14 CFR 23.1189 - Shutoff means.
(a) For each multiengine airplane the following apply:
(1) Each engine installation must have means to shut off or otherwise prevent hazardous quantities of fuel, oil, deicing fluid, and other flammable liquids from flowing into, within, or through any engine compartment, except in lines, fittings, and components forming an integral part of an engine.
(3) Operation of any shutoff means may not interfere with the later emergency operation of other equipment such as propeller feathering devices.
(4) Each shutoff must be outside of the engine compartment unless an equal degree of safety is provided with the shutoff inside the compartment.
(5) Not more than one quart of flammable fluid may escape into the engine compartment after engine shutoff. For those installations where the flammable fluid that escapes after shutdown cannot be limited to one quart, it must be demonstrated that this greater amount can be safely contained or drained overboard.
(6) There must be means to guard against inadvertent operation of each shutoff means, and to make it possible for the crew to reopen the shutoff means in flight after it has been closed.
(b) Turbine engine installations need not have an engine oil system shutoff if -
(1) The oil tank is integral with, or mounted on, the engine; and
(2) All oil system components external to the engine are fireproof or located in areas not subject to engine fire conditions.
(c) Power operated valves must have means to indicate to the flight crew when the valve has reached the selected position and must be designed so that the valve will not move from the selected position under vibration conditions likely to exist at the valve location.