(a) Installation. Each oil tank installation must meet the
requirements of §29.967.
(b) Expansion space. Oil tank expansion space must be provided
so that --
(1) Each oil tank used with a reciprocating engine has an expansion
space of not less than the greater of 10 percent of the tank capacity or
0.5 gallon, and each oil tank used with a turbine engine has an expansion
space of not less than 10 percent of the tank capacity;
(2) Each reserve oil tank not directly connected to any engine has an
expansion space of not less than two percent of the tank capacity; and
(3) It is impossible to fill the expansion space inadvertently with the
rotorcraft in the normal ground attitude.
(c) Filler connections. Each recessed oil tank filler connection
that can retain any appreciable quantity of oil must have a drain that
discharges clear of the entire rotorcraft. In addition --
(1) Each oil tank filler cap must provide an oil-tight seal under the
pressure expected in operation;
(2) For category A rotorcraft, each oil tank filler cap or filler cap
cover must incorporate features that provide a warning when caps are not
fully locked or seated on the filler connection; and
(3) Each oil filler must be marked under §29.1557(c)(2).
(d) Vent. Oil tanks must be vented as follows:
(1) Each oil tank must be vented from the top part of the expansion
space to that venting is effective under all normal flight conditions.
(2) Oil tank vents must be arranged so that condensed water vapor that
might freeze and obstruct the line cannot accumulate at any point;
(e) Outlet. There must be means to prevent entrance into the
tank itself, or into the tank outlet, of any object that might obstruct
the flow of oil through the system. No oil tank outlet may be enclosed by
a screen or guard that would reduce the flow of oil below a safe value at
any operating temperature. There must be a shutoff valve at the outlet of
each oil tank used with a turbine engine unless the external portion of
the oil system (including oil tank supports) is fireproof.
(f) Flexible liners. Each flexible oil tank liner must be
approved or shown to be suitable for the particular installation.