The US Marine Corps is preparing a major upgrade for its AH-1Z Viper attack helicopters and UH-1Y Venom utility helicopters by giving the aircraft stronger structures combined with more electrical power to handle heavier weapons and advanced combat systems.The program, called SPINE (Structural and Power Improvements for NextGen Effects), is moving towards modifications of operational aircraft in fiscal year 2027, following developmental testing of two upgraded helicopters.Stronger airframes and more electrical powerThe upgrade addresses two important limitations of the Marine Corps’ H-1 helicopter fleet: structural capacity and electrical power generation.Strengthening the air frames will allow the aircraft to handle heavier loads, while boosted electrical capacity will support additional weapons and mission equipment. One of the key additions is a digital weapons bus, which will allow aircraft computers to exchange information with compatible weapons before launch.This capability is expected to help integrate advanced systems, including the most advanced AIM-9X missiles, and make it easier to introduce future digital weapons.The program office, PMA-276, is using flight-test data from one upgraded AH-1Z and one UH-1Y to finalize the configuration before fleet-wide work begins.Bell prepares for operational modificationsDevelopmental testing is taking place at Naval Air Station Patuxent River in Maryland, involving PMA-276, Bell Textron and Air Test and Evaluation Squadron 21.Bell completed the structural and electrical modifications to both test aircraft in March 2026, following 19 months of work at its Amarillo Assembly Center in Texas. The project was previously known as the Structural Improvement and Electrical Power Upgrade, or SIEPU.The company is now preparing its Texas facility to handle operational helicopters. Work includes purchasing components, establishing production lines, preparing specialized tooling and organizing aircraft transportation.The teams are also coordinating SPINE with other planned H-1 upgrades to complete multiple modifications during the same visits and reduce the time helicopters spend out of service.Contracts cover up to 49 helicoptersThe first production work is backed by two US Navy contract awards.In July, Bell received a $33.6 million contract for SPINE Phase Three hardware, covering a potential batch of 49 aircraft, including 28 AH-1Zs and 21 UH-1Ys.In October, the Navy exercised a further $114.7 million option covering 15 aircraft kits, four mission kits and nine aircraft installations. The work is scheduled for completion by June 2028.The Marine Corps operates approximately 189 Vipers and 160 Venoms. Although production of the UH-1Y ended in 2020 and the AH-1Z in 2022, the aircraft share around 85 per cent of their components, allowing them to benefit from common improvements.The modernization comes as the Marine Corps explores new ways to combine helicopters with unmanned aircraft.During an exercise at Twentynine Palms, California, in May, Marine Light Attack Helicopter Squadron 169 used UH-1Y Venoms as airborne control stations for Neros Archer first-person-view drones. One drone was launched from a helicopter in flight, while another was launched from the ground before being taken over by the airborne team.“H-1 modernization is critical to maintaining a capable and ready force for aviation-delivered fires in support of Marine Air-Ground Task Force crisis response,” said Lieutenant Colonel Benjamin Carlton of PMA-276.He added that developmental testing was continuing ahead of the first operational modifications in fiscal year 2027, while engineers refine the configuration before the upgraded helicopters enter service.