JAR 25B955 Fuel flow
(a) The fuel system must provide at least
100% of the fuel flow required under each
intended operating condition and manoeuvre.
Compliance must be shown as follows:
(1) Fuel must be delivered to the APU
at a pressure within the limits specified in the
APU type approval.
(2) The quantity of fuel in the tank may
not exceed the amount established as the
unusable fuel supply for that tank under the
requirements of JAR 25.959 plus that necessary
to show compliance with this paragraph.
(3) Each main pump must be used that
is necessary for each operating condition and
attitude for which compliance with this
paragraph is shown, and the appropriate
emergency pump must be substituted for each
main pump so used.
(4) If there is a fuel flowmeter, it must
be blocked and the fuel must flow through the
meter or its bypass. (See ACJ 25.955 (a)(4).)
(b) If an APU can be supplied with fuel from
more than one tank, the fuel system must –
(2) For the APU, in addition to having
appropriate manual switching capability, be
designed to prevent interruption of fuel flow to
the APU, without attention by the flight crew,
when any tank supplying fuel to the APU is
depleted of usable fuel during normal operation
and any other tank, that normally supplies fuel
to the APU alone, contains usable fuel.
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