(1) May not be less than the greater of—
(i) That required to provide fluid at the rate specified in §23.1095 for a time equal to three percent of the maximum endurance of the airplane; or
(ii) 20 minutes at that flow rate; and
(2) Need not exceed that required for two hours of operation.
(b) If the available preheat exceeds 50 °F. but is less than 100 °F., the capacity of the system may be decreased in proportion to the heat rise available in excess of 50 °F.