH-1Y took place
in September 1998. Bell subsequently
produced ve ying prototypes by modifying
three AH-1Ws and two UH-1Ns to the new
con gurations. The project equipped each ofthe new variants, which received the names
Viper and Venom, with four-blade, composite
main and tail rotors and a new transmission
rated at 2,625shp (1,957kW).
The programme provided the UH-1Y with
two T700-GE-401C engines, while the AH-1Z
initially retained the AH-1W’s -401 version.
Although its design can be traced to the
earlier 680, the main rotor is more related
to the Bell 430’s and has 75% fewer parts
than other four-blade articulated systems. In
support of shipboard operations, it is capable
of semi-automatic folding and incorporates a
hydraulically operated rotor brake.
The rotor mechanism, which can continue
to operate after sustaining direct hits from
23mm weapons, delivers a 30% increase in
power over the AH-1W and allows the Zulu
to cruise at a maximum speed of 142kts
(263km/h) – a full 10kts faster than the
Whiskey.An auxiliary power unit (APU) provides the
AH-1Z with electrical and pneumatic power for
engine starting and ground operations, which
greatly improves its ability to operate fromunimproved and remote locations.
An integrated mechanical diagnostics/
health and usage monitoring system (IMD/
HUMS) is incorporated. It assesses thehealth and condition of aircraft engines, drive
train and other components, and records
maintenance-related data.
The AH-1W had an empty weight of
10,800lb (4,899kg) and a maximum gross
weight of 14,750lb (6,690kg). The Zulu’s
corresponding gures are 12,300lb (5,579kg)
and 18,500lb (8,391kg) respectively, making
the AH-1Z’s useful payload when hovering
out of ground effect (HOGE) 5,764lb
(2,615kg) compared with the AH-1W’s 3,986lb
(1,808kg).
Additionally, the internal fuel load has
increased from the AH-1W’s 2,086lb (946kg)
to 2,858lb (1,258kg) on the AH-1Z. The Viper
carries its fuel in crashworthy, self-sealing
tanks installed in the forward and aft fuselage
and each of the stub wings. The aircraft has
a maximum range of 370nm (685km) and
an endurance of 3.5 hours compared to just
280nm (519km) and 2.8 hours for the AH-1W.
Its range can be extended by external
tanks carried on each of the four wing store
stations (WSS). An onboard inert gas
generating system (OBIGGS) protects against
an internal explosion.
The remanufactured AH-1Z retained the
forward fuselage of the AH-1W. However,
the remainder of the airframe including the
tail boom and landing gear skids, which
are common with the UH-1Y, were newly
constructed. As part of the manufacturing
process, the forward fuselage is ‘zero-timed’
and the entire AH-1Z structure has a service
life of 10,000 hours.
The Viper’s conventional ight controlhttp://www.aviation-news.co.uk 23AH-1Z Zulu 4 was operated by air test and evaluation squadron VX-31 while conducting
weapons evaluation at Naval Air Weapons Station China Lake, California. The AH-1Z was one of
two that supported trials of the Optimized TopOwl Helmet-Mounted Sight Display system during
the second phase of Initial Operational Test & Evaluation, which concluded in late May 2008.
Naval Air Systems CommandAH-1Z Zulu 1 conducts an early test ight at NAS Patuxent River, Maryland. The rst of three
AH-1Z prototypes to be converted from AH-1W airframes and initially retained bureau number
162549 but was later re-serialled as 166477. Naval Air Systems CommandAn AH-1Z operated by HMLA-267 res an AGM-114 Hell re missile during a live- re drill at
Range 176 off the coast of Okinawa, Japan, during February 2017. The Stingers were deployed
to MCAS Futenma, Okinawa, in support of the 1st Marine Aircraft Wing’s Unit Deployment
Program. USMC/L Cpl Sean M Evans22-26_ah1zDC.mfDC.mf.indd 23 05/01/2018 14:01