CS 25J955 Fuel Flow

(See AMC 25J955)

(a)Each fuel system must provide at least 100 percent of the fuel flow required by the APU under each intended operating condition and manoeuvre. Compliance must be shown as follows:

(1)Fuel must be delivered at a pressure within the limits specified for the APU.

(2)For essential APUs:

(i)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 CS 25.959 plus that necessary to show compliance with this paragraph.

(ii)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.

(iii)If there is a fuel flowmeter, it must be blocked and the fuel must flow through the meter or its bypass. (See AMC 25J955(a)(2)(iii).)

(b)For essential APUs: If an APU can be supplied with fuel from more than one tank, the fuel system must, in addition to having appropriate manual switching capability, be designed to prevent interruption of fuel flow to that APU, without attention by the flight crew, when any tank supplying fuel to that APU is depleted of usable fuel during normal operation, and any other tank, that normally supplies fuel to that APU, contains usable fuel.

[Amdt 25/1]

[Amdt 25/18]