Military helicopter designers at Bell Helicopter in Fort Worth, Texas, are preparing to build 24 new-build AH-1Z Viper attack helicopters and associated avionics for the U.S. Marine Corps under terms of a $55.9 million U.S. Navy contract announced Tuesday.

Officials of the Naval Air Systems Command are asking Bell Helicopter, a Textron Inc. company, to buy long-lead parts and components necessary to build 24 Lot 14 AH-1Z helicopters as part of the H-1 upgrade program.

The AH-1Z is a twin-engine attack helicopter based on the AH-1W Super Cobra that features a four-blade rotor system, uprated transmission, and a new target sighting system. It has upgraded avionics, weapons, and electro-optical sensors designed to find targets at long ranges and attack them with precision weapons.

The Marine Corps H-1 upgrades program is building new helicopters, as well as rebuilding legacy AH-1W Super Cobra attack helicopters and UH-1N Twin Huey utility helicopters with state of the art designs. The program seeks to upgrade AH-1Ws to AH-1Zs, and UH-1Ns to UH-1Ys.