Studies for a Naval version of the Apache were begun during 1984 and since that time the McDonnell Douglas Helicopter Company has proposed several navalized Apaches to both the U.S. Marine Corps and U.S. Navy. The navalized Apache is viewed as a replacement for the aging Bell AH-1 Sea Cobras that are in service with the Navy and Marines. With the introduction of a four-blade rotor system to the current Marine Sea Cobra, the AH-1W, the Bell Cobra is believed to have reached the limit of its development. While older Sea Cobra airframes can be brought up to AH-1W standards, the Marines view the need for a replacement for the Sea Cobra with some urgency.

The proposed Sea Apache (also known as the Gray Thunder) is intended for operations from smaller Navy ships such as frigates and cruisers and by the Marines from Amphibious Assault Ships (LHA) and smaller helicopter capable amphibious ships of a Marine Amphibious Ready Group (ARG). These ships often operate outside the air cover of a carrier task group and the Sea Apache is also view as a limited air defense weapon and offensive surface strike platform.

Since 1984, several design studies and formal proposals have evolved with the Navy requesting changes in the Sea Apache configuration as it refined the aircraft's missions and roles. Each of the three proposed navalized versions of the Apache differed in several ways from the standard Army AH-64A, although all three proposals have the same powerplants in common, two 1,723shp naval standard General Electric T700-GE-401 engines. Also in common are increased corrosion preventive measures, improved electro-magnetic interference protection, a Doppler navigation system, upgraded brakes, additional tie down points, and a powered automatic rotor blade fold system.

Originally, the Sea Apache was to be a basic AH-64A airframe modified with a folding tail boom, a relocated tail wheel, a mast-mounted radar for surface/air search and attack, and provisions for Harpoon and Sidewinder missiles. Over time, however, the engineering studies and changing roles/missions requirements revealed that the Sea Apache's final configuration would have to be altered drastically.

One of the early problems encountered with navalizing the Apache was the narrow wheel base of the main landing gear. Engineering studies found that the standard Apache main wheel track was too narrow, causing the aircraft to be very unstable on the deck of a small ship. The roll of the deck in heavy seas, coupled with the aircraft's narrow wheel base, could easily cause the Sea Apache to tip over. To solve this problem, McDonnell Douglas engineers redesigned the main landing gear, relocating it from the fuselage to the tips of the stub wings. The revised main landing gear is also retractable, with the gear retracting into streamlined housings (although the wheel itself remains uncovered) on the end of each reinforced stub wing. These housings also have provisions for mounting Sidewinder missile launcher rails.

The revised landing gear configuration was put forward in the second proposal which also deleted the 30mm Chain Gun and its associated ammunition storage system, and replaced the TADS/PNVS with a nose mounted radar. The second Sea Apache featured a revised nose contour and extended fuselage side sponsons to carry additional electronics and fuel cells. The sponsons were smoothly faired into the fuselage to lower drag and extended almost to the tip of the nose. This aircraft was to also have provision for carrying two AIM-9L Sidewinder air-to-air missiles on short racks on the fuselage underside, a folding tail assembly and a retractable tail wheel.

The design has been refined still further, and the current Sea Apache proposal has the side fuselage sponsons deleted and a larger nose radome intended to house the APG-65 Sea Search radar. This radar, developed from the multi-mode radar used on the F/A-18 Hornet fighter/attack aircraft, is compatible for both air-to-surface attack and air-to-air engagements. The forward fuselage is deepened to house additional fuel cells and the relocated avionics bays.

Projected armament included both the Harpoon or Penguin air-to-surface missiles (although the number of stations has been reduced to two) and two Sidewinder air-to-air missiles. To extend the Sea Apache's time on station, an in-flight refueling probe would be mounted on the starboard fuselage side below the cockpit. Consideration is also being given to installing the Canadian developed Bear Trap automatic haul-down landing system, which allows operations during heavy sea states.

One proposed Marine Corps variant would retain the TADS/PNVS and Hellfire missile system, for use in the close air support role and for anti-shipping duties while escorting amphibious vessels. This aircraft would relocate the radar dome back to the top of the rotor mast. Another option favored by the Marines is the capability to use the four tube TOW missile system as a back-up to the Hellfire missile system.

Some of the missions envisioned by the Navy for the Sea Apache are; escort for amphibious assault craft, anti-shipping strike, Combat Air Patrol (CAP) with up to six Sidewinders, Over the Horizon (OTH) targeting for surface ships, air support for SEAL special warfare teams, standoff surveillance, and long range coastal patrol.

Marine variants are planned to be used as escorts for troop-carrying helicopters, close air support for landing forces, anti-armor support, Forward Air Control (FAC) for artillery and Naval gunfire spotting. The Marines view the Sea Apache as the best available replacement for the Sea Cobra. The Sea Apache would give the commander of an Amphibious Ready Group (ARG) a dedicated attack/limited air defense aircraft readily available stationed aboard the LHA/LPH/LPD classes of assault ships in his task force (this mission currently can only be partially covered by the AH-1W Sea Cobra and usually requires stationing a flight of Harriers aboard the LHA).

Weapons planned for use with the Sea Apache include Harpoon, Stinger, Sidewinder, Sidearm, AMRAAM, Penguin, and Hellfire missiles, as well as 127mm Zuni and 70mm FFAR rockets. The Harpoon, Penguin and He!Ifire missiles wouId be used against large naval targets, the Sidewinder and Stinger in the air-to-air mode, and the 127mm Zuni and 70mm FFAR rockets against smaller water borne targets and ground targets. A variety of missiles/rockets could be carried at the same time giving the Sea Apache the capability of engaging different types of targets on the same mission, making it a very versatile and useful naval aircraft.

Performance goals specified for the Sea Apache by the Navy include a 370km mission radius, and a four hour endurance on station.

Currently, the Navy is giving serious consideration to the purchase of the Sea Apache once adequate funding is made available to finance prototype construction. The Navy desires the Sea Apache not only for its capabilities, but also because the aircraft would cost far less to acquire than to undertake the design of a totally new aircraft to replace the AH-1W in service.

Al Adcock "AH-64 Apache in Action", 1989

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