History
The concept of the OA-4M Skyhawk originated when the two-seat TA-4F, itself based on the single-seat A-4F Skyhawk, saw operational use during the Vietnam War. The US Marine Corps employed this type primarily in the fast forward air control role, where crews directed strike aircraft toward enemy positions and coordinated close air support operations over the battlefield. The second crew member proved especially valuable in these missions, assisting with navigation, target identification, and radio coordination.
In response to operational experience gained with TA-4Fs in Vietnam, a limited number of 23 TA-4F aircraft were later modified to the OA-4M standard in the late 1970s for improved forward air control capability. Essentially, the OA-4M was a TA-4F upgraded with avionics and systems found in the A-4M.
The modifications included improved communications and navigation systems, a KY-28 secure voice system, an APN-194 radar altimeter, and upgraded radio equipment such as the ARC-159 and ARC-114 VHF radios. One distinctive feature was the addition of a dorsal avionics/electronics hump, similar in appearance to that of the A-4M, faired into the rear of the two-seat canopy section. Additional cockpit side armor plating was also installed for improved crew protection.
However, certain A-4M systems were not included. The Angle/Rate Bombing System was not fitted, and the laser tracking/spotting capability associated with it was omitted and faired over, as the OA-4M was not intended for a dedicated precision strike role.
At one point, consideration was given to re-engining the OA-4M with the Pratt & Whitney J52-P-408, producing approximately 11,200 lbf of thrust, similar to the A-4M. However, this was ultimately not pursued, likely due to cost and complexity. As a result, the OA-4M retained the J52-P-8 engine of the TA-4F.
The first OA-4M, BuNo 165294, was tested at NATC Patuxent River, Maryland in July 1978. The first operational unit to receive the OA-4M was Headquarters and Maintenance Squadron (H&MS)-32 at MCAS Cherry Point, North Carolina. Later, VMA-131 of Marine Aircraft Group 49 (the “Diamondbacks”) operated the type until retiring its last OA-4Ms on 22 June 1994, marking the end of the variant’s USMC service life.
