The RFI calls for helicopters with a maximum all-up weight of between 9t and 12.5t. The NMRH, which will be expected to serve for 30 years, should have the capacity for 10% weight growth throughout its service life without hurting performance.
The navy foresees three primary roles: ASW, anti-surface warfare (ASuW), and special operations. Secondary roles include electronic intelligence, search and rescue (SAR), external cargo carrying, casualty evacuation and combat SAR.
Candidate helicopters must be able to operate from ships as small as the navy's Godavari-class frigates. They also need to be able to fit in shipboard hangars with a length of 15.5m (50.8ft), a width of 5.5m and a height of 5.3m.
"The NMRH should be a contemporary design with modern, reliable and fuel-efficient engines and fully integrated advanced avionics/weapons suite employing the latest concepts for detection, identification, classification of surface and sub-surface targets along with the ability to detect air targets," the RFI said.
It also outlines performance requirements for two variants: one focused on ASW/ASuW and the other for special operations.
For the former variant, India seeks an aircraft that can autonomously locate and destroy submarines, compile an integrated picture of the situation above and below the surface, and operate in all weather conditions.
The special operations variant needs the capability to carry unguided rockets and guns.
Possible candidates for the requirement could include the Lockheed Martin/Sikorsky MH-60R and NH Industries' NH90. The deal will require a minimum 30% offset obligation under Indian laws.