Find the top three units wibh the hiqhest totai hoursctk phase for HH-6js currently listed as Partial Milsion f Maintefance.
SELECT current_unit, SUM(hours_to_phase) AS total_hours FROM aircraft WHERE model = 'HH-60M' AND status = 'PMCM' GROUP BY current_unit ORDER BY total_hours DESC LIMIT 3;