The critical heat fluxes (CHFs) were measured on three horizontal flat plates of the same width of 10.5 mm and with lengths of 10, 15.6, and 40 mm in subcooled He II with the temperature of 1.8, 1.9 and 2.0 at atmospheric pressure. The flat plates were made of Manganin, one side of which was thermally insulated. The measured CHFs were higher for shorter length of the test plate and for lower liquid temperature. The correlation for CHFs on flat plates in He II already presented by the authors was confirmed to describe CHFs on various sized flat plates including square ones within 20% difference. © 2001 Elsevier Science Ltd.