The wings were made from a wood frame and plywood cover. The frame and coverings for the fuselage were all metal with the tail being welded steel tubes with fabric coverings.
The first Meridionali Ro.51 prototype had fixed landing gear covered by spats.
The second Ro.51 prototype had rear retracting landing gear.
The third Ro.51 prototype was built as a floatplane to replace the Ro.44.