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AH-1Z (left) and UH-1Y (right)

The H-1 upgrade program refers to the United States Marine Corps's program to develop the AH-1Z Viper and UH-1Y Venom to replace its aging fleets of AH-1W SuperCobras and UH-1N Twin Hueys. The former is a twin-engine attack helicopter, while the latter is a medium-sized utility helicopter, also twin-engined. The contract was awarded to Bell Helicopter, the original designer and manufacturer of both helicopters, to design these new airframes as modernized attack and utility helicopters with considerable design commonality to reduce operating costs.



AH-1Z on the tarmac

In August 1995, the Secretary of the Navy authorized the Marine Corps to upgrade its utility and attack helicopters as a bridge until the Joint Replacement Aircraft was available in 2020.[1] In 1996, the Marine Corps launched the H-1 upgrade program by signing a contract with Bell for upgrading 180 AH-1Ws into AH-1Zs and upgrading 100 UH-1Ns into UH-1Ys.[2][3] While the original contract called for upgrading existing airframes, it was later modified in 2008 to manufacture completely new aircraft.[2][4][5] The program also includes aircraft simulators.[6]

The AH-1Z first flew on 8 December 2000.[7] Three prototype aircraft were delivered to NAVAIR's Naval Air Station Patuxent River in July 2002 for the flight test phase of the program. Low-rate initial production followed beginning in October 2003,[2][8] with deliveries to run through 2018,[9] however, full-rate production was delayed until 2005.[1]

The AH-1Z completed sea-trial flight testing in May 2005.[10] On 15 October 2005, the USMC, through the Naval Air Systems Command, accepted delivery of the first AH-1Z production helicopter to enter the fleet.[11] During the first quarter of 2006, the first production model UH-1Y completed its first flight, and the aircraft were transferred to the Operational Test Unit at the NAS Patuxent River to began operational evaluation (OPEVAL) testing.[12] In February 2008, Bell received a contract for the last 40 AH-1Zs to be built as new airframes instead of the previously planned rebuild of AH-1Ws.[5] Also that same month, the AH-1Z and UH-1Y began the second and final portion of OPEVAL testing.[13]

Bell delivered three upgraded H-1s to the Marine Corps in February 2008.[14] In September 2008, the NAVAIR proposed adding 46 additional AH-1Zs bringing the total number ordered to 226. The additional aircraft will appear on the 2010 fiscal budget request.[15] The final number of UH-1Y acquisitions was also set at 123.[16] Full-rate production was approved in late 2008.[17]

On September 30, 2008, Bell received a contract for Lot 5 H-1 aircraft. These 15 aircraft in Lot 5 include 11 UH-1Ys and four AH-1Zs, bringing the total contacted amount to 49 upgraded H-1 aircraft for the Marine Corps: 37 UH-1Ys and 12 AH-1Zs. At that time, the company had delivered 20 upgraded H-1 helicopters: 14 UH-1Ys and six AH-1Zs.[18][19] On March 27, 2009, the Navy Department ordered 16 Lot 6 H-1 helicopters. The 16 aircraft in Lot 6 include five AH-1Zs and 11 UH-1Ys, bringing the total contract to produce a total of 65 upgraded H-1 aircraft: 17 AH-1Zs and 48 UH-1Ys. At the time, Bell had delivered 23 upgraded H-1 helicopters: six AH-1Zs and 17 UH-1Ys. [20][21]

In May 2009, several helicopters were grounded after a manufacturer's defect was detected in the gearbox.[16] The aircraft deployed with the 13th Marine Expeditionary Unit were not affected.

In September 2009, the UH-1Y entered full rate production, with the Marine Corps scheduled to have 21 aircraft by the end of the year. The AH-1Z is still in low rate initial production and not expected to be declared to have initial operational capability until sometime in 2011. Decision on full rate production of the AH-1Z is expected in first quarter FY2011. [17]


UH-1Y landing on an amphibious assault ship

The stated mission of the H-1 upgrade progam is to "resolve existing safety deficiencies, significantly improve operational capabilities, and reduce life-cycle costs. Commonality between aircraft will greatly enhance the maintainability and deployability of the systems with the capability to support and operate both aircraft within the same squadron structure."[22] Reduced logistical burden and maintenance costs are possible by the increased commonality of the two airframes, as well as increased reliability of individual components.[1]



The AH-1Z and UH-1Y share a common tail boom, engines, rotor system, drive train, avionics architecture, software, controls and displays for over 84% identical components.[23][24] Both aircraft use twin General Electric T700-GE-401C turboshaft outputting 1,800 shp(1350 kW). Upgrades will also be made to the transmission and skid landing gear.[22][25]

The existing two-bladed semi-rigid, teetering rotor system is being replaced with a four-bladed, hingeless, bearingless composite rotor system. The improvement in flight characteristics provided by the four-bladed configuration has led to increases in flight envelope, maximum speed, vertical rate-of-climb, payload and reduced rotor vibration.[26] The rotor system has 75% fewer parts than that of four-bladed articulated systems. The blades are made of composites, which have an increased ballistic survivability, and there is a semiautomatic folding system for stowage aboard Amphibious assault ships.[23] Both helicopters will receive an upgraded, four blade tail rotor and drive system.[22]

The new integrated avionics system (IAS) has been developed by Northrop Grumman.[22] The system includes two mission computers, an automatic flight control system, and a glass cockpit. Each crew station has two 8x6-inch multifunction liquid crystal displays (LCD) and one 4.2x4.2-inch dual function LCD display. The communications suite combines a US Navy RT-1824 integrated radio, UHF/VHF, COMSEC and modem in a single unit.[6] The navigation suite includes an embedded GPS inertial navigation system (EGI), a digital map system and a low-airspeed air data subsystem, which allows weapons delivery when hovering.[26] The Lockheed Martin target sight system (TSS) incorporates a third-generation FLIR sensor.[22] The TSS provides target sighting in day, night or adverse weather conditions. The system has various view modes and can track with FLIR or by TV.[23] The new cockpit systems will increase joint interoperability, now able to transmit and receive date from ground and air systems from other branches.[1][22]

The pilot and copilot are equipped with the Thales "Top Owl" helmet-mounted sight and display system.[24][25] The Top Owl has a 24-hour day/night capability and a binocular display with a 40° field of view. Its visor projection provides forward looking infrared (FLIR) or video imagery.


Its two redesigned wing stubs are longer, with each adding a wing-tip station for a missile such as the AIM-9 Sidewinder. Each wing has two other stations for 2.75 in (70 mm) Hydra 70 rocket pods, or AGM-114 Hellfire quad missile launchers. The Longbow radar can also be mounted on a wing tip station.[2]

The AH-1Z has survivability equipment including the Hover Infared Suppression System (HIRSS) to cover engine exhausts, countermeasure dispensers, radar warning, missile warning, and laser warning systems.[23]


One of the most critical UH-1Y upgrades is in its powertrain. The UH-1N gradually became burdened with various upgrades: avionics, radios, modern door guns, and safety upgrades; all increasing the UH-1N's empty weight. With a maximum speed of approximately 100 knots and an inability to lift much more than its own crew, fuel and ammunition, the UH-1N became limited in its utility. However, the UH-1Y has upgraded engines and transmission, 170% increased payload, and almost 50% greater range and maximum speed.[24][27] The fuselage has been lengthened by 21 inches just forward of the main door for more capacity.[24]

See also

Related development

Comparable aircraft

Related lists


  1. ^ a b c d H-1 Upgrade Program on
  2. ^ a b c d Donald, David. Modern Battlefield Warplanes. AIRTime Publishing, 2004. ISBN 1-880588-76-5.
  3. ^ Bishop, Chris. Huey Cobra Gunships. Osprey Publishing, 2006. ISBN 1-84176-984-3.
  4. ^ Milliman, John (2005-04-22). "UH-1Ys to be built new starting in 06". Naval Air Systems Command. United States Navy. Retrieved 2008-12-06.  
  5. ^ a b Warwick, Graham. "Bell AH-1Z upgrade to switch to new airframes",, 15 February 2008.
  6. ^ a b USMC H-1 Upgrade Program, Advanced Simulation Technology, Inc., September 2005
  7. ^ "AH-1Z completes first flight", Bell Helicopter, 7 December 2000.
  8. ^ Defense Dept. `Green Lights' Bell's H-1 Upgrade Program Business Wire, October 2003
  9. ^ "AH-1Z/UH-1Y complete developmental testing", US Navy, 6 March 2006.
  10. ^ "AH-1Z/UH-1Y complete first sea trials", US Navy, 13 June 2005.
  11. ^ "Bell 449 SuperCobra and KingCobra", Jane's Information Group, 7 December 2005.
  12. ^ "AH-1Z/UH-1Y Start OPEVAL", US Navy, 6 May 2006.
  13. ^ Warwick, Graham. "US Marine Corps' Bell AH-1Z and UH-1Y enter final test phase",, 20 February 2008.
  14. ^ "Bell H-1 upgrade program delivers two UH-1Y and one AH-1Z in February". Bell Helicopter, 3 March 2008.
  15. ^ Trimble, Stephen (2008-08-22). "US Navy proposes more UH-1Ys, AH-1Zs despite test phase setback". Retrieved 2008-08-24.  
  16. ^ a b McCullough, Amy (May 5 2009). "Damaged gear boxes ground some new Hueys". Marine Corps Times (Gannett Company). Retrieved 2009-05-22.  
  17. ^ a b "Program Insider: H-1 Update". Rotor & Wing Magazine. September 1 2009.  
  18. ^ "Bell Helicopter Receives Contract for Additional H-1 Aircraft". Textron. October 10, 2008.  
  19. ^ "Bell Helicopter Receives Contract for Lot 5 H-1 Aircraft". September 30, 2008.  
  20. ^ "US Navy Orders More H-1 Aircraft from Bell Helicopter". Textron. April 2, 2009.  
  21. ^ "US Navy Orders 16 Lot 6 UH-1Y Helicopters". March 27, 2009.  
  22. ^ a b c d e f H-1 Upgrade Program (UH-1Y/AH-1Z), U.S. Marine Corps, 2007.
  23. ^ a b c d Bell AH-1Z Pocket Guide, Bell Helicopter, Retrieved 3 January 2008.
  24. ^ a b c d Bell UH-1Y pocket guide, Bell Helicopter, Retrieved 16 August 2008.
  25. ^ a b Bell AH-1Z page, Bell Helicopter, Retrieved 3 January 2008.
  26. ^ a b AH-1W/AH-1Z Super Cobra Attack Helicopter, USA, Retrieved 14 January 2008.
  27. ^ Bell UH-1Y page, Bell Helicopter, Retrieved 3 January 2008.

External links

H-1 upgrade program


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