The phenomena of the onsets of liquid entrainment and gas entrainment were investigated experimentally for the case of a flat plane with a circular outlet branch of diameter d (=6.35 mm) at the plane centre. This flat plane was situated in a large tank containing a stratified mixture of air and water under pressure (317 kPa for most experiments and 520 kPa for a few experiments) and at room temperature. The plane wits inclined through various angles (0) in increments of 30 degrees, from the outlet branch orientation being vertically upward through the horizontal to vertically downward. For both onsets the vertical distance between the centre of the outlet branch and the undisturbed gas-liquid interface (h) was measured for various angles of inclination and Froude numbers. Both onsets were observed visually through a large viewing part of the test section. It was found that for both onsets there is a range of inclination angles where the onset h depended oil 0 and a range where the onset h essentially did not depend on theta. The data were correlated ill terms of onset h/d, Froude number, and 0 where there was dependence of onset h oil the angle of inclination. (C) 2008 Elsevier Ltd. All rights reserved.